Earth’s icehouse conditions of the last several million years were driven laergely by geologically low values of atmospheric carbon dioxide. Credit: University of Oklahoma
A University of Oklahoma-led study recently found that explosive volcanic eruptions were at least 3-8 times more frequent during the peak of the Late Paleozoic Ice Age (~360 to 260 million years ago). Aerosols produced by explosive volcanism helped keep large ice sheets stable, even when CO2 levels increased, by blocking sunlight. But the volcanic emissions also may have started a cascade of effects on the climate system that resulted in additional CO2 removal from the atmosphere.
“The lessons from this period shed light on a spectrum of outcomes as we move forward on Earth with increasing levels of CO2. Stratospheric aerosol geoengineering increasingly is discussed as a way to mitigate climate change today, but the intended outcomes may lead to unintended consequences,” said Gerilyn (Lynn) S. Soreghan, professor and director of the School of Geology and Geophysics, Mewbourne College of Earth and Energy.
Earth’s climate has fluctuated between icehouse and greenhouse states that are defined by the presence or absence of ice sheets. During the LPIA, frequent explosive volcanism is thought to have caused increased reflection of sunlight, and increased atmospheric acidity, enhancing the reactivity of iron in abundant volcanic ash and glacially generated mineral dust, thus strengthening the climate impact of volcanism. Stimulation of phytoplankton growth in the oceans owing to iron fertilization contributed to CO2 drawdown, helping to sustain icehouse conditions.
In this study, geologic data were integrated with radiative calculations to explore the hypothesis that the onset, acme and prolonged extent of the LPIA was driven by unusually intense explosive volcanism prevalent during the tectonic assembly of Pangaea, operating in concert with CO2 and indirect forcings related to volcanism. Data on volcanic aerosols were compiled globally over ~400 to 200 million years ago.
Explosive volcanism during this time interval peaked approximately 310-290 million years ago, right on time to keep climate cool and support CO2 uptake in the ocean as other CO2 sinks like weathering of tropical mountains and verdant tropical rainforests decreased owing to increasingly arid conditions across Europe and North America.
The Carlin-type gold deposits in Nevada, USA, are the origin of five percent of the global production and 75 percent of the US production of gold. In these deposits, gold does not occur in the form of nuggets or veins, but is hidden — together with arsenic — in pyrite, also known as ‘fool’s gold’. A team of scientists from the Helmholtz Centre Potsdam — German Research Centre for Geosciences GFZ has now shown experimentally, for the first time, that the concentration of gold directly depends on the content of arsenic in the pyrite. The results were published in the journal Science Advances.
In the Earth’s crust, the element gold occurs in concentrations of 2.5 parts per billion (ppb). In order to mine it economically, the gold concentration must be thousands of times higher and it must be found in a focused area close to the surface. In the gold deposits of the Carlin-type, the gold in the rock is not visible to the human eye. Instead, the ‘invisible’ gold occurs in tiny pyrite rims that grow on older ‘fool’s gold’ grains which originate from sedimentary rocks. ” Recommended: States With Gold : Where Are Gold Mines In The United States? “
In the laboratory experiments, the researchers around Christof Kusebauch, lead author of the study showed that the element arsenic plays the crucial role in extracting gold from hot solutions probably from magmatic systems, passing through the rock. The higher the concentration of arsenic, the more frequently gold chemically binds with pyrite. The shape of the older pyrite is also important: the larger the surface area of the mineral, the more gold can accumulate.
Arsenic indicates gold deposits
Similar to the natural ore system, the authors used iron-rich carbonates and sulfur-rich solutions to synthesize their ‘fool´s gold’ crystals. “Only then we were able to show that the partition coefficient which controls how much gold is incorporated into pyrite depends on the amount of arsenic,” says Christof Kusebauch. “The major challenge was to experimentally grow gold and arsenic bearing pyrite crystals that were big enough to analyze.”
The new findings may also help to track down new gold deposits. The experiments show that if hot solutions containing gold and arsenic from magmatic sources pass through sedimentary rocks with large amounts of small ‘fools gold’ grains present, large gold deposits can be formed. ” Recommended: Mining : What Is Gold Mining? How Is Gold Mined? “
Background
What is gold? Gold is a chemical element of the copper group with the element symbol Au (from Latin: Aurum). In contrast to most other metals in nature, gold is mostly found in the pure form, meaning in the form of ‘nuggets‘ composed only of one chemical substance.
In contrast, in the Carlin-type gold deposits, gold must be released from ore by chemical extraction. Here, the gold is bound to the ore mineral pyrite and has whole rock concentrations between one and tens of grams per ton of rock material (1000 to 10.000 ppb). This type of gold deposit is formed in carbonate-rich sediments. The deposits in the US formed 42 to 30 million years ago at temperatures of 150 to 250 degree Celsius and at depths of over 2000 meters, before they reached the Earth’s surface through processes of plate tectonics.
How is gold formed? On the Earth’s surface accessible to mankind, gold has been transported from the Earth’s interior to the surface by volcanic and plate tectonic processes; a small part stems from meteorite impacts. Natural processes cannot produce new gold on Earth. The heavy chemical elements in the universe, such as lead, iron, and gold, are created by the collision of neutron stars. Gold is very rare, not only on Earth but throughout the universe.
Reference:
Kusebauch, C., Gleeson, S.A., Oelze, M. Coupled partitioning of Au and As into pyrite controls formation of giant Au deposits. Science Advances, 2019 DOI: 10.1126/sciadv.aav5891
The newly described millipede (Burmanopetalum inexpectatum) seen in amber. Credit: Leif Moritz
Even though we are led to believe that during the Cretaceous the Earth used to be an exclusive home for fearsome giants, including carnivorous velociraptors and arthropods larger than a modern adult human, it turns out that there was still room for harmless minute invertebrates measuring only several millimetres.
Such is the case of a tiny millipede of only 8.2 mm in length, recently found in 99-million-year-old amber in Myanmar. Using the latest research technologies, the scientists concluded that not only were they handling the first fossil millipede of the order (Callipodida) and also the smallest amongst its contemporary relatives, but that its morphology was so unusual that it drastically deviated from its contemporary relatives.
As a result, Prof. Pavel Stoev of the National Museum of Natural History (Bulgaria) together with his colleagues Dr. Thomas Wesener and Leif Moritz of the Zoological Research Museum Alexander Koenig (Germany) had to revise the current millipede classification and introduce a new suborder. To put it in perspective, there have only been a handful of millipede suborders erected in the last 50 years. The findings are published in the open-access journal ZooKeys.
To analyse the species and confirm its novelty, the scientists used 3D X-ray microscopy to ‘slice’ through the Cretaceous specimen and look into tiny details of its anatomy, which would normally not be preserved in fossils. The identification of the millipede also presents the first clue about the age of the order Callipodida, suggesting that this millipede group evolved at least some 100 million years ago. A 3D model of the animal is also available in the research article.
Curiously, the studied arthropod was far from the only one discovered in this particular amber deposit. On the contrary, it was found amongst as many as 529 millipede specimens, yet it was the sole representative of its order. This is why the scientists named it Burmanopetalum inexpectatum, where “inexpectatum” means “unexpected” in Latin, while the generic epithet (Burmanopetalum) refers to the country of discovery (Myanmar, formerly Burma).
Lead author Prof. Pavel Stoev says:
We were so lucky to find this specimen so well preserved in amber! With the next-generation micro-computer tomography (micro-CT) and the associated image rendering and processing software, we are now able to reconstruct the whole animal and observe the tiniest morphological traits which are rarely preserved in fossils. This makes us confident that we have successfully compared its morphology with those of the extant millipedes. It came as a great surprise to us that this animal cannot be placed in the current millipede classification. Even though their general appearance have remained unchanged in the last 100 million years, as our planet underwent dramatic changes several times in this period, some morphological traits in Callipodida lineage have evolved significantly.
Co-author Dr. Thomas Wesener adds:
“We are grateful to Patrick Müller, who let us study his private collection of animals found in Burmese amber and dated from the Age of Dinosaurs. His is the largest European and the third largest in the world collection of the kind. We had the opportunity to examine over 400 amber stones that contain millipedes. Many of them are now deposited at the Museum Koenig in Bonn, so that scientists from all over the world can study them. Additionally, in our paper, we provide a high-resolution computer-tomography images of the newly described millipede. They are made public through MorphBank, which means anyone can now freely access and re-use our data without even leaving the desk.”
Leading expert in the study of fossil arthropods Dr. Greg Edgecombe (Natural History Museum, London) comments:
“The entire Mesozoic Era — a span of 185 million years — has until now only been sampled for a dozen species of millipedes, but new findings from Burmese amber are rapidly changing the picture. In the past few years, nearly all of the 16 living orders of millipedes have been identified in this 99-million-year-old amber. The beautiful anatomical data presented by Stoev et al. show that Callipodida now join the club.”
Reference:
Pavel Stoev, Leif Moritz, Thomas Wesener. Dwarfs under dinosaur legs: a new millipede of the order Callipodida (Diplopoda) from Cretaceous amber of Burma. ZooKeys, 2019; 841: 79 DOI: 10.3897/zookeys.841.34991
Note: The above post is reprinted from materials provided by Pensoft Publishers. The original story is licensed under a Creative Commons License.
Caudipteryx robot for testing passive flapping flight. Credit: Talori et al.
Before they evolved the ability to fly, two-legged dinosaurs may have begun to flap their wings as a passive effect of running along the ground, according to new research by Jing-Shan Zhao of Tsinghua University, Beijing, and his colleagues.
The findings, published in PLOS Computational Biology, provide new insights into the origin of avian flight, which has been a point of debate since the 1861 discovery of Archaeopteryx. While a gliding type of flight appears to have matured earlier in evolutionary history, increasing evidence suggests that active flapping flight may have arisen without an intermediate gliding phase.
To examine this key point in evolutionary history, Zhao and his colleagues studied Caudipteryx, the most primitive, non-flying dinosaur known to have had feathered “proto-wings.” This bipedal animal would have weighed around 5 kilograms and ran up to 8 meters per second.
First, the researchers used a mathematical approach called modal effective mass theory to analyze the mechanical effects of running on various parts of Caudipteryx’s body. These calculations revealed that running speeds between about 2.5 to 5.8 meters per second would have created forced vibrations that caused the dinosaur’s wings to flap.
Real-world experiments provided additional support for these calculations. The scientists built a life-size robot of Caudipteryx that could run at different speeds, and confirmed that running caused a flapping motion of the wings. They also fitted a young ostrich with artificial wings and found that running indeed caused the wings to flap, with longer and larger wings providing a greater lift force.
“Our work shows that the motion of flapping feathered wings was developed passively and naturally as the dinosaur ran on the ground,” Zhao says. “Although this flapping motion could not lift the dinosaur into the air at that time, the motion of flapping wings may have developed earlier than gliding.”
Zhao says that the next step for this research is to analyze the lift and thrust of Caudipteryx’s feathered wings during the passive flapping process.
Reference:
Yaser Saffar Talori, Jing-Shan Zhao, Yun-Fei Liu, Wen-Xiu Lu, Zhi-Heng Li, Jingmai Kathleen O’Connor. Identification of avian flapping motion from non-volant winged dinosaurs based on modal effective mass analysis. PLOS Computational Biology, 2019; 15 (5): e1006846 DOI: 10.1371/journal.pcbi.1006846
Note: The above post is reprinted from materials provided by PLOS.
Snapshots of numerical modeling of the moon’s formation by a giant impact. The central part of the image is a proto-Earth; red points indicate materials from the ocean of magma in a proto-Earth; blue points indicate the impactor materials. Credit: Hosono, Karato, Makino, and Saitoh
For more than a century, scientists have squabbled over how Earth’s moon formed. But researchers at Yale and in Japan say they may have the answer.
Many theorists believe a Mars-sized object slammed into the early Earth, and material dislodged from that collision formed the basis of the moon. When this idea was tested in computer simulations, it turned out that the moon would be made primarily from the impacting object. Yet the opposite is true; we know from analyzing rocks brought back from Apollo missions that the moon consists mainly of material from Earth.
A new study published April 29 in Nature Geoscience, co-authored by Yale geophysicist Shun-ichiro Karato, offers an explanation.
The key, Karato says, is that the early, proto-Earth — about 50 million years after the formation of the Sun — was covered by a sea of hot magma, while the impacting object was likely made of solid material. Karato and his collaborators set out to test a new model, based on the collision of a proto-Earth covered with an ocean of magma and a solid impacting object.
The model showed that after the collision, the magma is heated much more than solids from the impacting object. The magma then expands in volume and goes into orbit to form the moon, the researchers say. This explains why there is much more Earth material in the moon’s makeup. Previous models did not account for the different degree of heating between the proto-Earth silicate and the impactor.
“In our model, about 80% of the moon is made of proto-Earth materials,” said Karato, who has conducted extensive research on the chemical properties of proto-Earth magma. “In most of the previous models, about 80% of the moon is made of the impactor. This is a big difference.”
Karato said the new model confirms previous theories about how the moon formed, without the need to propose unconventional collision conditions — something theorists have had to do until now.
For the study, Karato led the research into the compression of molten silicate. A group from the Tokyo Institute of Technology and the RIKEN Center for Computational Science developed a computational model to predict how material from the collision became the moon.
The first author of the study is Natsuki Hosono of RIKEN. Additional co-authors are Junichiro Makino and Takayuki Saitoh.
Reference:
Natsuki Hosono, Shun-ichiro Karato, Junichiro Makino, Takayuki R. Saitoh. Terrestrial magma ocean origin of the Moon. Nature Geoscience, April 29, 2019; DOI: 10.1038/s41561-019-0354-2
The skulls of three hadrosaur dinosaurs, Lambeosaurus lambei (top left), Gryposaurus notabilis (top right), Parasaurolophus walkeri (lower). Credit: Albert Prieto-Márquez
The duck-billed hadrosaurs walked the Earth over 90-million years ago and were one of the most successful groups of dinosaurs. But why were these 2-3 tonne giants so successful? A new study, published in Paleobiology, shows that their special adaptations in teeth and jaws and in their head crests were crucial, and provides new insights into how these innovations evolved.
Called the ‘sheep of the Mesozoic’as they filled the landscape in the Late Cretaceous period, hadrosaurs walked on their hind legs and were known for their powerful jaws with multiple rows of extremely effective teeth. They also had hugely varied head display crests that signalled which species each belonged to and were used to attract mates. Some even trumpeted and tooted their special call, using nasal passages through the head crests.
Researchers from the Universities of Bristol and the Catalan Institute of Paleontology in Barcelona used a large database describing morphological variety in hadrosaur fossils and computational methods that quantify morphological variety and the pace of evolution.
Dr Tom Stubbs, lead author of the study and a researcher from Bristol’s School of Earth Sciences, said: “Our study shows that the unique hadrosaur feeding apparatus evolved fast in a single burst, and once established, showed very little change. In comparison, the elaborate display crests kept diversifying in several bursts of evolution, giving rise to the many weird and wonderful shapes.”
Professor Mike Benton, the study’s co-author from Bristol’s School of Earth Sciences, added, “Variation in anatomy can arise in many ways. We wanted to compare the two famous hadrosaur innovations, and by doing so, provide new insights into the evolution of this important dinosaur group. New numerical methods allow us to test these kinds of complex evolutionary hypotheses.”
“Our methods allowed us to identify branches on the hadrosaur evolutionary tree that showed rapid evolution in different parts of the skeleton,” said co-author Dr Armin Elsler. “When we looked at the jaws and teeth, we only saw fast evolution on a single branch at the base of the group. On the other hand, the bones that form the display crests showed multiple fast rate branches.”
Dr Albert Prieto-Márquez, co-author and world-leading expert on hadrosaurs from the Catalan Institute of Paleontology in Barcelona, added: “Our results suggest that evolution can be driven in different ways by natural selection and sexual selection. Hadrosaurs apparently fixed on a feeding apparatus that was successful and did not require massive modification to process their food. On the other hand, sexual selection drove the evolution of more complex crest shapes, and this is reflected by multiple evolutionary bursts.”
Reference:
Thomas L. Stubbs, Michael J. Benton, Armin Elsler, Albert Prieto-Márquez. Morphological innovation and the evolution of hadrosaurid dinosaurs. Paleobiology, 2019; 45 (02): 347 DOI: 10.1017/pab.2019.9
Well-preserved fossils — like this Yanoconodon allini (Specimen No.: NJU P06001; Formation: Yixian; Age: 122.2-124.6 million years ago; Provenance: China) — enabled the team to infer ecology of these extinct mammal species, and look at changes in mammal community structure during the last 165 million years. Credit: Meng Chen
A new study published April 30 in the Proceedings of the National Academy of Sciences identified three factors critical in the rise of mammal communities since they first emerged during the Age of Dinosaurs: the rise of flowering plants, also known as angiosperms; the evolution of tribosphenic molars in mammals; and the extinction of non-avian dinosaurs, which reduced competition between mammals and other vertebrates in terrestrial ecosystems.
Previously, mammals in the Age of Dinosaurs were thought to be a relatively small part of their ecosystems and considered to be small-bodied, nocturnal, ground-dwelling insectivores. According to this long-standing theory, it wasn’t until the K-Pg mass extinction event about 66 million years ago, which wiped out all non-avian dinosaurs, that mammals were then able to flourish and diversify. An astounding number of fossil discoveries over the past 30 years has challenged this theory, but most studies looked only at individual species and none has quantified community-scale patterns of the rise of mammals in the Mesozoic Era.
Co-authors are Meng Chen, a University of Washington alumnus and current postdoctoral researcher at Nanjing University; Caroline Strömberg, a University of Washington biology professor and curator of paleobotany at the UW’s Burke Museum of Natural History & Culture; and Gregory Wilson, a UW associate professor of biology and Burke Museum curator of vertebrate paleontology. The team created a Rubik’s Cube-like structure identifying 240 “eco-cells” representing possible ecological roles of mammals in a given ecospace. These 240 eco-cells cover a broad range of body size, dietary preferences, and ways of moving of small-bodied mammals. When a given mammal filled a certain type of role or eco-cell, it filled a spot in the ‘Rubik’s Cube.’ This method provides the first comprehensive analysis of evolutionary and ecological changes of fossil mammal communities before and after K-Pg mass extinction.
“We cannot directly observe the ecology of extinct species, but body size, dietary preferences and locomotion are three aspects of their ecology that can be relatively easily inferred from well-preserved fossils,” said Chen. “By constructing the ecospace using these three ecological aspects, we can visually identify the spots filled by species and calculate the distance among them. This allows us to compare the ecological structure of extinct and extant communities even though they don’t share any of the same species.”
The team analyzed living mammals to infer how fossil mammals filled roles in their ecosystems. They examined 98 small-bodied mammal communities from diverse biomes around the world, an approach that has not been attempted at this scale. They then used this modern-day reference dataset to analyze five exceptionally preserved mammal paleocommunities — two Jurassic Period and two Cretaceous Period communities from northeastern China, and one Eocene Epoch community from Germany. Usually Mesozoic Era mammal fossils are incomplete and consist of fragmentary bones or teeth. Using these remarkably preserved fossils enabled the team to infer ecology of these extinct mammal species, and look at changes in mammal community structure during the last 165 million years.
The team found that, in current communities of present-day mammals, ecological richness is primarily driven by vegetation type, with 41 percent of small mammals filling eco-cells compared to 16 percent in the paleocommunities. The five mammal paleocommunities were also ecologically distinct from modern communities and pointed to important changes through evolutionary time. Locomotor diversification occurred first during the Mesozoic, possibly due to the diversity of microhabitats, such as trees, soils, lakes and other substrates to occupy in local environments. It wasn’t until the Eocene that mammals grew larger and expanded their diets from mostly carnivory, insectivory and omnivory to include more species with diets dominated by plants, including fruit. The team determined that the rise of flowering plants, new types of teeth and the extinction of dinosaurs likely drove these changes.
Before the rise of flowering plants, mammals likely relied on conifers and other seed plants for habitat, and their leaves and possibly seeds for food. By the Eocene, flowering plants were both diverse and dominant across forest ecosystems. Flowering plants provide more readily available nutrients through their fast-growing leaves, fleshy fruits, seeds and tubers. When becoming dominant in forests, they fundamentally changed terrestrial ecosystems by allowing for new modes of life for a diversity of mammals and other forest-dwelling animals, such as birds.
“Flowering plants really revolutionized terrestrial ecosystems,” said Strömberg. “They have a broader range of growth forms than all other plant groups — from giant trees to tiny annual herbs — and can produce nutrient-rich tissues at a faster rate than other plants. So when they started dominating ecosystems, they allowed for a wider variety of life modes and also for much higher ‘packing’ of species with similar ecological roles, especially in tropical forests.”
Tribosphenic molars — complex multi-functional cheek teeth — became prevalent in mammals in the late Cretaceous Period. Mutations and natural selection drastically changed the shapes of these molars, allowing them to do new things like grinding. In turn, this allowed small mammals with these types of teeth to eat new kinds of foods and diversify their diets.
Lastly, the K-Pg mass extinction event that wiped out all dinosaurs except birds 66 million years ago provided an evolutionary and ecological opportunity for mammals. Small body size is a way to avoid being eaten by dinosaurs and other large vertebrates. The mass extinction event not only removed the main predators of mammals, but also removed small dinosaurs that competed with mammals for resources. This ecological release allowed mammals to grow into larger sizes and fill the roles the dinosaurs once had.
“The old theory that early mammals were held in check by dinosaurs has some truth to it,” said Wilson. “But our study also shows that the rise of modern mammal communities was multifaceted and depended on dental evolution and the rise of flowering plants.”
Reference:
Meng Chen, Caroline A. E. Strömberg, Gregory P. Wilson. Assembly of modern mammal community structure driven by Late Cretaceous dental evolution, rise of flowering plants, and dinosaur demise. Proceedings of the National Academy of Sciences, 2019; 201820863 DOI: 10.1073/pnas.1820863116
Denisovans — an extinct sister group of Neandertals — were discovered in 2010, when a research team led by Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) sequenced the genome of a fossil finger bone found at Denisova Cave in Russia and showed that it belonged to a hominin group that was genetically distinct from Neandertals. “Traces of Denisovan DNA are found in present-day Asian, Australian and Melanesian populations, suggesting that these ancient hominins may have once been widespread,” says Jean-Jacques Hublin, director of the Department of Human Evolution at the MPI-EVA. “Yet so far the only fossils representing this ancient hominin group were identified at Denisova Cave.”
Mandible from Baishiya Karst Cave
In their new study, the researchers now describe a hominin lower mandible that was found on the Tibetan Plateau in Baishiya Karst Cave in Xiahe, China. The fossil was originally discovered in 1980 by a local monk who donated it to the 6th Gung-Thang Living Buddha who then passed it on to Lanzhou University. Since 2010, researchers Fahu Chen and Dongju Zhang from Lanzhou University have been studying the area of the discovery and the cave site from where the mandible originated. In 2016, they initiated a collaboration with the Department of Human Evolution at the MPI-EVA and have since been jointly analysing the fossil.
While the researchers could not find any traces of DNA preserved in this fossil, they managed to extract proteins from one of the molars, which they then analysed applying ancient protein analysis. “The ancient proteins in the mandible are highly degraded and clearly distinguishable from modern proteins that may contaminate a sample,” says Frido Welker of the MPI-EVA and the University of Copenhagen. “Our protein analysis shows that the Xiahe mandible belonged to a hominin population that was closely related to the Denisovans from Denisova Cave.”
Primitive shape and large molars
The researchers found the mandible to be well-preserved. Its robust primitive shape and the very large molars still attached to it suggest that this mandible once belonged to a Middle Pleistocene hominin sharing anatomical features with Neandertals and specimens from the Denisova Cave. Attached to the mandible was a heavy carbonate crust, and by applying U-series dating to the crust the researchers found that the Xiahe mandible is at least 160,000 years old. Chuan-Chou Shen from the Department of Geosciences at National Taiwan University, who conducted the dating, says: “This minimum age equals that of the oldest specimens from the Denisova Cave.”
“The Xiahe mandible likely represents the earliest hominin fossil on the Tibetan Plateau,” says Fahu Chen, director of the Institute of Tibetan Research, CAS. These people had already adapted to living in this high-altitude low-oxygen environment long before Homo sapiens even arrived in the region. Previous genetic studies found present-day Himalayan populations to carry the EPAS1 allele in their genome, passed on to them by Denisovans, which helps them to adapt to their specific environment.
“Archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene and successfully adapted to high-altitude low-oxygen environments long before the regional arrival of modern Homo sapiens,” says Dongju Zhang. According to Hublin, similarities with other Chinese specimens confirm the presence of Denisovans among the current Asian fossil record. “Our analyses pave the way towards a better understanding of the evolutionary history of Middle Pleistocene hominins in East Asia.”
Reference:
Fahu Chen, Frido Welker, Chuan-Chou Shen, Shara E. Bailey, Inga Bergmann, Simon Davis, Huan Xia, Hui Wang, Roman Fischer, Sarah E. Freidline, Tsai-Luen Yu, Matthew M. Skinner, Stefanie Stelzer, Guangrong Dong, Qiaomei Fu, Guanghui Dong, Jian Wang, Dongju Zhang & Jean-Jacques Hublin. A late Middle Pleistocene Denisovan mandible from the Tibetan Plateau. Nature, 2019 DOI: 10.1038/s41586-019-1139-x
The reassembled skull bones of Egernia gillespieae, a 15 million year old skink from Riversleigh World Heritage Area of northwestern Queensland
Reconstruction of the most complete fossil lizard found in Australia, a 15 million year old relative of our modern blue tongues and social skinks named Egernia gillespieae, reveals the creature was equipped with a robust crushing jaw and was remarkably similar to modern lizards.
A new study lead by Flinders University PHD student Kailah Thorn, published in the journal of Vertebrate Palaeontology, combined the anatomy of of living fossils with DNA data to put a time scale on the family tree of Australia’s ‘social skinks’.
“This creature looked like something in-between a tree skink and a bluetongue lizard. It would have been about 25 cm long, and unlike any of the living species it was equipped with robust crushing jaws,” says Ms Thorn.
The results show that our Australia’s bluetongue lizards split from Egernia as early as 25 million years ago.
“The new fossil is unusually well-preserved, with much of the skull, and some limb bones, all from a single individual. It belongs to the genus Egernia, a modern species in this group which are often called ‘social skinks’ and are known for living in family groups, sharing rocky outcrops and hollow tree stumps.”
Remarkably similar to modern social skinks, E. gillespieae instead is equipped with rounded crushing teeth and a deep, thick jaw.
The fossils are from the Riversleigh World Heritage fossil deposits in northwest Queensland, and were named after Dr Anna Gillespie, a UNSW palaeontologist responsible for preparing many of the spectacular fossils from that area.
“I have been preparing the Riversleigh fossil material for quite a few years now and lizard bones are rare elements. When the jaw appeared and was quickly followed by associated skull elements, I had a good feeling it would be a significant addition to the Riversleigh reptile story,” says Dr Gillespie.
Reference:
Kailah M. Thorn, Mark N. Hutchinson, Michael Archer, Michael S. Y. Lee. A new scincid lizard from the Miocene of Northern Australia, and the evolutionary history of social skinks (Scincidae: Egerniinae). Journal of Vertebrate Paleontology, 2019; e1577873 DOI: 10.1080/02724634.2019.1577873
Open cut hard rock mining, Kalgoorlie, Western Australia. Credit: Stephen Codrington
Mining
Mining is the extraction from the earth of valuable minerals or other geological materials, usually from a deposit of ore, lode, vein, seam, reef or placer. These deposits form an economically interesting mineralized package for the miner. “Related: What Is Gold Mining? How Is Gold Mined?”
Ores recovered through mining include metals, coal, oil shale, gemstones, calcareous stone, chalk, rock salt, potash, gravel, and clay. Mining is required to obtain any material that can not be grown or artificially created in a laboratory or factory through agricultural processes. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.
What are the main mining methods?
Four main methods of mining are available: underground, open surface (pit), placer and in-situ mining.
Underground mines are more expensive and often used to reach deposits that are deeper.
Surface mines are usually used for deposits that are shallower and less valuable.
Placer mining is used in river channels, beach sands, or other environments to sift valuable metals from sediments.
In-situ mining, primarily used in uranium mining, involves dissolving the existing mineral resource and then processing it on the surface without moving rock from the ground.
Mining techniques
Surface mining
Surface mining is done by removing (stripping) surface vegetation, dirt, and, if necessary, layers of bedrock in order to reach buried ore deposits. Techniques of surface mining include: open-pit mining, which is the recovery of materials from an open pit in the ground, quarrying, identical to open-pit mining except that it refers to sand, stone and clay; Strip mining consisting of stripping off surface layers to reveal ore / seams below ; and mountaintop removal, commonly associated with coal mining, involving removing the top of a mountain to reach deposits of ore at depth.
Underground mining
Sub-surface mining consists of digging into the earth tunnels or shafts to reach the deposits of buried ore. Ore is brought to the surface through tunnels and shafts for processing, and waste rock for disposal. Sub-surface mining can be classified according to the type of shafts used, the method of extraction or the technique used to reach the deposit. Drift mining uses horizontal access tunnels, diagonally sloping access shafts are used by slope mining, and shaft mining uses vertical access shafts. Mining requires different techniques in hard and soft rock formations.
Highwall mining
Highwall mining is another surface mining form that has evolved from auger mining. A continuous miner driven by a hydraulic Pushbeam Transfer Mechanism (PTM) penetrates the coal seam. A typical cycle includes sumping (launch-pushing forward) and shearing (cutterhead boom raising and lowering to cut the entire height of the coal seam).
As the cycle of coal recovery continues, the cutterhead is gradually launched at 19.72 feet (6.01 m) into the coal seam. The Pushbeam Transfer Mechanism (PTM) then automatically inserts a 19.72-foot (6.01 m) long rectangular Pushbeam (Screw-Conveyor Segment) between the Powerhead and the cutterhead into the center section of the machine.
June 2018 flow from Kilauea Volcano’s lower east Rift Zone. Credit: USGS/ A. Lerner
Ever since Hawaii’s Kilauea stopped erupting in August 2018, ceasing activity for the first time in 35 years, scientists have been wondering about the volcano’s future. Its similarities to the Hawaiian seamount Lo`ihi might provide some answers, according to Jacqueline Caplan-Auerbach at Western Washington University.
In her presentation at the 2019 SSA Annual Meeting, Caplan-Auerbach, a volcano seismologist, said Lo`ihi’s 1996 eruption has some remarkable parallels to 2018 activity at Kilauea. Lo`ihi is a submarine volcano located about 22 miles off the southwest coast of the island of Hawaii, with its summit about 3000 feet below sea level.
Caplan-Auerbach has studied Lo`ihi since she was a graduate student in 1996, with more recent work at Kilauea, using data from seismic instruments placed on the submarine flanks of both volcanoes.
After the sudden cessation of activity at Kilauea last summer, “it was very apparent to me that there were some very striking similarities between this eruption and what we saw at Lo`ihi in 1996,” she says.
Like the 2018 Kilauea eruptive sequence, the 1996 Lo`ihi eruption began with a dramatic increase in seismic activity that started in the volcano’s rift zone and transitioned to its summit. Then in both cases, “there was a long sequence of very large earthquakes for a volcano of that size,” says Caplan-Auerbach. Lo`ihi experienced more than 100 magnitude 4 or larger earthquakes, while there were more than 50 magnitude 5 or larger earthquakes at Kilauea.
In both cases, the swarms of earthquakes at the summits of each volcano led to a significant collapse, creating Pele’s Pit on Lo`ihi and enlarging the Halema`uma`u crater at Kilauea.
It’s rare to see the kind of caldera collapse that happened at Kilauea in action, says Caplan-Auerbach, although scientists have watched it occur at Fernandina volcano in the Galápagos Islands and Bárðarbunga volcano in Iceland. “One of the things I would like to know more about is whether this type of activity, this draining of the summit reservoir and this sort of collapse of a pit … indicates a volcano has kind of done its time,” she says.
After its 1996 eruption, Lo`ihi became quiet, with little to no seismicity recorded during two instrument deployments in 1997-1998 and 2010-2011. “It was a level of quiescence that we had never seen there before,” says Caplan-Auerbach. The seamount remained mostly quiet for almost twenty years, gradually increasing seismicity before beginning new earthquake swarms in 2015.
This might indicate that Lo`ihi is replenishing its magma reservoir. If Lo`ihi’s and Kilauea’s similarities are a guide to Kilauea’s future, Kilauea might be quiet for a decade before becoming active again, Caplan-Auerbach suggests.
“I think the good news is that volcanoes tend to talk to us before they do anything truly dramatic,” she says. “so I think we will know when it restores its magma system.”
How carbon is cycled near volcano chains. Credit: Patricia Barcala Dominguez
Up to about 19 percent more carbon dioxide than previously believed is removed naturally and stored underground between coastal trenches and inland chains of volcanoes, keeping the greenhouse gas from entering the atmosphere, according to a study in the journal Nature.
Surprisingly, subsurface microbes play a role in storing vast amounts of carbon by incorporating it in their biomass and possibly by helping to form calcite, a mineral made of calcium carbonate, Rutgers and other scientists found. Greater knowledge of the long-term impact of volcanoes on carbon dioxide and how it may be buffered by chemical and biological processes is critical for evaluating natural and human impacts on the climate. Carbon dioxide is the major greenhouse gas linked to global warming.
“Our study revealed a new way that tiny microorganisms can have an outsized impact on a large-scale geological process and the Earth’s climate,” said co-author Donato Giovannelli, a visiting scientist and former post-doc in the Department of Marine and Coastal Sciences at Rutgers University-New Brunswick. He is now at the University of Naples in Italy.
Giovannelli is a principal investigator for the interdisciplinary study, which involves 27 institutions in six nations. Professor Costantino Vetriani in the Department of Marine and Coastal Sciences and Department of Biochemistry and Microbiology in the School of Environmental and Biological Sciences is one of the Rutgers co-authors. The study covers how microbes alter the flow of volatile substances that include carbon, which can change from a solid or liquid to a vapor, in subduction zones. Such zones are where two tectonic plates collide, with the denser plate sinking and moving material from the surface into Earth’s interior.
The subduction, or geological process, creates deep-sea trenches and volcanic arcs, or chains of volcanoes, at the boundary of tectonic plates. Examples are in Japan and South and Central America. Arc volcanoes are hot spots for carbon dioxide emissions that re-enter the atmosphere from subducted material, which consists of marine sediment, oceanic crust and mantle rocks, Giovannelli said. The approximately 1,800-mile-thick mantle of semi-solid hot rock lies beneath the Earth’s crust.
The Earth’s core, mantle and crust account for 90 percent of carbon. The other 10 percent is in the ocean, biosphere and atmosphere. The subduction zone connects the Earth’s surface with its interior, and knowing how carbon moves between them is important in understanding one of the key processes on Earth and regulating the climate over tens of millions of years.
The study focused on the Nicoya Peninsula area of Costa Rica. The scientists investigated the area between the trench and the volcanic arc — the so-called forearc. The research reveals that volcanic forearc are a previously unrecognized deep sink for carbon dioxide.
Reference:
P. H. Barry, J. M. de Moor, D. Giovannelli, M. Schrenk, D. R. Hummer, T. Lopez, C. A. Pratt, Y. Alpízar Segura, A. Battaglia, P. Beaudry, G. Bini, M. Cascante, G. d’Errico, M. di Carlo, D. Fattorini, K. Fullerton, E. Gazel, G. González, S. A. Halldórsson, K. Iacovino, J. T. Kulongoski, E. Manini, M. Martínez, H. Miller, M. Nakagawa, S. Ono, S. Patwardhan, C. J. Ramírez, F. Regoli, F. Smedile, S. Turner, C. Vetriani, M. Yücel, C. J. Ballentine, T. P. Fischer, D. R. Hilton, K. G. Lloyd. Forearc carbon sink reduces long-term volatile recycling into the mantle. Nature, 2019; 568 (7753): 487 DOI: 10.1038/s41586-019-1131-5
The Campi Flegrei caldera cluster. Credit: NASA Earth
The caldera-forming eruption of Campi Flegrei (Italy) 40,000 years ago is the largest known eruption in Europe during the last 200,000 years, but little is known about other large eruptions at the volcano prior to a more recent caldera-forming event 15,000 years ago. A new Geology article by Paul Albert and colleagues discusses a 29,000-year-old eruption, here verified as coming from Campi Flegrei, that spread a volcanic ash layer more than 150,000 square kilometers of the Mediterranean.
Knowledge of large explosive eruptions is mostly established from geological investigations of the exposed deposits found around the source volcano, with the deposits of large eruptions forming thick sequences. However, since the late 1970s, a widespread volcanic ash layer, dated at about 29,000 years ago, was commonly identified in marine and lake sediment cores from across the Mediterranean, documenting the occurrence of a large-magnitude eruption. Despite this widespread distribution and relatively young age, no clear evidence of such an event was identified at any of the main active volcanoes in the region.
In this study, the team’s detailed chemical analysis (volcanic glass) of an eruption deposit found five kilometers northeast of Campi Flegrei caldera in Naples, Italy, are entirely consistent with the distinctive composition of this ash layer. This, combined with new dating of the near-source eruption deposit, verifies that Campi Flegrei was responsible for this widespread ash layer.
Constraints on the size of the eruption were determined by the team using a computational ash dispersal model which integrated the thicknesses of the near-source eruption deposits, named here the Masseria del Monte Tuff, with those of the related ash fall across the Mediterranean.
The results indicate that this eruption at Campi Flegrei caldera was similar in scale to the younger of two known large-magnitude, caldera-forming eruptions at the volcano, the Neapolitan Yellow Tuff (about 15,000 years ago). The Masseria del Monte Tuff eruption was smaller than the older caldera-forming eruption, the enormous Campanian Ignimbrite (about 40,000 years old), which dispersed ash as far as Russia (more than 2,500 km from the volcano).
The 29,000 year old Masseria del Monte Tuff eruption positioned between known caldera-forming events significantly reduces the recurrence interval of large magnitude events in the eruptive history of Campi Flegrei caldera.
In contrast to other large magnitude events at Campi Flegrei, the lack of thick, traceable, deposits for this eruption appear to be the result of the eruption dynamics and their destruction and burial by more recent activities. This research highlights the benefits of investigating explosive eruption records preserved as ash fall in sedimentary records when attempting to accurately reconstruct the tempo and magnitude of past activity at highly productive volcanoes such as Campi Flegrei.
Reference:
P.G. Albert, B. Giaccio, R. Isaia, A. Costa, E.M. Niespolo, S. Nomade, A. Pereira, P.R. Renne, A. Hinchliffe, D.F. Mark, R.J. Brown, V.C. Smith. Evidence for a large-magnitude eruption from Campi Flegrei caldera (Italy) at 29 ka. Geology, 2019; DOI: 10.1130/G45805.1
A raw diamond from Sierra Leone with sulfur-containing mineral inclusions. Credit: Courtesy of the Gemological Institute of America.
The longevity of Earth’s continents in the face of destructive tectonic activity is an essential geologic backdrop for the emergence of life on our planet. This stability depends on the underlying mantle attached to the landmasses. New research by a group of geoscientists from Carnegie, the Gemological Institute of America, and the University of Alberta demonstrates that diamonds can be used to reveal how a buoyant section of mantle beneath some of the continents became thick enough to provide long-term stability.
“We’ve found a way to use traces of sulfur from ancient volcanoes that made its way into the mantle and eventually into diamonds to provide evidence for one particular process of continent building,” explained Karen Smit of the Gemological Institute of America, lead author on the group’s paper, which appears this week in Science. “Our technique shows that the geologic activity that formed the West African continent was due to plate tectonic movement of ocean crust sinking into the mantle.”
Diamonds may be beloved by jewelry collectors, but they are truly a geologist’s best friend. Because they originate deep inside the Earth, tiny mineral grains trapped inside of a diamond, often considered undesirable in the gem trade, can reveal details about the conditions under which it formed.
“In this way, diamonds act as mineralogical emissaries from the Earth’s depths,” explained Carnegie co-author Steve Shirey.
About 150 to 200 kilometers, 93 to 124 miles, beneath the surface, geologic formations called mantle keels act as stabilizers for the continental crust. The material that comprises them must thicken, stabilize, and cool under the continent to form a strong, buoyant, keel that is fundamental for preserving the surface landmass against the relentless destructive forces of Earth’s tectonic activity. But how this is accomplished has been a matter of debate in the scientific community.
“Solving this mystery is key to understanding how the continents came to exist in their current incarnations and how they survive on an active planet,” Shirey explained. “Since this is the only tectonically active, rocky planet that we know, understanding the geology of how our continents formed is a crucial part of discerning what makes Earth habitable.”
Some scientists think mantle keels form by a process called subduction, by which oceanic plates sink from the Earth’s surface into its depths when one tectonic plate slides beneath another. Others think keels are created by a vertical process in which plumes of hot magma rise from much deeper in the Earth.
A geochemical tool that can detect whether the source of a mantle keel’s makeup originated from surface plates or from upwelling of deeper mantle material was needed to help resolve this debate. Luckily, mantle keels have the ideal conditions for diamond formation. This means scientists can reveal a mantle keel’s origin by studying inclusions from diamonds that formed in it.
The research group’s analysis of sulfur-rich minerals, called sulfides, in diamonds mined in Sierra Leone indicate that the region experienced two subduction events during its history.
They were able to make this determination because the chemistry of the sulfide mineral grains is only seen in samples from Earth’s surface more than 2.5 billion years ago — before oxygen became so abundant in our planet’s atmosphere. This means that the sulfur in these mineral inclusions must have once existed on the Earth’s surface and was then drawn down into the mantle by subduction.
The team’s comparison to diamonds from Botswana showed similar evidence of keel-creation through subduction. But comparison to diamonds mined from northern Canada does not show the same sulfur chemistry, meaning that the mantle keel in this region originated in some way that did not incorporate surface material.
The group’s findings suggest that thickening and stabilization of the mantle keel beneath the West African continent happened when this section of mantle was squeezed by collision with the sinking ocean floor material. This method of keel thickening and continent stabilization is not responsible for forming the keel under a portion of northern Canada. The sulfide minerals inside Canadian diamonds do not tell the researchers how this keel formed, only how it didn’t.
“Our work shows that sulfide inclusions in diamonds are a powerful tool to investigate continent construction processes,” Smit concluded.
This work was supported by the GIA, the University of Alberta, the NSF, and Carnegie. It is a contribution to the Deep Carbon Observatory.
Reference:
Karen V. Smit, Steven B. Shirey, Erik H. Hauri, Richard A. Stern. Sulfur isotopes in diamonds reveal differences in continent construction. Science, 2019 DOI: 10.1126/science.aaw9548
Neither the continents nor the oceans have always looked the way they do now. These ‘paleomaps’ show how the continents and oceans appeared before (top) and during (bottom) ‘the collision that changed the world,’ when the landmass that is now the Indian subcontinent rammed northward into Asia, closing the Tethys Sea and building the Himalayas. Global ocean levels were higher then, creating salty shallow seas (pale blue) that covered much of North Africa and parts of each of the continents. A team of Princeton researchers, using samples gathered at the three starred locations, created an unprecedented record of ocean nitrogen and oxygen levels from 70 million years ago through 30 million years ago that shows a major shift in ocean chemistry after the India-Asia collision. Another shift came 35 million years ago, when Antarctica began accumulating ice and global sea levels fell. Credit: Images created by Emma Kast, Princeton University, using paleogeographic reconstructions from Deep Time Maps, with their permission
When the landmass that is now the Indian subcontinent slammed into Asia about 50 million years ago, the collision changed the configuration of the continents, the landscape, global climate and more. Now a team of Princeton University scientists has identified one more effect: the oxygen in the world’s oceans increased, altering the conditions for life.
“These results are different from anything people have previously seen,” said Emma Kast, a graduate student in geosciences and the lead author on a paper coming out in Science on April 26. “The magnitude of the reconstructed change took us by surprise.”
Kast used microscopic seashells to create a record of ocean nitrogen over a period from 70 million years ago — shortly before the extinction of the dinosaurs — until 30 million years ago. This record is an enormous contribution to the field of global climate studies, said John Higgins, an associate professor of geosciences at Princeton and a co-author on the paper.
“In our field, there are records that you look at as fundamental, that need to be explained by any sort of hypothesis that wants to make biogeochemical connections,” Higgins said. “Those are few and far between, in part because it’s very hard to create records that go far back in time. Fifty-million-year-old rocks don’t willingly give up their secrets. I would certainly consider Emma’s record to be one of those fundamental records. From now on, people who want to engage with how the Earth has changed over the last 70 million years will have to engage with Emma’s data.”
In addition to being the most abundant gas in the atmosphere, nitrogen is key to all life on Earth. “I study nitrogen so that I can study the global environment,” said Daniel Sigman, Princeton’s Dusenbury Professor of Geological and Geophysical Sciences and the senior author on the paper. Sigman initiated this project with Higgins and then-Princeton postdoctoral researcher Daniel Stolper, who is now an assistant professor of Earth and planetary science at the University of California-Berkeley.
Every organism on Earth requires “fixed” nitrogen — sometimes called “biologically available nitrogen.” Nitrogen makes up 78% of our planet’s atmosphere, but few organisms can “fix” it by converting the gas into a biologically useful form. In the oceans, cyanobacteria in surface waters fix nitrogen for all other ocean life. As the cyanobacteria and other creatures die and sink downward, they decompose.
Nitrogen has two stable isotopes, 15N and 14N. In oxygen-poor waters, decomposition uses up “fixed” nitrogen. This occurs with a slight preference for the lighter nitrogen isotope, 14N, so the ocean’s 15N-to-14N ratio reflects its oxygen levels.
That ratio is incorporated into tiny sea creatures called foraminifera during their lives, and then preserved in their shells when they die. By analyzing their fossils — collected by the Ocean Drilling Program from the North Atlantic, North Pacific, and South Atlantic — Kast and her colleagues were able to reconstruct the 15N-to-14N ratio of the ancient ocean, and therefore identify past changes in oxygen levels.
Oxygen controls the distribution of marine organisms, with oxygen-poor waters being bad for most ocean life. Many past climate warming events caused decreases in ocean oxygen that limited the habitats of sea creatures, from microscopic plankton to the fish and whales that feed on them. Scientists trying to predict the impact of current and future global warming have warned that low levels of ocean oxygen could decimate marine ecosystems, including important fish populations.
When the researchers assembled their unprecedented geologic record of ocean nitrogen, they found that in the 10 million years after dinosaurs went extinct, the 15N-to-14N ratio was high, suggesting that ocean oxygen levels were low. They first thought that the warm climate of the time was responsible, as oxygen is less soluble in warmer water. But the timing told another story: the change to higher ocean oxygen occurred around 55 million years ago, during a time of continuously warm climate.
“Contrary to our first expectations, global climate was not the primary cause of this change in ocean oxygen and nitrogen cycling,” Kast said. The more likely culprit? Plate tectonics. The collision of India with Asia — dubbed “the collision that changed the world” by legendary geoscientist Wally Broecker, a founder of modern climate research — closed off an ancient sea called the Tethys, disturbing the continental shelves and their connections with the open ocean.
“Over millions of years, tectonic changes have the potential to have massive effects on ocean circulation,” said Sigman. But that doesn’t mean climate change can be discounted, he added. “On timescales of years to millenia, climate has the upper hand.”
Reference:
Emma R. Kast, Daniel A. Stolper, Alexandra Auderset, John A. Higgins, Haojia Ren, Xingchen T. Wang, Alfredo Martínez-García, Gerald H. Haug, Daniel M. Sigman. Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic. Science, 2019; 364 (6438): 386 DOI: 10.1126/science.aau5784
In the past decade scientists have been experimenting with metamaterials, artificial materials designed with periodic internal structures to give them properties not found in natural materials. Depending on their internal geometry and composition, researchers have found that they can control waves propagating through some of these materials, filtering sound or deflecting light so that an object appears “cloaked” or invisible, for instance.
Could this same principle be applied to controlling seismic waves? At the SSA 2019 Annual Meeting, seismologists from around the world will discuss how metamaterial theory might be applied to everything from developing deflective barriers to manipulating the layout of buildings within a city as a way to minimize the impact of damaging surface seismic waves.
Lav Joshi, a Ph.D. student and J. P. Narayan, a professor at the Indian Institute of Technology in Roorkee, India are exploring whether the metamaterial concept can be scaled up to the size of a city. They were inspired by earlier studies where researchers looked at how groups of trees could be used as a natural metamaterial to mitigate the damaging potential of Rayleigh waves, that “roll” across the ground spreading out from the epicentral zone of an earthquake.
“Borrowing ideas from these studies, we started working on the concept of existing structures as metamaterials or metastructures, combining our present knowledge of site-city interaction effects and seismic wave propagation,” said Joshi.
Joshi and colleagues conducted 3-D simulations of how Rayleigh waves pass through the structures of varying heights and widths within a city. They found that the structures act as “resonators” that pluck energy from the Rayleigh waves.
To maximize this effect on a city-wide basis, Joshi said, “the possible arrangement for a city would be that the height of a building should decrease radially inward, as the fundamental longitudinal mode of vibration of high-rise buildings can coincide with the flexural mode of vibration of shorter buildings, causing a significant reduction in their damage.”
Other factors, including features of the surrounding landscape like mountains and valleys, will interact with the pattern of buildings as well, affecting the extent of the damage, he added.
In another presentation at the meeting, Maria Todorovska of Tianjin University in China will present her work on how a periodic arrangement of large-scale barriers such as excavated holes and hills could act as a seismic metamaterial. Her modeling results show that periodic “valleys” appear to reduce more ground motion than deeper and narrower “canyons” or hills.
With more research, the idea of patterning the urban landscape as a seismic metamaterial might aid city planners and earthquake engineers as they build in areas where shallow damaging earthquakes are expected, the scientists say.
Image showing landslide failures around Orcas Island. The red line marks the newly discovered Skipjack fault zone. Credit: H. Gary Greene
The central Salish Sea of the Pacific Northwest is bounded by two active fault zones that could trigger rockfalls and slumps of sediment that might lead to tsunamis, according to a presentation at the 2019 SSA Annual Meeting.
These tsunamis might be directed toward the islands of San Juan Archipelago, Vancouver Island and low coastal areas of the United States including Bellingham, Washington.
Extensive seismic mapping of the seafloor by Canadian and U.S. scientists has revealed details of the extent and surrounding features of the Devils Mountain Fault Zone running south of the Archipelago, as well as the newly mapped Skipjack Island Fault Zone at its northern edge, said H. Gary Greene of Moss Landing Marine Laboratories. Both of the faults extend more than 55 kilometers (~34 miles) offshore, but might have the potential to rupture over 125 kilometers (~78 miles) if connected to onshore faults.
The faults are similar to the east-west trending faults under the cities of Seattle and Tacoma, lying in the brittle upper plate of the Cascadia Subduction Zone. Deformation of sediments along the Devils Mountain and Skipjack faults indicates that they were active at least 10,000 years ago, Greene said. Although there have not been any large recorded earthquakes along these faults, he said the similar Seattle and Tacoma fault zones have produced magnitude 6 to 7 earthquakes in the past.
The new seafloor mapping holds a few troubling signs for what might happen if an earthquake of that magnitude does occur along the Skipjack Island fault, in particular. For instance, Greene and his colleagues have identified an underwater rubble field from a past landslide along the steep northeastern face of Orcas Island near the Skipjack fault. A Skipjack earthquake could shake loose the massive rubble blocks here, he said, “and generate an impact tsunami from this material.”
The researchers also saw evidence of previous ground failure — slumps and slides of sediment — along the southern edge of the Canadian Fraser River Delta, which lies just north of the Skipjack Island fault zone. If an earthquake led to a massive slide of river delta sediments, the resulting tsunami might affect both the islands of the San Juan Archipelago and the Washington state coast.
Greene also noted that the sediments lining Bellingham Bay have “just a tremendous amount of pockmarks, which indicate that methane is seeping out of the seafloor and has in the past.” The gas might further destabilize sediment in the region.
Together, the faults and seafloor features suggest that seismologists should keep a close eye on the potential local tsunami risks in the central Salish Sea. “We have the two faults here, we know that they have moved fairly recently, and that they are in the upper plate of the Cascadia Subduction Zone, an unstable area that we know can fail,” Greene said.
Although Greene, Vaughn Barrie of the Geological Survey of Canada, and other colleagues have identified some of the potential causes of tsunami between the Devils Mountain and Skipjack Fault Zones, the next step would be to model in detail how the tsunami might occur. “Modeling could help us establish the volume of the material that would fail, and that would give us a better idea of the potential magnitude of the tsunami,” he said.
Visualization of the interior of the Earth’s core, as represented by a computer simulation model (view of the equatorial plane and a spherical surface near the inner core, seen from the North Pole). Magnetic field lines (in orange) are stretched by turbulent convection (in blue and red). Hydromagnetic waves are emitted from the inner core, and spread along the magnetic field lines up to the core’s boundary, where they are focused and give rise to geomagnetic jerks. Credit: Aubert et al./IPGP/CNRS Photo library
Initially described in 1978, geomagnetic jerks are unpredictable events that abruptly accelerate the evolution of the Earth’s magnetic field, and skew predictions of its behaviour on a multi-year scale. Our magnetic field affects numerous human activities, ranging from establishing the direction in smartphones to the flight of low-altitude satellites. It is therefore essential to accurately predict its evolution. Still, geomagnetic jerks have presented a problem for geophysicists for over forty years.
The Earth’s magnetic field is produced by the circulation of matter within its metallic core, via the energy released when this core cools. Researchers know of two types of movements that cause two types of variations in the magnetic field: those resulting from slow convection movement, which can be measured on the scale of a century, and those resulting from “rapid” hydromagnetic waves, which can be detected on the scale of a few years. They suspected that the latter played a role in the jerks, but the interaction of these waves with slow convection, along with their mechanism of propagation and amplification, had yet to be revealed.
To solve this mystery, Julien Aubert from l’Institut de physique du globe de Paris (CNRS/IPGP/IGN/Université de Paris) developed, with a colleague from the Technical University of Denmark (DTU), a computer simulation very close to the physical conditions of our core. The simulation required the equivalent of 4 million hours of calculation, and was carried out thanks to the supercomputers of GENCI.
Researchers were subsequently able to reproduce the succession of events leading to geomagnetic jerks, which arise in the simulation from hydromagnetic waves emitted in the inner core. These waves are focused and amplified as they approach the core’s surface, causing magnetic disturbances comparable in all ways to the jerks observed.
The digital reproduction and comprehension of these jerks paves the way for better predictions of the Earth’s magnetic field. Identifying the cause of magnetic field variations could also help geophysicists study the physical properties of the Earth’s core and inner mantle.
This research project was financed by the Fondation Simone et Cino Del Duca of Institut de France, which supports fundamental research in the Earth Sciences through one of its scientific grants.
Reference:
Julien Aubert & Christopher C. Finlay. Geomagnetic jerks and rapid hydromagnetic waves focusing at Earth’s core surface. Nature Geoscience, 2019 DOI: 10.1038/s41561-019-0355-1
Note: The above post is reprinted from materials provided by CNRS.
Life reconstruction of Callichimaera perplexa: The strangest crab that has ever lived. Credit: Oksana Vernygora, University of Alberta
The crab family just got a bunch of new cousins—including a 95-million-year-old chimera species that will force scientists to rethink the definition of a crab.
An international team of researchers led by Yale paleontologist Javier Luque announced the discovery of hundreds of exceptionally well-preserved specimens from Colombia and the United States that date back to the mid-Cretaceous period of 90-95 million years ago. The cache includes hundreds of tiny comma shrimp fossils, several true shrimp, and an entirely new branch of the evolutionary tree for crabs.
The most intriguing discovery, according to the researchers, is Callichimaera perplexa, the earliest example of a swimming arthropod with paddle-like legs since the extinction of sea scorpions more than 250 million years ago. The name derives from a chimera, a mythological creature that has body features from more than one animal. Callichimaera’s full name translates into “perplexing beautiful chimera.”
Luque noted that Callichimaera’s “unusual and cute” appearance, including its small size—about the size of a quarter—large compound eyes with no sockets, bent claws, leg-like mouth parts, exposed tail, and long body are features typical of pelagic crab larvae. This suggests that several of the larval traits seen in this “perplexing chimera” might have been retained and amplified in miniaturized adults via changes in the timing and rates of development. This is a process called “heterochrony,” which may lead to the evolution of novel body plans.
“Callichimaera perplexa is so unique and strange that it can be considered the platypus of the crab world,” said Luque. “It hints at how novel forms evolve and become so disparate through time. Usually we think of crabs as big animals with broad carapaces, strong claws, small eyes in long eyestalks, and a small tail tucked under the body. Well, Callichimaera defies all of these ‘crabby’ features and forces a re-think of our definition of what makes a crab a crab.”
A study about the discovery appears in the April 24 online edition of the journal Science Advances.
“It is very exciting that today we keep finding completely new branches in the tree of life from a distant past, especially from regions like the tropics, which despite being hotspots of diversity today, are places we know the least about in terms of their past diversity,” Luque said.
Reference:
J. Luque el al., “Exceptional preservation of mid-Cretaceous marine arthropods and the evolution of novel forms via heterochrony,” Science Advances (2019). DOI: 10.1126/sciadv.aav3875
This image of InSight’s seismometer was taken on the 110th Martian day, or sol, of the mission. The seismometer is called Seismic Experiment for Interior Structure, or SEIS. Credit: NASA/JPL-Caltech
NASA’s Mars InSight lander has measured and recorded for the first time ever a likely “marsquake.”
The faint seismic signal, detected by the lander’s Seismic Experiment for Interior Structure (SEIS) instrument, was recorded on April 6, the lander’s 128th Martian day, or sol. This is the first recorded trembling that appears to have come from inside the planet, as opposed to being caused by forces above the surface, such as wind. Scientists still are examining the data to determine the exact cause of the signal.
“InSight’s first readings carry on the science that began with NASA’s Apollo missions,” said InSight Principal Investigator Bruce Banerdt of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “We’ve been collecting background noise up until now, but this first event officially kicks off a new field: Martian seismology!”
The new seismic event was too small to provide solid data on the Martian interior, which is one of InSight’s main objectives. The Martian surface is extremely quiet, allowing SEIS, InSight’s specially designed seismometer, to pick up faint rumbles. In contrast, Earth’s surface is quivering constantly from seismic noise created by oceans and weather. An event of this size in Southern California would be lost among dozens of tiny crackles that occur every day.
“The Martian Sol 128 event is exciting because its size and longer duration fit the profile of moonquakes detected on the lunar surface during the Apollo missions,” said Lori Glaze, Planetary Science Division director at NASA Headquarters.
NASA’s Apollo astronauts installed five seismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon. Different materials can change the speed of seismic waves or reflect them, allowing scientists to use these waves to learn about the interior of the Moon and model its formation. NASA currently is planning to return astronauts to the Moon by 2024, laying the foundation that will eventually enable human exploration of Mars.
InSight’s seismometer, which the lander placed on the planet’s surface on Dec. 19, 2018, will enable scientists to gather similar data about Mars. By studying the deep interior of Mars, they hope to learn how other rocky worlds, including Earth and the Moon, formed.
Three other seismic signals occurred on March 14 (Sol 105), April 10 (Sol 132) and April 11 (Sol 133). Detected by SEIS’ more sensitive Very Broad Band sensors, these signals were even smaller than the Sol 128 event and more ambiguous in origin. The team will continue to study these events to try to determine their cause.
Regardless of its cause, the Sol 128 signal is an exciting milestone for the team.
“We’ve been waiting months for a signal like this,” said Philippe Lognonné, SEIS team lead at the Institut de Physique du Globe de Paris (IPGP) in France. “It’s so exciting to finally have proof that Mars is still seismically active. We’re looking forward to sharing detailed results once we’ve had a chance to analyze them.”
Most people are familiar with quakes on Earth, which occur on faults created by the motion of tectonic plates. Mars and the Moon do not have tectonic plates, but they still experience quakes — in their cases, caused by a continual process of cooling and contraction that creates stress. This stress builds over time, until it is strong enough to break the crust, causing a quake.
Detecting these tiny quakes required a huge feat of engineering. On Earth, high-quality seismometers often are sealed in underground vaults to isolate them from changes in temperature and weather. InSight’s instrument has several ingenious insulating barriers, including a cover built by JPL called the Wind and Thermal Shield, to protect it from the planet’s extreme temperature changes and high winds.
SEIS has surpassed the team’s expectations in terms of its sensitivity. The instrument was provided for InSight by the French space agency, Centre National d’Études Spatiales (CNES), while these first seismic events were identified by InSight’s Marsquake Service team, led by the Swiss Federal Institute of Technology.
“We are delighted about this first achievement and are eager to make many similar measurements with SEIS in the years to come,” said Charles Yana, SEIS mission operations manager at CNES.
JPL manages InSight for NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space in Denver built the InSight spacecraft, including its cruise stage and lander, and supports spacecraft operations for the mission.
A number of European partners, including CNES and the German Aerospace Center (DLR), support the InSight mission. CNES provided the SEIS instrument to NASA, with the principal investigator at IPGP. Significant contributions for SEIS came from IPGP; the Max Planck Institute for Solar System Research in Germany; the Swiss Federal Institute of Technology (ETH Zurich) in Switzerland; Imperial College London and Oxford University in the United Kingdom; and JPL. DLR provided the Heat Flow and Physical Properties Package (HP3) instrument, with significant contributions from the Space Research Center of the Polish Academy of Sciences and Astronika in Poland. Spain’s Centro de Astrobiología supplied the temperature and wind sensors.
