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Complex geology contributed to Deepwater Horizon disaster, new study finds

A new study from The University of Texas at Austin looks at the complex geology that contributed to the 2010 Deepwater Horizon disaster.
A new study from The University of Texas at Austin looks at the complex geology that contributed to the 2010 Deepwater Horizon disaster. Credit: US Coast Guard

A study from The University of Texas at Austin is the first published in a scientific journal to take an in-depth look at the challenging geologic conditions faced by the crew of the Deepwater Horizon drilling rig and the role those conditions played in the 2010 disaster.

The well blowout killed 11 people and spewed oil for three months, spilling about 4 million barrels of oil into the Gulf of Mexico before crews successfully capped the well. Researchers and investigators since then have focused mostly on the engineering decisions and mistakes that led to the blowout and the ecological impacts of the oil spill that became one of the country’s worst environmental catastrophes. But researchers from the UT Jackson School of Geosciences, aided by thousands of pages of documents made public during lawsuits and legal proceedings, have pieced together how the geologic conditions more than 2 miles under the Gulf floor made drilling difficult and drove engineering decisions that contributed to the well’s failure and the ensuing blowout.

The study, published May 7 in Scientific Reports, documents, among other things, a significant and steep drop in pore pressure inside the rock near the bottom of the well that influenced the decisions that contributed to the blowout.

“The paper tells the geological story behind the catastrophe,” said Will Pinkston, who authored the paper while earning a master’s degree at the Jackson School. “It is high impact science, and I’m excited to reach a wider audience of people who don’t think about these issues every day.”

The engineering and geosciences challenges posed by drilling wells miles under the surface of the earth are enormously complex. One of the most critical is to maintain the pressure within the well so that it is higher than the pressure within the fluid inside the rock but lower than the stress at which the rock fails. If pressure inside the well is too high, it will fracture the well wall and drive drilling fluids into the rock. If the well pressure is lower than the rock’s fluid pressure, fluids from inside the surrounding rock will flow into the well and potentially cause a blowout.

To successfully drill, crews use drilling “mud,” a slurry that can be mixed to varying weights and consistency, which is circulated throughout the well to help stabilize the hole and control pressure. Crews then line the exposed well with cement and steel casing to seal off exposed rock.

In the case of the Transocean Deepwater Horizon drilling rig, which was operated by the BP energy company at the time of the accident, the pore pressure was very high throughout the well, but then dropped abruptly by about 1,200 pounds per square inch near the bottom. Most of the pore pressure drop occurred in the 100 feet above the reservoir target of 18,000 feet below sea level.

BP planned to temporarily abandon the oil well, the initial well in the Macondo prospect, until it could be produced at a later date, by plugging the base with steel and cement. However, the sharp drop in pore pressure, and an associated decline in stress, drastically narrowed the range of options to seal off the well. This led to the decision to use a controversial low-density foam cement that failed to set properly. This was a key cause of the Macondo well blowout.

“The bottom line is that the geological conditions led to a decision to use a specialized cement that failed,” said Peter Flemings, a Jackson School professor and study author. “This decision was a root cause of the ultimate blowout.”

Flemings was a member of the Deepwater Horizon well integrity team assembled by then-U.S. Energy Secretary Steven Chu to help respond to the disaster.

Beyond describing the pressure and stress conditions in the well, the paper maps geologic conditions across the entire subterranean basin to show that the pressure drop is not a unique event in that area.

“Macondo isn’t a one-dimensional problem,” Pinkston said. “We found evidence of large-scale fluid connectivity across the basin, and this would have been hard to predict.”

Although the paper does not pinpoint any single reason for the catastrophe, Flemings said it offers important information for the larger drilling community.

“One of the significant things about this paper is to get all the data on the table so that the general community can understand the decisions that were made,” Flemings said.

“I broadly believe that if engineers and geoscientists are more aware of how pressure and stress and engineering decisions couple, better decisions will be made.”

The study was funded by Flemings and the UT GeoFluids consortium. Data from the consortium and the University of Texas Institute for Geophysics Gulf Basin Depositional Synthesis project were used in this study. BP is one of the companies that supports the consortium.

Reference:
F. William M. Pinkston, Peter B. Flemings. Overpressure at the Macondo Well and its impact on the Deepwater Horizon blowout. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-019-42496-0

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Radioactive carbon from nuclear bomb tests found in deep ocean trenches

The 37 kiloton 'Priscilla' nuclear test, detonated at the Nevada Test Site in 1957. Credit: US Department of Energy
The 37 kiloton ‘Priscilla’ nuclear test, detonated at the Nevada Test Site in 1957. Credit: US Department of Energy

Radioactive carbon released into the atmosphere from 20th-century nuclear bomb tests has reached the deepest parts of the ocean, new research finds.

A new study in AGU’s journal Geophysical Research Letters finds the first evidence of radioactive carbon from nuclear bomb tests in muscle tissues of crustaceans that inhabit Earth’s ocean trenches, including the Mariana Trench, home to the deepest spot in the ocean.

Organisms at the ocean surface have incorporated this “bomb carbon” into the molecules that make up their bodies since the late 1950s. The new study finds crustaceans in deep ocean trenches are feeding on organic matter from these organisms when it falls to the ocean floor. The results show human pollution can quickly enter the food web and make its way to the deep ocean, according to the study’s authors.

“Although the oceanic circulation takes hundreds of years to bring water containing bomb [carbon] to the deepest trench, the food chain achieves this much faster,” said Ning Wang, a geochemist at the Chinese Academy of Sciences in Guangzhou, China, and lead author of the new study.

“There’s a very strong interaction between the surface and the bottom, in terms of biologic systems, and human activities can affect the biosystems even down to 11,000 meters, so we need to be careful about our future behaviors,” said Weidong Sun, a geochemist at the Chinese Academy of Sciences in Qingdao, China, and co-author of the new study. “It’s not expected, but it’s understandable, because it’s controlled by the food chain.”

The results also help scientists better understand how creatures have adapted to living in the nutrient-poor environment of the deep ocean, according to the authors. The crustaceans they studied live for an unexpectedly long time by having extremely slow metabolisms, which the authors suspect may be an adaptation to living in this impoverished and harsh environment.

Creating radioactive particles

Carbon-14 is radioactive carbon that is created naturally when cosmic rays interact with nitrogen in the atmosphere. Carbon-14 is much less abundant than non-radioactive carbon, but scientists can detect it in nearly all living organisms and use it to determine the ages of archeological and geological samples.

Thermonuclear weapons tests conducted during the 1950s and 1960s doubled the amount of carbon-14 in the atmosphere when neutrons released from the bombs reacted with nitrogen in the air. Levels of this “bomb carbon” peaked in the mid-1960s and then dropped when atmospheric nuclear tests stopped. By the 1990s, carbon-14 levels in the atmosphere had dropped to about 20 percent above their pre-test levels.

This bomb carbon quickly fell out of the atmosphere and mixed into the ocean surface. Marine organisms that have lived in the decades since this time have used bomb carbon to build molecules within their cells, and scientists have seen elevated levels of carbon-14 in marine organisms since shortly after the bomb tests began.

Life at the bottom of the sea

The deepest parts of the ocean are the hadal trenches, those areas where the ocean floor is more than 6 kilometers (4 miles) below the surface. These areas form when one tectonic plate subducts beneath another. Creatures that inhabit these trenches have had to adapt to the intense pressures, extreme cold, and lack of light and nutrients.

In the new study, researchers wanted to use bomb carbon as a tracer for organic material in hadal trenches to better understand the organisms that live there. Wang and her colleagues analyzed amphipods collected in 2017 from the Mariana, Mussau, and New Britain Trenches in the tropical West Pacific Ocean, as far down as 11 kilometers (7 miles) below the surface. Amphipods are a type of small crustacean that live in the ocean and get food from scavenging dead organisms or consuming marine detritus.

Surprisingly, the researchers found carbon-14 levels in the amphipods’ muscle tissues were much greater than levels of carbon-14 in organic matter found in deep ocean water. They then analyzed the amphipods’ gut contents and found those levels matched estimated carbon-14 levels from samples of organic material taken from the surface of the Pacific Ocean. This suggests the amphipods are selectively feeding on detritus from the ocean surface that falls to the ocean floor.

Adapting to the deep ocean environment

The new findings allow researchers to better understand the longevity of organisms that inhabit hadal trenches and how they have adapted to this unique environment.

Interestingly, the researchers found the amphipods living in these trenches grow larger and live longer than their counterparts in shallower waters. Amphipods that live in shallow water typically live for less than two years and grow to an average length of 20 millimeters (0.8 inches). But the researchers found amphipods in the deep trenches that were more than 10 years old and had grown to 91 millimeters (3.6 inches) long.

The study authors suspect the amphipods’ large size and long life are likely the byproducts of their evolution to living in the environment of low temperatures, high pressure and a limited food supply. They suspect the animals have slow metabolisms and low cell turnover, which allows them to store energy for long periods of time. The long life time also suggests pollutants can bioaccumulate in these unusual organisms.

“Besides the fact that material mostly comes from the surface, the age-related bioaccumulation also increases these pollutant concentrations, bringing more threat to these most remote ecosystems,” Wang said.

The new study shows deep ocean trenches are not isolated from human activities, Rose Cory, an associate professor of earth and environmental sciences at the University of Michigan who was not involved in the new research, said in an email. The research shows that by using “bomb” carbon, scientists can detect the fingerprint of human activity in the most remote, deepest depths of the ocean, she added.

The authors also use “bomb” carbon to show that the main source of food for these organisms is carbon produced in the surface ocean, rather than more local sources of carbon deposited from nearby sediments, Cory said. The new study also suggests that the amphipods in the deep trenches have adapted to the harsh conditions in deep trenches, she added.

“What is really novel here is not just that carbon from the surface ocean can reach the deep ocean on relatively short timescales, but that the ‘young’ carbon produced in the surface ocean is fueling, or sustaining, life in the deepest trenches,” Cory said.

Reference:
Ning Wang, Chengde Shen, Weidong Sun, Ping Ding, Sanyuan Zhu, Weixi Yi, Zhiqiang Yu, Zhongli Sha, Mei Mi, Lisheng He, Jiasong Fang, Kexin Liu, Xiaomei Xu, Ellen R.M. Druffel. Penetration of Bomb 14 C into the Deepest Ocean Trench. Geophysical Research Letters, 2019; DOI: 10.1029/2018GL081514

Note: The above post is reprinted from materials provided by American Geophysical Union.

Tsunami signals to measure glacier calving in Greenland

The calving front of Bowdoin Glacier in northwestern Greenland, where icebergs are discharged and ice under the water melts.
The calving front of Bowdoin Glacier in northwestern Greenland, where icebergs are discharged and ice under the water melts. Credit: Photo taken by Shin Sugiyama

In recent years, glaciers near the North and South poles, as well as in mountainous areas, have been shrinking due to the effect of global warming, becoming a significant contributor to the recent sea level rise. Calving glaciers, which discharge icebergs into an ocean or lake, have retreated more rapidly than those on land because of sections collapsing at the glacier front and due to submarine melting.

It is, however, difficult to directly measure the volume of calving ice and submarine melting because conducting on-site examinations at the glacier front can be dangerous. Conventional methods that measure their volume based on satellite image analysis also yield only low temporal and spatial resolutions and do not allow continuous monitoring.

When icebergs break off into water, the so-called impulse waves or simply, tsunami waves, move over the ocean or lake. In this study, the team including Evgeny Podolskiy and Shin Sugiyama of Hokkaido University and Masahiro Minowa of the Austral University of Chile measured the volume of icebergs that broke off from Bowdoin Glacier, a calving glacier terminating at the head of Bowdoin Fjord. An underwater pressure sensor capable of making 20 measurements per second was placed in front of the glacier to record calving-generated tsunami waves measuring 10 centimeters to 1 meter high. The researchers then compared the data with high-resolution images of the glacier front taken by unmanned aerial vehicles (UAVs) as well as images by a time-lapse camera to find the relationship between calving events and tsunami-wave properties.

The team found a positive correlation between the volume of calving ice and wave amplitude, and confirmed that the distance to calving events can be measured with a single pressure sensor from a frequency dispersion of water waves. Based on their measurements, they estimated the temporal and spatial distribution of icebergs that broke off within the study period from Bowdoin Glacier. The estimated volume of calving ice was also compared with the speed the glacier was flowing, the tides, and fluctuations in air temperature.

The team found that the calving volume was higher at places where meltwater rises from the bottom of the glacier to the sea surface. The calving volume, or rate, was greater during periods of fast ice flow, high air temperature, and at falling/low tide. A satellite image analysis showed calving events caused only 20 percent of the mass loss at the glacier front, suggesting 80 percent of the ice mass loss was caused by submarine melting.

“Our study, which utilized tsunami signals to measure the calving flux, will help us understand the interplay between glaciers and oceans, a key factor in predicting future evolutions of glaciers,” says Evgeny Podolskiy.

The study was led by Masahiro Minowa and was conducted in collaboration with Austral University of Chile, ETH Zurich and the University of Florence.

Reference:
Masahiro Minowa, Evgeny A. Podolskiy, Guillaume Jouvet, Yvo Weidmann, Daiki Sakakibara, Shun Tsutaki, Riccardo Genco, Shin Sugiyama. Calving flux estimation from tsunami waves. Earth and Planetary Science Letters, 2019; 515: 283 DOI: 10.1016/j.epsl.2019.03.023

Note: The above post is reprinted from materials provided by Hokkaido University.

Moldavite : What is Moldavite Gemstones? How Moldavite is Formed?

Moldavite
Moldavite

Moldavite

It is a green forest, olive green or blue green vitreous silica projectile rock formed by a meteorite impact in southern Germany (Nördlinger Ries Crater) occurring around 15 million years ago. It’s a kind of tectitis.

Crystal system: Amorphous
Color: Forest green
Luster: Vitreous

What is Moldavite Made Of?

It was believed to have been formed after a meteorite impact by condensed rock vapors. It is part of the mineral group Tektite, a small family of natural glass rocks. Moldavite is sometimes claimed to be’ the only known alien gemstone on Earth’ or’ the gemstone born from the stars.’

How Moldavite is Formed?

According to the generally accepted theory, moldavites were formed during an impact of a huge meteorite 14.75 million years ago at high pressures and temperatures from superficial tertiary sediments in the Ries area of Germany.

What is Moldavite Worth?

The value of these Moldavites jumped from about USD 5 per gram about 20 years ago to about USD 75 and even up to USD 130 per gram today. The availability is extremely low and some Asian laboratories have perfected their production to provide the market with a very good look-alike man-made “Moldovite” glass.

Moldavite Gemstone

Moldavite Color

It occurs in a variety of shades of green, including deep, forest-green and pale to olive-green. Some materials from Moravia are known to occur with greenish-brown color. The most desirable color is a pure, light to medium green with no brown, and not too dark in tone.

Moldavite Clarity and Luster

It can be opaque and transparent. The finest specimens are transparent and very rare. Today’s most moldavite is opaque with slight translucency levels. Generally speaking, the higher the transparency, the better the stone. There is a big difference in price between moldavite’ regular grade’ and museum grade.

Moldavite Cut and Shape

It comes in a variety of shapes and cuts. Only the finest and most transparent materials are faced, while the rest are usually traded in their natural rough condition. The most common shapes are those resulting from its molten formation, such as drop shape, disk shape, oval, elliptical or spiral shape, as well as shapes that resemble spilled liquid patterns. Bohemian moldavite is usually drop-shaped, while spherical is Moravian moldavite.

Where Moldavite is Found?

Moldavite’s largest deposits were found in the upper Vltava River basin between Prachatice and Trhovými Sviny, particularly in the south and west of the Czech Republic of České Budějovice (Budweis). Also found in Moravia, mainly in the Jihlava river’s central area.

New 3-foot-tall relative of Tyrannosaurus rex

tyrannosauroid Suskityrannus hazelae
Reconstruction of the tyrannosauroid Suskityrannus hazelae from the Late Cretaceous (~92 million years ago) in current day New Mexico. Credit: Andrey Atuchin

A new relative of the Tyrannosaurus rex — much smaller than the huge, ferocious dinosaur made famous in countless books and films, including, yes, “Jurassic Park” — has been discovered and named by a Virginia Tech paleontologist and an international team of scientists.

The newly named tyrannosauroid dinosaur — Suskityrannus hazelae — stood roughly 3 feet tall at the hip and was about 9 feet in length, the entire animal only marginally longer than the just the skull of a fully grown Tyrannosaurus rex, according to Sterling Nesbitt, an assistant professor with Department of Geosciences in the Virginia Tech College of Science. In a wild twist to this discovery, Nesbitt found the fossil at age 16 whilst a high school student participating in a dig expedition in New Mexico in 1998, led by Doug Wolfe, an author on the paper.

In all, Suskityrannus hazelae is believed to have weighed between 45 and 90 pounds. The typical weight for a full-grown Tyrannosaurus rex is roughly 9 tons. Its diet likely consisted of the same as its larger meat-eating counterpart, with Suskityrannus hazelae likely hunting small animals, although what it hunted is unknown. The dinosaur was at least 3 years old at death based on an analysis of its growth from its bones.

The fossil dates back 92 million years to the Cretaceous Period, a time when some of the largest dinosaurs ever found lived.

“Suskityrannus gives us a glimpse into the evolution of tyrannosaurs just before they take over the planet,” Nesbitt said. “It also belongs to a dinosaurian fauna that just proceeds the iconic dinosaurian faunas in the latest Cretaceous that include some of the most famous dinosaurs, such as the Triceratops, predators like Tyrannosaurus rex, and duckbill dinosaurs like Edmotosaurus.”

The findings are published in the latest online issue of Nature Ecology & Evolution. In describing the new find, Nesbitt said, “Suskityrannus has a much more slender skull and foot than its later and larger cousins, the Tyrannosaurus rex. The find also links the older and smaller tyrannosauroids from North America and China with the much larger tyrannosaurids that lasted until the final extinction of non-avian dinosaurs.

(Tyrannosaurus rex small arm jokes abound. So, if you’re wondering how small the arms of Suskityrannus were, Nesbitt and his team are not exactly sure. No arm fossils of either specimen were found, but partial hand claws were found. And, they are quite small. Also not known: If Suskityrannus had two or three fingers.)

Two partial skeletons were found. The first included a partial skull that was found in 1997 by Robert Denton, now a senior geologist with Terracon Consultants, and others in the Zuni Basin of western New Mexico during an expedition organized by Zuni Paleontological Project leader Doug Wolfe.

The second, more complete specimen was found in 1998 by Nesbitt, then a high school junior with a burgeoning interest in paleontology, and Wolfe, with assistance in collection by James Kirkland, now of the Utah Geological Survey. “Following Sterling out to see his dinosaur, I was amazed at how complete a skeleton was lying exposed at the site,” Kirkland said.

For much of the 20 years since the fossils were uncovered, the science team did not know what they had.

“Essentially, we didn’t know we had a cousin of Tyrannosaurus rex for many years,” Nesbitt said. He added the team first thought they had the remains of a dromaeosaur, such as Velociraptor. During the late 1990s, close relatives Tyrannosaurus rex simply were not known or not recognized. Since then, more distant cousins of Tyrannosaurus rex, such as Dilong paradoxus, have been found across Asia.

The fossil remains were found near other dinosaurs, along with the remains of fish, turtles, mammals, lizards, and crocodilians. From 1998 until 2006, the fossils remain stored at the Arizona Museum of Natural History in Mesa, Arizona. After 2006, Nesbitt brought the fossils with him through various postings as student and researcher in New York, Texas, Illinois, and now Blacksburg. He credits the find, and his interactions with the team members on the expedition, as the start of his career.

“My discovery of a partial skeleton of Suskityrannus put me onto a scientific journey that has framed my career,” said Nesbitt, also a member of the Virginia Tech Global Change Center. “I am now an assistant professor that gets to teach about Earth history.”

The name Suskityrannus hazelae is derived from “Suski,” the Zuni Native American tribe word for “coyote,” and from the Latin word ‘tyrannus’ meaning king and ‘hazelae’ for Hazel Wolfe, whose support made possible many successful fossil expeditions in the Zuni Basin. Nesbitt said permission was granted from the Zuni Tribal Council to use the word “Suski.”

Reference:
Sterling J. Nesbitt, Robert K. Denton Jr, Mark A. Loewen, Stephen L. Brusatte, Nathan D. Smith, Alan H. Turner, James I. Kirkland, Andrew T. McDonald & Douglas G. Wolfe. A mid-Cretaceous tyrannosauroid and the origin of North American end-Cretaceous dinosaur assemblages. Nature Ecology & Evolution, 2019 DOI: 10.1038/s41559-019-0888-0

Note: The above post is reprinted from materials provided by Virginia Tech.

What does Earth’s core have in common with salad dressing?

A laser-heated diamond anvil cell is used to simulate the pressure and temperature conditions of Earth's core.
A laser-heated diamond anvil cell is used to simulate the pressure and temperature conditions of Earth’s core. Inset shows a scanning electron miscroscope image of a quenched melt spot with immiscible liquids. Credit: Sarah M. Arveson/Yale University

A Yale-led team of scientists may have found a new factor to help explain the ebb and flow of Earth’s magnetic field—and it’s something familiar to anyone who has made a vinaigrette for their salad.

Earth’s magnetic field, produced near the center of the planet, has long acted as a buffer from the harmful radiation of solar winds emanating from the Sun. Without that protection, life on Earth would not have had the opportunity to flourish. Yet our knowledge of Earth’s magnetic field and its evolution is incomplete.

In a new study published May 6 in the Proceedings of the National Academy of Sciences, Yale associate professor Kanani K.M. Lee and her team found that molten iron alloys containing silicon and oxygen form two distinct liquids under conditions similar to those in the Earth’s core. It is a process called immiscibility.

“We observe liquid immiscibility often in everyday life, like when oil and vinegar separate in salad dressing. It is surprising that liquid phase separation can occur when atoms are being forced very close together under the immense pressures of Earth’s core,” said Yale graduate student Sarah Arveson, the study’s lead author.

Immiscibility in complex molten alloys is common at atmospheric pressure and has been well documented by metallurgists and materials scientists. But studies of immiscible alloys at higher pressures have been limited to pressures found in Earth’s upper mantle, located between Earth’s crust and its core.

Even deeper, 2,900 kilometers beneath the surface, is the outer core—a more than 2,000-kilometer thick layer of molten iron. It is the source of the planet’s magnetic field. Although this hot liquid roils vigorously as it convects, making the outer core mostly well-mixed, it has a distinct liquid layer at the top. Seismic waves moving through the outer core travel slower in this top layer than they do in the rest of the outer core.

Scientists have offered several theories to explain this slow liquid layer, including the idea that immiscible iron alloys form layers in the core. But there has been no experimental or theoretical evidence to prove it until now.

Using laser-heated, diamond-anvil cell experiments to generate high pressures, combined with computer simulations, the Yale-led team reproduced conditions found in the outer core. They demonstrated two distinct, molten liquid layers: an oxygen-poor, iron-silicon liquid and an iron-silicon-oxygen liquid. Because the iron-silicon-oxygen layer is less dense, it rises to the top, forming an oxygen-rich layer of liquid.

“Our study presents the first observation of immiscible molten metal alloys at such extreme conditions, hinting that immiscibility in metallic melts may be prevalent at high pressures,” said Lee.

The researchers said the findings add a new variable for understanding conditions of the early Earth, as well as how scientists interpret changes in Earth’s magnetic field throughout history.

Additional authors of the study are Jie Deng of Yale and Bijaya Karki of Louisiana State University.

Reference:
Sarah M. Arveson el al., “Evidence for Fe-Si-O liquid immiscibility at deep Earth pressures,” PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1821712116

Note: The above post is reprinted from materials provided by Yale University.

Oxygen linked with the boom and bust of early animal evolution

Fossilized giant arthropod Phytophilaspis from the Cambrian Period.
Fossilized giant arthropod Phytophilaspis from the Cambrian Period. Credit: Andrey Zhuravlev, Lomonosov Moscow State University

Extreme fluctuations in atmospheric oxygen levels corresponded with evolutionary surges and extinctions in animal biodiversity during the Cambrian explosion, finds new study led by UCL and the University of Leeds.

The Cambrian explosion was a crucial period of rapid evolution in complex animals that began roughly 540 million years ago. The trigger for this fundamental phase in the early history of animal life is a subject of ongoing biological debate.

The study, published today in Nature Geoscience by scientists from the UK, China and Russia, gives strong support to the theory that oxygen content in the atmosphere was a major controlling factor in animal evolution.

The study is the first to show that during the Cambrian explosion there was significant correlation between surges in oxygen levels and bursts in animal evolution and biodiversity, as well as extinction events during periods of low oxygen.

Dr Tianchen He, study lead author and postdoctoral researcher at the University of Leeds, began this research while at UCL. He said: “The complex creatures that came about during the Cambrian explosion were the precursors to many of the modern animals we see today. But because there is no direct record of atmospheric oxygen during this time period it has been difficult to determine what factors might have kick started this crucial point in evolution.

“By analysing the carbon and sulphur isotopes found in ancient rocks, we are able to trace oxygen variations in Earth’s atmosphere and shallow oceans during the Cambrian Explosion. When compared to fossilised animals from the same time we can clearly see that evolutionary radiations follow a pattern of ‘boom and bust’ in tandem with the oxygen levels.

“This strongly suggests oxygen played a vital role in the emergence of early animal life.”

Study co-author Professor Graham Shields from UCL Earth Sciences, said: “This is the first study to show clearly that our earliest animal ancestors experienced a series of evolutionary radiations and bottlenecks caused by extreme changes in atmospheric oxygen levels.

“The result was a veritable explosion of new animal forms during more than 13 million years of the Cambrian Period. In that time, Earth went from being populated by simple, single-celled and immobile organisms to hosting the wonderful variety of intricate, energetic life forms we see today.”

The team analysed the carbon and sulphur isotopes from marine carbonate samples collected from sections along the Aldan and Lena rivers in Siberia. During the time of the Cambrian explosion this area would have been a shallow sea and the home for the majority of animal life on Earth.

The lower Cambrian strata in Siberia are composed of continuous limestone with rich fossil records and reliable age constraints, providing suitable samples for the geochemical analyses. The isotope signatures in the rocks relate to the global production of oxygen, allowing the team to determine oxygen levels present in the shallow ocean and atmosphere during the Cambrian Period.

Study co-author Dr Benjamin Mills, from the School of Earth and Environment at Leeds, said: “The Siberian Platform gives us a unique window into early marine ecosystems. This area contains over half of all currently known fossilised diversity from the Cambrian explosion.

“Combining our isotope measurements with a mathematical model lets us track the pulses of carbon and sulphur entering the sediments in this critical evolutionary cradle. Our model uses this information to estimate the global balance of oxygen production and destruction, giving us new insight into how oxygen shaped the life we have on the planet today.”

Study co-author Maoyan Zhu from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, said: “Understanding what triggered the Cambrian explosion requires multidisciplinary study. That’s why with Graham Shields we organized together such a multidisciplinary team funded by NERC and NSFC in past years. I am so excited about the results through this collaborative project.”

“On the other hand, it took a long time to get this result. We already got samples from Siberia in 2008. The sections in Siberia are difficult to access. It took time for us to organize the expedition and collect the samples there. Without support from Russian colleagues, we could not do the project.”

Study co-author Andrey Yu Zhuravlev from Lomonosov Moscow State University said: “This has been an incredibly successful and exciting joint study. The question of the Cambrian Explosion trigger has puzzled scientists for years. Now, the results give us convincing evidence to link the rapid appearance of animals as well as mass extinction during the early Cambrian with oxygen.”

Reference:
Tianchen He, Maoyan Zhu, Benjamin J. W. Mills, Peter M. Wynn, Andrey Yu. Zhuravlev, Rosalie Tostevin, Philip A. E. Pogge von Strandmann, Aihua Yang, Simon W. Poulton and Graham A. Shields. Possible links between extreme oxygen perturbations and the Cambrian radiation of animals. Nature Geoscience, 2019 DOI: 10.1038/s41561-019-0357-z

Note: The above post is reprinted from materials provided by University of Leeds.

The fossilization process of dinosaur remains

Dinosaur
Representative Image: Dinosaur. Credit: Public Domain

A study conducted between the UPV/EHU-University of the Basque Country and the University of Zaragoza has conducted an in-depth analysis of the dinosaur fossils at La Cantalera-1, one of the Iberian sites belonging to the Lower Cretaceous with the largest number of vertebrates. The structure of the fossilized bone tissue as well as the fossilization processes have been studied. It has been possible to confirm that most of the dinosaurs found at La Cantalera-1 were young individuals.

The site at La Cantalera-1 is located in Teruel (Spain) and regarded as hugely important by the scientific community, as it is one of the sites on the Iberian Peninsula with the greatest diversity of vertebrates of the Lower Cretaceous. Remains of dinosaurs, mammals, crocodiles, pterosaurs, lizards, tortoises, amphibians and fish dating back to approximately 130 million years ago have been discovered. A multidisciplinary study carried out by researchers in the Department of Stratigraphy and Palaeontology and the Department of Mineralogy and Petrology at the UPV/EHU’s Faculty of Science and Technology, together with the University of Zaragoza (Aragosaurus-IUCA Group), has explored not only the fossilization process (taphonomy) which took place in some of these remains, but also the internal structure displayed by the bones (palaeohistology).

The site has undergone thorough investigation. “No previous investigation had tackled it from these perspectives or with the depth that we have conducted in this study,” said Leire Perales-Gogenola, a member of the UPV/EHU’s Department of Stratigraphy and Palaeontology and lead author of the paper.

For their work, they selected two groups of dinosaurs: ornithopods (of which there are abundant remains at the site), and ankylosaurs (known as armoured dinosaurs as they had armour consisting of bony plates). Although large fossils exist, this research group resorted to “fragmentary remains, small pieces of bone and the dermal bones. The methodology we had to follow involved making sections in the samples and we did not want to damage the more important items,” said the researcher.

Wetland ecosystem with a wealth of young individuals

The study of the internal structures of the fossil bones (palaeohistology) “revealed that most of the ornithopod dinosaurs were young individuals. On inspecting the fossilized bones under the microscope, they were found to display the same structure as unfossilized bones as they retain all their characteristics. This enables us to identify the signs that tell us whether they belonged to adult or immature individuals; it is possible to know, for example, whether the individual in question was a large but young dinosaur or whether it was a small but adult dinosaur,” explained the UPV/EHU biologist and palaeontologist.

In the study of the internal part of the dermal bones they observed “various traces that other researchers had associated with a specific group of ankylosaurs, so in some cases we were able to determine more accurately what kind of dinosaurs they were.”

For the taphonomic study, the researcher emphasized the usefulness of analysing fragmentary remains, “as they are bones that have undergone fractures owing to the pressure of the subsequent burial itself, among other things, and this has allowed various sedimentary materials to filter through these fractures, which have been fossilized beside the bone remains; this provides hugely valuable information about the environment in which they were found.” In this part of the study, they were able to deduce that these bones were subjected to rapid burial, and soon reached the phreatic level in which the fossilization processes had already taken place. Microbial activity in the bones, the presence of bacterial forming microbial carpets, has also been detected, and this may have encouraged the fossilization process.

The results have increased the available knowledge about the site. “The features of the ecosystem and degree of maturity of the individuals present, which had already been described in previous studies, have been confirmed. The data indicate that it was a wetland ecosystem and was used as a feeding zone for the fauna in the area. Due to the wealth of young individuals and eggshell remains, which are also very abundant at the site, it has been suggested that it could have been a breeding or feeding area,” said Perales-Gogenola.

Forthcoming studies at the site anticipated by the University of Zaragoza are due to tackle the palaeohistology of the dinosaurs present at La Cantalera-1 and also to go further into the age of death of the herbivore dinosaurs to certify whether it was a natural population or whether there is an excessive number of youngsters owing to predation issues by theropod dinosaurs (carnivorous dinosaurs that could attack young individuals more frequently than adult individuals).

Reference:
Leire Perales-Gogenola et al, Taphonomy and palaeohistology of ornithischian dinosaur remains from the Lower Cretaceous bonebed of La Cantalera (Teruel, Spain), Cretaceous Research (2019). DOI: 10.1016/j.cretres.2019.01.024

Note: The above post is reprinted from materials provided by University of the Basque Country.

Earthquakes are triggered well beyond fluid injection zones

USGS map highlights earthquake risk zones. Blue boxes indicate areas of high activity of human-caused earthquake due to deep bore fluid injection.
USGS map highlights earthquake risk zones. Blue boxes indicate areas of high activity of human-caused earthquake due to deep bore fluid injection. Credit: USGS

Using data from field experiments and modeling of ground faults, researchers at Tufts University have discovered that the practice of subsurface fluid injection used in ‘fracking‘ and wastewater disposal for oil and gas exploration could cause significant, rapidly spreading earthquake activity beyond the fluid diffusion zone. Deep fluid injections — greater than one kilometer deep — are known to be associated with enhanced seismic activity — often thought to be limited to the areas of fluid diffusion. Yet the study, published today in the journal Science, tests and strongly supports the hypothesis that fluid injections are causing potentially damaging earthquakes further afield by the slow slip of pre-existing fault fracture networks, in domino-like fashion.

The results account for the observation that the frequency of human-made earthquakes in some regions of the country surpass natural earthquake hotspots.

The study also represents a proof of concept in developing and testing more accurate models of fault behavior using actual experiments in the field. Much of our current understanding about the physics of geological faults is derived from laboratory experiments conducted at sample length scales of a meter or less. However, earthquakes and fault rupture occur over vastly larger scales. Observations of fault rupture at these larger scales are currently made remotely and provide poor estimates of the physical parameters of fault behavior that would be used to develop a model of human-made effects. More recently, the earthquake science community has put resources behind field-scale injection experiments to bridge the scale gap and understand fault behavior in its natural habitat.

The researchers used data from these experimental field injections, previously conducted in France and led by a team of researchers based at the University of Aix-Marseille and the University of Nice Sophia-Antipolis. The experiments measured fault pressurization and displacement, slippage and other parameters that are fed into the fault-slip model used in the current study. The Tufts researchers’ analysis provides the most robust inference to date that fluid-activated slippage in faults can quickly outpace the spread of fluid underground.

“One important constraint in developing reliable numerical models of seismic hazard is the lack of observations of fault behavior in its natural habitat,” said Pathikrit Bhattacharya, a former post-doc in the department of civil and environmental engineering at Tufts University’s School of Engineering and lead author of the study. “These results demonstrate that, when available, such observations can provide remarkable insight into the mechanical behavior of faults and force us to rethink their hazard potential.” Bhattacharya is now assistant professor in the School of Earth, Ocean and Climate Sciences at the Indian Institute of Technology in Bhubaneswar, India.

The hazard posed by fluid-induced earthquakes is a matter of increasing public concern in the US. The human-made earthquake effect is considered responsible for making Oklahoma — a very active region of oil and gas exploration — the most productive seismic region in the country, including California. “It’s remarkable that today we have regions of human-made earthquake activity that surpass the level of activity in natural hot spots like southern California,” said Robert C. Viesca, associate professor of civil and environmental engineering at Tufts University’s School of Engineering, co-author of the study and Bhattacharya’s post-doc supervisor. “Our results provide validation for the suspected consequences of injecting fluid deep into the subsurface, and an important tool in assessing the migration and risk of induced earthquakes in future oil and gas exploration.”

Most earthquakes induced by fracking are too small — 3.0 on the Richter scale — to be a safety or damage concern. However, the practice of deep injection of the waste products from these explorations can affect deeper and larger faults that are under stress and susceptible to fluid induced slippage. Injection of wastewater into deep boreholes (greater than one kilometer) can cause earthquakes that are large enough to be felt and may cause damage.

According to the U.S. Geological Survey, the largest earthquake induced by fluid injection and documented in the scientific literature was a magnitude 5.8 earthquake in September 2016 in central Oklahoma. Four other earthquakes greater than 5.0 have occurred in Oklahoma as a result of fluid injection, and earthquakes of magnitude between 4.5 and 5.0 have been induced by fluid injection in Arkansas, Colorado, Kansas and Texas.

Reference:
Pathikrit Bhattacharya, Robert C. Viesca. Fluid-induced aseismic fault slip outpaces pore-fluid migration. Science, 2019; 364 (6439): 464 DOI: 10.1126/science.aaw7354

Note: The above post is reprinted from materials provided by Tufts University.

Study on explosive volcanism during ice age provides lessons for today’s rising CO2

Earth's icehouse conditions of the last several million years were driven laergely by geologically low values of atmospheric carbon dioxide
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.

Note: The above post is reprinted from materials provided by University of Oklahoma.

Resolving the ‘invisible’ gold puzzle

Gold
Gold

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

Note: The above post is reprinted from materials provided by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre.

99-million-year-old millipede discovered in Burmese amber

The newly described millipede (Burmanopetalum inexpectatum) seen in amber.
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.

Running may have made dinosaurs’ wings flap before they evolved to fly

Caudipteryx robot for testing passive flapping flight.
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.

Magma is the key to the moon’s makeup

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.
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

Note: The above post is reprinted from materials provided by Yale University.

Chewing versus sex in duck-billed dinosaurs

The skulls of three hadrosaur dinosaurs, Lambeosaurus lambei (top left), Gryposaurus notabilis (top right), Parasaurolophus walkeri (lower).
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

Note: The above post is reprinted from materials provided by University of Bristol.

Flowering plants, new teeth and no dinosaurs: New study sheds light on the rise of mammals

Well-preserved fossils -- like this Yanoconodon allini (Specimen No.: NJU P06001; Formation: Yixian; Age: 122.2-124.6 million years ago; Provenance: China)
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

Note: The above post is reprinted from materials provided by University of Washington.

First hominins on the Tibetan Plateau were Denisovans

The Xiahe mandible, only represented by its right half, was found in 1980 in Baishiya Karst Cave.
The Xiahe mandible, only represented by its right half, was found in 1980 in Baishiya Karst Cave. Credit: Dongju Zhang, Lanzhou University

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

Note: The above post is reprinted from materials provided by Max Planck Institute for Evolutionary Anthropology.

Australian blue tongue lizard ancestor was round-in-the-tooth

Australian blue tongue lizard ancestor
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

Note: The above post is reprinted from materials provided by Flinders University.

Mining : What is Mining? What are the 4 mining methods?

Open cut hard rock mining, Kalgoorlie, Western Australia.
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.

  1. Underground mines are more expensive and often used to reach deposits that are deeper.
  2. Surface mines are usually used for deposits that are shallower and less valuable.
  3. Placer mining is used in river channels, beach sands, or other environments to sift valuable metals from sediments.
  4. 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.

What does the future of Kilauea hold?

June 2018 flow from Kilauea Volcano’s lower east Rift Zone.
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.”

Note: The above post is reprinted from materials provided by Seismological Society of America.

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