The new fossil is the only record of an adult female insect from the Mesozoic, an era that spanned roughly 180 million years. Credit: CCBY 4.0 Wang et al.
Scientists have uncovered the earliest fossilised evidence of an insect caring for its young.
The findings, published in the journal eLife, push back the earliest direct evidence of insect brood care by more than 50 million years, to at least 100 million years ago when dinosaurs dominated the earth.
The new fossil is the only record of an adult female insect from the Mesozoic, an era that spanned roughly 180 million years. The Mesozoic era was the age of the reptiles and saw both the rise and fall of the dinosaurs, as well as the breakup of the supercontinent Pangaea.
The female ensign scale insect is preserved in a piece of amber retrieved from a mine in northern Myanmar (Burma). The specimen was trapped while carrying around 60 eggs and her first freshly hatched nymphs. The eggs and nymphs are encased in a wax-coated egg sac on the abdomen. This primitive form of brood care protects young nymphs from wet and dry conditions and from natural enemies until they have acquired their own thin covering of wax.
The behaviour has been so successful for promoting the survival of offspring that it is still common in insects today. Young nymphs hatch inside the egg sac and remain there for a few days before emerging into the outside world.
The findings may even offer an explanation for the early diversification of scale insects. The emergence of flowering plants and ants are thought to have been crucial for the rapid evolution of many new insect species, but they were not yet present during the evolutionary history of the ensign scale insects.
“Brood care could have been an important driver for the early radiation of scale insects, which occurred during the end of the Jurassic or earliest Cretaceous period during the Mesozoic era,” says lead author Bo Wang, an associate professor at the Chinese Academy of Sciences.
Fossilised evidence of animals caring for their young is extremely rare, especially in insects. Wingless females were largely immobile, so were less likely to be accidentally buried. A cockroach from a similar period was reported carrying a mass of eggs, but cockroaches often deposit their eggs rather than brooding them. The only other direct evidence of brood care is from Cenozoic ambers, the era that extends to the present and began about 65 million years ago with the extinction of the dinosaurs.
“Although analysis seemed to suggest that ancient insects evolved brood care, this is the first direct, unequivocal evidence for the fossil record,” says Wang.
The team have named this new species Wathondara kotejai after the goddess of earth in Buddhist mythology and the late Polish entomologist Jan Koteja.
Reference:
The paper ‘Brood care in a 100-million-year-old scale insect’ can be freely accessed online at DOI: 10.7554/eLife.05447
Note : The above story is based on materials provided by eLife.
At the UC Davis Bodega Marine Laboratory, Sarah Moffitt examines fossils within a marine sediment core. Credit: Copyright Joe Proudman, UC Davis
A 30-foot-long core sample of Pacific Ocean seafloor is changing what we know about ocean resiliency in the face of rapidly changing climate. A new study reports that marine ecosystems can take thousands, rather than hundreds, of years to recover from climate-related upheavals. The study’s authors–including Peter Roopnarine, PhD, of the California Academy of Sciences–analyzed thousands of invertebrate fossils to show that ecosystem recovery from climate change and seawater deoxygenation might take place on a millennial scale. The revolutionary study is the first of its kind, and is published today in the Early Edition of the journal PNAS.
The scientific collaborative–led by Sarah Moffitt, PhD, from the UC Davis Bodega Marine Laboratory and Coastal and Marine Sciences Institute–analyzed more than 5,400 invertebrate fossils, from sea urchins to clams, within a sediment core from offshore Santa Barbara, California.
“In this study, we used the past to forecast the future,” says Roopnarine, Academy curator of invertebrate zoology and geology. “Tracing changes in marine biodiversity during historical episodes of warming and cooling tells us what might happen in years to come. We don’t want to hear that ecosystems need thousands of years to recover from disruption, but it’s critical that we understand the global need to combat modern climate impacts.”
The tube-like sediment core is a slice of ocean life as it existed between 3,400 and 16,100 years ago, and provides a before-and-after snapshot of what happened during the last major deglaciation–a time of abrupt climate warming, melting polar ice caps, and expansion of low oxygen zones in the ocean. The new study documents how long it has historically taken for ecosystems to begin recovery following dramatic shifts in climate.
‘Complex’ invertebrates
Previous marine sediment studies reconstructing Earth’s climatic history rely heavily upon simple, single-celled organisms called Foraminifera. This week’s study explores multicellular life–in the form of invertebrates–in pursuit of a more complete picture of ocean ecosystem resilience during past periods of climate change.
“The complexity and diversity of a community depends on how much energy is available,” says Roopnarine. “To truly understand the health of an ecosystem and the food webs within, we have to look at the simple and small as well as the complex. In this case, marine invertebrates give us a better understanding of the health of ecosystems as a whole.”
The study’s all-important sediment core revealed an ancient history of abundant, diverse, and well-oxygenated seafloor ecosystems, followed by a period of oxygen loss and warming that seems to have triggered a rapid loss of biodiversity. The study reports that invertebrate fossils are nearly non-existent during times of lower-than-average oxygen levels.
Moffitt emphasized the importance of using a large, 30-foot core sample from one portion of the seafloor, saying the team “cut it up like a cake” to analyze the full, unbroken record.
In periods of fewer than 100 years, oceanic oxygen levels decreased between 0.5 and 1.5 mL/L. Sediment samples during these periods show that relatively minor oxygen fluctuations can result in dramatic changes for seafloor communities.
‘New normal’ of rapid climate change
The study results suggest that future periods of global climate change may result in similar ecosystem-level effects with millennial-scale recovery periods. As the planet warms, scientists expect to see much larger areas of low-oxygen “dead zones” in the world’s oceans.
“Folks in Oregon and along the Gulf of Mexico are all-too-familiar with the devastating impacts of low-oxygen ocean conditions on local ecosystems and economies,” says Roopnarine. “We must explore how ocean floor communities respond to upheaval as we adapt to a ‘new normal’ of rapid climate change. We humans have to think carefully about the planet we are leaving for future generations.”
Reference:
Sarah E. Moffitt, Tessa M. Hill, Peter D. Roopnarine, and James P. Kennett. Response of seafloor ecosystems to abrupt global climate change. PNAS, 2015 DOI: 10.1073/pnas.1417130112
Looking toward Svalbard, an archipelago off the coast of Norway, from the Isfjorden fjord. Credit: Joel Johnson
Research led by a University of New Hampshire professor has identified a new source of methane for gas hydrates — ice-like substances found in sediment that trap methane within the crystal structure of frozen water — in the Arctic Ocean. The findings, published online now in the May 2015 journal Geology, point to a previously undiscovered, stable reservoir for abiotic methane — methane not generated by decomposing carbon — that is “locked” away from the atmosphere, where it could impact global climate change.
“We’ve found an example where methane produced at a mid-ocean ridge is locked up in stable, deep water gas hydrate, preventing it from possibly getting out of the seafloor,” says lead author Joel Johnson, associate professor of geology at UNH and guest researcher at the Center for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT The Arctic University of Norway in Tromsø. Johnson notes that the findings, which pinpointed a source of abiotic methane ¬produced in seafloor crust, indicate gas hydrates throughout the Arctic may be supplied by a significant portion of abiotic gas.
The study, “Abiotic methane from ultraslow-spreading ridges can charge Arctic gas hydrates,” focused on the Arctic mid-ocean ridge system, one of two so-called ultraslow-spreading ridge regions on Earth. Scientists have known that abiotic methane can be generated in these ridges through a process called serpentization, which involves the reaction of seawater with hot mantle-derived rocks exposed during slow to ultraslow mid-ocean ridge spreading.
While on sabbatical last year (2013-14) at CAGE, Johnson and his co-authors from that institution embarked on two cruises in the unique geologic and oceanographic region called the Fram Strait, a deep, narrow gateway to the Arctic Ocean between Greenland and the Norwegian archipelago of Svalbard. There, fast-moving currents move sediment, uncommon on most mid-ocean ridges, into sediment drifts that cover the ridges. Using a seismic data acquisition system, they found a methane hydrate system within those sediments.
The discovery surprised the researchers. “We didn’t know whether or not abiotic methane could supply gas hydrate systems so close to mid-ocean ridges” Johnson says. “It had been thought that mid-ocean ridge environments might be too hot for gas hydrates to be stable.”
Indeed, those methane hydrates are remarkably stable: The researchers showed that the hydrate system is long-lived, about two million years old. Further, because the hydrates exist under very deep water — more than 1500 meters — the methane is less vulnerable to potential release due to changing sea levels or ocean warming. Such stability has important implications for climate change; as a greenhouse gas, methane is 20 times more potent than carbon dioxide.
“This work shows there are parts of the Arctic where abiotic methane is coming up to the seafloor and instead of coming out, it is trapped in gas hydrates; it’s finding itself in a stable environment for millions of years,” says Johnson. Where climate change is concerned, he adds, “this is not the part of the gas hydrate system that is most susceptible to change in a warming Arctic Ocean.”
Although his focus is on the crust of Earth, not interplanetary space, Johnson notes that these findings are interesting, as some researchers have suggested abiotic methane formed by serpentinization may exist and reside as gas hydrates on Mars. And as gas hydrates gain popularity as potential fuel for the future here on Earth, the energy sector is likely to take notice as well. “This is a new source of methane for gas hydrates in the Arctic that could be quite extensive,” Johnson says.
Reference:
J. E. Johnson, J. Mienert, A. Plaza-Faverola, S. Vadakkepuliyambatta, J. Knies, S. Bunz, K. Andreassen, B. Ferre. Abiotic methane from ultraslow-spreading ridges can charge Arctic gas hydrates. Geology, 2015; DOI: 10.1130/G36440.1
This image shows a freshly excavated fossil specimen of Yawunik kootenayi. Credit: Robert Gaines
What do butterflies, spiders and lobsters have in common? They are all surviving relatives of a newly identified species called Yawunik kootenayi, a marine creature with two pairs of eyes and prominent grasping appendages that lived as much as 508 million years ago – more than 250 million years before the first dinosaur.
The fossil was identified by an international team led by palaeontologists at the University of Toronto (U of T) and the Royal Ontario Museum (ROM) in Toronto, as well as Pomona College in California. It is the first new species to be described from the Marble Canyon site, part of the renowned Canadian Burgess Shale fossil deposit.
Yawunik had evolved long frontal appendages that resemble the antennae of modern beetles or shrimps, though these appendages were composed of three long claws, two of which bore opposing rows of teeth that helped the animal catch its prey.
“This creature is expanding our perspective on the anatomy and predatory habits of the first arthropods, the group to which spiders and lobsters belong,” said Cedric Aria, a PhD candidate in U of T’s Department of Ecology & Evolutionary Biology and lead author of the resulting study published this week in Palaeontology. “It has the signature features of an arthropod with its external skeleton, segmented body and jointed appendages, but lacks certain advanced traits present in groups that survived until the present day. We say that it belongs to the ‘stem’ of arthropods.”
The study presents evidence that Yawunik was capable of moving its frontal appendages backward and forward, spreading them out during an attack and then retracting them under its body when swimming. Coupled with the long, sensing whip-like flagella extending from the tip of the claws, this makes the frontal appendages of the animal some of the most versatile and complex in all known arthropods.
“Unlike insects or crustaceans, Yawunik did not possess additional appendages in the head that were specifically modified to process food,” said Aria. “Evolution resulted here in a combination of adaptations onto the frontal-most appendage of this creature, maybe because such modifications were easier to acquire.
“We know that the larvae of certain crustaceans can use their antennae to both swim and gather food. But a large active predator such as a mantis shrimp has its sensory and grasping functions split up between appendages. Yawunik and its relatives tell us about the condition existing before such a division of tasks among parts of the organism took place.”
The Marble Canyon site is located in British Columbia’s Kootenay National Park, 40 kilometres south from the original Burgess Shale in Yoho National Park. Aria was part of the team that discovered the site in 2012, led by Jean-Bernard Caron, an associate professor at U of T’s Departments of Earth Sciences and Ecology & Evolutionary Biology and curator of invertebrate palaeontology at the ROM, and Robert Gaines, associate professor at the Department of Geology at Pomona College in California, both co-authors of the study.
“Yawunik is the most abundant of the large new species of the Marble Canyon site, and so, as a predator, it held a key position in the food network and had an important impact on this past ecosystem,” said Caron. “This animal is therefore important for the study of Marble Canyon, and shows how the site increases the significance of the Burgess Shale in understanding the dawn of animals.”
The study benefited from cutting-edge techniques of fossil imagery, including so-called “elemental mapping,” which consists in detecting the atomic composition of the fossil and the sediment surrounding it.
“Our understanding of these organisms rests upon interpreting their fossil remains,” said Gaines. “These fossils are a composed of a mosaic of delicate original organic material and minerals that replicate parts of fossil anatomy.
“The scanning electron microscope allows us to make maps of the fossils that reveal their composition. This gives us a remarkable perspective on the fossils, allowing anatomical structures to be visualized more precisely. This technique also provides insight into the unusual fossilization process that was at work here.”
The new creature is named in tribute to the Ktunaxa People who have long inhabited the Kootenay area where the Marble Canyon locality was found. It owes its name to “Yawu?nik?”, a mythological figure described as a huge and fierce marine creature, killing and causing such mayhem that it triggered an epic hunt by other animals to bring the threat down.
“We wanted to acknowledge the Ktunaxa culture, and given the profile of Yawunik, it looked like a natural choice of name,” Aria said.
“Yawu?nik? is a central figure in the Ktunaxa creation story, and, as such, is a vital part of Ktunaxa oral history,” said Donald Sam, Ktunaxa Nation Council Director of Traditional Knowledge and Language. “I am ecstatic that the research team recognizes how important our history is in our territory, and chose to honour the Ktunaxa through this amazing discovery.”
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Reference:
Cédric Aria, Jean-Bernard Caron and Robert Gaines. A large new leanchoiliid from the Burgess Shale and the influence of inapplicable states on stem arthropod phylogeny. Palaeontology, 27 MAR 2015 DOI: 10.1111/pala.12161
Figure 1 is from Pondrelli et al. (A) Location map of the study area on MOLA-based shaded relief map. Topographic contours (in black, 1000 m spacing) are indicated. (B) High Resolution Stereo Camera (HRSC) mosaic of the mapped area. Topographic contours (in white, 500 m spacing) are indicated. (C) Excerpt of the geological map by Scott and Tanaka (1986) on an HRSC mosaic. Geologic units (see text for more details): Npl1–Noachian cratered unit of the plateau sequence; Npl2–Noachian subdued crater unit of the plateau sequence; Hr–Hesperian ridged plains material. (D) Footprints of High Resolution Imaging Science Experiment (HiRISE) coverage on an HRSC mosaic. The white fi lling indicates stereo pairs. The area is fully covered by Context Camera (CTX) imagery. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) scenes used in this study are recognizable by the hourglass shape. Click on the figure for a larger image. Credit: Pondrelli et al. and GSA Bulletin
Monica Pondrelli and colleagues investigated the Equatorial Layered Deposits (ELDs) of Arabia Terra in Firsoff crater area, Mars, to understand their formation and potential habitability. On the plateau, ELDs consist of rare mounds, flat-lying deposits, and cross-bedded dune fields. Pondrelli and colleagues interpret the mounds as smaller spring deposits, the flat-lying deposits as playa, and the cross-bedded dune fields as aeolian. They write that groundwater fluctuations appear to be the major factor controlling ELD deposition.
Pondrelli and colleagues also note that the ELDs inside the craters would likely have originated by fluid upwelling through the fissure ridges and the mounds, and that lead to evaporite precipitation. The presence of spring and playa deposits points to the possible presence of a hydrological cycle, driving groundwater upwelling on Mars at surface temperatures above freezing. Pondrelli and colleagues write that such conditions in a similar Earth environment would have been conducive for microbial colonization.
As a basis for their research, Pondrelli and colleagues produced a detailed geological map of the Firsoff crater area. The new map includes crater count dating, a survey of the stratigraphic relations, and analysis of the depositional geometries and compositional constraints. They note that this ELD unit consists of sulfates and shows other characteristics typical of evaporites such as polygonal pattern and indications of dissolution.
Reference:
Equatorial layered deposits in Arabia Terra, Mars: Facies and process variability
M. Pondrelli et al., International Research School of Planetary Sciences, Università d’Annunzio, Pescara, Italy. Published online ahead of print on 10 Mar. 2015; DOI: 10.1130/B31225.1.
Modern technology relies on virtually all of the stable elements of the periodic table. This figure, which pictures the concentrations (in parts per million) of elements on a printed circuit board, provides an illustration of that fact. The concentrations of copper and iron are obviously the highest, and others such as cesium are much lower, but concentration clearly does not reflect elemental importance: all the elements are required in order to maintain the functions for which the board was designed. Credit: Thomas Graedel, et al
In a new paper, a team of Yale researchers assesses the “criticality” of all 62 metals on the Periodic Table of Elements, providing key insights into which materials might become more difficult to find in the coming decades, which ones will exact the highest environmental costs — and which ones simply cannot be replaced as components of vital technologies.
During the past decade, sporadic shortages of metals needed to create a wide range of high-tech products have inspired attempts to quantify the criticality of these materials, defined by the relative importance of the elements’ uses and their global availability.
Many of the metals traditionally used in manufacturing, such as zinc, copper, and aluminum, show no signs of vulnerability. But other metals critical in the production of newer technologies — like smartphones, infrared optics, and medical imaging — may be harder to obtain in coming decades, said Thomas Graedel, the Clifton R. Musser Professor of Industrial Ecology at the Yale School of Forestry & Environmental Studies and lead author of the paper.
The study — which was based on previous research, industry information, and expert interviews — represents the first peer-reviewed assessment of the criticality of all of the planet’s metals and metalloids.
“The metals we’ve been using for a long time probably won’t present much of a challenge. We’ve been using them for a long time because they’re pretty abundant and they are generally widespread geographically,” Graedel said. “But some metals that have become deployed for technology only in the last 10 or 20 years are available almost entirely as byproducts. You can’t mine specifically for them; they often exist in small quantities and are used for specialty purposes. And they don’t have any decent substitutes.”
These findings illustrate the urgency for new product designs that make it easier to reclaim materials for re-use, Graedel said.
The paper, published in the Proceedings of the National Academy of Sciences, encapsulates the Yale group’s five-year assessment of the criticality of the planet’s metal resources in the face of rising global demand and the increasing complexity of modern products.
According to the researchers, criticality depends not only on geological abundance. Other important factors include the potential for finding effective alternatives in production processes, the degree to which ore deposits are geopolitically concentrated, the state of mining technology, regulatory oversight, geopolitical initiatives, regional instabilities, and economic policies.
In order to assess the state of all metals, researchers developed a methodology that characterizes criticality in three areas: supply risk, environmental implications, and vulnerability to human-imposed supply restrictions.
They found that supply limits for many metals critical in the emerging electronics sector (including gallium and selenium) are the result of supply risks. The environmental implications of mining and processing present the greatest challenges with platinum-group metals, gold, and mercury. For steel alloying elements (including chromium and niobium) and elements used in high-temperature alloys (tungsten and molybdenum), the greatest vulnerabilities are associated with supply restrictions.
Among the factors contributing to extreme criticality challenges are high geopolitical concentration of primary production (for example, 90 to 95% of the global supply of rare Earth metals comes from China); lack of available substitutes (there is no adequate substitute for indium, which is used in computer and cell phone displays); and political instability (a significant fraction of tantalum, used widely in electronics, comes from the war-ravaged Democratic Republic of the Congo).
The researchers also analyzed how recycling rates have evolved over the years and the degree to which different industries are able to utilize “non-virgin” sources of materials. Some materials, such as lead, are highly recycled because they are typically used in bulk, Graedel said. But the relatively rare materials that have become critical in some modern electronics are far more difficult to recycle because they are used in such miniscule amounts — and can be difficult to extricate from the increasingly complex and compact new technologies.
“I think these results should send a message to product designers to spend more time thinking about what happens after their products are no longer being used,” he said. “So much of what makes the recycling of these materials difficult is their design. It seems as if it’s time to think a little bit more about the end of these beautiful products.”
Reference:
T. E. Graedel, E. M. Harper, N. T. Nassar, Philip Nuss, Barbara K. Reck. Criticality of metals and metalloids. Proceedings of the National Academy of Sciences, 2015; 201500415 DOI: 10.1073/pnas.1500415112
This is a cast of the ‘Nariokotome Boy’ (Homo ergaster) skeleton. Credit: Jay Stock
New research harnessing fragmentary fossils suggests our genus has come in different shapes and sizes since its origins over two million years ago, and adds weight to the idea that humans began to colonise Eurasia while still small and lightweight.
One of the dominant theories of our evolution is that our genus, Homo, evolved from small-bodied early humans to become the taller, heavier and longer legged Homo erectus that was able to migrate beyond Africa and colonise Eurasia. While we know that small-bodied Homo erectus — averaging less than five foot (152cm) and under 50kg — were living in Georgia in southern Europe by 1.77 million years ago, the timing and geographic origin of the larger body size that we associate with modern humans has, until now, remained unresolved.
But a joint study by researchers at the Universities of Cambridge and Tübingen (Germany), published today in the Journal of Human Evolution, has now shown that the main increase in body size occurred tens of thousands of years after Homo erectus left Africa, and primarily in the Koobi Fora region of Kenya. According to Manuel Will, a co-author of the study from the Department of Early Prehistory and Quaternary Ecology at Tübingen, “the evolution of larger bodies and longer legs can thus no longer be assumed to be the main driving factor behind the earliest excursions of our genus to Eurasia.”
Researchers say the results from a new research method, using tiny fragments of fossil to estimate our earliest ancestors’ height and body mass, also point to the huge diversity in body size we see in humans today emerging much earlier than previously thought.
“What we’re seeing is perhaps the beginning of a unique characteristic of our own species — the origins of diversity,” said Dr Jay Stock, co-author of the study from the University of Cambridge’s Department of Archaeology and Anthropology. “It’s possible to interpret our findings as showing that there were either multiple species of early human, such as Homo habilis, Homo ergaster and Homo rudolfensis, or one highly diverse species. This fits well with recent cranial evidence for tremendous diversity among early members of the genus Homo.”
“If someone asked you ‘are modern humans 6 foot tall and 70kg?’ you’d say ‘well some are, but many people aren’t,’ and what we’re starting to show is that this diversification happened really early in human evolution,” said Stock.
The study is the first in 20 years to compare the body size of the humans who shared earth with mammoths and sabre-toothed cats between 2.5 and 1.5 million years ago. It is also the first time that many fragmentary fossils — some as small as toes and tiny ankle bones no more than 5cm long — have been used to make body size estimates.
Comparing measurements of fossils from sites in Kenya, Tanzania, South Africa, and Georgia, the researchers found that there was significant regional variation in the size of early humans during the Pleistocene. Some groups, such as those who lived in South African caves, averaged 4.8 feet tall; some of those found in Kenya’s Koobi Fora region would have stood at almost 6 foot, comparable to the average of today´s male population in Britain.
“Basically every textbook on human evolution gives the perspective that one lineage of humans evolved larger bodies before spreading beyond Africa. But the evidence for this story about our origins and the dispersal out of Africa just no longer really fits,” said Stock. “The first clues came from the site of Dmanisi in Georgia where fossils of really small-bodied people date to 1.77 million years ago. This has been known for several years, but we now know that consistently larger body size evolved in Eastern Africa after 1.7 million years ago, in the Koobi Fora region of Kenya.”
“We tend to simplify our interpretations because the fossil record is patchy and we have to explain it in some way. But revealing the diversity that exists is just as important as those broad, sweeping explanations.”
Previous studies have been based on small samples of only 10-15 fossils because techniques for calculating the height and body mass of individuals required specific pieces of bone such as the hip joint or most of a leg bone. Stock and Will have used a sample size three times larger, estimating body size for over 40 specimens contained in collections all over Africa and Georgia, making it the largest comparative study conducted so far.
Instead of waiting for new fossils to be discovered and hoping that they contained these specific bones, Stock and Will decided to try a different approach and make use of previously over-looked fossils. In what Stock describes as a “very challenging project,” they spent a year developing new equations that allowed them to calculate the height and body mass of individuals using much smaller bones, some as small as toes. By comparing these bones to measurements taken from over 800 modern hunter-gatherer skeletons from around the world and applying various regression equations, the researchers were able to estimate body size for many new fossils that have never been studied in this way before.
“In human evolution we see body size as one of the most important characteristics, and from examining these ‘scrappier’ fossils we can get a much better sense of when and where human body size diversity arose. Before 1.7 million years ago our ancestors were seldom over 5 foot tall or particularly heavy in body mass.
“When this significant size shift to much heavier, taller individuals happened, it occurred primarily in one particular place — in a region called Koobi Fora in northern Kenya around 1.7 million years ago. That means we can now start thinking about what regional conditions drove the emergence of this diversity, rather than seeing body size as a fixed and fundamental characteristic of a species,” said Stock.
Reference:
Manuel Will, Jay T. Stock. Spatial and temporal variation of body size among early Homo. Journal of Human Evolution, 2015 DOI: 10.1016/j.jhevol.2015.02.009
Note: The above story is based on materials provided by University of Cambridge. The original story is licensed under a Creative Commons Licence.
Debris from the 2011 Tohoku earthquake and tsunami. A new study is the first to look at how the earthquake affected the release of halocarbons into the atmosphere. Credit: National Institute for Environmental Studies
Buildings destroyed by the 2011 Tohoku earthquake released thousands of tons of climate-warming and ozone-depleting chemicals into the atmosphere, according to a new study.
New research suggests that the thousands of buildings destroyed and damaged during the 9.0 magnitude earthquake and tsunami that struck Japan four years ago released 6,600 metric tons (7,275 U.S. tons) of gases stored in insulation, appliances and other equipment into the atmosphere.
Emissions of these chemicals, called halocarbons, increased by 21 percent to 91 percent over typical levels, according to the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
First look
The study is the first to look at how the Tohoku earthquake affected the release of halocarbons into the atmosphere and likely one of the first to examine emissions of these gases following a natural disaster, according to the study’s authors.
“What we found is a new mechanism of halocarbon emissions coming from the earthquake,” said Takuya Saito, a senior researcher at the National Institute for Environmental Studies in Tsukuba, Japan, and lead author of the new paper.
Halocarbons released as a result of the earthquake include chemicals that deplete the ozone layer and contribute to global warming — including some gases that are no longer used because of those harmful effects on the environment. These include chlorofluorocarbons like CFC-11, a powerful ozone-depleting chemical used in foam insulation until it was phased out in 1996, and hydrochlorofluorocarbons like HCFC-22, an ozone-depleting refrigerant that is also a powerful greenhouse gas and is in the process of being phased out of use. Among other halocarbons released by the earthquake were hydrofluorocarbons, or HFCs, and sulfur hexafluoride, both potent greenhouse gases.
The emissions of the six halocarbons released from Japan in 2011 are equivalent to the discharge of 1,300 metric tons (1,433 U.S. tons) of CFC-11 alone — equal to the amount of CFC-11s found in 2.9 million refrigerators manufactured before the chemical was banned. The total emissions of the six chemicals are also equivalent to the release of 19.2 million metric tons (21.2 million U.S. tons) of carbon dioxide into the atmosphere — an amount equal to about 10 percent of Japanese vehicle emissions in 2011, according to the study’s authors.
Post-quake surprise
Saito and his colleagues decided to investigate halocarbon emissions and their relationship to the earthquake after ground-based air monitoring stations in Japan recorded surprising high levels of these chemicals. The stations are on Hateruma Island, east of Taiwan; Cape Ochiishi, on the east side of Hokkaido; and Ryori, north of Tokyo on Honshu.
The study’s authors combined these measurements with an atmospheric model and other mathematical methods to figure out that increased emissions from the earthquake were involved, how much of the emissions could be attributed to the disaster and how they compared to previous years.
They found that emissions of all six halocarbons were higher from March 2011 to February 2012, following the earthquake, than they were during the same time the year before the event and during the same period the year after it.
About 50 percent of the halocarbon emissions after the earthquake were of HCFC-22, likely due to damage to refrigerators and air conditioners. Emissions of the gas were 38 percent higher than the years before and after the earthquake. Emissions of CFC-11 were 72 percent higher than emissions before and after the earthquake, likely due to damage to insulation foams used in appliances and buildings, according to the study. Emissions of two types of HFCs — HFC-134a and HFC-32 — rose by 49 percent and 63 percent compared to the years before and after the disaster.
Impacts assessed
The new study also calculates the total impact of the increased emissions on ozone depletion and global warming. The earthquake-triggered surge of halocarbons increased ozone loss from Japanese emissions of those six gases by 38 percent from March 2011 to February 2012 compared to the same time period in the years before and after the event. The amount of heat trapped in the atmosphere because of Japan’s emissions of those six gases rose 36 percent from March 2011 to February 2012 compared to earlier and later years because of the extra emissions from the earthquake, according to the new study.
Saito said the new study shows the importance of including the release of gases from natural disasters in emissions estimates. Although the global effect of one event is small — emissions associated with the Tohoku earthquake accounted for 4 percent or less of global emissions in 2011 — the cumulative effect could be larger, he said. Natural disasters accelerate the release of halocarbons and replacement of these gases could lead to the use of more halocarbons, according to the study.
National halocarbon emissions estimates by the Japanese government did not factor in the release of the chemicals due to the earthquake and are likely underestimating the amount of these substances in the atmosphere, according to Saito. Governments rely on inventories of chemicals and generic data about how they are used to estimate their amounts in the atmosphere — called a “bottom-up” approach” — whereas the new study uses actual measurements of the gases — called a “top-down” approach. “It is apparent that there are unreported emissions,” Saito said.
The new study shows that there could be a need to include the amount of halocarbons released by catastrophic events in emissions estimates, said Steve Montzka, a research chemist at the National Oceanic and Atmospheric Administration in Boulder, Colorado, who was not involved in the research. It also highlights the need for more measurements of halocarbons in the atmosphere, he added, rather than relying on bottom-up emissions estimates from inventories.
“Atmospheric scientists often say that relying solely on bottom-up inventories to tell you how greenhouse gas emissions change is like going on a diet without weighing yourself,” Montzka said.
Reference:
Takuya Saito, Xuekun Fang, Andreas Stohl, Yoko Yokouchi, Jiye Zeng, Yukio Fukuyama, Hitoshi Mukai. Extraordinary halocarbon emissions initiated by the 2011 Tohoku earthquake. Geophysical Research Letters, 2015; DOI: 10.1002/2014GL062814
USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.
The Mariana Trench or Marianas Trench is the deepest part of the world’s oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 2,550 kilometres (1,580 mi) long but has an average width of only 69 kilometres (43 mi). It reaches a maximum-known depth of 10,994 m (± 40 m) or 6.831 mi (36,070 ± 131 ft) at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end, although some unrepeated measurements place the deepest portion at 11.03 kilometres (6.85 mi).
At the bottom of the trench the water column above exerts a pressure of 1,086 bars (15,750 psi), over 1000 times the standard atmospheric pressure at sea level. At this pressure the density of water is increased by 4.96%, making 95 litres of water under the pressure of the Challenger Deep contain the same mass as 100 litres at the surface. The temperature at the bottom is 1 to 4 °C.
The trench is not the part of the seafloor closest to the center of the Earth. This is because the Earth is not a perfect sphere: its radius is about 25 kilometres (16 mi) less at the poles than at the equator. As a result, parts of the Arctic Ocean seabed are at least 13 kilometres (8.1 mi) closer to the Earth’s center than the Challenger Deep seafloor.
Xenophyophores have been found in the trench by Scripps Institution of Oceanography researchers at a record depth of 10.6 km (6.6 mi) below the sea surface. On 17 March 2013, researchers reported data that suggested microbial life forms thrive within the trench.
Names
The Mariana Trench is named for the nearby Mariana Islands (in turn named Las Marianas in honor of Spanish Queen Mariana of Austria, widow of Philip IV of Spain). The islands are part of the island arc that is formed on an over-riding plate, called the Mariana Plate (also named for the islands), on the western side of the trench.
Geology
The Mariana Trench is part of the Izu-Bonin-Mariana subduction system that forms the boundary between two tectonic plates. In this system, the western edge of one plate, the Pacific Plate, is subducted (i.e., thrust) beneath the smaller Mariana Plate that lies to the west. Crustal material at the western edge of the Pacific Plate is some of the oldest oceanic crust on earth (up to 170 million years old), and is therefore cooler and more dense; hence its great height difference relative to the higher-riding (and younger) Mariana Plate. The deepest area at the plate boundary is the Mariana Trench proper.
The movement of the Pacific and Mariana plates is also indirectly responsible for the formation of the Mariana Islands. These volcanic islands are caused by flux melting of the upper mantle due to release of water that is trapped in minerals of the subducted portion of the Pacific Plate.
Measurements
The trench was first sounded during the Challenger expedition in 1875, which recorded a depth of 4,475 fathoms (8.184 km). In 1877 a map was published called Tiefenkarte des Grossen Ozeans by Petermann, which showed a Challenger Tief at the location of that sounding. In 1899 USS Nero, a converted collier, recorded a depth of 5269 fathoms (9,636 m, 31,614 ft). Challenger II surveyed the trench using echo sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. During this survey, the deepest part of the trench was recorded when the Challenger II measured a depth of 5,960 fathoms (10,900 m, 35,760 ft) at 11°19′N 142°15′E, known as the Challenger Deep.
In 1957, the Soviet vessel Vityaz reported a depth of 11,034 m (36,201 ft), dubbed the Mariana Hollow.
In 1962, the surface ship M.V. Spencer F. Baird recorded a maximum depth of 10,915 m (35,840 ft), using precision depth gauges.
In 1984, the Japanese survey vessel Takuyō , collected data from the Mariana Trench using a narrow, multi-beam echo sounder; it reported a maximum depth of 10,924 m, also reported as 10,920 ± 10 metres.
Remotely Operated Vehicle KAIKO reached the deepest area of Mariana trench and made the deepest diving record of 10,911 m on March 24, 1995.
During surveys carried out between 1997 and 2001, a spot was found along the Mariana Trench that had depth similar to that of the Challenger Deep, possibly even deeper. It was discovered while scientists from the Hawaii Institute of Geophysics and Planetology were completing a survey around Guam; they used a sonar mapping system towed behind the research ship to conduct the survey. This new spot was named the HMRG (Hawaii Mapping Research Group) Deep, after the group of scientists who discovered it.
On 1 June 2009 sonar mapping of the Challenger Deep by the Simrad EM120 sonar multibeam bathymetry system for deep water (300–11,000 m) mapping aboard the RV Kilo Moana (mothership of the Nereus vehicle), has indicated a spot with a depth of 10,971 m (35,994 ft). The sonar system uses phase and amplitude bottom detection, with an accuracy of better than 0.2% of water depth across the entire swath (implying the depth figure is accurate to less than ± 22 metres).
In 2011, it was announced at the American Geophysical Union Fall Meeting that a US Navy hydrographic ship equipped with a multibeam echosounder conducted a survey which mapped the entire trench to 100 m resolution. The mapping revealed the existence of four rocky outcrops thought to be former seamounts.
The Mariana Trench is a site chosen by researchers at Washington University and the Woods Hole Oceanographic Institution in 2012 for a seismic survey to investigate the subsurface water cycle. Using seismometers and hydrophones the scientists are able to map structures as deep as 60 mi (97 km) beneath the surface.
How deep is the ocean?
The average ocean depth is 2.65 miles.
The average depth of the ocean is about 14,000 feet. The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench, which runs several hundred kilometers southwest of the U.S. territorial island of Guam. Challenger Deep is approximately 36,200 feet deep. It is named after the HMS Challenger, whose crew first sounded the depths of the trench in 1875.
The image correlates types of volcanoes with their respective eruption, highlighting the differences. Credit: ChiaraCingottini, DensityDesign Research Lab
During a volcanic eruption, lava, tephra (ash, lapilli, volcanic bombs and blocks), and various gases are expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.
There are three different meta types of eruptions. The most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of volcanic eruption, driven by the compression of gas within magma, the direct opposite of the process powering magmatic activity. The last eruptive metatype is the phreatic eruption, which is driven by the superheating of steam via contact with magma; these eruptive types often exhibit no magmatic release, instead causing the granulation of existing rock.
Within these wide-defining eruptive types are several subtypes. The weakest are Hawaiian and submarine, then Strombolian, followed by Vulcanian and Surtseyan. The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions; the strongest eruptions are called “Ultra Plinian.” Subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of eruptive strength is Volcanic Explosivity Index (VEI), an order of magnitude scale ranging from 0 to 8 that often correlates to eruptive types.
Eruption mechanisms
Volcanic eruptions arise through three main mechanisms:
Gas release under decompression causing magmatic eruptions
Thermal contraction from chilling on contact with water causing phreatomagmatic eruptions
Ejection of entrained particles during steam eruptions causing phreatic eruptions
There are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra.Effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption.
Volcanic eruptions vary widely in strength. On the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are typically not very dangerous. On the other extreme, Plinian eruptions are large, violent, and highly dangerous explosive events. Volcanoes are not bound to one eruptive style, and frequently display many different types, both passive and explosive, even the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a single crater near their peak, either. Some volcanoes exhibit lateral and fissure eruptions. Notably, many Hawaiian eruptions start from rift zones, and some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to take several thousands of years. But Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was likely triggered by magma that took a nonstop route from the mantle over just a few months.
Magmatic eruptions
Magmatic eruptions produce juvenile clasts during explosive decompression from gas release. They range in intensity from the relatively small lava fountains on Hawaii to catastrophic Ultra Plinian eruption columns more than 30 km (19 mi) high, bigger than the eruption of Mount Vesuvius in 79 that buried Pompeii.
Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of volcanic events, characterized by the effusive eruption of very fluid basalt-type lavas with low gaseous content. The volume of ejected material from Hawaiian eruptions is less than half of that found in other eruptive types. Steady production of small amounts of lava builds up the large, broad form of a shield volcano. Eruptions are not centralized at the main summit as with other volcanic types, and often occur at vents around the summit and from fissure vents radiating out of the center.
Hawaiian eruptions often begin as a line of vent eruptions along a fissure vent, a so-called “curtain of fire.” These die down as the lava begins to concentrate at a few of the vents. Central-vent eruptions, meanwhile, often take the form of large lava fountains (both continuous and sporadic), which can reach heights of hundreds of meters or more. The particles from lava fountains usually cool in the air before hitting the ground, resulting in the accumulation of cindery scoria fragments; however, when the air is especially thick with clasts, they cannot cool off fast enough due to the surrounding heat, and hit the ground still hot, the accumulation of which forms spatter cones. If eruptive rates are high enough, they may even form splatter-fed lava flows. Hawaiian eruptions are often extremely long lived; Pu’u O’o, a cinder cone of Kilauea, has been erupting continuously since 1983. Another Hawaiian volcanic feature is the formation of active lava lakes, self-maintaining pools of raw lava with a thin crust of semi-cooled rock; there are currently only 5 such lakes in the world, and the one at Kīlauea’s Kupaianaha vent is one of them.
Strombolian eruptions are a type of volcanic eruption, named after the volcano Stromboli, which has been erupting continuously for centuries. Strombolian eruptions are driven by the bursting of gas bubbles within the magma. These gas bubbles within the magma accumulate and coalesce into large bubbles, called gas slugs. These grow large enough to rise through the lava column. Upon reaching the surface, the difference in air pressure causes the bubble to burst with a loud pop, throwing magma in the air in a way similar to a soap bubble. Because of the high gas pressures associated with the lavas, continued activity is generally in the form of episodic explosive eruptions accompanied by the distinctive loud blasts. During eruptions, these blasts occur as often as every few minutes.
The term “Strombolian” has been used indiscriminately to describe a wide variety of volcanic eruptions, varying from small volcanic blasts to large eruptive columns. In reality, true Strombolian eruptions are characterized by short-lived and explosive eruptions of lavas with intermediate viscosity, often ejected high into the air. Columns can measure hundreds of meters in height. The lavas formed by Strombolian eruptions are a form of relatively viscous basaltic lava, and its end product is mostly scoria. The relative passivity of Strombolian eruptions, and its non-damaging nature to its source vent allow Strombolian eruptions to continue unabated for thousands of years, and also makes it one of the least dangerous eruptive types.
Strombolian eruptions eject volcanic bombs and lapilli fragments that travel in parabolic paths before landing around their source vent. The steady accumulation of small fragments builds cinder cones composed completely of basaltic pyroclasts. This form of accumulation tends to result in well-ordered rings of tephra.
Strombolian eruptions are similar to Hawaiian eruptions, but there are differences. Strombolian eruptions are noisier, produce no sustained eruptive columns, do not produce some volcanic products associated with Hawaiian volcanism (specifically Pele’s tears and Pele’s hair), and produce fewer molten lava flows (although the eruptive material does tend to form small rivulets).
Vulcanian eruptions are a type of volcanic eruption, named after the volcano Vulcano, which means the word Volcano. It was named so following Giuseppe Mercalli’s observations of its 1888-1890 eruptions. In Vulcanian eruptions, highly viscous magma within the volcano make it difficult for vesiculate gases to escape. Similar to Strombolian eruptions, this leads to the buildup of high gas pressure, eventually popping the cap holding the magma down and resulting in an explosive eruption. However, unlike Strombolian eruptions, ejected lava fragments are not aerodynamic; this is due to the higher viscosity of Vulcanian magma and the greater incorporation of crystalline material broken off from the former cap. They are also more explosive than their Strombolian counterparts, with eruptive columns often reaching between 5 and 10 km (3 and 6 mi) high. Lastly, Vulcanian deposits are andesitic to dacitic rather than basaltic.
Initial Vulcanian activity is characterized by a series of short-lived explosions, lasting a few minutes to a few hours and typified by the ejection of volcanic bombs and blocks. These eruptions wear down the lava dome holding the magma down, and it disintegrates, leading to much more quiet and continuous eruptions. Thus an early sign of future Vulcanian activity is lava dome growth, and its collapse generates an outpouring of pyroclastic material down the volcano’s slope.
Peléan eruptions (or nuée ardente) are a type of volcanic eruption, named after the volcano Mount Pelée in Martinique, the site of a massive Peléan eruption in 1902 that is one of the worst natural disasters in history. In Peléan eruptions, a large amount of gas, dust, ash, and lava fragments are blown out the volcano’s central crater, driven by the collapse of rhyolite, dacite, and andesite lava dome collapses that often create large eruptive columns. An early sign of a coming eruption is the growth of a so-called Peléan or lava spine, a bulge in the volcano’s summit preempting its total collapse. The material collapses upon itself, forming a fast-moving pyroclastic flow (known as a block-and-ash flow) that moves down the side of the mountain at tremendous speeds, often over 150 km (93 mi) per hour. These massive landslides make Peléan eruptions one of the most dangerous in the world, capable of tearing through populated areas and causing massive loss of life. The 1902 eruption of Mount Pelée caused tremendous destruction, killing more than 30,000 people and competely destroying the town of St. Pierre, the worst volcanic event in the 20th century.
Peléan eruptions are characterized most prominently by the incandescent pyroclastic flows that they drive. The mechanics of a Peléan eruption are very similar to that of a Vulcanian eruption, except that in Peléan eruptions the volcano’s structure is able to withstand more pressure, hence the eruption occurs as one large explosion rather than several smaller ones.
Plinian eruptions (or Vesuvian) are a type of volcanic eruption, named for the historical eruption of Mount Vesuvius in 79 of Mount Vesuvius that buried the Roman towns of Pompeii and Herculaneum, and specifically for its chronicler Pliny the Younger. The process powering Plinian eruptions starts in the magma chamber, where dissolved volatile gases are stored in the magma. The gases vesiculate and accumulate as they rise through the magma conduit. These bubbles agglutinate and once they reach a certain size (about 75% of the total volume of the magma conduit) they explode. The narrow confines of the conduit force the gases and associated magma up, forming an eruptive column. Eruption velocity is controlled by the gas contents of the column, and low-strength surface rocks commonly crack under the pressure of the eruption, forming a flared outgoing structure that pushes the gases even faster.
These massive eruptive columns are the distinctive feature of a Plinian eruption, and reach up 2 to 45 km (1 to 28 mi) into the atmosphere. The densest part of the plume, directly above the volcano, is driven internally by gas expansion. As it reaches higher into the air the plume expands and becomes less dense, convection and thermal expansion of volcanic ash drive it even further up into the stratosphere. At the top of the plume, powerful prevailing winds drive the plume in a direction away from the volcano.
Plinian eruptions are similar to both Vulcanian and Strombolian eruptions, except that rather than creating discrete explosive events, Plinian eruptions form sustained eruptive columns. They are also similar to Hawaiian lava fountains in that both eruptive types produce sustained eruption columns maintained by the growth of bubbles that move up at about the same speed as the magma surrounding them.
Phreatomagmatic eruptions
Phreatomagmatic eruptions are eruptions that arise from interactions between water and magma. They are driven from thermal contraction (as opposed to magmatic eruptions, which are driven by thermal expansion) of magma when it comes in contact with water. This temperature difference between the two causes violent water-lava interactions that make up the eruption. The products of phreatomagmatic eruptions are believed to be more regular in shape and finer grained than the products of magmatic eruptions because of the differences in eruptive mechanisms.
There is debate about the exact nature of phreatomagmatic eruptions, and some scientists believe that fuel-coolant reactions may be more critical to the explosive nature than thermal contraction. Fuel coolant reactions may fragment the volcanic material by propagating stress waves, widening cracks and increasing surface area that ultimetly lead to rapid cooling and explosive contraction-driven eruptions.
A Surtseyan eruption (or hydrovolcanic) is a type of volcanic eruption caused by shallow-water interactions between water and lava, named so after its most famous example, the eruption and formation of the island of Surtsey off the coast of Iceland in 1963. Surtseyan eruptions are the “wet” equivalent of ground-based Strombolian eruptions, but because of where they are taking place they are much more explosive. This is because as water is heated by lava, it flashes in steam and expands violently, fragmenting the magma it is in contact with into fine-grained ash. Surtseyan eruptions are the hallmark of shallow-water volcanic oceanic islands, however they are not specifically confined to them. Surtseyan eruptions can happen on land as well, and are caused by rising magma that comes into contact with an aquifer (water-bearing rock formation) at shallow levels under the volcano. The products of Surtseyan eruptions are generally oxidized palagonite basalts (though andesitic eruptions do occur, albeit rarely), and like Strombolian eruptions Surtseyan eruptions are generally continuous or otherwise rhythmic.
Submarine eruptions are a type of volcanic eruption that occurs underwater. An estimated 75% of the total volcanic eruptive volume is generated by submarine eruptions near mid ocean ridges alone, however because of the problems associated with detecting deep sea volcanics, they remained virtually unknown until advances in the 1990s made it possible to observe them.
Submarine eruptions may produce seamounts which may break the surface to form volcanic islands and island chains.
Submarine volcanism is driven by various processes. Volcanoes near plate boundaries and mid-ocean ridges are built by the decompression melting of mantle rock that rises on an upwelling portion of a convection cell to the crustal surface. Eruptions associated with subducting zones, meanwhile, are driven by subducting plates that add volatiles to the rising plate, lowering its melting point. Each process generates different rock; mid-ocean ridge volcanics are primarily basaltic, whereas subduction flows are mostly calc-alkaline, and more explosive and viscous.
Subglacial eruptions are a type of volcanic eruption characterized by interactions between lava and ice, often under a glacier. The nature of glaciovolcanism dictates that it occurs at areas of high latitude and high altitude. It has been suggested that subglacial volcanoes that are not actively erupting often dump heat into the ice covering them, producing meltwater. This meltwater mix means that subglacial eruptions often generate dangerous jökulhlaups (floods) and lahars.
The study of glaciovolcanism is still a relatively new field. Early accounts described the unusual flat-topped steep-sided volcanoes (called tuyas) in Iceland that were suggested to have formed from eruptions below ice. The first English-language paper on the subject was published in 1947 by William Henry Mathews, describing the Tuya Butte field in northwest British Columbia, Canada. The eruptive process that builds these structures, originally inferred in the paper, begins with volcanic growth below the glacier. At first the eruptions resemble those that occur in the deep sea, forming piles of pillow lava at the base of the volcanic structure. Some of the lava shatters when it comes in contact with the cold ice, forming a glassy breccia called hyaloclastite. After a while the ice finally melts into a lake, and the more explosive eruptions of Surtseyan activity begins, building up flanks made up of mostly hyaloclastite. Eventually the lake boils off from continued volcanism, and the lava flows become more effusive and thicken as the lava cools much more slowly, often forming columnar jointing. Well-preserved tuyas show all of these stages, for example Hjorleifshofdi in Iceland.
Products of volcano-ice interactions stand as various structures, whose shape is dependent on complex eruptive and environmental interactions. Glacial volcanism is a good indicator of past ice distribution, making it an important climatic marker. Since they are imbedded in ice, as ice retracts worldwide there are concerns that tuyas and other structures may destabalize, resulting in mass landslides. Evidence of volcanic-glacial interactions are evident in Iceland and parts of British Columbia, and it’s even possible that they play a role in deglaciation.
Phreatic eruptions (or steam-blast eruptions) are a type of eruption driven by the expansion of steam. When cold ground or surface water come into contact with hot rock or magma it superheats and explodes, fracturing the surrounding rock and thrusting out a mixture of steam, water, ash, volcanic bombs, and volcanic blocks. The distinguishing feature of phreatic explosions is that they only blast out fragments of pre-existing solid rock from the volcanic conduit; no new magma is erupted. Because they are driven by the cracking of rock stata under pressure, phreatic activity does not always result in an eruption; if the rock face is strong enough to withstand the explosive force, outright eruptions may not occur, although cracks in the rock will probably develop and weaken it, furthering future eruptions.
Often a precursor of future volcanic activity, phreatic eruptions are generally weak, although there have been exceptions. Some phreatic events may be triggered by earthquake activity, another volcanic precursor, and they may also travel along dike lines. Phreatic eruptions form base surges, lahars, avalanches, and volcanic block “rain.” They may also release deadly toxic gas able to suffocate anyone in range of the eruption.
Photos
Eruption type : Hawaiian Looking up the slope of Kilauea, a shield volcano on the island of Hawaii. In the foreground, the Puu Oo vent has erupted fluid lava to the left. The Halemaumau crater is at the peak of Kilauea, visible here as a rising vapor column in the background. The peak behind the vapor column is Mauna Loa, a volcano that is separate from Kilauea.Eruption type: Hawaiian/Strombolian Mt. Stromboli Stromboli is a small island in the Tyrrhenian Sea, off the north coast of SicilyEruption type: Vulcanian Nevado del Ruiz Steam on the mountain in July 2007Eruption type: Plinian/Ultra Plinian Krakatoa or Krakatau or Krakatao is a volcanic island in the Sunda Strait between Java and Sumatra in Indonesia (http://en.wikipedia.org/wiki/Krakatoa).
Aerial view of Back Bay, Boston. Credit: Ornella Iuorio
In 1755, a major earthquake shook the Boston area, toppling chimneys and inspiring sermons and poems about the wrath of God, such as “Earthquakes the Works of God and Tokens of his Just Displeasure” and “The Duty of a People, Under Dark Providences.” The quake, whose epicenter was about 25 miles from Massachusetts’ Cape Anne and 50 miles out to sea from Boston, measured an estimated 6.0 to 6.3 on the Richter scale. Since then, Bostonians have not had to worry much about the ground beneath them. In fact, preparing for earthquakes is probably near the bottom of the city’s to do list. But what if another major earthquake were to strike? According to SUTD-MIT postdoctoral fellow Ornella Iuorio, it would not be good.
Iuorio, who hails from earthquake-prone Italy, is spending one year at MIT, followed by a second year at the Singapore University of Technology and Design (SUTD), carrying out collaborative research with MIT Professor John Ochsendorf and SUTD professor Jeffrey Huang. For a large part of her career, Iuorio has focused on designing resilient new buildings that can withstand seismic events. Now, she is turning her attention to making historic buildings and neighborhoods earthquake-safe, with the ultimate aim of developing a tool that urban planners could use to decide which retrofit options make the most sense in a particular area.
Her project, “Smart Retrofit for Resilient Historic Cities,” is part of a comprehensive case study of Boston’s historic Back Bay neighborhood. Other researchers, including professor and MIT-SUTD International Design Center director John Fernandez and visiting scholar Nino Barbalace, have already begun studying Back Bay with an eye toward environmental retrofits. Therefore, Iuorio and Ochsendorf decided to complement that work by focusing on structural aspects.
Although it may seem unusual to examine earthquake resilience in an area seldom struck by earthquakes, Back Bay is an excellent site for the study. Like many historically valuable and beautiful urban neighborhoods, it is also extremely vulnerable to damage. Back Bay homes were primarily constructed of unreinforced masonry, which crumbles fairly easily. Furthermore, the entire development sits on what was once a mud flat, which was filled over the course of the 19th century. Although filled land is solid enough to build on, it still contains water. When the earth moves, it tends to liquefy. The fill layer can also settle and sink, exposing foundation posts to air and leaving them vulnerable to dry rot. In 1755, Boston’s population was much smaller, and Back Bay did not exist, so the Cape Anne earthquake caused only minor damage. It is estimated that an earthquake of similar magnitude today would cost billions of dollars and hundreds or even thousands of lives.
If planners hope to mitigate destruction in a place like Back Bay, the challenge, as Iuorio sees it, is to balance the various, often competing, factors involved, including safety, economic cost, environmental cost of the retrofit materials, and the historical value of the buildings. There are structural retrofits that can be easily applied, such as chains or fibrous mesh to hold the walls together as a unit. However, such retrofits can be costly, and may destroy some of the historical character of a neighborhood like Back Bay. Iuorio’s model would generate multiple solutions for structural retrofitting depending on the relative weight given to each of the factors. From the various options, city planners could choose the one that makes the most sense for the area in question.
The first phase of this project is a detailed classification of the thousand or so buildings that make up the neighborhood. Iuorio has been combing through old records and conducting on-site inspections to determine the type of construction used in each building, and to analyze potential vulnerabilities. Once this work is complete, she can begin to generate her model of retrofit options. In doing so, she says, it is important to consider the whole neighborhood, not just the individual structures. Since the buildings are directly adjacent, they act as a unit. If one begins to fold, those next to it will be affected as well. Therefore, not all retrofits would be equally effective. Reinforcing a structure at the end of a block, for example, may have more of an impact than reinforcing one in the middle of a row. Her model would make optimal suggestions based on the whole picture.
Will the mayor’s office be clamoring for the results and revising the city’s budget to allocate money for seismic retrofits? That’s unlikely, given the low probability of another major earthquake in the near future and more pressing concerns like snow removal and rising sea levels. However, the data provided by Iuorio’s study of the Back Bay neighborhood and the model she creates could serve other cities seeking to make their historic structures safer. In her second year of research, when she travels to Singapore, she may also apply the principles of her process on a larger scale, analyzing not just one neighborhood, but whole cities.
Scientists have learned a lot about why earthquakes occur since the Cape Anne event in the 18th century, but they still cannot predict when or where the next big quake may happen. Planners must make difficult decisions about how far to go in preparing for the unknown, and Iuorio is trying to make that process a little bit easier.
Chronic beach erosion is a global problem. Modeling now indicates that, in Hawai’i, increased sea level rise associated with the climate crisis may cause a doubling of this problem by mid-century. Credit: C. Fletcher, UH SOEST.
Chronic erosion dominates the sandy beaches of Hawai’i, causing beach loss as it damages homes, infrastructure, and critical habitat. Researchers have long understood that global sea level rise will affect the rate of coastal erosion. However, new research from scientists at the University of Hawaii – M?noa (UHM) and the Hawai’i Department of Land and Natural Resources brings into clearer focus just how dramatically Hawai’i beaches might change.
For the study, published this week in Natural Hazards, the research team developed a simple model to assess future erosion hazards under higher sea levels – taking into account historical changes of Hawai’i shorelines and the projected acceleration of sea level rise reported from the Intergovernmental Panel on Climate Change (IPCC). The results indicate that coastal erosion of Hawai’i’s beaches may double by mid-century.
Like the majority of Hawaii’s sandy beaches, most shorelines at the 10 study sites on Kauai, Oahu, and Maui are currently retreating. If these beaches were to follow current trends, an average 20 to 40 feet of shoreline recession would be expected by 2050 and 2100, respectively.
“When we modeled future shoreline change with the increased rates of sea level rise (SLR) projected under the IPCC’s “business as usual” scenario, we found that increased SLR causes an average 16 – 20 feet of additional shoreline retreat by 2050, and an average of nearly 60 feet of additional retreat by 2100,” said Tiffany Anderson, lead author and post-doctoral researcher at the UHM School of Ocean and Earth Science and Technology.
“This means that the average amount of shoreline recession roughly doubles by 2050 with increased SLR, compared to historical extrapolation alone. By 2100, it is nearly 2.5 times the historical extrapolation. Further, our results indicate that approximately 92% and 96% of the shorelines will be retreating by 2050 and 2100, respectively, except at Kailua, Oahu which is projected to begin retreating by mid-century.”
The model accounts for accretion of sand onto beaches and long-term sediment processes in making projections of future shoreline position. As part of ongoing research, the resulting erosion hazard zones are overlain on aerial photos and other geographic layers in a geographic information system to provide a tool for identifying resources, infrastructure, and property exposed to future coastal erosion.
“This study demonstrates a methodology that can be used by many shoreline communities to assess their exposure to coastal erosion resulting from the climate crisis,” said Chip Fletcher, Associate Dean at the UHM School of Ocean and Earth Science and Technology and co-author on the paper.
Mapping historical shoreline change provides useful data for assessing exposure to future erosion hazards, even if the rate of sea level rise changes in the future. The predicted increase in erosion will threaten thousands of homes, many miles of roadway and other assets in Hawai’i. Globally the asset exposure to erosion is enormous.
“With these new results government agencies can begin to develop adaptation strategies, including new policies, for safely developing the shoreline,” said Anderson.
To further improve the estimates of climate impacts, the next step for the team of researchers will be to combine the new model with assessments of increased flooding by waves.
The research was sponsored by the Hawaii Department of Land and Natural Resources, and the U.S. Geological Survey Pacific Islands Climate Science Center.
Reference:
Tiffany R. Anderson, Charles H. Fletcher, Matthew M. Barbee, L. Neil Frazer & Bradley M. Romine (2015). Doubling of coastal erosion under rising sea level by mid-century in Hawai’i. Natural Hazards doi:10.1007/s11069-015-1698-6
Map of the Amazon Basin with the Japurá River highlighted
The Japurá River or Caquetá River is a river about 2,820 kilometres (1,750 mi) long rising as the Caquetá River in the Andes in the Southwet of Colombia. It flows southeast into Brazil, where it is called the Japurá. The Japurá enters the Amazon River through a network of channels. It is navigable by small boats in Brazil.
The river is home to a wide variety of fish and reptiles, including enormous catfish weighing up to 91 kg (201 lb) and measuring up to 1.8 metres (5.9 ft) in length, electric eels, piranhas, turtles, and caimans. It also serves as a principal means of transportation, being plied by tiny dugout canoes, larger ones, motorboats, and riverboats known locally as lanchas. The boats carry a multitude of cargoes, sometimes being chartered, sometimes even being traveling general stores. In the Colombian section, the presence of guerrillas and soldiers often severely limits river traffic.
Much of the jungle through which the eastern Caquetá originally flowed has been cleared for pasture, crops of rice, corn, manioc, and sugar cane, and in the past two decades, particularly coca crops.
West of the Rio Negro, the Solimões River (as the Amazon’s upper Brazilian course is called) receives three more imposing streams from the northwest—the Japurá, the Içá (referred to as the Putumayo before it crosses over into Brazil), and the Napo. The Caquetá River, later to become the Japurá, rises in the Colombian Andes, nearly in touch with the sources of the Magdalena River, and augments its volume from many branches as it courses through Colombia.
The 19th-century Brazilian historian and geographer José Coelho da Gama e Abreu, the Baron of Marajó, attributed 970 kilometres (600 mi) of navigable stretches to it. Jules Crevaux, who descended it, described it as full of obstacles to navigation, the current very strong and the stream frequently interrupted by rapids and cataracts. It was initially supposed to have eight mouths, but colonial administrator Francisco Xavier Ribeiro Sampaio, in the historic report of his voyage of 1774, determined that there was but one real mouth, and that the supposed others are all furos or canos, as the diverting secondary channels of the Amazonian rivers are known.
In 1864–1868, the Brazilian government made a somewhat careful examination of the Brazilian part of the river, as far up as the rapid of Cupati. Several very easy and almost complete water routes exist between the Japurá and Negro across the low, flat intervening country. The Baron of Marajó wrote that there were six of them, and one which connects the upper Japurá with the Vaupés branch of the Negro; thus the indigenous tribes of the respective valleys have easy contact with each other.
Note : The above story is based on materials provided by Wikipedia.
A simplified image of a slab from one of Earth’s tectonic plates sinking through the upper mantle above, through the boundary between the upper and lower mantle 410 miles deep, then stalling and pooling at a depth of 930 miles, where University of Utah experiments suggest the existence of an extremely stiff or viscous layer in Earth. Such a layer may explain why tectonic plate slabs seem to pool at 930 miles under Indonesia and South America’s Pacific coast. Below the highly viscous zone, slabs can continue to sink to the core-mantle boundary. Credit: Lowell Miyagi, University of Utah
By crushing minerals between diamonds, a University of Utah study suggests the existence of an unknown layer inside Earth: part of the lower mantle where the rock gets three times stiffer. The discovery may explain a mystery: why slabs of Earth’s sinking tectonic plates sometimes stall and thicken 930 miles underground.
The findings – published today in the journal Nature Geoscience – also may explain some deep earthquakes, hint that Earth’s interior is hotter than believed, and suggest why partly molten rock or magmas feeding midocean-ridge volcanoes such as Iceland’s differ chemically from magmas supplying island volcanoes like Hawaii’s.
“The Earth has many layers, like an onion,” says Lowell Miyagi, an assistant professor of geology and geophysics at the University of Utah. “Most layers are defined by the minerals that are present. Essentially, we have discovered a new layer in the Earth. This layer isn’t defined by the minerals present, but by the strength of these minerals.”
Earth’s main layers are the thin crust 4 to 50 miles deep (thinner under oceans, thicker under continents), a mantle extending 1,800 miles deep and the iron core. But there are subdivisions. The crust and some of the upper mantle form 60- to 90-mile-thick tectonic or lithospheric plates that are like the top side of conveyor belts carrying continents and seafloors.
Oceanic plates collide head-on with continental plates offshore from Chile, Peru, Mexico, the Pacific Northwest, Alaska, Kamchatka, Japan and Indonesia. In those places, the leading edge of the oceanic plate bends into a slab that dives or “subducts” under the continent, triggering earthquakes and volcanism as the slabs descend into the mantle, which is like the bottom part of the conveyor belt. The subduction process is slow, with a slab averaging roughly 300 million years to descend, Miyagi estimates.
Miyagi and fellow mineral physicist Hauke Marquardt, of Germany’s University of Bayreuth, identified the likely presence of a superviscous layer in the lower mantle by squeezing the mineral ferropericlase between gem-quality diamond anvils in presses. They squeezed it to pressures like those in Earth’s lower mantle. Bridgmanite and ferropericlase are the dominant minerals in the lower mantle.
The researchers found that ferropericlase’s strength starts to increase at pressures equivalent to those 410 miles deep – the upper-lower mantle boundary – and the strength increases threefold by the time it peaks at pressure equal to a 930-mile depth.
And when they simulated how ferropericlase behaves mixed with bridgmanite deep underground in the upper part of the lower mantle, they calculated that the viscosity or stiffness of the mantle rock at a depth of 930 miles is some 300 times greater than at the 410-mile-deep upper-lower mantle boundary.
“The result was exciting,” Miyagi says. “This viscosity increase is likely to cause subducting slabs to get stuck – at least temporarily – at about 930 miles underground. In fact, previous seismic images show that many slabs appear to ‘pool’ around 930 miles, including under Indonesia and South America’s Pacific coast. This observation has puzzled seismologists for quite some time, but in the last year, there is new consensus from seismologists that most slabs pool.”
How stiff or viscous is the viscous layer of the lower mantle? On the pascal-second scale, the viscosity of water is 0.001, peanut butter is 200 and the stiff mantle layer is 1,000 billion billion (or 10 to the 21st power), Miyagi says.
Slab subduction triggers earthquakes and volcanoes
For the new study, Miyagi’s funding came from the U.S. National Science Foundation and Marquardt’s from the German Science Foundation.
“Plate motions at the surface cause earthquakes and volcanic eruptions,” Miyagi says. “The reason plates move on the surface is that slabs are heavy, and they pull the plates along as they subduct into Earth’s interior. So anything that affects the way a slab subducts is, up the line, going to affect earthquakes and volcanism.”
He says the stalling and buckling of sinking slabs at due to a stiff layer in the mantle may explain some deep earthquakes higher up in the mantle; most quakes are much shallower and in the crust. “Anything that would cause resistance to a slab could potentially cause it to buckle or break higher in the slab, causing a deep earthquake.”
Miyagi says the stiff upper part of the lower mantle also may explain different magmas seen at two different kinds of seafloor volcanoes
Recycled crust and mantle from old slabs eventually emerges as new seafloor during eruptions of volcanic vents along midocean ridges – the rising end of the conveyor belt. The magma in this new plate material has the chemical signature of more recent, shallower, well-mixed magma that had been subducted and erupted through the conveyor belt several times. But in island volcanoes like Hawaii, created by a deep hotspot of partly molten rock, the magma is older, from deeper sources and less well-mixed.
Miyagi says the viscous layer in the lower mantle may be what separates the sources of the two different magmas that supply the two different kinds of volcanoes.
Another implication of the stiff layer is that “if you decrease the ability of the rock in the mantle to mix, it’s also harder for heat to get out of the Earth, which could mean Earth’s interior is hotter than we think,” Miyagi says.
He says scientists believe the average temperature and pressure 410 miles deep at the upper-lower mantle boundary is 2,800 degrees Fahrenheit and 235,000 times the atmospheric pressure on Earth’s surface. He calculates that at the viscous layer’s stiffest area, 930 miles deep, the temperature averages 3,900 degrees Fahrenheit and pressure is 640,000 times the air pressure at Earth’s surface.
Studying Earth’s interior by squeezing crystals
Such conditions prevent geophysicists from visiting Earth’s mantle, so “we know a lot more about the surface of Mars than we do Earth’s interior,” Miyagi says. “We can’t get down there, so we have to do experiments to see how these minerals behave under a wide range of conditions, and use that to simulate the behavior of the Earth.”
To do that, “you take two gem quality diamonds and trap a sample between the tips,” he says. “The sample is about the diameter of a human hair. Because the diamond tips are so small, you generate very high pressure just by turning the screws on the press by hand with Allen wrenches.”
Using diamond anvils, the researchers squeezed thousands of crystals of ferropericlase at pressures up to 960,000 atmospheres. They used ferropericlase with 10 percent and 20 percent iron to duplicate the range found in the mantle.
To observe and measure the spacing of atoms in ferropericlase crystals as they were squeezed in diamond anvils, the geophysicists bombarded the crystals with X-rays from an accelerator at Lawrence Berkeley National Laboratory in California, revealing the strength of the mineral at various pressures and allowing the simulations showing how the rock becomes 300 times more viscous at the 930-mile depth than at 410 miles.
The finding was a surprise because researchers previously believed that viscosity varied only a little bit at temperatures and pressures in the planet’s interior.
The study’s simulations also determined that just below the 930-mile-deep zone of highest viscosity, slabs sink more easily again as the lower mantle becomes less stiff, which happens because atoms can move more easily within ferropericlase crystals.
Descending slabs have been seen as deep as the core-mantle boundary 1,800 miles underground. As the bottom of the conveyor-belt-like mantle slowly moves, the slabs mix with the surrounding rock before the mixture erupts anew millions of years later and thousands of miles away at midocean ridges.
Reference:
Hauke Marquardt, Lowell Miyagi. Slab stagnation in the shallow lower mantle linked to an increase in mantle viscosity. Nature Geoscience, 2015; DOI: 10.1038/ngeo2393
A rare early copy of William Smith’s 1815 Geological Map of England and Wales, previously thought lost, has been uncovered by Geological Society archivists. The new map has been digitised and made available online in time for the start of celebrations of the map’s 200th anniversary, beginning with an unveiling of a plaque at Smith’s former residence by Sir David Attenborough.
The map, the first geological map of a nation ever produced, shows the geological strata of England, Wales and part of Scotland. The newly discovered copy is thought to have been one of the first ten produced by William Smith (1769-1839), who went on to produce an estimated 370 hand-coloured copies of the map in his lifetime.
Now fully restored and digitised, images of the new map can be viewed on the Geological Society’s image library from March 23 — William Smith’s birthday. It will also be on display at the Geological Society during a number of events celebrating the map’s bicentennial.
Often called ‘the Father of English Geology’, William Smith pioneered the science of stratigraphy and geological mapping. His map of England and Wales became the basis for all future geological maps of Britain, and influenced geological surveys around the world.
‘Smith’s importance to the history of our science cannot be overstated’ says John Henry, Chair of the Geological Society’s History of Geology Group. ‘His map is a remarkable piece of work. It helped shape the economic and scientific development of Britain, at a time before geological surveys existed.’
Smith’s story was popularised by Simon Winchester’s 2001 book, ‘The Map that Changed the World’, which tells the story of his relationship with the Geological Society, who produced their own geological map of Britain in 1820.
‘These maps are extremely rare’ says Henry. ‘Each one is a treasure, and to have one of the very first produced is tremendously exciting.’
Although it is difficult to estimate the value of individual William Smith maps, an early copy was recently made available for sale at £150,000. The newly discovered map was found by the Society’s then Archive Assistant Victoria Woodcock in 2014, during an audit of the Society’s archives led by Geological Society Archivist Caroline Lam.
‘The map was found among completely unrelated material, so at first I didn’t realise the significance of what I’d uncovered’ says Woodcock. ‘Once we had worked out that it was an early copy of one of the earliest geological maps ever made, I was astonished. It’s the kind of thing that anyone working in archives dreams of, and definitely the highlight of my career so far!’
The map was identified as a first edition due to its lack of serial number, and geological features which Smith was known to have updated on later versions.
‘The very first batch of maps Smith produced did not have a series number or signature’ says Henry. ‘Other indications that it is a first edition is the geology depicted on the Isle of Wight, the lack of an engraved line on the Welsh border, and lack of granite around Eskdale in the Lake District.’
Records of the Geological Society’s Council minutes from 1815 suggest the map was purchased by the Society in that year for the sum of £5 5s. Since then, its ‘disappearance’ means it has rarely been exposed to light, preserving the incredibly bright original colours.
A number of organisations, including the Geological Society, the Natural History Museum, the British Geological Survey and National Museum Wales, are joining together throughout 2015 to celebrate the bicentennial of William Smith’s map through a range of events.
‘We’re incredibly excited by the discovery’ says Geological Society President Professor David Manning. ‘It’s wonderful that the map has been restored and made publicly available in time for the bicentennial celebrations, and we’re very grateful to the sponsors who have made this possible.’
Ten Sentinel-1A radar scans acquired between 7 October 2014 and 12 March 2015 were combined to create this image of ground deformation around the city of Naples, which includes the active volcanic areas of Italy’s Phlegraean Fields – or Campi Flegrei – and the Vesuvius volcano. Dark blue indicates areas that experienced an uplift of about 0.5 cm per month, while red areas show subsidence down to 0.5 per month. The purple square over the city of Naples indicates the location of the calibration point. Credit: Copernicus data (2015)/ESA/DLR Microwaves and Radar Institute/INGV/e-GEOS/GFZ–SEOM INSARAP study
Scientists are making advances in the use of satellite radar data – such as those from the Sentinel-1 mission – to monitor Earth’s changing surface.
Italy’s Phlegraean Fields – or Campi Flegrei – is a large, active volcanic area near the city of Naples and Mount Vesuvius, characterised by continuous ground deformations owing to its volcanic nature.
“In 2012, deformation rates up to 3 cm a month prompted the Italian Civil Protection Department to move from the base (green) alert level of the Campi Flegrei Emergency Plan to the attention (yellow) level,” said Sven Borgstrom from Italy’s National Institute for Geophysics and Volcanology.
“The uplift continues today: radar imagery from the Sentinel-1A satellite captured over the area between October 2014 and March 2015 show that the ground is rising by about 0.5 cm per month.”
This is just one of the many findings being presented this week at the Fringe Workshop on advances in the science and applications of ‘SAR interferometry’ held at ESRIN, ESA’s centre for Earth observation, in Frascati, Italy.
Interferometric Synthetic Aperture Radar, or InSAR, is a remote sensing technique where two or more images of the same area are combined to detect slight changes occurring between acquisitions.
Tiny changes on the ground cause changes in the radar signal and lead to rainbow-coloured interference patterns in the combined image, known as an ‘interferogram’.
The Fringe Workshop takes its name from these coloured fringes seen in the interferograms.
Small movements – down to a scale of a few millimetres – can be detected across wide areas. Tectonic plates grinding past one another, the slow ‘breathing’ of active volcanoes, the slight sagging of a city street through groundwater extraction, and even the thermal expansion of a building on a sunny day.
This year, the workshop is paying particular attention to new results from the Sentinel-1 mission. Launched in April of last year, Sentinel-1A became the first satellite in orbit for Europe’s Copernicus programme, and has been delivering important data for an array of operational and scientific applications.
In Norway’s Svalbard archipelago, Sentinel-1 data are being used to monitor ice loss from the Austfonna ice cap. Earlier this year, the satellite captured the ice cap’s outlet glacier flowing at 3 cm per day.
With over 420 participants, this year’s Fringe workshop has seen the largest turnout since its inauguration in 1991 – when four specialists met to discuss the early InSAR results from the ERS-1 mission. Radar interferometry has come a long way since, with contributions from satellites such as Envisat and now Sentinel-1A.
Satellite radar image of the magnitude 6.0 South Napa earthquake. The “fringe” rainbow pattern appears where the earthquake deformed the ground’s surface, with one full cycle of the color spectrum (magenta to magenta) showing 3 centimeters of change. Satellite data like this can now be used to give researchers an understanding of an earthquake and its impacts within days. Photo courtesy of the European Space Agency.
When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure—and lives—can be saved.
New research from the University of Iowa, along with the United States Geological Survey (USGS), shows that GPS and satellite data can be used in a real-time, coordinated effort to fully characterize a fault line within 24 hours of an earthquake, ensuring that aid is delivered faster and more accurately than ever before.
Earth and Environmental Sciences assistant professor William Barnhart used GPS and satellite measurements from the magnitude 6.0 South Napa, California earthquake on August 24, 2014, to create a three-dimensional map of how the ground surface moved in response to the earthquake. The map was made without using traditional rapid response instruments, such as seismometers, which may not afford the same level of detail for similar events around the globe.
“By having the 3D knowledge of the earthquake itself, we can make predictions of the ground shaking, without instruments to record that ground shaking, and then can make estimates of what the human and infrastructure impacts will be— in terms of both fatalities and dollars,” Barnhart says.
The study, “Geodetic Constraints on the 2014 M 6.0 South Napa Earthquake” published in the March/April edition of Seismological Research Letters, is the first USGS example showing that GPS and satellite readings can be used as a tool to shorten earthquake response times.
And while information about an earthquake’s impact might be immediately known in an area such as southern California, Barnhart says the technique will be most useful in the developing world. The catastrophic magnitude 7.0 earthquake that hit Haiti in 2010 is the perfect example for the usefulness of this kind of tool, Barnhart says. The earthquake struck right under the capital city of Port Au Prince, killing up to 316,000 people, depending on estimates, and costing billions of dollars in aid.
“On an international scale, it dramatically reduces the time between when an earthquake happens, when buildings start to fall down, and when aid starts to show up,” Barnhart says.
To accurately map the South Napa earthquake for this study, Barnhart and a team of researchers created a complex comparison scenario.
They first used GPS and satellite readings to measure the very small- millimeter-to-centimeter-sized-displacements of the ground’s surface that were caused by the earthquake. They fed those measurements into a mathematical equation that inverts the data and relates how much the ground moved to the degree of slip on the fault plane. Slip describes the amount, timing, and distribution of fault plane movement during an earthquake.
This allowed the group to determine the location, orientation, and dimensions of the entire fault without setting foot on the ground near the earthquake. The mathematical inversion gave the researchers predictions of how much the ground might be displaced, and they compared those results to their initial estimations, bit by bit, until their predictions and observations match. The resulting model is a 3D map of fault slip beneath the Earth’s surface. The entire procedure takes only a few minutes to complete.
Nationally, there is a push to create an earthquake early-warning system, which is already being tested internally by the USGS in coordination with the University of California, Berkeley; the California Institute of Technology; and the University of Washington. While only researchers, first responders, and other officials received the early warning message, it did work in testing for the Bay Area during the Napa earthquake. Individuals in Berkeley received nearly 10 seconds of advanced warning before the ground began shaking. The information contained in Barnhart’s study could be used to create further tools for predicting the economic and human tolls of earthquakes.
“That’s why this is so important. It really was the chance to test all these tools that have been put into place,” Barnhart says. “It happened in a perfect place, because now we’re much more equipped for a bigger earthquake.”
Metoposaurus algarvensis. Credit: Marc Boulay, Cossima Productions
A previously undiscovered species of crocodile-like amphibian that lived during the rise of dinosaurs was among Earth’s top predators more than 200 million years ago, a study shows.
Palaeontologists identified the prehistoric species – which looked like giant salamanders – after excavating bones buried on the site of an ancient lake in southern Portugal.
The species was part of a wider group of primitive amphibians that were widespread at low latitudes 220-230 million years ago, the team says.
The creatures grew up to 2m in length and lived in lakes and rivers during the Late Triassic Period, living much like crocodiles do today and feeding mainly on fish, researchers say.
The species – Metoposaurus algarvensis – lived at the same time as the first dinosaurs began their dominance, which lasted for over 150 million years, the team says. These primitive amphibians formed part of the ancestral stock from which modern amphibians – such as frogs and newts – evolved, researchers say.
The species were distant relatives of the salamanders of today, the team says. The discovery reveals that this group of amphibians was more geographically diverse than previously thought.
The species is the first member of the group to be discovered in the Iberian Peninsula, the team says.
Fossil remains of species belonging to the group have been found in parts of modern day Africa, Europe, India and North America. Differences in the skull and jaw structure of the fossils found in Portugal revealed they belong to a separate species.
The new species was discovered in a large bed of bones where up to several hundred of the creatures may have died when the lake they inhabited dried up, researchers say. Only a fraction of the site – around 4 square meters – has been excavated so far, and the team is continuing work there in the hope of unearthing new fossils.
Most members the group of giant salamander-like amphibians was wiped out during a mass extinction 201 million years ago, long before the death of the dinosaurs. This marked the end of the Triassic Period, when the supercontinent of Pangea – which included all the world’s present-day continents – began to break apart. The extinction wiped out many groups of vertebrates, such as big amphibians, paving the way for dinosaurs to become dominant.
The study, published in the Journal of Vertebrate Paleontology, was funded by the German Research Foundation and the National Science Foundation, the Jurassic Foundation, CNRS, Columbia University Climate Center and the Chevron Student Initiative Fund. Additional support was provided by the Municipality of Loulé, Camara Municipal de Silves and Junta de Freguesia de Salir in Portugal.
Dr Steve Brusatte, of the University of Edinburgh’s School of GeoSciences, who led the study, said: “This new amphibian looks like something out of a bad monster movie. It was as long as a small car and had hundreds of sharp teeth in its big flat head, which kind of looks like a toilet seat when the jaws snap shut. It was the type of fierce predator that the very first dinosaurs had to put up with if they strayed too close to the water, long before the glory days of T. rex and Brachiosaurus.”
Dr Richard Butler, of the School of Geography, Earth and Environmental Sciences at the University of Birmingham, said: “Most modern amphibians are pretty tiny and harmless. But back in the Triassic these giant predators would have made lakes and rivers pretty scary places to be.”
Dr Steve Brusatte will discuss his work on recently discovered species and other aspects of palaeontology at a series of events at the Edinburgh International Science Festival, which runs from 4-19 April.
