Moraines, or rocks and soil deposited by glaciers during the Last Glacial Maximum, are spread across the landscape near Mt. Cook, New Zealand’s tallest mountain, and Lake Pukaki. Credit: Aaron Putnam
A new international study casts doubt on the leading theory of what causes ice ages around the world — changes in the way the Earth orbits the sun.
The researchers found that glacier movement in the Southern Hemisphere is influenced primarily by sea surface temperature and atmospheric carbon dioxide rather than changes in the Earth’s orbit, which are thought to drive the advance and retreat of ice sheets in the Northern Hemisphere.
The findings appear in the journal Geology.
The study raises questions about the Milankovitch theory of climate, which says the expansion and contraction of Northern Hemisphere continental ice sheets are influenced by cyclic fluctuations in solar radiation intensity due to wobbles in the Earth’s orbit; those orbital fluctuations should have an opposite effect on Southern Hemisphere glaciers.
“Records of past climatic changes are the only reason scientists are able to predict how the world will change in the future due to warming. The more we understand about the cause of large climatic changes and how the cooling or warming signals travel around the world, the better we can predict and adapt to future changes,” says lead author Alice Doughty, a glacial geologist at Dartmouth College who studies New Zealand mountain glaciers to understand what causes large-scale global climatic change such as ice ages. “Our results point to the importance of feedbacks — a reaction within the climate system that can amplify the initial climate change, such as cool temperatures leading to larger ice sheets, which reflect more sunlight, which cools the planet further. The more we know about the magnitude and rates of these changes and the better we can explain these connections, the more robust climate models can be in predicting future change.”
The researchers used detailed mapping and beryllium-10 surface exposure dating of ice-age moraines — or rocks deposited when glaciers move — in New Zealand’s Southern Alps, where the glaciers were much bigger in the past. The dating method measures beryllium-10, a nuclide produced in rocks when they are struck by cosmic rays. The researchers identified at least seven episodes of maximum glacier expansion during the last ice age, and they also dated the ages of four sequential moraine ridges. The results showed that New Zealand glaciers were large at the same time that large ice sheets covered Scandinavia and Canada during the last ice age about 20,000 years ago. This makes sense in that the whole world was cold at the same time, but the Milankovitch theory should have opposite effects for the Northern and Southern Hemispheres, and thus cannot explain the synchronous advance of glaciers around the globe. Previous studies have shown that Chilean glaciers in the southern Andes also have been large at the same time as Northern Hemisphere ice sheets.
The ages of the four New Zealand ridges — about 35,500; 27,170; 20,270; and 18,290 years old — instead align with times of cooler sea surface temperatures off the coast of New Zealand based on offshore marine sediment cores. The timing of the Northern Hemisphere’s ice ages and large ice sheets is still paced by how Earth orbits the Sun, but how the cooling and warming signals are transferred around the world has not been fully explained, although ocean currents (flow direction, speed and temperature) play a significant role.
Reference:
Alice M. Doughty, Joerg M. Schaefer, Aaron E. Putnam, George H. Denton, Michael R. Kaplan, David J.a. Barrell, Bjørn G. Andersen, Samuel E. Kelley, Robert C. Finkel, And Roseanne Schwartz. Mismatch of glacier extent and summer insolation in Southern Hemisphere mid-latitudes. Geology, 2015 DOI: 10.1130/G36477.1
Note: The above story is based on materials provided by Dartmouth College.
In this March 13, 2015 photo, a woman and a boy walk up a hill, 11-meter (36 feet) above sea level, with a tsunami evacuation sign standing at the “Millennium Hope Hills” park in Iwanuma, Miyagi prefecture, northeastern Japan. Four years after a towering tsunami ravaged much of Japan’s northeastern coast, efforts to fend off future disasters are focusing on a nearly 400-kilometer (250 mile) chain of cement sea walls, at places nearly five stories high. (AP Photo/Koji Ueda)
Four years after a towering tsunami ravaged much of Japan’s northeastern coast, efforts to fend off future disasters are focusing on a nearly 400-kilometer (250-mile) chain of cement sea walls, at places nearly five stories high.
Opponents of the 820 billion yen ($6.8 billion) plan argue that the massive concrete barriers will damage marine ecology and scenery, hinder vital fisheries and actually do little to protect residents who are mostly supposed to relocate to higher ground. Those in favor say the sea walls are a necessary evil, and one that will provide some jobs, at least for a time.
In the northern fishing port of Osabe, Kazutoshi Musashi chafes at the 12.5-meter (41-foot)-high concrete barrier blocking his view of the sea.
“The reality is that it looks like the wall of a jail,” said Musashi, 46, who lived on the seaside before the tsunami struck Osabe and has moved inland since.
Pouring concrete for public works is a staple strategy for the ruling Liberal Democratic Party and its backers in big business and construction, and local officials tend to go along with such plans.
The paradox of such projects, experts say, is that while they may reduce some damage, they can foster complacency. That can be a grave risk along coastlines vulnerable to tsunamis, storm surges and other natural disasters. At least some of the 18,500 people who died or went missing in the 2011 disasters failed to heed warnings to escape in time.
Tsuneaki Iguchi was mayor of Iwanuma, a town just south of the region’s biggest city, Sendai, when the tsunami triggered by a magnitude-9 earthquake just off the coast inundated half of its area.
A 7.2-meter (24-foot) -high sea wall built years earlier to help stave off erosion of Iwanuma’s beaches slowed the wall of water, as did stands of tall, thin pine trees planted along the coast. But the tsunami still swept up to 5 kilometers (3 miles) inland. Passengers and staff watched from the upper floors and roof of the airport as the waves carried off cars, buildings and aircraft, smashing most homes in densely populated suburbs not far from the beach.
The city repaired the broken sea walls but doesn’t plan to make them any taller. Instead, Iguchi was one of the first local officials to back a plan championed by former Prime Minister Morihiro Hosokawa to plant mixed forests along the coasts on tall mounds of soil or rubble, to help create a living “green wall” that would persist long after the concrete of the bigger, man-made structures has crumbled.
“We don’t need the sea wall to be higher. What we do need is for everyone to evacuate,” Iguchi said.
“The safest thing is for people to live on higher ground and for people’s homes and their workplaces to be in separate locations. If we do that, we don’t need to have a ‘Great Wall,'” he said.
While the lack of basic infrastructure can be catastrophic in developing countries, too heavy a reliance on such safeguards can lead communities to be too complacent at times, says Margareta Wahlstrom, head of the U.N.’s Office for Disaster Risk Reduction.
“There’s a bit of an overbelief in technology as a solution, even though everything we have learned demonstrates that people’s own insights and instincts are really what makes a difference, and technology in fact makes us a bit more vulnerable,” Wahlstrom said in an interview ahead of a recent conference in Sendai convened to draft a new framework for reducing disaster risks.
In the steelmaking town of Kamaishi, more than 1,000 people died in the 2011 tsunami, but most school students fled to safety zones immediately after the earthquake, thanks to training by a civil engineering professor, Toshitaka Katada.
The risk is not confined to Japan, said Maarten van Aalst, director of the Red Cross/Red Crescent Climate Center, who sees this in the attitudes of fellow Dutch people who trust in their low-lying country’s defenses against the sea.
“The public impression of safety is so high, they would have no idea what to do in case of a catastrophe,” he said.
Despite pockets of opposition, getting people to agree to forego the sea walls and opt instead for Hosokawa’s “Great Forest Wall” plan is a tough sell, says Tomoaki Takahashi, whose job is to win support for the forest project in local communities.
“Actually, many people are in favor of the sea walls, because they will create jobs,” said Takahashi. “But even people who really don’t like the idea also feel as if they would be shunned if they don’t go along with those who support the plan,” he said.
While the “Great Forest Wall” being planted in some areas would not stave off flooding, it would slow tsunamis and weaken the force of their waves. As waters recede, the vegetation would help prevent buildings and other debris from flowing back out to sea. Such projects would also allow rain water to flow back into the sea, a vital element of marine ecology.
Some voices in unexpected places are urging a rethink of the plan.
Prime Minister Shinzo Abe’s wife, Akie, offered numerous objections to cementing the northeast coast in a speech in New York last September. She said the walls may prevent residents from keeping an eye out for future tsunamis and would be costly to maintain for already dwindling coastal communities.
“Please do not proceed even if it’s already decided,” she said. Instead of a one-size-fits-all policy, she suggested making the plan more flexible. “I ask, is building high sea walls to shield the coast line really, really the best?”
Rikuzentakata, a small city near Osabe whose downtown area was wiped out by the tsunami, is building a higher sea wall, but also moving many tons of earth to raise the land well above sea level.
Local leader Takeshi Konno said no construction project will eliminate the need for coastal residents to protect themselves.
“What I want to stress is that no matter what people try to create, it won’t beat nature, so we humans need to find a way to co-exist with nature,” Konno said. “Escaping when there is danger . the most important thing is to save your life.”
Note : The above story is based on materials provided by The Associated Press. All rights reserved..
Figure 4 in B.A. Black et al.: This image shows annually averaged temperature anomalies in excess of 3°C for the first year after the Campanian Ignimbrite (CI) eruption compared with spatial distribution of hominin sites with radiocarbon ages close to that of the eruption. Credit: B.A. Black et al. and the journal Geology
The Campanian Ignimbrite (CI) eruption in Italy 40,000 years ago was one of the largest volcanic cataclysms in Europe and injected a significant amount of sulfur-dioxide (SO2) into the stratosphere. Scientists have long debated whether this eruption contributed to the final extinction of the Neanderthals. This new study by Benjamin A. Black and colleagues tests this hypothesis with a sophisticated climate model.
Black and colleagues write that the CI eruption approximately coincided with the final decline of Neanderthals as well as with dramatic territorial and cultural advances among anatomically modern humans. Because of this, the roles of climate, hominin competition, and volcanic sulfur cooling and acid deposition have been vigorously debated as causes of Neanderthal extinction.
They point out, however, that the decline of Neanderthals in Europe began well before the CI eruption: “Radiocarbon dating has shown that at the time of the CI eruption, anatomically modern humans had already arrived in Europe, and the range of Neanderthals had steadily diminished. Work at five sites in the Mediterranean indicates that anatomically modern humans were established in these locations by then as well.”
“While the precise implications of the CI eruption for cultures and livelihoods are best understood in the context of archaeological data sets,” write Black and colleagues, the results of their study quantitatively describe the magnitude and distribution of the volcanic cooling and acid deposition that ancient hominin communities experienced coincident with the final decline of the Neanderthals.
In their climate simulations, Black and colleagues found that the largest temperature decreases after the eruption occurred in Eastern Europe and Asia and sidestepped the areas where the final Neanderthal populations were living (Western Europe). Therefore, the authors conclude that the eruption was probably insufficient to trigger Neanderthal extinction.
However, the abrupt cold spell that followed the eruption would still have significantly impacted day-to-day life for Neanderthals and early humans in Europe. Black and colleagues point out that temperatures in Western Europe would have decreased by an average of 2 to 4 degrees Celsius during the year following the eruption. These unusual conditions, they write, may have directly influenced survival and day-to-day life for Neanderthals and anatomically modern humans alike, and emphasize the resilience of anatomically modern humans in the face of abrupt and adverse changes in the environment.
Reference:
B. A. Black, R. R. Neely, M. Manga. Campanian Ignimbrite volcanism, climate, and the final decline of the Neanderthals. Geology, 2015; DOI: 10.1130/G36514.1
This is a life reconstruction of Carnufex carolinensis. Credit: Copyright Jorge Gonzales. Open access
A newly discovered crocodilian ancestor may have filled one of North America’s top predator roles before dinosaurs arrived on the continent. Carnufex carolinensis, or the “Carolina Butcher,” was a 9-foot long, land-dwelling crocodylomorph that walked on its hind legs and likely preyed upon smaller inhabitants of North Carolina ecosystems such as armored reptiles and early mammal relatives.
Paleontologists from North Carolina State University and the North Carolina Museum of Natural Sciences recovered parts of Carnufex’s skull, spine and upper forelimb from the Pekin Formation in Chatham County, North Carolina. Because the skull of Carnufex was preserved in pieces, it was difficult to visualize what the complete skull would have looked like in life. To get a fuller picture of Carnufex’s skull the researchers scanned the individual bones with the latest imaging technology — a high-resolution surface scanner. Then they created a three-dimensional model of the reconstructed skull, using the more complete skulls of close relatives to fill in the missing pieces.
The Pekin Formation contains sediments deposited 231 million years ago in the beginning of the Late Triassic (the Carnian), when what is now North Carolina was a wet, warm equatorial region beginning to break apart from the supercontinent Pangea. “Fossils from this time period are extremely important to scientists because they record the earliest appearance of crocodylomorphs and theropod dinosaurs, two groups that first evolved in the Triassic period, yet managed to survive to the present day in the form of crocodiles and birds,” says Lindsay Zanno, assistant research professor at NC State, director of the Paleontology and Geology lab at the museum, and lead author of a paper describing the find. “The discovery of Carnufex, one of the world’s earliest and largest crocodylomorphs, adds new information to the push and pull of top terrestrial predators across Pangea.”
Typical predators roaming Pangea included large-bodied rauisuchids and poposauroids, fearsome cousins of ancient crocodiles that went extinct in the Triassic Period. In the Southern Hemisphere, “these animals hunted alongside the earliest theropod dinosaurs, creating a predator pile-up,” says Zanno. However, the discovery of Carnufex indicates that in the north, large-bodied crocodylomorphs, not dinosaurs, were adding to the diversity of top predator niches. “We knew that there were too many top performers on the proverbial stage in the Late Triassic,” Zanno adds. “Yet, until we deciphered the story behind Carnufex, it wasn’t clear that early crocodile ancestors were among those vying for top predator roles prior to the reign of dinosaurs in North America.”
As the Triassic drew to a close, extinction decimated this panoply of predators and only small-bodied crocodylomorphs and theropods survived. “Theropods were ready understudies for vacant top predator niches when large-bodied crocs and their relatives bowed out,” says Zanno. “Predatory dinosaurs went on to fill these roles exclusively for the next 135 million years.”
Still, ancient crocodiles found success in other places. “As theropod dinosaurs started to make it big, the ancestors of modern crocs initially took on a role similar to foxes or jackals, with small, sleek bodies and long limbs,” says Susan Drymala, graduate student at NC State and co-author of the paper. “If you want to picture these animals, just think of a modern day fox, but with alligator skin instead of fur.”
Reference:
Lindsay E. Zanno, Susan Drymala, Sterling J. Nesbitt, Vincent P. Schneider. Early crocodylomorph increases top tier predator diversity during rise of dinosaurs. Scientific Reports, 2015; 5: 9276 DOI: 10.1038/srep09276
Scientists at the University of York provided the key to solving the evolutionary puzzle surrounding what Charles Darwin called the ‘strangest animals ever discovered’. Credit: Copyright Peter Schouten
Scientists have resolved pieces of a nearly 200-year-old evolutionary puzzle surrounding the group of mammals that Charles Darwin called the “strangest animals ever discovered.” New research led by the Natural History Museum, the American Museum of Natural History and the University of York shows that South America’s native ungulates, or hooved mammals — the last of which disappeared only 10,000 years ago — are actually related to mammals like horses rather than elephants and other species with ancient evolutionary ties to Africa as some taxonomists have maintained. Published today in the journal Nature, the findings are based on fossil protein sequences, which allow researchers to peek back in time up to 10 times farther than they can with DNA.
Ian Barnes, Research Leader at the Natural History Museum and one of the paper’s authors, explained: “Although the bones of these animals had been studied for over 180 years, no clear picture of their origins had been reached. Our analyses began by investigating ancient DNA to try to resolve the problem.”
“Fitting South American ungulates to the mammalian family tree has always been a major challenge for palaeontologists, because anatomically they were these weird mosaics, exhibiting features found in a huge variety of quite unrelated species living all over the place,” said Ross MacPhee, one of the paper’s authors and a curator in the American Museum of Natural History’s Department of Mammalogy. “This is what puzzled Darwin and his collaborator Richard Owen so much in the early 19th century. With all of these conflicting signals, they couldn’t say whether these ungulates were related to giant rodents, or elephants, or camels — or what have you.”
However, the team soon realized that ancient DNA — that is, genetic material extracted from fossils — did not survive in these fossils, because the DNA molecule survives poorly in the warm, wet conditions like those typical of South America. The breakthrough came when the researchers switched to analysing collagen, a structural protein found in all animal bones that can survive for a million years or more in a wide range of conditions. The chemical structure of the amino acids that make up a protein is ultimately dictated by specific coding sequences in the organism’s DNA. Because of this key relationship, amino acid compositions of the same protein in different species can be analysed and compared, providing insight into how closely the species are related.
“People have been successful in retrieving collagen sequences from specimens dating up to 4 million years old, and this is just the start,” said University of York Professor Matthew Collins, whose lab did the sequencing work. “On theoretical grounds, with material recovered from permafrost conditions, we might be able to reach back 10 million years.”
The scientists used proteomic analysis to screen 48 fossils of Toxodon platensis and Macrauchenia patachonica, the very species whose remains Darwin discovered 180 years ago in Uruguay and Argentina. “By selecting only the very best preserved bone specimens and with various improvements in proteomic analysis, we were able to obtain roughly 90 percent of the collagen sequence for both species,” said lead author Frido Welker, a Ph.D. student at the Max Planck Institute for Evolutionary Anthropology and the University of York. “This opens the way for various other applications in paleontology and paleoanthropology, which we are currently exploring.”
With modern techniques, the researchers were able to conclusively show that the closest living relatives of these species were the perissodactyls, the group that includes horses, rhinos, and tapirs. This makes them part of Laurasiatheria, one of the major groups of placental mammals. The molecular evidence corroborates a view held by some leading paleontologists that the ancestors of these South American ungulates came from North America more than 60 million years ago, probably just after the mass extinction that killed off non-avian dinosaurs and many other vertebrates.
Reference:
Frido Welker, Matthew J. Collins, Jessica A. Thomas, Marc Wadsley, Selina Brace, Enrico Cappellini, Samuel T. Turvey, Marcelo Reguero, Javier N. Gelfo, Alejandro Kramarz, Joachim Burger, Jane Thomas-Oates, David A. Ashford, Peter D. Ashton, Keri Rowsell, Duncan M. Porter, Benedikt Kessler, Roman Fischer, Carsten Baessmann, Stephanie Kaspar, Jesper V. Olsen, Patrick Kiley, James A. Elliott, Christian D. Kelstrup, Victoria Mullin et al. Ancient proteins resolve the evolutionary history of Darwin’s South American ungulates. Nature, 2015 DOI: 10.1038/nature14249
An artist’s concept shows a celestial body about the size of our moon slamming at great speed into a body the size of Mercury. Credit: Image courtesy of NASA/JPL-Caltech
Researchers at Sandia National Laboratories’ Z machine have helped untangle a long-standing mystery of astrophysics: why iron is found spattered throughout Earth’s mantle, the roughly 2,000-mile thick region between Earth’s core and its crust.
At first blush, it seemed more reasonable that iron arriving from collisions between Earth and planetesimals — ranging from several meters to hundreds of kilometers in diameter — during Earth’s late formative stages should have powered bullet-like directly to Earth’s core, where so much iron already exists.
A second, correlative mystery is why the moon proportionately has much less iron in its mantle than does Earth. Since the moon would have undergone the same extraterrestrial bombardment as its larger neighbor, what could explain the relative absence of that element in the moon’s own mantle?
To answer these questions, scientists led by Professor Stein Jacobsen at Harvard University and Professor Sarah Stewart at the University of California at Davis (UC Davis) wondered whether the accepted theoretical value of the vaporization point of iron under high pressures was correct. If vaporization occurred at lower pressures than assumed, a solid piece of iron after impact might disperse into an iron vapor that would blanket the forming Earth instead of punching through it. A resultant iron-rich rain would create the pockets of the element currently found in the mantle.
As for the moon, the same dissolution of iron into vapor could occur, but the satellite’s weaker gravity would be unable to capture the bulk of the free-floating iron atoms, explaining the dearth of iron deposits on Earth’s nearest neighbor.
Looking for experimental rather than theoretical values, researchers turned to Sandia’s Z machine and its Fundamental Science Program, coordinated by Sandia manager Thomas Mattsson. This led to a collaboration among Sandia, Harvard University, UC Davis, and Lawrence Livermore National Laboratory (LLNL) to determine an experimental value for the vaporization threshold of iron that would replace the theoretical value used for decades.
Rick Kraus at LLNL (formerly at Harvard) and Sandia researchers Ray Lemke and Seth Root used Z to accelerate metals to extreme speeds using high magnetic fields. The researchers created a target that consisted of an iron plate 5 millimeters square and 200 microns thick, against which they launched aluminum flyer plates travelling up to 25 kilometers per second. At this impact pressure, the powerful shock waves created in the iron cause it to compress, heat up and — in the zero pressure resulting from waves reflecting from the iron’s far surface — vaporize.
The result, published March 2 in Nature Geosciences under the title “Impact vaporization of planetesimal cores in the late stages of planet formation,” shows the shock pressure experimentally required to vaporize iron is approximately 507 gigapascals (GPa), undercutting by more than 40 percent the previous theoretical estimate of 887 GPa. Astrophysicists say that this lower pressure is readily achieved during the end stages of planetary growth through accretion.
Principal investigator Kraus said, “Because planetary scientists always thought it was difficult to vaporize iron, they never thought of vaporization as an important process during the formation of Earth and its core. But with our experiments, we showed that it’s very easy to impact-vaporize iron.”
He continued, “This changes the way we think of planet formation, in that instead of core formation occurring by iron sinking down to the growing Earth’s core in large blobs (technically called diapirs), that iron was vaporized, spread out in a plume over the surface of Earth and rained out as small droplets. The small iron droplets mixed easily with the mantle, which changes our interpretation of the geochemical data we use to date the timing of Earth’s core formation.”
Reference:
Richard G. Kraus, Seth Root, Raymond W. Lemke, Sarah T. Stewart, Stein B. Jacobsen, Thomas R. Mattsson. Impact vaporization of planetesimal cores in the late stages of planet formation. Nature Geoscience, 2015; DOI: 10.1038/ngeo2369
The rich diversity seen in modern-day beetles could have more to do with extinction resistance than a high rate of new species originations. Credit: Dena Smith
Today’s rich variety of beetles may be due to an historically low extinction rate rather than a high rate of new species emerging, according to a new study. These findings were revealed by combing through the fossil record.
“Much of the work to understand why beetles are diverse has really focused on what promotes speciation,” says lead author Dena Smith, Curator of Invertebrate Paleontology and Associate Professor of Geological Sciences at the University of Colorado Museum of Natural History. “By looking at the fossil history of the group, we can see that extinction, or rather lack of extinction may be just as important, if not more important, than origination. Perhaps we should be focusing more on why beetles are so resistant to extinction.” Smith’s study with her coauthor, Jonathan Marcot, Research Assistant Professor of Animal Biology at the University of Illinois, will appear in the Proceedings of the Royal Society B.
To fully explore the evolution of the insect order, Coleoptera, Smith and Marcot used publications that document the fossil record of beetles from international literature as far back as the early 19th century and open access database projects including the EDNA Fossil Insect Database and the Catalogue of Fossil Coleoptera. The team constructed a database of 5,553 beetle species from 221 unique locations. Given the patchy nature of the data at the species level, they performed analyses at the family level and found that the majority of families that are living today also preserved in the fossil record.
The study explores beetles as far back as their origins in the Permian period, 284 million years ago. When compared to the fossil record of other animal groups such as clams, corals, and vertebrates, beetles have among the lowest family-level extinction rates ever calculated. In fact, no known families in the largest beetle subgroup, Polyphaga, go extinct in their evolutionary history. The negligible beetle extinction rate is likely caused by their flexible diets, particularly in the Polyphaga, which include algae, plants, and other animals.
“There are several things about beetles that make them extremely flexible and able to adapt to changing situations,” Smith says. She points to beetles’ ability to metamorphose–a trait shared by many insects–when considering their environmental flexibility. Soft-bodied larvae vary greatly from winged, exoskeleton-ensconced adults. “This means that they can take advantage of very different types of habitats as a larva and then as an adult,” she adds. “Adult beetles can be highly mobile and research that has focused on glacial-interglacial cycles has shown that they can move quickly in response to any climate fluctuations.”
The study explores beetles as far back as their origins in the Permian period, 284 million years ago. Both authors emphasize that illustrating such a history would not have been possible without the fossil record–an often underutilized resource in exploring the evolution of insects.
“I think people have been hesitant to jump into studying insect fossils because there has been the misperception that they are so fragile and rarely fossilize,” Smith says. “I am hoping that this study demonstrates that the fossil record is quite good and can be used in many ways to study the evolution of this diverse and important group.”
Marcot adds, “Not only have these groups gone un-studied, but there are certain things that we can learn from the fossil record that we just can’t learn any place else.”
Other insect groups might be similar to Coleoptera in terms of their extinction resistance, and Smith hopes that their work will inspire other entomologists to delve into the fossil record of their favorite insect. For now she is actively working to digitize more fossil specimens, paving the way for future studies to be conducted on a finer scale. The project, known as the Fossil Insect Collaborative and funded by the National Science Foundation, is expected to make available more than half a million fossil insect specimens from the major U.S. collections–many with associated images–in a searchable online database.
“Being a curator of a museum collection, I know that there are many species in our cabinets that have not yet been studied and described,” Smith says. “Once we are able to bring those specimens out of the cabinets and make them more accessible to the broader research community, I think we will be able to look at species level patterns and other really interested questions about the macroevolutionary history of insect groups.”
Reference:
D. M. Smith, J. D. Marcot. The fossil record and macroevolutionary history of the beetles. Proceedings of the Royal Society B: Biological Sciences, 2015; 282 (1805): 20150060 DOI: 10.1098/rspb.2015.0060
This is a digital elevation model of the Uncompahgre Plateau and greater study region with key features labeled. Credit: Figure 1 from Soreghan et al.; Soreghan et al. and Geosphere
Unaweep Canyon is a puzzling landscape — the only canyon on Earth with two mouths. First formally documented by western explorers mapping the Colorado Territory in the 1800s, Unaweep Canyon has inspired numerous hypotheses for its origin. This new paper for Geosphere by Gerilyn S. Soreghan and colleagues brings together old and new geologic data of this region to further the hypothesis that Unaweep Canyon was formed in multiple stages.
The inner gorge originated ~300 million years ago, was buried, was then revealed about five million years ago when the ancestral Gunnison River began incising the Uncompaghre Plateau as part of the incision of the larger Colorado Plateau, and then the Gunnison River then abandoned the canyon upon landslide damming, ultimately joining the Colorado River.
This work highlights that incision of the Colorado Plateau by the Colorado River and its tributaries (including the Gunnison River) began synchronously across the entire Plateau, linking the incision of the Grand Canyon on the southern Plateau to events on the northern Plateau. It also highlights the intriguing possibility of preservation of very ancient landscapes from Earth’s deep-time past, and the role of exhumation of those landscapes in shaping the modern face of the planet.
Reference:
G. S. Soreghan, D. E. Sweet, S. N. Thomson, S. A. Kaplan, K. R. Marra, G. Balco, T. M. Eccles. Geology of Unaweep Canyon and its role in the drainage evolution of the northern Colorado Plateau. Geosphere, 2015; DOI: 10.1130/GES01112.1
Reconstruction of ‘Indeterminate Plesiochelyidae’ on a coastal landscape of Upper Jurassic Iberia. Credit: Iván Gromicho
Little is known about the oldest sea turtles that inhabited Earth millions of years ago. The finding in the Baetic Cordillera, in Jaén, of the remains of a supposed new species of turtle, Hispaniachelys prebetica — considered the oldest in southern Europe — brought new clues six years ago. However, it was still not clear what group the primitive turtle belonged to.
To resolve the matter, Adán Pérez-García, a researcher in the Evolutionary Biology group of the UNED, studied the as-yet-unanalysed fossils of the specimen, reinterpreted some of its features and provided new information on the morphology of these reptiles. The results marked a radical shift in fossil interpretation.
As Pérez-García clarifies: “Hispaniachelys prebetica cannot be recognised as a valid species. Nevertheless, it is identified as a member of a group of turtles exclusive to the European Jurassic called Plesiochelyidae, which were very diverse.”
The study, published in ‘Acta Palaeontologica Polonica’, demonstrates that some of the characteristics of Hispaniachelys prebetica, such as the relatively large carapace, were no different from turtles of the Plesiochelyidae group. However, due to the scarce information about this, the only example, “the specimen is reinterpreted as an indeterminate member of this group of turtles,” the study expounds.
According to the researcher, “Hispaniachelys prebetica is no longer deemed a valid name but is now what is technically known as nomen dubium,” and he adds that a more precise classification ‘Indeterminate Plesiochelyidae’ is not possible. “This specimen is an indeterminate species of Plesiochelyidae, which could be one of the other previously defined species,” the scientist asserts.
Clumsy Jurassic turtles
Around 160 million years ago, in countries such as the United Kingdom, France, Switzerland, Germany, Portugal and Spain, a group of primitive turtles lived called Plesiochelyids, which “do not resemble any currently existing turtle,” the expert continues. In Spain there were several species, many of them recently identified, on which there is abundant material. Now, with the identification of the specimen in Jaén, the record expands to attribute it to this group.
These European reptiles inhabited warm, shallow seas of the continent, but “they were not as agile in this environment as today’s sea turtles, who are able to cover very large distances and cross seas and even oceans,” the expert explains. “Due to their anatomy, these Jurassic turtles were restricted to coastlines.”
Because of their dependency on coastal environments, the changes in the sea level which occurred at the end of the Jurassic period — around 145 million years ago — had a drastic impact upon the environments they lived in. As a result, “these turtles, in addition to other groups of sea reptiles, became extinct at that time,” Pérez-García confirms.
Through several projects he is carrying out at the Geology Centre at the University of Lisbon (Portugal) and the UNED, the researcher continues working on reviewing Plesiochelyidae on the Iberian Peninsula and other regions in Europe. “We are attempting to discover the real diversity in the fossil record of this, until now, little-known group,” he concludes.
Reference:
Adán Pérez-García. Reinterpretation of the Spanish Late Jurassic “Hispaniachelys prebetica” as an indeterminate plesiochelyid turtle (Testudines, Pancryptodira). Acta Palaeontologica Polonica, 2013; DOI: 10.4202/app.2012.0115
Using a technique that is similar to a medical CT (“CAT”) scan, researchers at Princeton are using seismic waves from earthquakes to create images of the Earth’s subterranean structures — such as tectonic plates, magma reservoirs and mineral deposits — which will help better understand how earthquakes and volcanoes occur. The team is using the Titan supercomputer at the U.S. Department of Energy’s Oak Ridge National Laboratory in Tennessee to map the entire mantle, creating a three-dimensional map of the Earth to a depth of 1,800 miles below the surface. Credit: Ebru Bozdağ, University of Nice Sophia Antipolis, and David Pugmire, Oak Ridge National Laboratory
When a 7.9-magnitude earthquake struck central China’s Sichuan province in 2008, seismic waves rippled through the region, toppling apartment houses in the city of Chengdu and swaying office buildings 1,000 miles away in Shanghai.
Though destructive, earthquakes provide benefit in one respect: they help researchers learn about the structure of the Earth, which in turn could lead to more accurate predictions of damage from future quakes and volcanic activity. By eavesdropping on the seismic vibrations of quakes as they rumble through the Earth, researchers can detect the existence of structures such as mineral deposits, subterranean lakes, and upwellings of magma. Thanks to a growing earthquake detection network and superfast computers, geoscientists are now able to explore the Earth’s interior, a region that has been more inaccessible than the deepest ocean or the farthest planet in our solar system.
Princeton geosciences professor Jeroen Tromp and his team have embarked on an ambitious project to use earthquakes to map the Earth’s entire mantle, the semisolid rock that stretches to a depth of 1,800 miles, about halfway down to the planet’s center and about 300 times deeper than humans have drilled. For the task, his team will use one of the world’s fastest supercomputers, Titan, which can perform more than 20 quadrillion calculations per second and is located at the Department of Energy’s Oak Ridge National Laboratory in Tennessee.
“Seismology is changing at a fundamental level due to advances in computing power,” said Tromp, who earned his Ph.D. in geology from Princeton and is Princeton’s Blair Professor of Geology, professor of applied and computational mathematics, and associate director of the Princeton Institute for Computational Science and Engineering. “If someone had told me what seismology would look like 20 years from when I graduated from Princeton in 1992, I would have never believed it.”
For the project, Tromp will use seismic waves from roughly 3,000 quakes of magnitude 5.5 and greater, recorded at thousands of seismographic stations worldwide and distributed via the National Science Foundation’s Incorporated Research Institutions for Seismology. These stations make recordings, or seismograms, that detail the movement produced by seismic waves, which typically travel at speeds of several miles per second and last several minutes.
“The ultimate goal is a 3-D map on a global scale,” said Tromp, who expects to have preliminary results at the end of this year. “We are specifically interested in the structure of mantle upwellings and plumes,” he said, “but much of it will be investigating the images for unusual features.”
These unusual features could include, for example, a fragment of a tectonic plate that broke off and sank into the mantle. The resulting map could tell seismologists more about the precise locations of underlying tectonic plates, which can trigger earthquakes when they shift or slide against each other. The maps could also reveal the locations of magma that, if it comes to the surface, causes volcanic activity.
As seismic waves travel, they slow or speed up depending on the density, temperature and type of rock. For example, they slow down when traveling through an underground aquifer or magma. By combining seismograms from many earthquakes recorded at many stations, geologists can produce a three-dimensional model of the structure under the Earth’s surface.
This technique is called seismic tomography and is analogous to computerized tomography used in medical (“CAT”) scans, in which a scanner captures a series of X-ray images from different viewpoints, creating cross-sectional images that can be combined into 3-D images.
Over the past eight years, Tromp has been at the forefront of research on how to improve seismic tomography to obtain high-definition, accurate images of the Earth’s interior. Past approaches for making these images incorporate only three types of seismic waves: primary or compressional waves, secondary or shear waves, and surface waves. Tromp has pioneered techniques for using much more of the information in seismograms, utilizing both waves that travel from the quake epicenter to the detector as well as those that travel from the detector to the quake, which are called adjoint waves.
“If we are going to do better, we need to use everything in the picture, in other words, everything and anything in the seismograms,” Tromp said.
Tromp’s team feeds data from seismograms into a computer model, which simulates each wave as it propagates from the epicenter. The resulting “synthetic seismograms” are compared to real seismograms, and the differences are fed back into the model to improve it. The researchers do this over and over, comparing data with simulations and extracting differences. With each pass, they improve their model.
Before attempting to map the entire Earth, Tromp and his team, with funding from the National Science Foundation, showed that their technique worked in smaller regions, first in Southern California using data from 143 quakes, which was published in the journal Science in 2009, and later in Europe using 190 quakes. The Europe study, published in the journals Nature Geosciences in 2012 and Science in 2013, included work by then graduate student Hejun Zhu, now a postdoctoral researcher at the University of Texas-Austin; postdoctoral researcher Ebru Bozdağ, now an assistant professor at the University of Nice Sophia Antipolis; postdoctoral researcher Daniel Peter, who today is a senior scientist at ETH Zurich; and David Pugmire, a visualization scientist at the Oak Ridge Leadership Computing Facility (OLCF).
More recently, Tromp and collaborators published a study on the structure of the Earth beneath East Asia using 227 quakes, including the 2008 quake in Sichuan. The study, accepted for publication in the Journal of Geophysical Research: Solid Earth and conducted with colleagues at Rice University, the University of Toronto, the China University of Petroleum and the China Earthquake Administration, plumbed East Asia to a depth of 560 miles.
These smaller projects enabled Tromp’s team to compete for and obtain 50 million processor hours on Titan this year as part of a prestigious 2015 Innovative and Novel Computational Impact of Theory and Experiment (INCITE) award from the U.S. Department of Energy.
One of the major challenges for Tromp’s team was to figure out how to compare real data to modeled results, which are given in the language of the computer code that created them. “You need to bring the data and the simulation into the same framework, to put them on equal footing,” Tromp said. “Then you can start to compare real data to the simulations and extract differences.”
Nor is Titan easy to program given its unique architecture—it is supercharged with graphics processors originally developed for gaming systems. “The challenge is to get the data onto the graphics cards and get the cards to do the right thing with the data,” Tromp said.
For postdoctoral researcher Matthieu Lefebvre, who earned a Ph.D. in mathematics prior to coming to Princeton, working on the project was an opportunity to work with one of the most powerful computers on the planet. “The project offers a lot of opportunities and challenges, such as how to optimize computational algorithms and workflows at large scales,” Lefebvre said.
For help, Tromp relies on the OLCF’s “science liaisons,” experts in mathematics and computer science such as Judith Hill who work with university scientists to prepare code for Titan.
“The team’s seismographic data originally were laid out in such a way that a significant fraction of the simulation time would be spent reading the data off the disks,” Hill said. “Professor Tromp worked with our data liaisons to develop a new data format for the seismic community that was optimal for large-scale computers such as Titan and the file systems that go along with them.”
The OLCF is also helping the Princeton team with the task of visualizing the results of the calculations. “Once you run the models, you have to mine the images to see what you have,” Tromp explained. “You need techniques like volume rendering and feature extraction to show you what you have discovered. For example, you might discover a new plume, an upwelling of magma that traverses the mantle, or you might discover hot spots.”
Added Tromp: “You don’t know what it is you are looking for, you are hunting. That is the real challenge, and that is the wonderful part of this project—waiting to see what we will discover.”
Reference:
“Mapping tectonic deformation in the crust and upper mantle beneath Europe and the North Atlantic Ocean.” Science 23 August 2013: Vol. 341 no. 6148 pp. 871-875. DOI: 10.1126/science.1241335
“Multi-parameter adjoint tomography of the crust and upper mantle beneath East Asia – Part I: Model construction and comparisons” Journal of Geophysical Research: Solid Earth. DOI: 10.1002/2014JB011638
This is a perspective view of the December 1974 lava flow in Hawaii. This image is not a photograph, but rather it was constructed by draping kite-based aerial photography over a digital terrain model. Credit: Christopher Hamilton
Scientists of the University of Arizona’s Lunar and Planetary Laboratory have taken to kites that they fly above lava flows blanketing the Hawaiian landscape to unravel the past mysteries that shaped Mars.
A kite, equipped with off-the-shelf instruments such as a camera, a GPS, and orientation sensors, scans the terrain from high above. The team then employs parallel computing and powerful software algorithms to assemble tens of thousands of images into extremely detailed and accurate 3D digital terrain models.
In terms of studying volcanic landscapes, the project is unprecedented in its scope and in the quality of the data it produces, with a spatial resolution of approximately half an inch per pixel, according to the researchers. They will present their results and methodology at the 46th Lunar and Planetary Science Conference, which is held March 16-20 in The Woodlands, Texas.
The insights gained from these terrain models are used to inform interpretations of images of the surface of Mars, taken with the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter, which has been examining Mars with six instruments since 2006. Led by the UA, HiRISE stands for the High Resolution Imaging Science Experiment and has revealed never-before seen details of the Martian surface.
“The idea is to understand places we can’t go by analyzing places we can go,” said Christopher Hamilton, the principal investigator of the research team, who joined LPL in 2014 to establish a terrestrial analog research group. Hamilton studies volcanic surfaces on Mars to understand the thermal history of the red planet, in other words, how the planet’s internal processes manifest on the surface.
“We can use geologically young and vegetation-free surface features here on Earth — such as Hawaiian lava flows — as terrestrial analogs that can provide us with insights into processes that shape other planets,” he added. “Instead of just saying, ‘this feature looks like X,’ we try to develop diagnostics that help us recognize the actual processes that led to the formation of a certain feature.”
Hamilton’s team chose Kilauea Volcano on the Island of Hawaii as their study area, a “chemical desert” with several geologically very young lava flows, in particular the December 1974 flow, which poured out of the volcano on New Year’s Eve 1974 in a short-lived eruption, which is currently accessible by foot.
When the researchers compared to images of the Martian surface taken by HiRISE, striking similarities appear.
“We think this is how the big lava flows formed on Mars, which strongly suggests they may not be what they seem,” Hamilton said. For example, many features that have been interpreted as channels carved by running water in the red planet’s past are more likely to be the result of volcanic process that Hamilton describes as a “fill-and-spill” lava emplacement, which developed when lava accumulated in enormous “perched ponds” that breached like an overtopped dam, giving way to catastrophic floods of lava.
“It is easy to draw conclusions based on our intuition of how water flows,” Hamilton said, “so it is tempting to interpret similar features on Mars in the same way. But in fact these features formed by flowing lava, not water.”
Pointing to the terrain model of the December 1974 flow, Hamilton said, “We see that in certain areas, the surface is broken up into plates and what superficially looks like channels carved by running water. However, these turn out to be not carved at all, but rather are the result of a complex pattern of lava movements within the flow.”
Hamilton explained that first, liquid lava filled the area between the cliffs from older lava lows like a big bathtub, and when the perched lava pond breached, the lava surged forward causing plates of cooled lava on the surface to break apart and fresh lava to well up from underneath. As the plates were floating toward the drain, they became crumpled.
The digital terrain models even revealed a “bathtub ring” formed when lava filled the pool.
“The question that drives us is, ‘how can we assemble this kind of data for Mars landscapes and decide whether a feature is volcanic or fluvial — shaped by water — and allow us to develop a story?'” Hamilton said, “A single surface texture doesn’t tell you anything if you can’t see the way in which the building blocks combine, such as the tiles that make up the pattern of a mosaic. The relationships between textures allow you where to look and what to look for.”
Stephen Scheidt, a postdoctoral fellow at LPL who studies dune-building processes, designed and built the terrain-mapping kite system that was used for the project in Hawaii. To acquire the images, he launched a robotic camera attached to a delta-wing kite with an 11-foot-wingspan into the wind and steered it by skillfully tugging on its tethering line. This involved spending days crisscrossing jagged lava formations on foot, trying not to be dragged around by the kite, all the while watching carefully to avoid toxic fumes wafting down from the volcanic vent.
“The kite is pretty stable in the air, and depending on the wind swings from side to side only by five to ten degrees or so,” Scheidt explained. “That small motion gives us enough parallax, or difference in viewing angle, to allow the software to calculate a three-dimensional terrain model.”
Although the technique, called Multi-View Stereo-Photogrammetry, produces images that appear like aerial photographs taken from an airplane, they are not actually photographs, they are image mosaics projected onto digital terrain models, Hamilton explained.
“The kite takes an image every two seconds, producing up to tens of thousands of photos of a site,” Scheidt said. “The software then removes any distortion, and stitches those images together to create a virtual representation of the terrain that you would never have otherwise.”
This process, called orthorectification, uses massive computing power and still takes weeks to render a terrain model. The end result boasts a resolution high enough to clearly show footprints in the sand blanketing the lava flow.
“Our approach shows how the combination of ground-based observations and an aerial perspective can help us to decipher the geologic history of Earth and Mars,” Hamilton said.
Note: The above story is based on materials provided by University of Arizona. The original article was written by Daniel Stolte.
270 million-year-old fossils from Texas show that early conifers produced a variety of winged seeds to aid dispersal by the wind. Cindy Looy and her team made identical models to test their effectiveness at seed dispersal and find out why only one variety of whirling seed – ones with single wings (left) – exists in today’s conifers. Credit: Cindy Looy
The whirling, winged seeds of today’s conifers are an engineering wonder and, as University of California, Berkeley, scientists show, a result of about 270 million years of evolution by trees experimenting with the best way to disperse their seeds.
The first conifer species that produced seeds that whirl when they fall used a variety of single- and double-winged designs. Whirling, or helicoptering, keeps a seed aloft longer, increasing the chance that a gust of wind will carry a seed to a clearing where it can sprout and grow unimpeded by competitors
“Winged seeds may have contributed to the success of these conifers,” said paleobotanist Cindy Looy, an assistant professor of integrative biology at UC Berkeley, a member of the Berkeley Initiative for Global Change Biology (BiGCB) and a curator with UC Berkeley’s Museum of Paleontology.
Today, however, all conifer species whose seeds whirl as they fall appear to have settled on only one type of design: asymmetrical and single-winged. Several different conifer lineages independently came upon this single-winged design after experimenting with helicoptering winged seeds over millions of years of evolution.
To convince herself that later conifers settled on the most efficient design for windborne seed dispersal, Looy and her colleagues built model seeds inspired by the variety of seed designs found in a unique collection of 270 million-year-old fossil seeds from Texas.
By dropping these model seeds and filming their descent with high-speed cameras, they demonstrated that whirling, single-winged seeds were the most effective at aerial dispersal. Symmetric, double-winged seeds often failed to initiate the descent-slowing spin, but even if they did, they remained airborne only half as long as the single-winged ones.
Moreover, the difference in flight performance of single-winged whirling seeds and asymmetrical or symmetrical double-winged ones increased with increased seed weight or in turbulent air.
Looy, former research assistant Robert Stevenson and former graduate student Dennis Evangelista, now at the University of North Carolina at Chapel Hill, will publish their experimental findings in a featured article in the March 2015 issue of the journal Paleobiology.
Looy has been studying fossils of early conifer groups from deposits in Texas dating to the Permian Period, about 270 million years ago. She was struck by the fact that one of the conifer species produced a range of seed shapes, ranging from single-winged to asymmetrical and symmetrical double-winged seeds
This is unusual, she said, because the single-winged seeds have the clear advantage of enhanced dispersal efficiency, especially during the Permian when seed dispersal by animals was virtually absent. Even more unusual was the fact that different conifer species that independently evolved whirling, or autorotating, seeds ended up with only one optimal seed shape up in today’s conifer species. The same is true for other trees that developed similar seeds or fruits, such as the maple and ash.
The Permian conifer, which she and Stevenson formally described last year and named Manifera talaris, produced the oldest known autorotating conifer seeds roughly 40 million years before dinosaurs evolved.
“Rotating seeds in living conifers are generally asymmetrical and single-winged, so I wondered if the function of the double-winged seeds was very different,” she said. “Until you actually see them in action and compare them, you don’t have any proof.”
Paper wings and plastic seeds
Looy knew that people had tested the aerodynamics of single-winged, autorotating seeds, but no one had ever studied the other designs because they aren’t found today. Using special tissue paper for wings and plastic film for the heavy seed, she and her colleagues built models of the single-winged seeds of a living conifer that resembled those of the fossil conifer. The actual seeds of this tree, the New Zealand kauri (Agathis australis), were used to confirm that the fabricated models behaved like the real thing.
They then altered the design of the models to match the symmetric and asymmetric double-winged as well as the single-winged seeds common among the Texas fossils. The researchers dropped the seeds from a height of 3 meters (9 feet) and filmed their fall with a high-speed camera. This enabled them to observe the flight performance and measure a range of flight characteristics and aerodynamic properties of the various shapes. They enlisted half a dozen UC Berkeley undergraduates to help determine which type of winged seed works best for wind dispersal and to digitize the flight behavior of the seeds captured on camera.
They found that, in contrast to the single-winged seeds, the symmetric and asymmetric double-winged seeds did not spin as effectively; instead of a slow helicopter descent, they usually fluttered or just plummeted to the ground. But even when seeds with double-winged shapes managed to autorotate, the experiments demonstrated conclusively that single-winged seeds stayed airborne almost twice as long.
Early seed dispersal
Air- and waterborne seeds became more common between the late Carboniferous — 320 million years ago — and early Permian, which began about 300 million years ago. At the time, most plant life consisted of lycopods, ferns, horsetails and seed ferns, with a few of the first cone-bearing trees, like conifers and cycads, appearing.
“There were very different plants around at the time,” Looy said. “Several of these groups produced seeds, but they lacked most of the tricks we see today to spread them.”
Vertebrates, only a few of which were herbivores, were typically large and did not climb trees. The only flying animals were insects, and as far as we know they did not disperse seeds, Looy said.
“For a seed at that time, having wings was actually one of the few ways to spread widely,” she said.
The conifer fossils, which are from north-central Texas, date from a time when Texas was located near the equator, and North America was part of the massive continent of Pangea. Looy studied these fossils when she worked as a postdoctoral researcher at the Smithsonian Institution from 2004 to 2008, and was struck by the seed variety within a single species compared to today.
“In these conifers you can see steps from making winged seeds to making autorotating seeds. It seems that the Permian conifer Manifera first figured out how to produce a range of winged seed shapes -including the highly functional autorotating ones,” she said. “However, fossils of closely related end-Permian conifers suggest that it wasn’t until much later that they discovered how to not produce the less functional types. Around that time, we also see the first slightly succulent conifer seeds appearing in the fossil record, which are attractive to animals and potentially indicative of animal dispersal. Slowly the seeds start to diversify to all the different types we have nowadays.”
A 17-million-year-old whale fossil stranded far inland in Kenya now sheds light on the timing and starting elevation of East Africa’s puzzling tectonic uplift, says paleontologist Louis Jacobs, Southern Methodist University, Dallas, who rediscovered the fossil. Credit: Southern Methodist University
Uplift associated with the Great Rift Valley of East Africa and the environmental changes it produced have puzzled scientists for decades because the timing and starting elevation have been poorly constrained.
Now paleontologists have tapped a fossil from the most precisely dated beaked whale in the world — and the only stranded whale ever found so far inland on the African continent — to pinpoint for the first time a date when East Africa’s mysterious elevation began.
The 17 million-year-old fossil is from the beaked Ziphiidae whale family. It was discovered 740 kilometers inland at an elevation of 620 meters in modern Kenya’s harsh desert region, said vertebrate paleontologist Louis L. Jacobs, Southern Methodist University, Dallas.
At the time the whale was alive, it would have been swimming far inland up a river with a low gradient ranging from 24 to 37 meters over more than 600 to 900 kilometers, said Jacobs, a co-author of the study.
The study, published in the Proceedings of the National Academy of Sciences, provides the first constraint on the start of uplift of East African terrain from near sea level.
“The whale was stranded up river at a time when east Africa was at sea level and was covered with forest and jungle,” Jacobs said. “As that part of the continent rose up, that caused the climate to become drier and drier. So over millions of years, forest gave way to grasslands. Primates evolved to adapt to grasslands and dry country. And that’s when — in human evolution — the primates started to walk upright.”
Identified as a Turkana ziphiid, the whale would have lived in the open ocean, like its modern beaked cousins. Ziphiids, still one of the ocean’s top predators, are the deepest diving air-breathing mammals alive, plunging to nearly 10,000 feet to feed, primarily on squid.
In contrast to most whale fossils, which have been discovered in marine rocks, Kenya’s beached whale was found in river deposits, known as fluvial sediments, said Jacobs, a professor in the Roy M. Huffington Department of Earth Sciences of SMU’s Dedman College of Humanities and Sciences. The ancient large Anza River flowed in a southeastward direction to the Indian Ocean. The whale, probably disoriented, swam into the river and could not change its course, continuing well inland.
“You don’t usually find whales so far inland,” Jacobs said. “Many of the known beaked whale fossils are dredged by fishermen from the bottom of the sea.”
Determining ancient land elevation is very difficult, but the whale provides one near sea level.
“It’s rare to get a paleo-elevation,” Jacobs said, noting only one other in East Africa, determined from a lava flow.
Beaked whale fossil surfaced after going missing for more than 30 years
The beaked whale fossil was discovered in 1964 by J.G. Mead in what is now the Turkana region of northwest Kenya.
Mead, an undergraduate student at Yale University at the time, made a career at the Smithsonian Institution, from which he recently retired. Over the years, the Kenya whale fossil went missing in storage. Jacobs, who was at one time head of the Division of Paleontology for the National Museums of Kenya, spent 30 years trying to locate the fossil. His effort paid off in 2011, when he rediscovered it at Harvard University and returned it to the National Museums of Kenya.
The fossil is only a small portion of the whale, which Mead originally estimated was 7 meters long during its life. Mead unearthed the beak portion of the skull, 2.6 feet long and 1.8 feet wide, specifically the maxillae and premaxillae, the bones that form the upper jaw and palate.
The researchers reported their findings in “A 17 million-year-old whale constrains onset of uplift and climate change in East Africa” online at the PNAS web site.
Modern cases of stranded whales have been recorded in the Thames River in London, swimming up a gradient of 2 meters over 70 kilometers; the Columbia River in Washington state, a gradient of 6 meters over 161 kilometers; the Sacramento River in California, a gradient of 4 meters over 133 kilometers; and the Amazon River in Brazil, a gradient of 1 meter over 1,000 kilometers.
Reference:
Henry Wichura, Louis L. Jacobs, Andrew Lin, Michael J. Polcyn, Fredrick K. Manthi, Dale A. Winkler, Manfred R. Strecker, Matthew Clemens. A 17-My-old whale constrains onset of uplift and climate change in east Africa. Proceedings of the National Academy of Sciences, 2015; 201421502 DOI: 10.1073/pnas.1421502112
The UMass Amherst lab is one of only a handful worldwide to use a state-of-the-art modeling technique based on kaolin clay rather than sand to understand the behavior of the Earth’s crust. Credit: UMass Amherst
New modeling and analyses of fault geometry in the Earth’s crust by geoscientist Michele Cooke and colleagues at the University of Massachusetts Amherst are advancing knowledge about fault development in regions where one geologic plate slides past or over another, such as along California’s San Andreas Fault and the Denali Fault in central Alaska.
Findings may help more accurately predict earthquake hazards and allow scientists to better understand how Earth evolved.
Geologists have long been uncertain about the factors that govern how new faults grow, says Cooke, who was recently elected to the board of directors for the Southern California Earthquake Center. This month in an early online issue of the Journal of Geophysical Research, she and colleagues explain fault evolution near fault bends in greater detail than ever before with experiments using kaolin, or china clay, prepared so its strength scales to that of the Earth’s crust when confined in a clay box.
Fault efficiency refers to a dynamic fault system’s effectiveness at transforming input energy from the motions of tectonic plates into movement. For example, a straight fault is more efficient at accommodating strain than a curving fault. An important question is how the efficiency of fault bends evolves with increasing deformation of Earth’s crust.
Master’s student Alex Hatem, who did much of the work in these experiments, with Cooke and postdoctoral scholar Elizabeth Madden, report that fault efficiency increases as new faults grow and link, then reaches a steady state. This implies that bends along crustal faults may persist. The straight fault is the most efficient geometry, Cooke points out. “It’s interesting that bends increase in efficiency through new fault growth but they never become as efficient as straight faults.”
Because earthquakes may stop at restraining bends, it further suggests a new understanding: faults segmented by restraining bends may remain in a sort of stasis rather than developing into systems where earthquakes would rupture the entire length of the fault. Here Cooke explains that comparing a straight fault with a fault at a bend, it is more likely that the fault with the bend will have smaller earthquakes that stop at the bend rather than long earthquake ruptures that pass all the way along the fault.
Her UMass Amherst lab is one of only a handful worldwide to use a state-of-the-art modeling technique based on kaolin clay rather than sand to understand the behavior of the Earth’s crust. Their advanced techniques with the clay include pixel tracking and other quantitative measurements that allow rich details to be obtained from the models and compared with faults around the world.
When scaled properly, data from clay experiments conducted over several hours in a table-top device are useful in modeling restraining bend evolution over thousands of years and at the scale of tens of kilometers. Digital image correlation allows Cooke’s team to measure the details of deformation throughout the experiments.
For this work, they conducted kaolin experiments to model strike-slip rates measured in a restraining bend along a Dead Sea fault in Israel, a fault growth along the Denali Fault in Alaska, and through the San Gorgonio Knot along the San Andreas Fault in southern California.
“We apply the results to the southern San Andreas Fault where a restraining bend has persisted for 25 million years, but during that time its active fault configuration has changed in ways that resemble what we observed in our experiments,” the authors note.
They add, “Results of the clay box experiments provide critical insights into the evolution of restraining bends. Because the experiments scale to crustal lengths and strengths, we can extrapolate from the experiments to kilometer-scale systems. The models show progressive deformation by the successive outboard growth of dipping faults in some cases and persistence of vertical fault in others.”
Understanding the conditions that foster these distinct patterns helps us interpret the geometry and loading of faults within Earth’s crust in order to better constrain earthquake behavior.
Cooke says, “Using new digital image correlation techniques allows us very detailed measurements of the displacement in the experiments to provide insights we didn’t have before. For the fault bends that we tested, the new analysis reveals that efficiency of the faults increases as new faults grow and link and then reaches a steady state. This suggests that restraining bends along crustal faults may persist,” Cooke says.
Video
Reference:
Alex E. Hatem, Michele L. Cooke, Elizabeth H. Madden. Evolving efficiency of restraining bends within wet kaolin analog experiments. Journal of Geophysical Research: Solid Earth, 2015; DOI: 10.1002/2014JB011735
A sediment core from the South Pacific gyre is analyzed for its dissolved oxygen content. Credit: Photo courtesy of Fumio Inagaki
An international team of scientists led by a University of Rhode Island oceanographer has found oxygen and oxygen-breathing microbes all the way through the sediment from the seafloor to the igneous basement at seven sites in the South Pacific gyre, considered the “deadest” location in the ocean. Their findings contrast with previous discoveries that oxygen was absent from all but the top few millimeters to decimeters of sediment in biologically productive regions of the ocean.
Their research was published this week in the journal Nature Geoscience.
“Our objective was to understand the microbial community and microbial habitability of sediment in the deadest part of the ocean,” said Professor Steven D’Hondt at the URI Graduate School of Oceanography. “Our results overturn a 60-year-old conclusion that the depth limit to life is in the sediment just meters below the seafloor in such regions. We found that there is no limit to life within this sediment. Oxygen and aerobic microbes hang in there all the way to the igneous basement, to at least 75 meters below the seafloor.”
Based on the researchers’ predictive model and core samples they collected in 2010 from the Integrated Ocean Drilling Program’s research ship JOIDES Resolution, the researchers believe that oxygen and aerobic microbes occur throughout the sediment in up to 37 percent of the world’s oceans and 44 percent of the Pacific. They found that the best predictors of oxygen penetration to the igneous basement are a low sedimentation accumulation rate and a relatively thin sediment layer. Sediment accumulates at just a few decimeters to meters per million years in the regions where the core samples were collected.
In the remaining 63 percent of the ocean, most of the sediment beneath the seafloor is expected to lack dissolved oxygen and to contain anaerobic communities.
While the research team found evidence of life throughout the sediment, it did not detect a great deal of it. The team found extremely slow rates of respiration and approximately 1,000 cells per cubic centimeter of subseafloor sediment in the South Pacific gyre — rates and quantities that were nearly undetectable by previous techniques. “It’s really hard to detect life when it’s not very active and in extremely low concentrations,” said D’Hondt.
According to D’Hondt and co-author Fumio Inagaki of the Japan Agency for Marine-Earth Science and Technology, the discovery of oxygen throughout the sediment may have significant implications for Earth’s chemical evolution. The oxidized sediment is likely carried into the mantle at subduction zones, regions of the seafloor where tectonic plates collide and force one plate beneath the other.
“Subduction of these big regions where oxygen penetrates through the sediment and into the igneous basement introduces oxidized minerals to the mantle, which may affect the chemistry of the upper mantle and the long-term evolution of Earth’s surface oxidation,” D’Hondt said.
The principal research funders were the U.S. National Science Foundation (NSF) and Japan’s Ministry of Education, Culture, Sports, Science and Technology. The project is part of the NSF-funded Center for Dark Energy Biosphere Investigations, which explores life beneath the seafloor. The research is also part of the Deep Carbon Observatory, a decade-long international science initiative to investigate the 90 percent of Earth’s carbon located deep inside the planet.
“We take a holistic approach to the subseafloor biosphere,” said Rick Murray, co-author of the study. Murray is on leave from Boston University, currently serving as director of the NSF Division of Ocean Sciences. “Our team includes microbiologists, geochemists, sedimentologists, physical properties specialists, and others — a hallmark of interdisciplinary research.”
The research team includes 35 scientists from 12 countries. In addition to D’Hondt, URI scientists contributing to the research are oceanography professors Arthur Spivack and David C. Smith, Marine Research Scientist Robert Pockalny and graduate student Justine Sauvage.
Reference:
Steven D’Hondt et al. Presence of Oxygen an Aerobic Communities from Seafloor to Basement in Deep-Sea Sediments. Nature Geoscience, 2015 DOI: 10.1038/NGEO2387
Monserrat Volcano as seen from the JR research ship. Credit: Adam Stilton, Volcanologist
Tsunamis triggered by the partial collapse of the Caribbean Monserrat volcano, 13,000 years ago, would have been much smaller than previously thought, according to research soon to be published in Geochemistry, Geophysics and Geosystems.
The collapse of a volcano can lead to explosive eruptions or tsunamis, the size of which depends on the dynamics of the failure. For example, the abrupt collapse of a large volume of material into the sea will cause larger tsunamis than a gradual or submarine landslide, although this relationship has been the subject of vigorous debate. It is also important to determine where the slide material comes from. Material that falls a long way from the subaerial part of the volcano will create a bigger tsunami than failure of sediment layers around the submerged base of the volcano.
It was previously thought that a large submarine deposit of sediment at the base of the Monserrat volcano was the result of the abrupt, large scale collapse of the volcanic island into the sea. Therefore it had been thought that a high magnitude tsunami must have followed.
However, by analysing sediment cores drilled during the $8M ‘International Ocean Discovery Programme’ (IODP) expedition to Monserrat in 2012, this research shows that this deposit was in fact largely seafloor sediment. This finding infers that an initial landslide from the volcano triggered much more extensive failure of submarine sediment layers, around the base of the volcano. This would have generated a much smaller tsunami than if all of the material had fallen from the main volcanic edifice.
An international team of geologists including Dr Peter Talling, who leads a NOC group dedicated to studying submarine mass movements and their associated hazard, helped to collect and describe these cores. This involved noting the coarseness and nature of the material in each layer of sediment within the cores and describing the nature of the contact between each layer. In addition, the various physical properties of the sediment were measured, the sediment chemistry was analysed, and specific layers were dated using fossils. From this information the team was able to deduce that the deposits mostly comprised seafloor sediments, and not coarse volcanic debris from the subaerial volcano.
This IODP mission was the first time that sediment from the large-scale collapse of a volcanic island has been successfully drilled for scientific purposes.
Reference:
A. Le Friant, O. Ishizuka, G. Boudon, M. R. Palmer, P. J. Talling, B. Villemant, T. Adachi, M. Aljahdali, C. Breitkreuz, M. Brunet, B. Caron, M. Coussens, C. Deplus, D. Endo, N. Feuillet, A. J. Fraas, A. Fujinawa, M. B. Hart, R. G. Hatfield, M. Hornbach, M. Jutzeler, K. S. Kataoka, J.-C. Komorowski, E. Lebas, S. Lafuerza, F. Maeno, M. Manga, M. Martínez-Colón, M. McCanta, S. Morgan, T. Saito, A. Slagle, S. Sparks, A. Stinton, N. Stroncik, K. S. V. Subramanyam, Y. Tamura, J. Trofimovs, B. Voight, D. Wall-Palmer, F. Wang, S. F. L. Watt. Submarine record of volcanic island construction and collapse in the Lesser Antilles arc: First scientific drilling of submarine volcanic island landslides by IODPExpedition 340. Geochemistry, Geophysics, Geosystems, 2015; DOI: 10.1002/2014GC005652
Pictured is the site of Batadomba-lena where the oldest human teeth (c. 20,000 years old) used in the study were excavated. Credit: Patrick Roberts
An international research team has shed new light on the diet of some of the earliest recorded humans in Sri Lanka. The researchers from Oxford University, working with a team from Sri Lanka and the University of Bradford, analysed the carbon and oxygen isotopes in the teeth of 26 individuals, with the oldest dating back 20,000 years. They found that nearly all the teeth analysed suggested a diet largely sourced from the rainforest.
This study, published in the early online edition of the journal, Science, shows that early modern humans adapted to living in the rainforest for long periods of time. Previously it was thought that humans did not occupy tropical forests for any length of time until 12,000 years after that date, and that the tropical forests were largely ‘pristine’, human-free environments until the Early Holocene, 8,000 years ago. Scholars reasoned that compared with more open landscapes, humans might have found rainforests too difficult to navigate, with less available food to hunt or catch.
The Science paper also notes, however, that previous archaeological research provides ‘tantalising hints’ of humans possibly occupying rainforest environments around 45,000 years ago. This earlier research is unclear as to whether those early human dwellers of the rainforest were engaging in a specialised activity or whether they entered the rainforest for only limited periods of time in certain seasons rather than remaining there all year round.
Co-author Professor Julia Lee-Thorp from Oxford University said: ‘The isotopic methodology applied in our study has already been successfully used to study how primates, including African great apes, adapt to their forest environment. However, this is the first time scientists have investigated ancient human fossils in a tropical forest context to see how our earliest ancestors survived in such a habitat.’
The researchers studied the fossilised teeth of 26 humans of a range of dates — from 20,000 to 3,000 years ago. All of the teeth were excavated from three archaeological sites in Sri Lanka, which are today surrounded by either dense rainforest or more open terrain. The analysis of the teeth showed that all of the humans had a diet sourced from slightly open ‘intermediate rainforest’ environments. Only two of them showed a recognisable signature of a diet found in open grassland. However, these two teeth were dated to around 3,000 years, the start of the Iron Age, when agriculture developed in the region. The new evidence published in this paper argues this shows just how adaptable our earliest ancestors were.
Lead author, Patrick Roberts, a doctoral student specialising in the investigation of early human adaptations from Oxford’s Research Laboratory for Archaeology and the History of Art, said: ‘This is the first study to directly test how much early human forest foragers depended on the rainforest for their diet. The results are significant in showing that early humans in Sri Lanka were able to live almost entirely on food found in the rainforest without the need to move into other environments. Our earliest human ancestors were clearly able to successfully adapt to different extreme environments.’
Co-author Professor Mike Petraglia from Oxford University said: ‘Our research provides a clear timeline showing the deep level of interaction that early humans had with the rainforest in South Asia. We need further research to see if this pattern was also followed in other similar environments in Southeast Asia, Melanesia, Australasia and Africa.’
Reference:
Patrick Roberts, Nimal Perera, Oshan Wedage, Siran Deraniyagala, Jude Perera, Saman Eregama, Andrew Gledhill, Michael D. Petraglia, Julia A. Lee-Thorp. Direct evidence for human reliance on rainforest resources in late Pleistocene Sri Lanka. Science, 2015 DOI: 10.1126/science.aaa1230
An asteroid smashing into a planet can dramatically alter the planet’s habitability by setting back evolution or even encouraging biodiversity.
In order to understand how cosmic impacts influence life and the environment, scientists study the craters left behind. Some of these impact craters come in pairs, most likely caused by binary asteroids. A binary asteroid is two asteroids that are orbiting each other, as well as orbiting the Sun.
The Clearwater lakes in Canada are a double crater, but geologist Martin Schmieder of the University of Western Australia, and colleagues, now believe that the craters were formed in two separate events. Their research was recently published in the journal Geochimica et Cosmochimica Acta.
A number of double impact craters exist on Earth. In 1965, researchers proposed that the craters forming the Clearwater lakes were the result of such a single incident. West Clearwater Lake has a diameter of 36 kilometers (22.5 miles), while its eastern cousin is 10 kilometers smaller. During an impact, rocks from the Earth’s crust can be uplifted to form a central peak, or ring, within the center of the crater.
In the West Lake, this is evident as a ring of islands in the middle of the lake. The East Lake also has a central peak, but it is below the waters of the lake and was only revealed when the Geological Survey of Canada drilled into the frozen lake in the 1960s.
Measuring the ages of craters
There are a number of different ways to measure the age of an impact crater. Sometimes the layers of rock tell the story as the impact might have occurred at the boundary between two geological time periods. Fossils preserved within rocks can also help place constraints on the age.
It is also possible to use the decay of radioactive isotopes in samples of rocks that were created at the time of the impact to find out the age of a crater. Isotopes can be stable or radioactive, and if they are radioactive, then they will decay into “daughter” products over a known period of time.
There is evidence that the asteroid that formed the East crated impacted a marine environment, which would place the impact during the Ordovician period. The West crater was created in the Permian period and impacted the landmass Pangaea. Credit: Reprinted from Geochimica et Cosmochimica Acta, in press, Schmieder, M. et al., New 40Ar/39Ar dating of the Clearwater Lake impact structures (Québec, Canada) – Not the binary asteroid impact it seems?, Credit: Elsevier
Potassium-40 decays slowly into argon-40, so that the more argon-40 present, the older the sample is. However, measuring the ratio of potassium-40 to argon-40 has the disadvantage of the potassium and argon needing to be measured separately. A more reliable variant of this method is to convert the potassium into argon-39. The rock sample is heated to release both the argon-39 and argon-40, so that the two isotopes can be measured at the same time. The amount of argon-39 that it is released indicates how much potassium-40 was originally in the rock. For the Clearwater dating study, this method was applied at the University of Heidelberg in Germany.
The heating of the sample occurs incrementally, in what is known as “step heating.” Ideally each argon degassing step should yield the same age, so that when all the individual ages are plotted together on a graph, the age is constant for the entire sample and yields a plateau. This is known as a “plateau age.” However, in some cases a plateau age is not found. Instead, the individual steps often make up a “u-shaped” or “staircase” pattern.
Two separate impacts
The West Clearwater Lake has accurate plateau ages from the argon dating. Different rock samples all indicate that the crater was formed around 290 million years ago. The new argon ages of 286 million years determined by Schmieder, and his collaborators also agree with this.
The age of the East Clearwater Lake crater is much more difficult to determine. In previous work performed by other scientists, a different isotope method was used to measure the age of the crater. The rubidium (Rb) to strontium (Sr) ratio suggested that this crater is also around 290 million years old, roughly the same age as the West crater. However, this method of dating is rather unreliable when it comes to dating impact craters.
“Even as a well-established method, Rb/Sr dating has commonly failed in impact crater dating” explains Schmieder. “This is mostly because rubidium is very mobile and the Rb/Sr system is therefore easily disturbed by heating and weathering that affect the impact rocks after their formation.”
As a rock sample ages, the radiometric isotope decays into more and more daughter products. Measuring the ratio of the original isotope to the daughter products can yield the age of the sample. Credit: John Schmidt
Argon ages for the East Lake also show a u-shaped spectrum, rather than a clear plateau age. This makes it more difficult to determine an accurate argon age, but suggests a maximum age of around 460 million years, which would be far older than the dating of the West Clearwater Lake crater. In 1990, researchers initially calculated a 460 million age for the East Lake, but then assumed it to be incorrect out of suspicion that excess argon was contaminating the sample and mimicking an older age for the crater.
However, Schmieder and colleagues also determined an argon age of 460 to 470 million years for the East crater. They consider it highly unlikely that four different rock samples that were collected at different locations and depths at the impact melt layer inside the crater would all yield the same false age.
“We think that the accurate age for the East Clearwater crater was, in fact, already measured back in 1990,” says Schmieder.
Further evidence
Another point in favor of the older age of the East crater comes from studying the magnetization of rocks. The magnetic field of the Earth can be “captured” by certain types of rocks, and this magnetic signature can be used to study the Earth’s magnetic field throughout history. The magnetic poles of the Earth are not fixed, and pole reversals have occurred many times in the past.
The rocks from the West Lake show that they were formed during a “superchron,” which is an unusually extended period of time where no reversals occurred. This superchron, known as the Permo-Carboniferous Reversed Superchron, lasted from 316 to 265 million years ago, which agrees with the age found by the argon dating.
The rocks from the East Lake tell a different story. They have a number of different magnetic polarizations, which indicate viscous remnant magnetization. This is magnetization that is acquired slowly over a long period of time. The more complex magnetic history points to the rocks being much older than the West Lake, as they have had more time to be altered.
The argon-argon age of 460 to 470 million years for the East crater suggests that this impact occurred in the Ordovician time period in a near-coastal environment, when large parts of eastern Canada were occupied by a shallow ocean. There are geological clues that point towards an impact in a shallow marine or coastal environment at the East crater. The rocks from the East crater have more chlorine in them than the West crater, which might be indicative of the presence of sea water. There is also some evidence of the increased movement of hot fluids after the East impact, which altered the rocks. The West crater was formed during the Permian, when the asteroid would have struck the Pangaea landmass.
Despite the fact that it is statistically very unlikely for the two craters to have been formed in two separate impact events, the new evidence unearthed by Schmieder and his team shows that in this case the more unlikely scenario is true.
“Overall, the doublet theory has been so compellingly advocated over the decades that alternative scenarios seem to have been abandoned. In our view, there is a whole line of geologic evidence that argues against the double impact.”
The impact on life
Impacts that leave behind a 100 kilometer (62.5 mile) diameter crater or less, such as those that struck the Clearwater lakes, are widely thought to have no global effects. In fact, impacts can even increase biodiversity. For example, the Great Ordovician Biodiversification Event, which saw an explosion in the number of animal species around 470 million years ago, has been linked to frequent impact events at the time. This is possibly due to the fact that an impact could disrupt local life just enough to let another species dominate, or because slowly cooling craters can provide habitats for life.
Even if the Clearwater Lakes impacts were caused by a double impact, the extra energy released by two bodies smashing into the Earth simultaneously would have had no significant effect on life. While the fireball and earthquake would have decimated any life within a few hundred kilometers, the impacts were not big enough to cause much chaos on a global scale.
Reference:
Martin Schmieder, Winfried H. Schwarz, Mario Trieloff, Eric Tohver, Elmar Buchner, Jens Hopp, Gordon R. Osinski, New 40Ar/39Ar dating of the Clearwater Lake impact structures (Québec, Canada) – Not the binary asteroid impact it seems?, Geochimica et Cosmochimica Acta, Volume 148, 1 January 2015, Pages 304-324, ISSN 0016-7037, dx.doi.org/10.1016/j.gca.2014.09.037
Note : The above story is based on materials provided by Astrobio.net This story is republished courtesy of NASA’s Astrobiology Magazine. Explore the Earth and beyond at www.astrobio.net .
Here are the articulated cranium and lower jaws shown in oblique right lateral view (A). Right facial skeleton and skull roof shown in “exploded” view to illustrate the nature of sutural contacts (B); the left side of the cranium (braincase omitted) is shown in internal view (C). The right lower jaw in “exploded” view to illustrate sutural morphology. Individual bones shown in various colors. Credit: Porro et al.; CC-BY
The first 3D reconstruction of the skull of a 360 million-year-old near-ancestor of land vertebrates has been created by scientists from the Universities of Bristol and Cambridge, UK. The 3D skull, which differs from earlier 2D reconstructions, suggests such creatures, which lived their lives primarily in shallow water environments, were more like modern crocodiles than previously thought.
The researchers applied high-resolution X-ray computed tomography (CT) scanning to several specimens of Acanthostega gunnari, one of the ‘four-footed’ vertebrates known as tetrapods which invaded the land during one of the great evolutionary transitions in Earth’s history, 380-360 million years ago. Tetrapods evolved from lobe-finned fishes and display a number of adaptations to help them survive on land.
An iconic fossil species, Acanthostega gunnari is crucial for understanding the anatomy and ecology of the earliest tetrapods. However, after hundreds of millions of years in the ground fossils are often damaged and deformed. No single specimen of Acanthostega preserves a skull that is complete and three-dimensional which has limited scientists’ understanding of how this key animal fed and breathed — until now.
The original fossil skull of Acanthostega gunnari Image Credit: Dr Laura Porro
Using special software, the Bristol and Cambridge researchers ‘digitally prepared’ a number of Acanthostega specimens from East Greenland, stripping away layers of rock to reveal the underlying bones.
They uncovered a number of bones deep within the skull, including some that had never before been seen or described, resulting in a detailed anatomical description of the Acanthostega skull.
Once all of the bones and teeth were digitally separated from each other, cracks were repaired and missing elements duplicated. Bones could then be manipulated individually in 3D space. Using information from other specimens, the bones were fitted together like puzzle pieces to produce the first 3D reconstruction of the skull of Acanthostega, with surprising results.
Lead author, Dr Laura Porro, formerly of Bristol’s School of Earth Sciences and now at the Royal Veterinary College, said: “Because early tetrapods skulls are often ‘pancaked’ during the fossilization process, these animals are usually reconstructed having very flat heads. Our new reconstruction suggests the skull of Acanthostega was taller and somewhat narrower than previously interpreted, more similar to the skull of a modern crocodile.”
The researchers also found clues to how Acanthostega fed. The size and distribution of its teeth and the shape of contacts between individual bones of the skull (called sutures) suggest Acanthostega may have initially seized prey at the front of its jaws using its large front teeth and hook-shaped lower jaw.
Co-author, Professor Emily Rayfield, also from Bristol’s School of Earth Sciences, said: “These new analyses provide fresh clues about the evolution of the jaws and feeding system as the earliest animals with limbs and digits began to conquer the land.”
The researchers plan to apply these methods to other flattened fossils of the earliest tetrapods to better understand how these early animals modified their bones and teeth to meet the challenges of living on land.
Digital models of the original fossils and the 3D reconstruction are also useful in scientific research and education. They can be accessed by researchers around the world, without risking damage to fragile original fossils and without scientists having to travel thousands of miles to see original specimens. Furthermore, digital models and 3D printouts can be easily and safely handled by students taking courses and by the public during outreach events.
Reference:
Laura B. Porro, Emily J. Rayfield, Jennifer A. Clack. Descriptive Anatomy and Three-Dimensional Reconstruction of the Skull of the Early Tetrapod Acanthostega gunnari Jarvik, 1952. PLOS ONE, 2015; 10 (3): e0118882 DOI: 10.1371/journal.pone.0118882
The human-dominated geological epoch known as the Anthropocene probably began around the year 1610, with an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds, according to new research published today in Nature.
Previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents. Human actions are now changing the planet, but are we really a geological force of nature driving Earth into a new epoch that will last millions of years?
Scientists at UCL have concluded that humans have become a geological power and suggest that human actions have produced a new geological epoch.
Defining an epoch requires two main criteria to be met. Long-lasting changes to the Earth must be documented. Scientists must also pinpoint and date a global environmental change that has been captured in natural material, such as rocks, ancient ice or sediment from the ocean floor. Such a marker — like the chemical signature left by the meteorite strike that wiped out the dinosaurs — is called a golden spike.
The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years against these two formal requirements. Just two dates met the criteria: 1610, when the collision of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.
The scientists say the 1492 arrival of Europeans in the Americas, and subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in Earth’s history.
They argue that the joining of the two hemispheres is an unambiguous event after which the impacts of human activity became global and set Earth on a new trajectory. The first fossil pollen of maize, a Latin American species, appears in marine sediment in Europe in 1600, becoming common over subsequent centuries. This irreversible exchange of species satisfies the first criteria for dating an epoch — long-term changes to Earth.
The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right — as Earth-changing as a meteorite strike
The researchers also found a golden spike that can be dated to the same time: a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records. The drop occurred as a direct result of the arrival of Europeans in the Americas. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox. The abrupt near-cessation of farming across the continent and the subsequent re-growth of Latin American forests and other vegetation removed enough carbon dioxide from the atmosphere to produce a drop in CO2. Thus, the second requirement of a golden spike marker is met.
The researchers have named the 1610 dip in carbon dioxide the ‘Orbis Spike’. They chose the Latin word for ‘world’ because this golden spike was caused by once-disconnected peoples becoming globally linked.
Lead author, Dr Simon Lewis (UCL Geography and University of Leeds), said: “In a hundred thousand years scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species. Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right — as Earth-changing as a meteorite strike.”
He added: “Historically, the collision of the Old and New Worlds marks the beginning of the modern world. Many historians regard agricultural imports into Europe from the vast new lands of the Americas, alongside the availability of coal, as the two essential precursors of the Industrial Revolution, which in turn unleashed further waves of global environmental changes. Geologically, this boundary also marks Earth’s last globally synchronous cool moment before the onset of the long-term global warmth of the Anthropocene.”
The authors also considered the merits of dating the Anthropocene to 1964, which saw a peak in radioactive fallout following nuclear weapons testing. This marker is seen in many geological deposits, and by the 1960s human impact on the Earth was large. However, the researchers note that while nuclear war could dramatically alter Earth, so far it has not. While the fallout from nuclear bomb tests is a very good marker, the testing of nuclear weapons has not been — in geological terms — an Earth-changing event.
The beginning of the Industrial Revolution, in the late 18th century, has most commonly been suggested as the start of the Anthropocene. This linked a clear turning point in human history, and the rise of atmospheric carbon dioxide from fossil fuel use is a long-term global environmental change of critical importance. However, the researchers did not find a golden spike at that time because most effects were local, while the global exponential rise in carbon dioxide was too smooth an increase to form a precisely dated marker.
The authors’ new paper ends by highlighting some implications of formally defining the Anthropocene.
Co-author, geologist Professor Mark Maslin (UCL Geography) said: “A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment. But we should not despair, because the power that humans wield is unlike any other force of nature, it is reflexive and therefore can be used, withdrawn or modified. The first stage of solving our damaging relationship with our environment is recognising it.”
An official decision on whether to formally recognise the Anthropocene, including when it began, will be initiated by a recommendation of the Anthropocene Working Group of the Subcommission of Quaternary Stratigraphy, due in 2016.
Reference:
Simon L. Lewis, Mark A. Maslin. Defining the Anthropocene. Nature, 2015; 519 (7542): 171 DOI: 10.1038/nature14258
