Darkness, not cold, likely responsible for dinosaur-killing extinction

March 21, 2020

Roughly 66 million years ago an asteroid slammed into the Yucatan peninsula. New research shows darkness, not cold, likely drove a mass extinction after the impact. Credit: NASA

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New research finds soot from global fires ignited by an asteroid impact could have blocked sunlight long enough to drive the mass extinction that killed most life on Earth, including the dinosaurs, 66 million years ago.

The Cretaceous–Paleogene extinction event wiped out about 75 percent of all species on Earth. An asteroid impact at the tip of Mexico’s Yucatán Peninsula caused a period of prolonged cold and darkness, called an impact winter, that likely fueled a large part of the mass extinction. But scientists have had a hard time teasing out the details of the impact winter and what the exact mechanism was that killed life on Earth.

A new study in AGU’s journal Geophysical Research Letters simulates the contributions of the impact’s sulfur, dust, and soot emissions to the extreme darkness and cold of the impact winter. The results show the cold would have been severe but likely not devastating enough to drive a mass extinction. However, soot emissions from global forest fires darkened the sky enough to kill off photosynthesizers at the base of the food web for well over a year, according to the study.

“This low light seems to be a really big signal that would potentially be devastating to life,” said Clay Tabor, a geoscientist at the University of Connecticut and lead author of the new study. “It seems like these low light conditions are a probable explanation for a large part of the extinction.”

The results help scientists better understand this intriguing mass extinction that ultimately paved the way for humans and other mammals to evolve. But the study also provides insight into what might happen in a nuclear winter scenario, according to Tabor.

“The main driver of a nuclear winter is actually from soot in a similar type situation,” Tabor said. “What it really highlights is just how potentially impactful soot can be on the climate system.”

The impact and extinction

The Chicxulub asteroid impact spewed clouds of ejecta into the upper atmosphere that then rained back down to Earth. The returning particles would have had enough energy to broil Earth’s surface and ignite global forest fires. Soot from the fires, along with sulfur compounds and dust, blocked out sunlight, causing an impact winter lasting several years. Previous research estimates average global temperatures plummeted by at least 26 degrees Celsius (47 degrees Fahrenheit).

Scientists know the extreme darkness and cold were devastating to life on Earth but are still teasing apart which component was more harmful to life and whether the soot, sulfate, or dust particles were most disruptive to the climate.

In the new study, Tabor and his colleagues used a sophisticated climate model to simulate the climatic effects of soot, sulfates, and dust from the impact.

Their results suggest soot emissions from global fires absorbed the most sunlight for the longest amount of time. The model showed soot particles were so good at absorbing sunlight that photosynthesis levels dropped to below one percent of normal for well over a year.

“Based on the properties of soot and its ability to effectively absorb incoming sunlight, it did a very good job at blocking sunlight from reaching the surface,” Tabor said. “In comparison to the dust, which didn’t stay in the atmosphere for nearly as long, and the sulfur, which didn’t block as much light, the soot could actually block almost all light from reaching the surface for at least a year.”

A refuge for life

The darkness would have been devastating to photosynthesizers and could explain the mass extinction through a collapse of the food web, according to the researchers. All life on Earth depends on photosynthesizers like plants and algae that harvest energy from sunlight.

Interestingly, the temperature drop likely wasn’t as disturbing to life as the darkness, according to the study.

“It’s interesting that in their model, soot doesn’t necessarily cause a much larger cooling when compared other types of aerosol particles produced by the impact-but soot does cause surface sunlight to decline a lot more,” said Manoj Joshi, a climate dynamics professor at the University of East Anglia in the United Kingdom who was not connected to the new study.

In regions like the high latitudes, the results suggest oceans didn’t cool significantly more than they do during a normal cycle of the seasons.

“Even though the ocean cools by a decent amount, it doesn’t cool by that much everywhere, particularly in the higher latitude regions,” Tabor said. “In comparison to the almost two years without photosynthetic activity from soot, it seems to be a secondary importance.”

As a result, high latitude coastal regions may have been refuges for life in the months after the impact. Plants and animals living in the Arctic or Antarctic are already used to large temperature swings, extreme cold, and low light, so they may have had a better chance of surviving the impact winter, according to the researchers.

Reference:

Clay R. Tabor et al. Causes and Climatic Consequences of the Impact Winter at the Cretaceous‐Paleogene Boundary, Geophysical Research Letters (2020). DOI: 10.1029/2019GL085572
Julia Brugger et al. Baby, it’s cold outside: Climate model simulations of the effects of the asteroid impact at the end of the Cretaceous, Geophysical Research Letters (2016). DOI: 10.1002/2016GL072241

Note: The above post is reprinted from materials provided by American Geophysical Union. The original article was written by Lauren Lipuma.

Blue Quartz : What is Blue Quartz? How does Blue Quartz Form?

March 17, 2020

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What is Quartz?

Quartz is a crystalline, strong mineral made up of silicon and oxygen atoms. The atoms are linked in a continuous SiO4 Silicon–oxygen tetrahedra structure, with each oxygen being shared between two tetrahedra, giving SiO2 an overall chemical formula. Quartz is the second most abundant of minerals in the continental crust of Earth, behind feldspar.

Quartz occurs in two types, normal α-quartz and high-temperature β-quartz, both chiral. The transformation from α-quartz to β-quartz occurs abruptly at 573 ° C (846 K; 1.063 ° F). Since the transformation is followed by a major volume change, it can easily trigger the fracturing of ceramics or rocks that pass this temperature threshold.

There are several different quartz types and some semi-precious gemstones. Quartz varieties have been the most widely used minerals in jewelry making and hardstone carvings since the antiquity, particularly in Eurasia.

Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned (with twin right-handed and left-handed quartz crystals), distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a ‘bed’ that has unconstrained growth into a void; usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, for instance within gypsum. A quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.

What is Blue Quartz?

An opaque to translucent, blue quartz variety due to inclusions of its color, typically fibrous magnesioriebeckite or crocidolite, or tourmaline. The color can be caused by the color of the minerals used, or by microscopic inclusions of Rayleigh light scattering.

Blue quartz contains inclusions of fibrous magnesio-riebeckite or crocidolite.

How does Blue Quartz from?

Blue quartz formation may depend on the type of inclusion to which it relates. Within metamorphic rocks, the blue quartz with mineral inclusions typically crystallizes. Nevertheless, those where tourmaline inclusions predominate usually occur in igneous rocks and pegmatites. Coarse-grained blue quartz is often used to form the constituents of igneous rocks.

Where does Blue Quartz come from?

Quartz is a very common mineral throughout the world, having important deposits in the Americas, specifically in the United States, Colombia, Venezuela, and Brazil, in the European continent, this precious mineral can also be found in Spain, Switzerland, Italy and even in more remote areas such as the island of Madagascar.

How to identify Blue Quartz?

In the jewelry world one of the most common fakes is selling tinted glass as if it were blue quartz. In order to avoid anything like this from happening to us, you need to learn certain quartz physical characteristics this separate them from the rest.

While it sounds like a natural science lesson, identifying them in a very simple way is very useful knowledge. The first thing you should know about quartz is that it has a higher hardness than glass so you can do a simple test to verify whether you have an authentic piece.

A piece of quartz would be able to crack glass with a higher hardness, and you can try a glass bottle and if the stone scratches it is quartz with ease. In the other side, if it takes an enormous effort to create a crack in the bottle we can face a plain piece of glass.

The trick we’ve just discussed is a piece of homemade advice you can do at any time, but if you’d like anything more sophisticated you’ll need some jeweler loupes. Magnifying glasses are required to test whether or not there are bubbles in the composition of the rock.

How the Bungle Bungles got their stripes

March 17, 2020

Arial view of the Bungle Bungle range, May 2016. Credit: Creative Commons Attribution-Share Alike 4.0 International license. Nichollas Harrison

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Their distinctive stripes made Purnululu world famous and have helped the striking sandstone formations survive for generations.

The story of the Bungle Bungles begins about 360 million years ago with a river not so different from the Ord River that flows nearby today.

That river flowed downhill towards the ocean until it hit a broad low basin. There, it spread out, slowed down and deposited its load of sediment before drying up.

Every wet season and every flood, the river left the sand and stone it carried behind, layer upon layer.

Strange and fantastic formations

After a few million years, the landscape shifted upwards. The plateau formed mountains and hills, and the river began to flow downstream again.

After megayears of adding new layers, the rivers began to take them away. In that time, the earliest layers buried kilometers below the surface had become sandstone.

But unlike regular sandstone, the Bungle Bungles are held together by nothing but pressure.

“If you reach out and touch them, you’ll feel sand coming away at your fingertips,” says Chris Done, Chairperson of the Purnululu World Heritage Committee.

“The grains of sand are held together by their own pressure on each other. There’s no cementing,” he explains.

(That’s the stuff between the grains that helps them stick together.)

“They’re just pressed down with enough weight above them that they’re forced together.”

There’s some debate among geologists about just how this happened. Some think that the rock formed with cementing and later lost it, while others think it never had cementing at all.

However it formed, once that soft sandstone was uncovered, wind and water carved through it easily. A surreal landscape reflecting the twisting paths of rivers and streams emerged, and the layers deposited years ago were exposed to the elements.

As Edward Hardman, the first European geologist to encounter the formation, described it: “The prevailing nature of the rock, however, is that of a yellow or reddish freestone, very soft in places, and susceptible to ‘weathering’, owing to which the rock-masses often assume strange and fantastic forms.”

The hills are alive

Once they were exposed, each layer reacted differently.

Layers slightly richer in iron developed a rust-colored red color, as the iron percolated through to the surface and oxidized.

Other layers, richer in clay, were able to hold onto more water. These became home to colonies of dark-colored cyanobacteria, sometimes called blue-green algae.

“Those algae are about some of the toughest lifeforms you can think of,” Chris says.

“They go dormant when it’s dry, and they thrive when it’s wet.

“If you go up there when it’s been raining, it’s a shiny deep green or black, whereas during the dry season, they’re more of a gray color.”

So while the layers run throughout the hills, the stripes are only visible on the surface. Underground, it’s pale sandstone all the way through.

Nothing but footprints

As well as giving the hills their striking colors, the protective crust of iron and bacteria slows erosion of the sandstone.

So without their distinctive appearance, the Bungle Bungles may not have endured the forces of nature for so long.

But are the stripes attracting a new force of erosion? As more and more tourists explore the spectacular site, could their feet crush the Bungle Bungles back to sand?

Humans have visited and lived in Purnululu for thousands of years. Aboriginal people hunted and traded in the area long before tourists arrived.

They recognised the range as a site of great significance long before it was World Heritage listed, and Rangers from their descendants still live in and care for the area.

They think an increase in tourists isn’t an immediate threat “as long as people do the right thing and stay on the trails”, says Chris.

So if you visit the Bungle Bungles, stick to the path and let the stripes do their job. With care, they’ll still be amazing us for megayears to come.

Note: The above post is reprinted from materials provided by Particle. The original article was written by Rockwell McGellin.

Ancient shell shows days were half-hour shorter 70 million years ago

March 17, 2020

Fossil rudist bivalves (Vaccinites) from the Al-Hajar Mountains, United Arab Emirates. Credit: Wikipedia, Wilson44691 – Own work, Public Domain — Fossil rudist bivalves (Vaccinites) from the Al-Hajar Mountains, United Arab Emirates.
Credit: Wikipedia, Wilson44691 – Own work, Public Domain

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Earth turned faster at the end of the time of the dinosaurs than it does today, rotating 372 times a year, compared to the current 365, according to a new study of fossil mollusk shells from the late Cretaceous. This means a day lasted only 23 and a half hours, according to the new study in AGU’s journal Paleoceanography and Paleoclimatology.

The ancient mollusk, from an extinct and wildly diverse group known as rudist clams, grew fast, laying down daily growth rings. The new study used lasers to sample minute slices of shell and count the growth rings more accurately than human researchers with microscopes.

The growth rings allowed the researchers to determine the number of days in a year and more accurately calculate the length of a day 70 million years ago. The new measurement informs models of how the Moon formed and how close to Earth it has been over the 4.5-billion-year history of the Earth-Moon gravitational dance.

The new study also found corroborating evidence that the mollusks harbored photosynthetic symbionts that may have fueled reef-building on the scale of modern-day corals.

The high resolution obtained in the new study combined with the fast growth rate of the ancient bivalves revealed unprecedented detail about how the animal lived and the water conditions it grew in, down to a fraction of a day.

“We have about four to five datapoints per day, and this is something that you almost never get in geological history. We can basically look at a day 70 million years ago. It’s pretty amazing,” said Niels de Winter, an analytical geochemist at Vrije Universiteit Brussel and the lead author of the new study.

Climate reconstructions of the deep past typically describe long term changes that occur on the scale of tens of thousands of years. Studies like this one give a glimpse of change on the timescale of living things and have the potential to bridge the gap between climate and weather models.

Chemical analysis of the shell indicates ocean temperatures were warmer in the Late Cretaceous than previously appreciated, reaching 40 degrees Celsius (104 degrees Fahrenheit) in summer and exceeding 30 degrees Celsius (86 degrees Fahrenheit) in winter. The summer high temperatures likely approached the physiological limits for mollusks, de Winter said.

“The high fidelity of this data-set has allowed the authors to draw two particularly interesting inferences that help to sharpen our understanding of both Cretaceous astrochronology and rudist palaeobiology,” said Peter Skelton, a retired lecturer of palaeobiology at The Open University and a rudist expert unaffiliated with the new study.

Ancient reef-builders

The new study analyzed a single individual that lived for over nine years in a shallow seabed in the tropics — a location which is now, 70-million-years later, dry land in the mountains of Oman.

Torreites sanchezi mollusks look like tall pint glasses with lids shaped like bear claw pastries. The ancient mollusks had two shells, or valves, that met in a hinge, like asymmetrical clams, and grew in dense reefs, like modern oysters. They thrived in water several degrees warmer worldwide than modern oceans.

In the late Cretaceous, rudists like T. sanchezi dominated the reef-building niche in tropical waters around the world, filling the role held by corals today. They disappeared in the same event that killed the non-avian dinosaurs 66 million years ago.

“Rudists are quite special bivalves. There’s nothing like it living today,” de Winter said. “In the late Cretaceous especially, worldwide most of the reef builders are these bivalves. So they really took on the ecosystem building role that the corals have nowadays.”

The new method focused a laser on small bits of shell, making holes 10 micrometers in diameter, or about as wide as a red blood cell. Trace elements in these tiny samples reveal information about the temperature and chemistry of the water at the time the shell formed. The analysis provided accurate measurements of the width and number of daily growth rings as well as seasonal patterns. The researchers used seasonal variations in the fossilized shell to identify years.

The new study found the composition of the shell changed more over the course of a day than over seasons, or with the cycles of ocean tides. The fine-scale resolution of the daily layers shows the shell grew much faster during the day than at night

“This bivalve had a very strong dependence on this daily cycle, which suggests that it had photosymbionts,” de Winter said. “You have the day-night rhythm of the light being recorded in the shell.”

This result suggests daylight was more important to the lifestyle of the ancient mollusk than might be expected if it fed itself primarily by filtering food from the water, like modern day clams and oysters, according to the authors. De Winter said the mollusks likely had a relationship with an indwelling symbiotic species that fed on sunlight, similar to living giant clams, which harbor symbiotic algae.

“Until now, all published arguments for photosymbiosis in rudists have been essentially speculative, based on merely suggestive morphological traits, and in some cases were demonstrably erroneous. This paper is the first to provide convincing evidence in favor of the hypothesis,” Skelton said, but cautioned that the new study’s conclusion was specific to Torreites and could not be generalized to other rudists.

Moon retreat

De Winter’s careful count of the number of daily layers found 372 for each yearly interval. This was not a surprise, because scientists know days were shorter in the past. The result is, however, the most accurate now available for the late Cretaceous, and has a surprising application to modeling the evolution of the Earth-Moon system.

The length of a year has been constant over Earth’s history, because Earth’s orbit around the Sun does not change. But the number of days within a year has been shortening over time because days have been growing longer. The length of a day has been growing steadily longer as friction from ocean tides, caused by the Moon’s gravity, slows Earth’s rotation.

The pull of the tides accelerates the Moon a little in its orbit, so as Earth’s spin slows, the Moon moves farther away. The moon is pulling away from Earth at 3.82 centimeters (1.5 inches) per year. Precise laser measurements of distance to the Moon from Earth have demonstrated this increasing distance since the Apollo program left helpful reflectors on the Moon’s surface.

But scientists conclude the Moon could not have been receding at this rate throughout its history, because projecting its progress linearly back in time would put the Moon inside the Earth only 1.4 billion years ago. Scientists know from other evidence that the Moon has been with us much longer, most likely coalescing in the wake of a massive collision early in Earth’s history, over 4.5 billion years ago. So the Moon’s rate of retreat has changed over time, and information from the past, like a year in the life of an ancient clam, helps researchers reconstruct that history and model of the formation of the moon.

Because in the history of the Moon, 70 million years is a blink in time, de Winter and his colleagues hope to apply their new method to older fossils and catch snapshots of days even deeper in time.

Reference:
Niels J. Winter, Steven Goderis, Stijn J.M. Van Malderen, Matthias Sinnesael, Stef Vansteenberge, Christophe Snoeck, Joke Belza, Frank Vanhaecke, Philippe Claeys. Subdaily‐Scale Chemical Variability in a Torreites Sanchezi Rudist Shell: Implications for Rudist Paleobiology and the Cretaceous Day‐Night Cycle. Paleoceanography and Paleoclimatology, 2020; 35 (2) DOI: 10.1029/2019PA003723

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

Earth’s Mantle, Not Its Core, May Have Generated Planet’s Early Magnetic Field

March 17, 2020

New research lends credence to an unorthodox retelling of the story of early Earth first proposed by a geophysicist at Scripps Institution of Oceanography at UC San Diego.

In a study appearing March 15 in the journal Earth and Planetary Science Letters, Scripps Oceanography researchers Dave Stegman, Leah Ziegler, and Nicolas Blanc provide new estimates for the thermodynamics of magnetic field generation within the liquid portion of the early Earth’s mantle and show how long that field was available.

The paper provides a “door-opening opportunity” to resolve inconsistencies in the narrative of the planet’s early days. Significantly, it coincides with two new studies from UCLA and Arizona State University geophysicists that expand on Stegman’s concept and apply it in new ways.

“Currently we have no grand unifying theory for how Earth has evolved thermally,” Stegman said. “We don’t have this conceptual framework for understanding the planet’s evolution. This is one viable hypothesis.”

The trio of studies are the latest developments in a paradigm shift that could change how Earth history is understood.

It has been a bedrock tenet of geophysics that Earth’s liquid outer core has always been the source of the dynamo that generates its magnetic field. Magnetic fields form on Earth and other planets that have liquid, metallic cores, rotate rapidly, and experience conditions that make the convection of heat possible.

In 2007, researchers in France proposed a radical departure from the long-held assumption that the Earth’s mantle has remained entirely solid since the very beginnings of the planet. They argued that during the first half of the planet’s 4.5-billion-year history, the bottom third of Earth’s mantle would have had to have been molten, which they call “the basal magma ocean.” Six years later, Stegman and Ziegler expanded upon that idea, publishing the first work showing how this once-liquid portion of the lower mantle, rather than the core, could have exceeded the thresholds needed to create Earth’s magnetic field during that time.

The Earth’s mantle is made of silicate material that is normally a very poor electrical conductor. Therefore, even if the lowermost mantle were liquid for billions of years, rapid fluid motions inside it wouldn’t produce large electrical currents needed for magnetic field generation, similar to how Earth’s dynamo currently works in the core. Stegman’s team asserted the liquid silicate might actually be more electrically conductive than what was generally believed.

“Ziegler and Stegman first proposed the idea of a silicate dynamo for the early Earth,” said UCLA geophysicist Lars Stixrude. The idea was met with skepticism because their early results “showed that a silicate dynamo was only possible if the electrical conductivity of silicate liquid was remarkably high, much higher than had been measured in silicate liquids at low pressure and temperature.”

A team led by Stixrude used quantum-mechanical computations to predict the conductivity of silicate liquid at basal magma ocean conditions for the first time.

According to Stixrude, “we found very large values of the electrical conductivity, large enough to sustain a silicate dynamo.” The UCLA study appeared in the Feb. 25 issue of Nature Communications.

In another paper, Arizona State geophysicist Joseph O’Rourke applied Stegman’s concept to consider whether it’s possible that Venus might have at one point generated a magnetic field within a molten mantle.

These new studies are signs that the premise is starting to take hold, but is still far from being widely accepted.

“No one is going to believe it until they do it themselves and now two other highly esteemed scientists have done it themselves,” said Stegman.

“The pioneering studies of Dave Stegman and his collaborators directly inspired my work on Venus,” said O’Rourke. “Their recent paper helps answer a question that vexed scientists for many years: How has Earth’s magnetic field survived for billions of years?”

If Stegman’s premise is correct, it would mean the mantle could have provided the young planet’s first magnetic shield against cosmic radiation. It could also underpin studies of how tectonics evolved on the planet later in history.

“If the magnetic field was generated in the molten lower mantle above the core, then Earth had protection from the very beginning and that might have made life on Earth possible sooner,” Stegman said.

“Ultimately, our papers are complementary because they demonstrate that basal magma oceans are important to the evolution of terrestrial planets,” said O’Rourke. “Earth’s basal magma ocean has solidified but was key to the longevity of our magnetic field.”

The Scripps Oceanography study was funded by the National Science Foundation, the U.S. Department of Energy, and a UC San Diego SEED Fellowship.

References:

Nicolas A. Blanc, Dave R. Stegman, Leah B. Ziegler. Thermal and magnetic evolution of a crystallizing basal magma ocean in Earth’s mantle. Earth and Planetary Science Letters, 2020; 534: 116085 DOI: 10.1016/j.epsl.2020.116085
J. G. O’Rourke. Venus: A Thick Basal Magma Ocean May Exist Today. Geophysical Research Letters, 2020; 47 (4) DOI: 10.1029/2019GL086126
Lars Stixrude, Roberto Scipioni, Michael P. Desjarlais. A silicate dynamo in the early Earth. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-14773-4

Note: The above post is reprinted from materials provided by University of California – San Diego.

Building blocks for life on Earth arrived much later than we thought, billion-year-old rocks show

March 17, 2020

The rocks the team analysed are the oldest preserved mantle rocks. They allow us to see into the early history of the Earth as if through a window. Credit: UNSW

Ancient rocks from Greenland have shown that the elements necessary for the evolution of life did not come to Earth until very late in the planet’s formation—much later than previously thought.

An international team of geologists—led by the University of Cologne and involving UNSW scientists—have published important new findings about the origin of oceans and life on Earth: they have found evidence that a large proportion of the elements that are essential to the formation of oceans and life—such as water, carbon and nitrogen—only came to Earth very late in its history.

Many scientists previously believed that these elements had already been there at the beginning of our planet’s formation. However, the geological investigations published in Nature today have shown that most of the water in fact only came to Earth when its formation was almost complete.

Volatile elements such as water originate from asteroids, the planetary building blocks that formed in the outer solar system. There has been a lot of discussion and controversy in the scientific community around when precisely these building blocks came to Earth.

Dr. Mario Fischer-Gödde from the Institute of Geology and Mineralogy at the University of Cologne, who led the work, says we are now able to narrow down the timeframe more precisely.

“The rocks we analyzed are the oldest preserved mantle rocks. They allow us to see into the early history of the Earth as if through a window.

“We compared the composition of the oldest, approximately 3.8 billion-year-old, mantle rocks from the Archean Eon with the composition of the asteroids from which they formed, and with the composition of the Earth’s mantle today.”

To understand the temporal process, the researchers determined the isotope abundances of a very rare platinum metal called ruthenium, which the Archean mantle of the Earth contained.

Like a genetic fingerprint, the rare platinum metal is an indicator for the late growth phase of the Earth.

“Platinum metals like ruthenium have an extremely high tendency to combine with iron. Therefore, when the Earth formed, ruthenium must have been completely discharged into the Earth’s metallic core,” says Professor Fischer-Gödde.

Professor Martin Van Kranendonk, the UNSW scientist who was part of the research, says the reason why this is of such interest relates directly to understanding the origins of life on Earth, how we humans came to be, and in fact, to whether we might be alone, or have neighbours in the universe.

“This is because the results show that Earth did not really become a habitable planet until relatively late in its accretionary history,” he says.

“If you combine this with the evidence for very ancient life on Earth, it reveals that life got started on our planet surprisingly quickly, within only a few hundred million years. Now this might sound like a lot of time, and it is, but it is far different from what we used to think, that life took half a billion, or even a billion years to get started.

“And this gives hope for finding life on other planets that had a shorter geological history and period of ‘warm and wet’ conditions than Earth, because if life could get started quickly here, then perhaps it got started quickly elsewhere.”

Professor Dr. Carsten Münker, also at the University of Cologne, added: “The fact that we are still finding traces of rare platinum metals in the Earth’s mantle means that we can assume they were only added after the formation of the core was completed—they were certainly the result of later collisions of the Earth with asteroids or smaller planetesimals.”

Scientists refer to the very late building blocks of Earth, which arrived through these collisions, as the ‘late veneer.”

“Our findings suggest that water and other volatile elements such as carbon and nitrogen did indeed arrive on Earth very late in the ‘late veneer’ phase,” Professor Fischer-Gödde says.

The new findings are the result of collaboration among scientists from Germany, Denmark, England, Australia and Japan. The scientists are planning further field trips to India, northwestern Australia, and Greenland to investigate more rock samples.

Reference:
Mario Fischer-Gödde et al. Ruthenium isotope vestige of Earth’s pre-late-veneer mantle preserved in Archaean rocks, Nature (2020). DOI: 10.1038/s41586-020-2069-3

Note: The above post is reprinted from materials provided by University of New South Wales.

‘Fossil earthquakes’ offer new insight into seismic activity deep below Earth’s surface

March 17, 2020

The grey line in the rock, running from the foreground away under the boulder towards the mountains, is one of the shear zones from the study area. Credit: Lucy Campbell

A major international study has shed new light on the mechanisms through which earthquakes are triggered up to 40km beneath the earth’s surface.

While such earthquakes are unusual, because rocks at those depth are expected to creep slowly and aseismically, they account for around 30 per cent of intracontinental seismic activity. Recent examples include a significant proportion of seismicity in the Himalaya as well as aftershocks associated with the 2001 Bhuj earthquake in India.

However, very little is presently known about what causes them, in large part due to the fact that any effects are normally hidden deep underground.

The current study, published in Nature Communications and funded by the Natural Environment Research Council, sought to understand how such deep earthquakes may be generated.

They showed that earthquake ruptures may be encouraged by the interaction of different shear zones that are creeping slowly and aseismically. This interaction loads the adjacent blocks of stiff rocks in the deep crust, until they cannot sustain the rising stress anymore, and snap — generating earthquakes.

Emphasising observations of quite complex networks created by earthquake-generated faults, they suggest that this context is characterised by repeating cycles of deformation, with long-term slow creep on the shear zones punctuated by episodic earthquakes.

Although only a transient component of such deformation cycles, the earthquakes release a significant proportion of the accumulated stress across the region.

The research was led by the University of Plymouth (UK) and University of Oslo (Norway), with scientists conducting geological observations of seismic structures in exhumed lower crustal rocks on the Lofoten Islands.

The region is home to one of the few well-exposed large sections of exhumed continental lower crust in the world, exposed during the opening of the North Atlantic Ocean.

Scientists spent several months in the region, conducting a detailed analysis of the exposed rock and in particular pristine pseudotachylytes (solidified melt produced during seismic slip regarded as ‘fossil earthquakes’) which decorate fault sets linking adjacent or intersecting shear zones.

They also collected samples from the region which were then analysed using cutting edge technology in the University’s Plymouth Electron Microscopy Centre.

Lead author Dr Lucy Campbell, Post-Doctoral Research Fellow at the University of Plymouth, said: “The Lofoten Islands provide an almost unique location in which to examine the impact of earthquakes in the lower crust. But by looking at sections of exposed rock less than 15 metres wide, we were able to see examples of slow-forming rock deformation working to trigger earthquakes generated up to 30km beneath the surface. The model we have now developed provides a novel explanation of the causes and effects of such earthquakes that could be applied at many locations where they occur.”

Project lead Dr Luca Menegon, Associate Professor at the University of Plymouth and the University of Oslo, added: “Deep earthquakes can be as destructive as those nucleating closer to the Earth’s surface. They often occur in highly populated areas in the interior of the continents, like in Central Asia for example. But while a lot is known about what causes seismic activity in the upper crust, we know far less about those which occur lower. This study gives us a fascinating insight into what is happening deep below the Earth’s surface, and our challenge is now to take this research forward and see if we can use it to make at-risk communities more aware of the dangers posed by such activity.”

As part of the study, scientists also worked with University of Plymouth filmmaker Heidi Morstang to produce a 60-minute documentary film about their work. Pseudotachylyte premiered at the 2019 Bergen International Film Festival, and will be distributed internationally once it has screened at various other festivals globally.

Reference:
L. R. Campbell, L. Menegon, Å. Fagereng, G. Pennacchioni. Earthquake nucleation in the lower crust by local stress amplification. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-15150-x

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

What causes an ice age to end?

March 17, 2020

Galleria delle Stalattiti, Corchia Cave. Credit: Linda Tegg

New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth’s axis was approaching high values.

During these times, longer and stronger summers melted the large Northern Hemisphere ice sheets, propelling the Earth’s climate into a warm ‘interglacial’ state, like the one we’ve experienced over the last 11,000 years.

The study by PhD candidate, Petra Bajo, and colleagues also showed that summer energy levels at the time these ‘ice-age terminations’ were triggered controlled how long it took for the ice sheets to collapse, with higher energy levels producing fast collapse.

Researchers are still trying to understand how often these periods happen and how soon we can expect another one.

Since the mid 1800s, scientists have long suspected that changes in the geometry of Earth’s orbit are responsible for the coming and going of ice ages — the uncertainty has been over which orbital property is most important.

Petra Bajo’s paper “Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition,” published today in Science, moves closer to resolving some of the mystery of why ice ages end by establishing when they end.

The team combined data from Italian stalagmites with information from ocean sediments drilled off the coast of Portugal.

“Colleagues from the University of Cambridge and Portugal’s Instituto Português do Mar e da Atmosfera compiled detailed records of the North Atlantic’s response to ice-sheet collapse,” said Associate Professor Russell Drysdale, from the research team.

“We could identify in the stalagmite growth layers the same changes that were being recorded in the ocean sediments. This allowed us to apply the age information from the stalagmite to the ocean sediment record, which cannot be dated for this time period.”

Using the latest techniques in radiometric dating, the international team determined the age of two terminations that occurred about 960,000 and 875,000 years ago.

The ages suggest that the initiation of both terminations is more consistent with increases in Earth’s tilt angle. These increases produce warmer summers over the regions where the Northern Hemisphere ice sheets are situated, causing melting.

“Both terminations then progressed to completion at a time when Northern Hemisphere summer energy over the ice sheets approached peak values,” said Dr Drysdale. “A comparison of these findings with previously published data from younger terminations shows this pattern has been a recurring feature of the last million years.”

The team plan to have a closer look next at the Middle Pleistocene Transition when the average length of ice-age cycles suddenly doubled in length.

Reference:
Petra Bajo, Russell N. Drysdale, Jon D. Woodhead, John C. Hellstrom, David Hodell, Patrizia Ferretti, Antje H. L. Voelker, Giovanni Zanchetta, Teresa Rodrigues, Eric Wolff, Jonathan Tyler, Silvia Frisia, Christoph Spötl, Anthony E. Fallick. Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition. Science, 2020; 367 (6483): 1235 DOI: 10.1126/science.aaw1114

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

Under-sea freshwater reserves found near Canterbury

March 17, 2020

Scientists have discovered an extensive body of freshwater off the Canterbury coast between Timaru and Ashburton.

NIWA marine geologist Dr. Joshu Mountjoy says the discovery is one of the few times a significant offshore aquifer has been located around the world and may lead to a new freshwater resource for the region.

The aquifer lies just 20 metres below the seafloor, making the find one of the shallowest in the world. It extends up to 60 kilometres from the coastline and may contain as much as 2000 cubic kilometres of water which is equivalent to half the volume of groundwater across Canterbury.

Derived from rainfall, the aquifer is partly being replenished by groundwater flow from the coastline between Timaru and Ashburton. However, most of the freshwater became trapped offshore during the last three Ice Ages, when sea level was more than 100 metres lower than it is today.

First indications that the offshore groundwater was there was a chance find that arose when a scientific drilling project in 2012 found brackish water—or salt and freshwater mixed together—50km off the coast and about 50m below the seafloor.

Dr. Mountjoy says that discovery led to a 2017 voyage aboard NIWA research vessel Tangaroa to carry out further investigation in which scientists collected electromagnetic data. An electrical source was towed behind the ship and behind that was a line of receivers which record different signals depending on the electrical resistivity of the ground. Resistivity is strongly influenced by the amount of salt in the water locked up in sediments beneath the seafloor. This was then integrated with seismic reflection profiling and numerical modelling to determine the amount of freshwater beneath the seabed.

The findings have been published today in leading scientific journal Nature Communications.

“One of the most important aspects of this study is the improved understanding it offers to water management,” Dr. Mountjoy says.

“If you’re going to manage the groundwater on shore and near the coast, you need to understand what the downstream limits are.”

The project attracted funding from the European Research Council through the MARCAN project which is a five-year international programme investigating how offshore groundwater influences continental margins.

The structure of the aquifer has been mapped in 3-D and reveals complex variations in shape and salinity, according to paper lead-author Aaron Micallef of the University of Malta who also says the approach to characterising this aquifer could potentially be used to revise estimations of their number and volume globally.

Dr. Mountjoy says while there are other places where offshore groundwater is known about, this is only the second time such intensive surveying has been carried out to define the extent of the water body. “By defining how big it is we’re getting a handle on understanding it.”

The next step is to take samples for analysis. “At the moment we have used remote techniques, modelling and geophysics. We really need to go out there and ground-truth our findings and we are investigating options for that.”

Dr. Mountjoy says there are several places around New Zealand facing significant issues with their groundwater, such as Christchurch and Hawke’s Bay which are feeling the pressure of increasing populations and regular prolonged dry periods.

“Hawke’s Bay is an example of a region needing to manage what they’re dealing with onshore. They’ve only got half the picture if they don’t know how far out it goes, and how much is leaking into the ocean.

“We need to set the groundwork in place for the future. Our primary goal is to help people manage their onshore resources. Our groundwater systems are a critical resource for society, they are increasingly under pressure, and we need every bit of information we can get.”

Reference:
Aaron Micallef et al. 3-D characterisation and quantification of an offshore freshened groundwater system in the Canterbury Bight, Nature Communications (2020). DOI: 10.1038/s41467-020-14770-7

Note: The above post is reprinted from materials provided by National Institute of Water and Atmospheric Research (NIWA) .

Shifts in deep geologic structure may have magnified great 2011 Japan tsunami

March 17, 2020

Japan's risk of giant tsunamis may have grown when the angle of a down-going slab of ocean crust declined. Top: ocean crust (right) slides under continental crust at a steep angle, causing faulting (red lines) in seafloor sediments piled up behind. Bottom: as the angle shallows, stress is transferred to sediments piled onto the continental crust, and faults develop there. Blue dots indicate resulting earthquakes. At left in both images, the change in angle also shifts the region where magma fueling volcanoes is generated, pushing eruptions further inland. Credit: Adapted from Oryan and Buck, Nature Geoscience 2020 — Japan’s risk of giant tsunamis may have grown when the angle of a down-going slab of ocean crust declined. Top: ocean crust (right) slides under continental crust at a steep angle, causing faulting (red lines) in seafloor sediments piled up behind. Bottom: as the angle shallows, stress is transferred to sediments piled onto the continental crust, and faults develop there. Blue dots indicate resulting earthquakes. At left in both images, the change in angle also shifts the region where magma fueling volcanoes is generated, pushing eruptions further inland. Credit: Adapted from Oryan and Buck, Nature Geoscience 2020

On March 11, 2011, a magnitude 9 earthquake struck under the seabed off Japan — the most powerful quake to hit the country in modern times, and the fourth most powerful in the world since modern record keeping began. It generated a series of tsunami waves that reached an extraordinary 125 to 130 feet high in places. The waves devastated much of Japan’s populous coastline, caused three nuclear reactors to melt down, and killed close to 20,000 people.

The tsunami’s obvious cause: the quake occurred in a subduction zone, where the tectonic plate underlying the Pacific Ocean was trying to slide under the adjoining continental plate holding up Japan and other landmasses. The plates had been largely stuck against each other for centuries, and pressure built up. Finally, something gave. Hundreds of square miles of seafloor suddenly lurched horizontally some 160 feet, and thrust upward by up to 33 feet. Scientists call this a megathrust. Like a hand waved vigorously underwater in a bathtub, the lurch propagated to the sea surface and translated into waves. As they approached shallow coastal waters, their energy concentrated, and they grew in height. The rest is history.

But scientists soon realized that something did not add up. Tsunami sizes tend to mirror earthquake magnitudes on a predictable scale; This one produced waves three or four times bigger than expected. Just months later, Japanese scientists identified another, highly unusual fault some 30 miles closer to shore that seemed to have moved in tandem with the megathrust. This fault, they reasoned, could have magnified the tsunami. But exactly how it came to develop there, they could not say. Now, a new study in the journal Nature Geoscience gives an answer, and possible insight into other areas at risk of outsize tsunamis.

The study’s authors, based at Columbia University’s Lamont-Doherty Earth Observatory, examined a wide variety of data collected by other researchers before the quake and after. This included seafloor topographic maps, sediments from underwater boreholes, and records of seismic shocks apart from the megathrust.

The unusual fault in question is a so-called extensional fault — one in which the Earth’s crust is pulled apart rather than being pushed together. Following the megathrust, the area around the extensional fault moved some 200 feet seaward, and a series of scarps 10 to 15 feet high could be seen there, indicating a sudden, powerful break. The area around the extensional fault was also warmer than the surrounding seabed, indicating friction from a very recent movement; that suggested the extensional fault had been jolted loose when the megathrust struck. This in turn would have added to the tsunami’s power.

Extensional faults are in fact common around subduction zones — but only in oceanic plates, not the overriding continental ones, where this one was found. How did it get there? And, might such dangerous features lurk in other parts of the world?

The authors of the new paper believe the answer is the angle at which the ocean plate dives under the continental; they say it has been gradually shallowing out over millions of years. “Most people would say it was the megathrust that caused the tsunami, but we and some others are saying there may have been something else at work on top of that,” said Lamont PhD. student Bar Oryan, the paper’s lead author. “What’s new here is we explain the mechanism of how the fault developed.”

The researchers say that long ago, the oceanic plate was moving down at a steeper angle, and could drop fairly easily, without disturbing the seafloor on the overriding continental plate. Any extensional faulting was probably confined to the oceanic plate behind the trench — the zone where the two plates meet. Then, starting maybe 4 million or 5 million years ago, it appears that angle of subduction began declining. As a result, the oceanic plate began exerting pressure on sediments atop the continental plate. This pushed the sediments into a huge, subtle hump between the trench and Japan’s shoreline. Once the hump got big and compressed enough, it was bound to break, and that was probably what happened when the megathrust quake shook things loose. The researchers used computer models to show how long-term changes in the dip of the plate could produce major changes in the short-term deformation during an earthquake.

There are multiple lines of evidence. For one, material taken from boreholes before the quake show that sediments had been squeezed upward about midway between the land and the trench, while those closer to both the land and the trench had been subsiding — similar to what might happen if one laid a piece of paper flat on a table and then slowly pushed in on it from opposite sides. Also, recordings of aftershocks in the six months after the big quake showed scores of extensional-fault-type earthquakes carpeting the seabed over the continental plate. This suggests that the big extensional fault is only the most obvious one; strain was being released everywhere in smaller, similar quakes in surrounding areas, as the hump relaxed.

Furthermore, on land, Japan hosts numerous volcanoes arranged in a neat north-south arc. These are fueled by magma generated 50 or 60 miles down, at the interface between the subducting slab and the continental plate. Over the same 4 million to 5 million years, this arc has been migrating westward, away from the trench. Since magma generation tends to take place at a fairly constant depth, this adds to the evidence that the angle of subduction has gradually been growing shallower, pushing the magma-generating zone further inland.

Lamont geophysicist and coauthor Roger Buck said that the study and the earlier ones it builds on have global implications. “If we can go and find out if the subduction angle is moving up or down, and see if sediments are undergoing this same kind of deformation, we might be better able to say where this kind of risk exists,” he said. Candidates for such investigation would include areas off Nicaragua, Alaska, Java and others in the earthquake zones of the Pacific Ring of Fire. “These are areas that matter to millions of people,” he said.

Reference:
Bar Oryan, W. Roger Buck. Larger tsunamis from megathrust earthquakes where slab dip is reduced. Nature Geoscience, 2020; DOI: 10.1038/s41561-020-0553-x

Note: The above post is reprinted from materials provided by Earth Institute at Columbia University. Original written by Kevin Krajick.

Hummingbird : Smallest Known Dinosaur Found in Amber

March 11, 2020

Burmese amber with Oculudentavis skull nearly perfectly preserved inside. Credit: Lida Xing

The discovery of a small, bird-like skull, described in an article published in Nature, reveals a new species, Oculudentavis khaungraae, that could represent the smallest known Mesozoic dinosaur in the fossil record.

While working on fossils from in northern Myanmar, Lars Schmitz, associate professor of biology at the W.M. Keck Science Department, and a team of international researchers discovered a seemingly mature skull specimen preserved in Burmese amber. The specimen’s size is on par with that of the bee hummingbird, the smallest living bird.

“Amber preservation of vertebrates is rare, and this provides us a window into the world of dinosaurs at the lowest end of the body-size spectrum,” Schmitz said. “Its unique anatomical features point to one of the smallest and most ancient birds ever found.”

The team studied the specimen’s distinct features with high-resolution synchrotron scans to determine how the skull of the Oculudentavis khaungraae differs from those of other bird-like dinosaur specimens of the era. They found that the shape and size of the eye bones suggested a diurnal lifestyle, but also revealed surprising similarities to the eyes of modern lizards. The skull also shows a unique pattern of fusion between different bone elements, as well as the presence of teeth. The researchers concluded that the specimen’s tiny size and unusual form suggests a never-before-seen combination of features.

The discovery represents a specimen previously missing from the fossil record and provides new implications for understanding the evolution of birds, demonstrating the extreme miniaturization of avian body sizes early in the evolutionary process. The specimen’s preservation also highlights amber deposits’ potential to reveal the lowest limits of vertebrate body size.

“No other group of living birds features species with similarly small crania in adults,” Schmitz said. “This discovery shows us that we have only a small glimpse of what tiny vertebrates looked like in the age of the dinosaurs.”

Reference:
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar, Nature (2020). DOI: 10.1038/s41586-020-2068-4

Note: The above post is reprinted from materials provided by Scripps College.

Desert Rose : What is Desert Rose? How Do Desert Roses Form?

March 11, 2020

Huge Desert Rose Selenite Crystal cluster. Photo Copyright © Crystalminer Minerals

Table of Contents

Desert Rose Rock

Desert rose is the colloquial name given to rose-like formations of gypsum or baryte crystal clusters which contain abundant grains of sand. The ‘petals’ are crystals flattened on the c crystallographic axis, fanning open in radiating flattened crystal clusters.

The rosette crystal habit tends to occur when the crystals form under arid sandy conditions, such as a shallow salt basin becoming evaporated. The crystals form a circular series of flat plates that give the rock a similar shape to a rose blossom.

How Do Desert Rose Rock Form?

Gypsum roses tend to have sharper edges better defined than baryt roses. Celestine and other minerals bladed with evaporite may also form clusters of rosettes. These can either appear as a single rose-like bloom, or as bloom clusters, with most sizes ranging from pea size to 4 inches (10 cm) in diameter.

The ambient sand that is incorporated into the crystal structure, or otherwise encrusts the crystals, varies with the local environment. If iron oxides are present, the rosettes take on a rusty tone.

The desert rose may also be known by the names: sand rose, rose rock, selenite rose, gypsum rose and baryte (barite) rose.

Where to find desert rose rock ?

Rose rocks are found in Tunisia, Libya, Morocco, Algeria, Jordan, Saudi Arabia, Qatar, Egypt, the United Arab Emirates, Spain (Fuerteventura, Canary Islands; Canet de Mar, Catalonia; La Almarcha, Cuenca), Mongolia (Gobi), Germany (Rockenberg), the United States (central Oklahoma; Cochise County, Arizona; Texas), Mexico (Ciudad Juárez, Chihuahua), Australia, South Africa and Namibia.

Desert Rose Rock Size

he average size of rose rocks are anywhere from 0.5 inches (1.3 cm) to 4 inches (10 cm) in diameter. The largest recorded by the Oklahoma Geological Survey was 17 inches (43 cm) across and 10 inches (25 cm) high, weighing 125 pounds (57 kg). Clusters of rose rocks up to 39 inches (99 cm) tall and weighing more than 1,000 pounds (454 kg) have been found.

Fluorescence : Why Minerals Fluoresce?

March 10, 2020

Collection of various fluorescent minerals under ultraviolet UV-A, UV-B and UV-C light. Chemicals in the rocks absorb the ultraviolet light and emit visible light of various colors, a process called fluorescence. Credit: Hannes Grobe/AWI

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation.

The most striking example of fluorescence happens when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, whereas the light emitted is in the visible region, giving the fluorescent material a distinct color that can only be seen when exposed to UV light. Fluorescent materials almost immediately cease to glow when the source of radiation ceases, unlike phosphorescent materials that tend to emit light for some time.

Fluorescence has many practical applications, including mineralogy, gemology, medicine, chemical sensors (fluorescence spectroscopy), fluorescent marking, coloring biological detectors, and detection of cosmic rays. Its most common everyday use is in energy-saving fluorescent lamps and LED lamps, where fluorescent coatings are used to transform short-wavelength UV or blue light into longer-wavelength yellow light, thereby mimicking the warm light of energy-inefficient incandescent lamps. Fluorescence also occurs frequently in nature in some minerals and in various biological forms in many branches of the animal kingdom.

Fluorescent Minerals

Gemstones, minerals, may have a distinctive fluorescence or may fluoresce differently under short-wave ultraviolet, long-wave ultraviolet, visible light, or X-rays.

Many types of calcite and amber will fluoresce under shortwave UV, longwave UV and visible light. Rubies, emeralds, and diamonds exhibit red fluorescence under long-wave UV, blue and sometimes green light; diamonds also emit light under X-ray radiation.

Mineral fluorescence is caused by a wide array of activators. In some situations, the activator concentration must be restricted to below a certain level, to prevent the fluorescent emission from quenching. In addition, the mineral must be free of impurities such as iron or copper, in order to prevent possible fluorescence from quenching. Divalent manganese is present in concentrations up to several per cent. Hexavalent uranium, in the form of uranyl cation, fluoresces at all concentrations in a yellow color, causing the fluorescence of minerals such as autunite or andersonite, and causing the fluorescence of materials such as certain samples of hyalite opal at low concentrations. Trivalent, low-concentration chromium is the source of ruby red fluorescence. Divalent europium, when seen in the mineral fluorite, is the source of blue fluoresce. Trivalent lanthanides such as terbium and dysprosium are the primary activators of the creamy yellow fluorescence shown by the mineral fluorite yttrofluorite type, and contribute to the zircon’s orange fluorescence. Powellite (calcium molybdate) and scheelite (calcium tungstate) fluoresce intrinsically in yellow and blue, respectively. When present together in solid solution, energy is transferred from the higher-energy tungsten to the lower-energy molybdenum, such that fairly low levels of molybdenum are sufficient to cause a yellow emission for scheelite, instead of blue. Low-iron sphalerite (zinc sulfide), fluoresces and phosphoresces in a range of colors, influenced by the presence of various trace impurities.

Crude oil (petroleum) fluoresces in a range of colors, from dull-brown for heavy oils and tars through to bright-yellowish and bluish-white for very light oils and condensates. This phenomenon is used in oil exploration drilling to identify very small amounts of oil in drill cuttings and core samples.

Meganeura : The largest insect ever existed was a giant dragonfly

March 10, 2020

Table of Contents

Meganeura

Meganeura is a genus of extinct insects from the Carboniferous period (approximately 300 million years ago), which resembled and are related to the present-day dragonflies. Its wingspans from 65 cm (25.6 in) to more than 70 cm (28 in), M.Monyi is one of the largest known species of flying insects. Meganeura was predatory and their diet consisted mainly of other insects.

Fossils were discovered in the French Stephanian Coal Measures of Commentry in 1880. In 1885, French paleontologist Charles Brongniart described and named the fossil “Meganeura” (large-nerved), which refers to the network of veins on the insect’s wings. Another fine fossil specimen was found in 1979 at Bolsover in Derbyshire. The holotype is housed in the National Museum of Natural History, in Paris.

Meganeura Size

There was some controversy over how Carboniferous Period insects were able to grow so large.

Oxygen levels and atmospheric density

The way in which oxygen is diffused through the body of the insect through its tracheal respiration system puts an upper limit on body size, which ancient insects seem to have far surpassed. Harlé (1911) originally suggested that Meganeura could only fly because at that time the atmosphere provided more oxygen than the present 20 per cent. This theory was initially rejected by fellow scientists, but was more recently approved through further analysis of the relationship between the availability of gigantism and oxygen.

If this hypothesis is correct, these insects would have been vulnerable to declining oxygen levels and in our current atmosphere could probably not survive. Some research suggests that insects breathe with “rapid cycles of compression and expansion of trachea.” Recent analysis of modern insects and birds ‘ flight energetics suggests that both the oxygen levels and air density provide an upper bound on size.

In the case of the giant dragonflies, the presence of very large Meganeuridae with wing spans rivaling those of Meganeura during the Permian, when the atmospheric oxygen content was already much lower than in the Carboniferous, presented a problem for the oxygen-related explanations. However, despite the fact that Meganeurids had the largest known wing spans, their bodies were not very heavy, being less colossal than those of many living Coleoptera; therefore, they were not true giant insects, only giant in comparison with their living relatives.

Lack of predators

Other explanations for the large size of Meganeurids compared to living relatives are warranted. Bechly (2004) suggested that the lack of aerial vertebrate predators allowed pterygote insects to evolve to maximum sizes during the Carboniferous and Permian periods, perhaps accelerated by an evolutionary “arms race” for increase in body size between plant-feeding Palaeodictyoptera and Meganisoptera as their predators.

Aquatic larvae stadium

Another theory suggests that insects that developed in water before becoming terrestrial as adults grew bigger as a way to protect themselves against the high levels of oxygen.

Ancient Armadillo The Size Of A Car Discovered By Farmer In Argentina

March 10, 2020

A farmer has found the 20,000-year-old remains of four prehistoric armadillos that grew to the size of a car at the bottom of a dried-out riverbed.

Local media said that the farmer stumbled across the ‘four glyptodonts’, a heavily armoured mammal that lived during the Pleistocene epoch and were relatives of present-day armadillos.

They developed in South America around 20 million years ago and spread to southern regions of North America after the continents connected several million years ago.

The large fossils were discovered on a dried riverbed in the Argentine capital Buenos Aires and experts from the Institute of Archaeological and Palaeontological Investigations of the Pampa Quaternary (Incuapa-Conicet) will spend the next week extracting the remains.

Archaeologist Pablo Messineo told reporters that a man named Juan de Dios Sota was taking his cows to graze in a nearby field when he noticed the odd shapes on the dried riverbed as they did not appear to be the remains of horses or cows.

Messineo and a team of scientists arrived on the scene to dig out the prehistoric mega beast.

Messineo said: ‘We went there expecting to find two glyptodonts when the excavation started and then two more were found!

‘It is the first time there have been four animals like this in the same site. Most of them were facing the same direction like they were walking towards something.’

He added that the sizes indicate the group was comprised of two adults and two younglings.

The science team will require diggers to remove the shells as they can weigh up to one ton.

The fossils will then undergo further research to establish their age and sex and possibly cause of death.

At the moment, it is believed the four glyptodonts lived around 20,000 years ago.

Glyptodonts were a genus of large heavily armoured mammals with a rounded, bony shell and squat limbs similar to a turtle.

They are believed to have weighed around 1,000 kilogrammes (2,205 lbs) and could grow to the size of a Volkswagen Beetle.

The animal’s remains have been found in Brazil, Uruguay and Argentina and it is believed they became extinct 10,000 years ago.

Based on their jaw morphology, Glyptodons were herbivores and they were also hairy with very slow movements due to their size.

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

Amber specimens reveal origin of long mouthpart of scorpionflies

March 8, 2020

Aneuretopsychidae from Late Cretaceous Burmese amber. Credit: NIGPAS

An international research group led by Prof. Wang Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) has found a new genus, including two new aneuretopsychid species from early Late Cretaceous (99 million years ago) Burmese amber, which reveals new anatomically significant details of the elongate mouthpart elements.

Mesopsychoid scorpionflies are peculiar Mesozoic insects with a distinctly elongate mouthpart and are considered to be a critical group of pollinators prior to the rise of angiosperms.

A new genus found from 99-million-year-old Burmese amber reveals the origin of scorpionflies’ long mouthpart. This discovery was reported in Science Advances on March 4. Aneuretopsychidae is a family of mecopteran insects with a long siphonate mouthpart. In particular, this family is the key to understanding both the early evolution of highly modified mouthparts in Mesopsychoidea and arguably the origin of fleas.

Previously, all known aneuretopsychids were from compression fossils, and the detailed structure of their mouthparts was still unclear.

Now, however, an international research group led by Prof. Wang Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) has found a new genus, including two new aneuretopsychid species from early Late Cretaceous (99 million years ago) Burmese amber, which reveals new anatomically significant details of the elongate mouthpart elements.

The aneuretopsychid mouthpart in the new amber fossils consists of one pair of galeae and one unpaired central hypopharynx. During feeding, the galeae would come together temporarily and enclose the hypopharynx thus forming a functional tube.

The structures of the new three-dimensionally preserved fossils thus reveal that the aneuretopsychid mouthpart is not labial but maxillary in origin.

The phylogenetic results based on 38 taxa and 54 discrete characters support the monophyly of Mesopsychoidea and demonstrate that an elongate mouthpart is one of its key synapomorphies, challenging the view that the long-proboscid condition independently originated two or three times in this clade.

In addition, the mouthpart of Mesopsychoidea differs structurally from the highly modified piercing mouthparts of Siphonaptera. So, neither Aneuretopsychidae nor Mesopsychoidea is a sister group to Siphonaptera.

In the Burmese amber forest, at least five families of long-proboscid insects have been discovered, further revealing the variety and complexity of mid-Cretaceous pollinating insects.

This study provides new insights into the separate origin of the long mouthpart of Mesopsychoidea and fleas, and the evolution of Cretaceous pollinating insects.

Reference:
X. Zhao el al., “Mouthpart homologies and life habits of Mesozoic long-proboscid scorpionflies,” Science Advances (2020). DOI: 10.1126/sciadv.aay1259

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

Where is the greatest risk to our mineral resource supplies?

March 8, 2020

Bastnaesite (the reddish parts) in Carbonatite. Bastnaesite is an important ore for rare earth elements, one of the mineral commodities identified as most at-risk of supply disruption by the USGS in a new methodology. Credit: Scott Horvath, USGS

Policymakers and the U.S. manufacturing sector now have a powerful tool to help them identify which mineral commodities they rely on that are most at risk to supply disruptions, thanks to a new methodology by the U.S. Geological Survey and its partners.

“This methodology is an important part of how we’re meeting our goals in the President Trump’s Strategy to ensure a reliable supply of critical minerals,” said USGS director Jim Reilly. “It provides information supporting American manufacturers’ planning and sound supply-chain management decisions.”

The methodology evaluated the global supply of and U.S. demand for 52 mineral commodities for the years 2007 to 2016. It identified 23 mineral commodities, including some rare earth elements, cobalt, niobium and tungsten, as posing the greatest supply risk for the U.S. manufacturing sector. These commodities are vital for mobile devices, renewable energy, aerospace and defense applications, among others.

“Manufacturers of new and emerging technologies depend on mineral commodities that are currently sourced largely from other countries,” said USGS scientist Nedal Nassar, lead author of the methodology. “It’s important to understand which commodities pose the greatest risks for which industries within the manufacturing sector.”

The supply risk of mineral commodities to U.S. manufacturers is greatest under the following three circumstances: U.S. manufacturers rely primarily on foreign countries for the commodities, the countries in question might be unable or unwilling to continue to supply U.S. manufacturers with the minerals; and U.S. manufacturers are less able to handle a price shock or from a disruption in supply.

“Supply chains can be interrupted for any number of reasons,” said Nassar. “International trade tensions and conflict are well-known reasons, but there are many other possibilities. Disease outbreaks, natural disasters, and even domestic civil strife can affect a country’s mineral industry and its ability to export mineral commodities to the U.S.”

Risk is not set in stone; it changes based on global market conditions that are specific to each individual mineral commodity and to the industries that use them. However, the analysis indicates that risk typically does not change drastically over short periods, but instead remains relatively constant or changes steadily.

“One thing that struck us as we were evaluating the results was how consistent the mineral commodities with the highest risk of supply disruption have been over the past decade,” said Nassar. “This is important for policymakers and industries whose plans extend beyond year-to-year changes.”

For instance, between 2007 and 2016, the risk for rare earth elements peaked in 2011 and 2012 when China halted exports during a dispute with Japan. However, the supply of rare earth elements consistently remained among the highest risk commodities throughout the entire study period.

In 2019, the U.S. Department of Commerce, in coordination with the Department of the Interior and other federal agencies, published the interagency report entitled “A Federal Strategy to Ensure a Reliable Supply of Critical Minerals,” in response to President Trump’s Executive Order 13817. Among other things, the strategy commits the U.S. Department of the Interior to improve the geophysical, geologic, and topographic mapping of the U.S.; make the resulting data and metadata electronically accessible; support private mineral exploration of critical minerals; make recommendations to streamline permitting and review processes enhancing access to critical mineral resources.

The methodology is entitled “Evaluating the Mineral Commodity Supply Risk of the U.S. Manufacturing Sector,” and is published in Science Advances.

Reference:
Evaluating the mineral commodity supply risk of the U.S. manufacturing sector, Science Advances 21 Feb 2020: Vol. 6, no. 8, eaay8647, DOI: 10.1126/sciadv.aay8647

Note: The above post is reprinted from materials provided by United States Geological Survey. The original article was written by Alex Demas.

What other planets can teach us about Earth

March 8, 2020

The rising Earth from the perspective of the moon. Credit: NASA Goddard

Table of Contents

Sometimes, you need to leave home to understand it. For Stanford planetary geologist Mathieu Lapôtre, “home” encompasses the entire Earth.

“We don’t only look at other planets to know what’s out there. It’s also a way for us to learn things about the planet that’s under our own feet,” said Lapôtre, an assistant professor of geological sciences in the School of Earth, Energy, & Environmental Sciences (Stanford Earth).

Scientists since Galileo have sought to understand other planetary bodies through an earthly lens. More recently, researchers have recognized planetary exploration as a two-way street. Studies of space have helped to explain aspects of climate and the physics of nuclear winter, for example. Yet revelations have not permeated all geoscience fields equally. Efforts to explain processes closer to the ground—at Earth’s surface and deep in its belly—are only beginning to benefit from knowledge gathered in space.

Now, as telescopes acquire more power, exoplanet studies grow more sophisticated and planetary missions produce new data, there’s potential for much broader impacts across Earth sciences, as Lapôtre and co-authors from Arizona State University, Harvard University, Rice University, Stanford and Yale University argue in the journal Nature Reviews Earth & Environment.

“The multitude and variety of planetary bodies within and beyond our solar system,” they write in a paper published March 2, “might be key to resolving fundamental mysteries about the Earth.”

In the coming years, studies of these bodies may well alter the way we think about our place in the universe.

Alien forms

Observations from Mars have already changed the way scientists think about the physics of sedimentary processes on Earth. One example got underway when NASA’s Curiosity Rover crossed a dune field on the red planet in 2015.

“We saw that there were big sand dunes and small, decimeter-scale ripples like the ones we see on Earth,” said Lapôtre, who worked on the mission as a Ph.D. student at Caltech in Pasadena, Calif. “But there was also a third type of bedform, or ripple, that does not exist on Earth. We couldn’t explain how or why this shape existed on Mars.”

The strange patterns prompted scientists to revise their models and invent new ones, which ultimately led to the discovery of a relationship between the size of a ripple and the density of the water or other fluid that created it. “Using these models developed for the environment of Mars, we can now look at an old rock on Earth, measure ripples in it and then draw conclusions about how cold or salty the water was at the time the rock formed,” Lapôtre said, “because both temperature and salt affect fluid density.”

This approach is applicable across the geosciences. “Sometimes when exploring another planet, you make an observation that challenges your understanding of geological processes, and that leads you to revise your models,” Lapôtre explained.

Planets as experiments

Other planetary bodies can also help to show how frequent Earth-like bodies are in the universe and what, exactly, makes Earth so different from the average planet.

“By studying the variety of outcomes that we see on other planetary bodies and understanding the variables that shape each planet, we can learn more about how things might have happened on Earth in the past,” explained co-author Sonia Tikoo-Schantz, a geophysics professor at Stanford Earth whose research centers on paleomagnetism.

Consider, she suggested, how studies of Venus and Earth have helped scientists better understand plate tectonics. “Venus and Earth are about the same size, and they probably formed under fairly similar conditions,” Tikoo-Schantz said. But while Earth has tectonic plates moving around and abundant water, Venus has a mostly solid lid, no water on its surface and a very dry atmosphere.

“From time to time, Venus has some kind of catastrophic disruption and a resurfacing of much of the world,” Tikoo-Schantz said, “but we don’t see this continuous steady state tectonic environment that we have on Earth.”

Scientists are increasingly convinced that water may explain much of the difference. “We know that subduction of tectonic plates brings water down into the Earth,” Tikoo-Schantz said. “That water helps lubricate the upper mantle, and helps convection happen, which helps drive plate tectonics.”

This approach—using planetary bodies as grand experiments—can be applied to answer more questions about how Earth works. “Imagine you want to see how gravity might affect certain processes,” Lapôtre said. “Going to other planets can let you run an experiment where you can observe what happens with a lower or higher gravity—something that’s impossible to do on Earth.”

Core paradox

Studies measuring magnetism in ancient rocks suggest that Earth’s magnetic field has been active for at least 3.5 billion years. But the cooling and crystallization of the inner core that scientists believe sustains Earth’s magnetic field today started less than 1.5 billion years ago. This 2-billion-year gap, known as the new core paradox, has left researchers puzzling over how Earth’s dynamo could have started so early, and persisted for so long.

Answers may lie in other worlds.

“In our circle of close neighbors—the Moon, Mars, Venus—we’re the only planet with a magnetic field that’s been going strong since the beginning and remains active today,” Lapôtre said. But Jupiter-sized exoplanets orbiting close to their star have been identified with magnetic fields, and it may soon be technically feasible to detect similar fields on smaller, rocky, Earth-like worlds. Such discoveries would help clarify whether Earth’s long-lived dynamo is a statistical anomaly in the universe whose startup required some special circumstance.

Ultimately, the mystery around the origin and engine behind Earth’s dynamo is a mystery about what creates and sustains the conditions for life. Earth’s magnetic field is essential to its habitability, protecting it against dangerous solar winds that can strip a planet of water and atmosphere. “That’s part of why Mars is such a dry desert compared to Earth,” Tikoo-Schantz said. “Mars started to dehydrate when its magnetic field died.”

Earth everchanging

Much of the impetus to look far beyond Earth when trying to decode its inner workings has to do with our planet’s restless nature. At many points in its 4.5 billion-year existence, Earth looked nothing like the blue-green marble it is today.

“We’re trying to get to the point where we can characterize planets that are like the Earth, and hopefully, someday find life on one of them,” said co-author Laura Schaefer, a planetary scientist at Stanford Earth who studies exoplanets. Chances are it will be something more like bacteria than E.T., she said.

“Just having another example of life anywhere would be amazing,” Schaefer said. It would also help to illuminate what happened on Earth during the billions of years before oxygen became abundant and, through processes and feedback loops that remain opaque, complex life burst forth.

“We’re missing information from different environments that existed on the surface of the Earth during that time period,” Schaefer explained. Plate tectonics constantly recycles rocks from the surface, plunging them into the planet’s fiery innards, while water sloshing around oceans, pelting down from rainclouds, hanging in the air, and slipping in rivers and streams tends to alter the geochemistry of rocks and minerals that remain near the surface.

Earth’s very liveliness makes it a poor archive for evidence of life and its impacts. Other planetary bodies—some of them dead still and bone dry, others somehow akin to the ancient Earth—may prove better suited to the task.

That’s part of why scientists were so excited to find, in 2019, that a rock sample collected by the Apollo 14 astronauts in 1971 may in fact hold minerals that rocketed off of Earth as a meteorite billions of years ago. “On the Moon, there is no plate tectonics or aqueous weathering,” Lapôtre said. “So this piece of rock has been sitting there intact for the last few billion years just waiting for us to find it.”

To be sure, planetary scientists do not expect to find many ancient Earth time capsules preserved in space. But continued exploration of other worlds in our solar system and beyond could eventually yield a small statistical sample of planets with life on them—not carbon copies of Earth’s systems, but systems nonetheless where interactions between life and atmosphere can come into sharper focus.

“They’re not going to be at the same stage of life as we have today on Earth, and so we’ll be able to learn about how planets and life evolve together,” Schaefer said. “That would be pretty revolutionary.”

Reference:
Mathieu G. A. Lapôtre et al. Probing space to understand Earth, Nature Reviews Earth & Environment (2020). DOI: 10.1038/s43017-020-0029-y

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

Half billion-year-old ‘social network’ observed in early animals

March 8, 2020

Fossilised threads - some as long as four metres - connecting organisms known as rangeomorphs, which dominated Earth's oceans half a billion years ago. Credit: Alex Liu — Fossilised threads – some as long as four metres – connecting organisms known as rangeomorphs, which dominated Earth’s oceans half a billion years ago. Credit: Alex Liu

Some of the first animals on Earth were connected by networks of thread-like filaments, the earliest evidence yet found of life being connected in this way.

Scientists from the Universities of Cambridge and Oxford discovered the fossilised threads—some as long as four metres—connecting organisms known as rangeomorphs, which dominated Earth’s oceans half a billion years ago.

The team found these filament networks—which may have been used for nutrition, communication or reproduction -in seven species across nearly 40 different fossil sites in Newfoundland, Canada. Their results are reported in the journal Current Biology.

Towards the end of the Ediacaran period, between 571 and 541 million years ago, the first diverse communities of large and complex organisms began to appear: prior to this, almost all life on Earth had been microscopic in size.

Fern-like rangeomorphs were some of the most successful life forms during this period, growing up to two metres in height and colonising large areas of the sea floor. Rangeomorphs may have been some of the first animals to exist, although their strange anatomies have puzzled palaeontologists for years; these organisms do not appear to have had mouths, organs or means of moving. One suggestion is that they absorbed nutrients from the water around them.

Since rangeomorphs could not move and are preserved where they lived, it is possible to analyse whole populations from the fossil record. Earlier studies of rangeomorphs have looked at how these organisms managed to reproduce and be so successful in their time.

“These organisms seem to have been able to quickly colonise the sea floor, and we often see one dominant species on these fossil beds,” said Dr. Alex Liu from Cambridge’s Department of Earth Sciences, and the paper’s first author. “How this happens ecologically has been a longstanding question—these filaments may explain how they were able to do that.”

Most of the filaments were between two and 40 centimetres in length, although some were as long as four metres. Since they are so thin however, the filaments are only visible in places where the fossil preservation is exceptionally good, which is one of the reasons they were not identified sooner. The fossils for this study were found on five sites in eastern Newfoundland, one of the world’s richest sources of Ediacaran fossils.

It’s possible that the filaments were used as a form of clonal reproduction, like modern strawberries, but since the organisms in the network were the same size, the filaments may have had other functions. For example, the filaments may have provided stability against strong ocean currents. Another possibility is that they enabled organisms to share nutrients, a prehistoric version of the ‘wood wide web’ observed in modern-day trees. What is known however, is that some reconsideration of how Ediacaran organisms lived may be in order.

“We’ve always looked at these organisms as individuals, but we’ve now found that several individual members of the same species can be linked by these filaments, like a real-life social network,” said Liu. “We may now need to reassess earlier studies into how these organisms interacted, and particularly how they competed for space and resources on the ocean floor. The most unexpected thing for me is the realisation that these things are connected. I’ve been looking at them for over a decade, and this has been a real surprise.”

“It’s incredible the level of detail that can be preserved on these ancient sea floors; some of these filaments are only a tenth of a millimetre wide,” said co-author Dr. Frankie Dunn from the Oxford University Museum of Natural History. “Just like if you went down the beach today, with these fossils, it’s a case of the more you look, the more you see.”

Reference:
Current Biology (2020). DOI: 10.1016/j.cub.2020.01.052

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

Sinking sea mountains make and muffle earthquakes

March 8, 2020

The SHIRE project, which contributed resources to this research, is investigating seamounts within the Hikurangi Trench, to learn how they generate or dampen earthquakes at different stages of subduction. This seismic image shows a seamount known as Puke Seamount, colliding with New Zealand. Image: SHIRE/Andrew Gase.

Subduction zones — places where one tectonic plate dives beneath another — are where the world’s largest and most damaging earthquakes occur. A new study has found that when underwater mountains — also known as seamounts — are pulled into subduction zones, not only do they set the stage for these powerful quakes, but also create conditions that end up dampening them.

The findings mean that scientists should more carefully monitor particular areas around a subducting seamount, researchers said. The practice could help scientists better understand and predict where future earthquakes are most likely to occur.

“The Earth ahead of the subducting seamount becomes brittle, favoring powerful earthquakes while the material behind it remains soft and weak, allowing stress to be released more gently,” said co-author Demian Saffer, director of the University of Texas Institute for Geophysics (UTIG), a research unit of The University of Texas at Austin Jackson School of Geosciences.

The study was published on March 2 in Nature Geoscience and was led by Tian Sun, who is currently a research scientist at the Geological Survey of Canada. Other co-authors include Susan Ellis, a scientist at the New Zealand research institute GNS Science. Saffer supervised the project and was Sun’s postdoctoral advisor at Penn State when they began the study.

The researchers used a computer model to simulate what happens when seamounts enter ocean trenches created by subduction zones. According to the model, when a seamount sinks into a trench, the ground ahead of it becomes brittle, as its slow advance squeezes out water and compacts the Earth. But in its wake, the seamount leaves a trail of softer wet sediment. The hard, brittle rock can be a source for powerful earthquakes, as forces generated by the subducting plate build up in it — but the weakened, wet material behind the seamount creates an opposite, dampening effect on these quakes and tremors.

Although seamounts are found all over the ocean floor, the extraordinary depths at which subduction occurs means that studying or imaging a subducting seamount is extremely difficult. This is why until now, scientists were not sure whether seamounts could affect the style and magnitude of subduction zone earthquakes.

The current research tackled the problem by creating a realistic computer simulation of a subducting seamount and measuring the effects on the surrounding rock and sediment, including the complex interactions between stresses in the Earth and fluid pressure in the surrounding material. Getting realistic data for the model involved conducting experiments on rock samples collected from subduction zones by scientific ocean drilling offshore Japan.

The scientists said the model’s results took them completely by surprise. They had expected water pressure and stress to break up material at the head of the seamount and thus weaken the rocks, not strengthen them.

“The seamount creates a feedback loop in the way fluids get squeezed out and the mechanical response of the rock to changes fluid pressure,” said Ellis, who co-developed the numerical code at the heart of the study.

The scientists are satisfied their model is robust because the earthquake behavior it predicts consistently matches the behavior of real earthquakes.

While the weakened rock left in the wake of seamounts may dampen large earthquakes, the researchers believe that it could be an important factor in a type of earthquake known as a slow slip event. These slow-motion quakes are unique because they can take days, weeks and even months to unfold.

Laura Wallace, a research scientist at UTIG and GNS Science, who was the first to document New Zealand slow slip events, said that the research was a demonstration of how geological structures in the Earth’s crust, such as seamounts, could influence a whole spectrum of seismic activity.

“The predictions from the model agree very nicely with what we are seeing in New Zealand in terms of where small earthquakes and tremors are happening relative to the seamount,” said Wallace, who was not part of the current study.

Sun believes that their investigations have helped address a knowledge gap about seamounts, but that research will benefit from more measurements.

“We still need high resolution geophysical imaging and offshore earthquake monitoring to better understand patterns of seismic activity,” said Sun.

The research was funded by the Seismogenesis at Hikurangi Integrated Research Experiment (SHIRE), an international project co-led by UT Austin to investigate the origin of earthquakes in subduction zones.

The study was also supported by the National Science Foundation, the New Zealand Ministry of Business, Innovation and Employment, and GNS Science.

Reference:
Tianhaozhe Sun, Demian Saffer, Susan Ellis. Mechanical and hydrological effects of seamount subduction on megathrust stress and slip. Nature Geoscience, 2020; DOI: 10.1038/s41561-020-0542-0

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

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