This slab of sandstone has been on display since 1896, showing off the scaly footprints of a prosauropod dinosaur. Scientists only recently realized that the deep grooves on the left may be the track of a sailing stone. Credit: Lull, R.S., 1915
A sandstone slab prized for its detailed dinosaur footprints may also contain the track of a sailing stone or “walking rock.” Paleontologist Paul Olsen from Lamont-Doherty Earth Observatory announced this discovery in a presentation at the meeting of the American Geophysical Union on Monday. He and his colleagues think the trail of the walking rock is evidence of a brief freezing event in the tropics some 200 million years ago—the first evidence that volcanic winters reached into the humid tropics during the dawn of the dinosaur age.
The slab has been on display since 1896—most recently at Dinosaur State Park in Connecticut, the state where it was originally discovered. It shows off the scaly footprints of a Brontosaurus predecessor that lived in the tropics during the Early Jurassic period. But nobody noticed the sailing stone track until Olsen and his colleagues came along in 2017.
Sailing stones are rocks and boulders move across flat landscapes without the help of gravity, people, or animals, carving tracks as they go. How do they move? Scientists know of two ways: by sliding on thick, slimy microbial mats, and when they’re pushed by thin ice sheets that form temporarily over shallow lakes.
The researchers can’t say for sure whether it was one sailing stone or several that scraped this particular surface, but whatever it was, it was heavy enough to dig significant grooves in the ancient mud. A heavy object requires a thick microbial mat to lubricate its movement, but if such a thick mat was present, it would have prevented the detailed dinosaur footprints from forming.
“When the microbial mat gets thick, it actually shields the mud from the details of the foot,” explains Olsen. Furthermore, he adds, the surface doesn’t bear any of the usual markings of a thick microbial mat.
That left the other explanation: that the object was pushed by ice. That was surprising, because the track was laid down back when Connecticut was located at around the same latitude as the modern-day Yucatan peninsula. The site was at a relatively low elevation that would have experienced a tropical climate, and through most of the beginning of the Age of Dinosaurs, many of the animals and plants in the region were frost-intolerant. “There are no reasons to think that freezing would be a normal situation there,” says Olsen.
However, he and his colleagues have a potential explanation. The sandstone was deposited during the last of a series of eruptions that caused a mass extinction. The eruptions also blasted huge amounts of sulfur aerosols into the atmosphere that likely produced brief periods of global cooling, by shielding the Earth from receiving a normal amount of sunlight. However, paleoclimatologists don’t know how much sulfur was dumped into the atmosphere or how much cooling occurred. The new finding suggests that the planet may have cooled to such an extent that even the tropics froze.
“This may be evidence of the cooling caused by the volcanic winter,” says Olsen.
If the massive cooling event did reach the tropics, it is possible that the dinosaurs’ feathers provided insulation that helped them to survive the cold.
At the global scale, the freezing conditions during this time wiped out large non-insulated reptiles on land, opening up ecological space for insulated dinosaurs to dominant the planet.
Olsen cautions that the volcanic winter interpretation is “is not iron-clad,” because the team can’t entirely rule out the possibility that microbial mats allowed the rocks to sail.
Fortunately, there is a way to solve the mystery: If there were thin ice sheets in this region, then they likely moved other rocks as well. “If you could find them moving in synchrony, that would really indicate that it was ice, without a question,” says Olsen.
The team also discovered the footprints of a primitive mammal in the same sandstone slab, which had similarly gone unnoticed for more than 100 years. The mammal, sailing stone, and dinosaur likely passed by the same spot within a few days or weeks of each other.
Stones do not float in water. This is a truism. But there is hardly a rule without exception. In fact, some volcanic eruptions produce a very porous type of rock with a density so low that it does float: Pumice. An unusually large amount of it is currently drifting in the Southwest Pacific towards Australia. When it was first sighted in the waters of the island state of Tonga at the beginning of August, it almost formed a coherent layer on the ocean’s surface. The “pumice raft” made it into headlines all over the world.
Various underwater volcanoes were discussed at that time as the potential source. But a direct proof for the exact origin of the pumice was missing so far. Researchers at the GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), together with colleagues from Canada and Australia, are now publishing evidence in the Journal of Volcanology and Geothermal Research that clearly identifies the culprit. It is a so far nameless underwater volcano just 50 kilometres northwest of the Tongan island of Vava’u. “In the international scientific literature, it appears so far only under the number 243091 or as Volcano F,” says Dr. Philipp Brandl of GEOMAR, first author of the study.
Only in January of this year Dr. Brandl and several of his co-authors were working in the region on the German research vessel SONNE. The expedition, named ARCHIMEDES, aimed at studying the formation of new crust in the geologically extremely dynamic region between Fiji and Tonga. “When I then saw the reports on the pumice raft in the media in the summer, I became curious and started researching with my colleagues,” says the geologist.
The team found what they were looking for on of freely accessible satellite images. On an image of the ESA satellite Copernicus Sentinel-2 taken on 6 August 2019, clear traces of an active underwater eruption can be seen on the water surface. Since the images are exactly georeferenced, they could be compared with corresponding bathymetric maps of the seafloor. “The eruption traces fit exactly to Volcano F,” says Dr. Brandl.
To be on the safe side, the researchers also compared this position with information from stations of the global seismic network that recorded signals from the eruption. “Unfortunately, the density of such stations in the region is very low. There were only two stations that recorded seismic signals of a volcanic eruption. However, their data is consistent with Volcano F as the origin,” says Dr. Brandl.
Pumice can form during volcanic eruptions when viscous lava is foamed by volcanic gases such as water vapour and carbon dioxide. This creates so many pores in the cooling rock that its density is lower than that of water. “During an underwater eruption, the probability to generate pumice is particularly high,” explains Dr. Brandl.
With the help of additional satellite images, the team traced the drift and dispersal of the pumice raft until mid-August. It slowly drifted west and reached an area of up to 167 square kilometres. This is about twice the size of Manhattan. The team was also able to constrain the magnitude of the underwater eruption. It corresponded to a volcanic eruption index of 2 or 3, which is similar to recent eruptions of Mount Stromboli, for example.
With the current direction and speed, the pumice raft is expected to hit the Great Barrier Reef off the eastern coast of Australia at the end of January or beginning of February. Biologists, in particular, are eagerly awaiting this event because pumice rafts may play an important role in the dispersion of fauna in the vastness of the Pacific Ocean. The Kiel team of geologists would like to examine samples of the pumice in order to determine the geochemistry of Volcano F more precisely. “Maybe our Australian colleagues will send us a few samples next year,” says Dr. Brandl.
Reference:
Philipp A. Brandl, Florian Schmid, Nico Augustin, Ingo Grevemeyer, Richard J. Arculus, Colin W. Devey, Sven Petersen, Margaret Stewart, Heidrun Kopp, Mark D. Hannington. The 6–8 Aug 2019 eruption of ‘Volcano F’ in the Tofua Arc, Tonga. Journal of Volcanology and Geothermal Research, 2019; 106695 DOI: 10.1016/j.jvolgeores.2019.106695
A new petit-spot volcano at the oldest section of the Pacific Plate Credit: Tohoku University
Researchers from Tohoku University have discovered a new petit-spot volcano at the oldest section of the Pacific Plate. The research team, led by Associate Professor Naoto Hirano of the Center for Northeast Asian Studies, published their discovery in the in the journal Deep-Sea Research Part I.
Petit-spot volcanoes are a relatively new phenomenon on Earth. They are young, small volcanoes that come about along fissures from the base of tectonic plates. As the tectonic plates sink deeper into the Earth’s upper mantle, fissures occur where the plate begins to bend causing small volcanoes to erupt. The first discovery of petit-spot volcanoes was made in 2006 near the Japan Trench, located to the northeast of Japan.
Rock samples collected from previous studies of petit-spot volcanoes signify that the magma emitted stems directly from the asthenosphere—the uppermost part of Earth’s mantle which drives the movement of tectonic plates. Studying petit-spot volcanoes provides a window into the largely unknown asthenosphere giving scientists a greater understanding of plate tectonics, the kind of rocks existing there, and the melting process undergone below the tectonic plates.
The volcano was discovered in the western part of the Pacific Ocean, near Minamitorishima Island, Japan’s easternmost point, also known as Marcus Island. The volcano is thought to have erupted less than 3 million years ago due to the subduction of the Pacific Plate deeper into the mantle of the Marina Trench. Previously, this area is thought to have contained only seamounts and islands formed 70-140 million years ago.
The research team initially suspected the presence of a small volcano after observing bathymetric data collected by the Japan Coast Guard. They then analyzed rock samples collected by the Shnkai6500, a manned submersible that can dive to depths of 6,500 meters, which observed the presence of volcano.
“The discovery of this new Volcano provides and exciting opportunity for us to explore this area further, and hopefully reveal further petit-spot volcano,” says Professor Hirano. He adds, “This will tell us more about the true nature of the asthenosphere.” Professor Hirano and his team will continue to explore the site for similar volcanoes since mapping data demonstrates that the discovered volcano is part of a cluster.
Reference:
Naoto Hirano et al. Petit-spot volcanoes on the oldest portion of the Pacific plate, Deep Sea Research Part I: Oceanographic Research Papers (2019). DOI: 10.1016/j.dsr.2019.103142
A modern-day sea lily in the Marianas region. Credit: (c) NOAA Ocean Research and Exploration
Sea lilies, despite their name, aren’t plants. They’re animals related to starfish and sea urchins, with long feathery arms resting atop a stalk that keeps them anchored to the ocean floor. Sea lilies have been around for at least 480 million years—they first evolved hundreds of millions of years before the dinosaurs. For nearly two centuries, scientists have thought about how modern sea lilies evolved from their ancient ancestors. In a new study in the Journal of Paleontology, researchers are rewriting the sea lily family tree, aided by newly-discovered fossils that help show how these animals’ arms evolved.
“These early fossils provide new key evidence showing that what we had thought about the origin of sea lilies since 1846 is wrong,” says Tom Guensburg, the paper’s lead author and a research associate at the Field Museum in Chicago. “It’s not very often that we’re challenging ideas that are almost two hundred years old.”
Sea lilies are more formally known as crinoids, but they’ve earned their nickname—they really do look like flowers growing at the bottom of the ocean. They spend their adult lives stuck in one place, with stem-like stalks that attach them to the sea floor. At the top of these stalks are a cluster of arms, maybe the size of the palm of your hand. These arms trap tiny plankton floating through the water, which the sea lily then eats.
“Some people actually consider sea lilies and their relatives, the feather stars, the most beautiful animals. They come in any color—purple, bright red, green,” says Guensburg. “They look plant-like, but when you actually look at their bodies, you find all the usual anatomy of complex animals like a digestive tract and nervous system—they’re closer to vertebrates, and us, than almost any other invertebrate animals.”
In the new paper, Guensburg and his colleagues describe a new kind of fossil sea lily they named Athenacrinus broweri, after the Greek goddess Athena. “Athena is often depicted with rangy, almost gangly limbs on ancient Greek vases; this fossil’s arms are long and thin too,” explains Guensburg. And, he adds, “Athena is the goddess of wisdom, and this fossil tells us something important about the origin of this group. This fossil has great significance.”
This discovery has been a long time coming. In 1846, scientists were putting together the family tree of the echinoderms—animals like sea lilies, starfish, sand dollars, sea urchins, sea cucumbers, and a host of extinct groups. In the fossil record, they found ancient animals that look like modern sea lilies, with stalks ending in a bunch of delicate arms, called cystoids. They figured that both of these ancient animals must be closely related. But beginning in the 1950s, some scientists expressed doubts that cystoids belonged with the sea lilies—that similarities were superficial only. Still, evidence used to argue that crinoids and cystoids were only distantly related has been criticized to this day by those favoring the old traditional idea of crinoid origin.
Arm structure of Athenacrinus turned out to be key to figuring out how sea lilies evolved from earliest-known echinoderms, some of these up to 515 million years old. These earliest echinoderms didn’t have arms yet, but they did have plates in their bodies similar to those found in earliest crinoid arms. So some of the plates in earliest crinoid arms preceded the origin of arms themselves. These plates are nowhere to be found in sea lilies beginning 450 million years ago. And while modern sea lilies have different arm plating, they have tissues that are remnants inherited from this ancient pattern. The new paper in the Journal of Paleontology shows that early sea lilies from 480 million years ago are the missing link between the earliest sea lily ancestors and what we see in living crinoids.
Cystoids, meanwhile have different arms structures that, says Guensburg, indicate that cystoids don’t even belong to the same class of animals as sea lilies. “These new fossils provide for the first time an accurate picture of what the earliest crinoid arms were like, and they are unlike any cystoid in important ways,” says Guensburg; “No cystoid has such anatomy.” That means, Guensburg says, that crinoids and cystoids are related only at the deepest, most primitive level in echinoderm history. “One of the most fascinating branches of the tree of life, echinoderms, needs rearranging,” he notes. “That’s a big deal.”
And, he says, piecing together how sea lilies evolved helps broadens our understanding of all life: “What makes humans different from other animals is that we’re curious about understanding our place in the universe and understanding our place in the history of life. This is a piece of that—it’s what makes life interesting.”
The deep structure of the continent Antarctica. Credit: Planetary Visions (credit: ESA/Planetary Visions)
The Antarctic is one of the parts of earth that we know the least about. Due to the massive ice shield, the collection of geophysical information on site is extremely difficult and expensive. Satellite data from the European Space Agency (ESA) has now been used as the basis for new insights on the deep structure of the continent. Scientists from Kiel University (CAU) recently published their discoveries in the Journal of Geophysical Research: Solid Earth in cooperation with scientists from the British Antarctic Survey, Great Britain, and Delft University of Technology in the Netherlands.
Looking into the deep from space
The newly evaluated data from the ESA’s GOCE satellite mission dedicated to the earth’s gravitational field, combined with seismological models, enables unprecedented insights into the lithosphere, which consists of the crust and the earth’s upper mantle below the frozen continent. To do so, Folker Pappa, doctoral researcher at Kiel University and lead author of the study, along with Jörg Ebbing, Professor for Geophysics at Kiel University, used special gradient data of the satellite, among other information: “This allows a much greater level of detail when analysing deep earth structures,” says Pappa. It enables the researchers to draw conclusions about such things as the depth of the transition from crust to mantle — and these measurements are dramatically different over the 14 million square kilometre region. “Under West Antarctica, which is geologically young, the earth’s crust is comparatively thin with about 25 kilometres, and the earth’s mantle is viscous at a depth of less than 100 kilometres. East Antarctica, on the other hand, is an old cratonic shield and more than one billion years old. Here, the mantle rocks still have solid properties at a depth of more than 200 kilometres.”
Representation of the deep 3D structure of the Antarctic now also permits new findings about the so-called glacial-isostatic adjustment, explains co-author Professor Wouter van der Wal from Delft University of Technology: “This is a key process that determines how the continent responds to current and past ice sheet thinning. We found large variations in mantle temperature beneath the continent, which lead to the uplifting and subsiding of the ground with very different speeds across the continent. These new constraints on crustal and lithosphere thickness are also pivotal in the quest to estimate Antarctic geothermal heat flux and how it affects subglacial melting and ice sheet flow.”
“These are natural interactions between the ice and the solid earth. Until now, it was not possible to examine these processes more closely in the Antarctic in detail due to a lack of earth models,” added Pappa. His personal highlight are the Gamburtsev Subglacial Mountains that are still barely explored and over three thousand metres high: “The solid earth is the thickest here, at around 260 kilometres. This is an exciting structure, and we don’t know exactly what it looks like because the mountain range is completely covered with ice shields.”
Antarctica as a 3D model and its connection to other continents
The research was funded by the European Space Agency within the projects GOCE+Antarctica and 3D Earth. The international consortium of both projects consists of nine institutions in six European countries. “3D Earth offers us tantalising new geophysical findings about the deep structure and development of Antarctica. These new models showing the thickness of the crust and the lithosphere are crucial to understanding the fundamental composition and tectonic architecture of the Antarctic, for example,” emphasises Dr Fausto Ferraccioli, head geophysicist at the British Antarctic Survey and co-author of the study. “Further findings that we can derive from the study concern are the former connections between Antarctica and other continents such as Australia, Africa and India,” said Ferraccioli.
“We are finally getting to know the Antarctic properly,” says Ebbing. In addition to the temperature distribution, the researchers have also determined other properties of the solid earth, such as the composition and the rock density.
Part of the project is an impressive 3D model of the Antarctic, created by the ESA. ESA’s Roger Haagmans noted: “These are important findings also in the context of understanding sea-level change as a consequence of ice loss from Antarctica. When ice mass is lost, the solid Earth rebounds and this effect needs to be accounted for in ice volume changes. This can be better determined once the structure and composition of the Earth interior are better understood.”
Reference:
F. Pappa, J. Ebbing, F. Ferraccioli, W. Wal. Modeling Satellite Gravity Gradient Data to Derive Density, Temperature, and Viscosity Structure of the Antarctic Lithosphere. Journal of Geophysical Research: Solid Earth, 2019; DOI: 10.1029/2019JB017997
Illustration of the newly described Kupoupou stilwelli by Jacob Blokland, Flinders University. Credit: Jacob Blokland, Flinders University
What waddled on land but swam supremely in subtropical seas more than 60 million years ago, after the dinosaurs were wiped out on sea and land?
Fossil records show giant human-sized penguins flew through Southern Hemisphere waters—along side smaller forms, similar in size to some species that live in Antarctica today.
Now the newly described Kupoupou stilwelli has been found on the geographically remote Chatham Islands in the southern Pacific near New Zealand’s South Island. It appears to be the oldest penguin known with proportions close to its modern relatives.
It lived between 62.5 million and 60 million years ago at a time when there was no ice cap at the South Pole and the seas around New Zealand were tropical or subtropical.
Flinders University Ph.D. palaeontology candidate and University of Canterbury graduate Jacob Blokland made the discovery after studying fossil skeletons collected from Chatham Island between 2006 and 2011.
He helped build a picture of an ancient penguin that bridges a gap between extinct giant penguins and their modern relatives.
“Next to its colossal human-sized cousins, including the recently described monster penguin Crossvallia waiparensis, Kupoupou was comparatively small—no bigger than modern King Penguins which stand just under 1.1 metres tall,” says Mr Blokland, who worked with Professor Paul Scofield and Associate Professor Catherine Reid, as well as Flinders palaeontologist Associate Professor Trevor Worthy on the discovery.
“Kupoupou also had proportionally shorter legs than some other early fossil penguins. In this respect, it was more like the penguins of today, meaning it would have waddled on land.
“This penguin is the first that has modern proportions both in terms of its size and in its hind limb and foot bones (the tarsometatarsus) or foot shape.”
As published in the US journal Palaeontologica Electronica, the animal’s scientific name acknowledges the Indigenous Moriori people of the Chatham Island (Rēkohu), with Kupoupou meaning ‘diving bird’ in Te Re Moriori.
The discovery may even link the origins of penguins themselves to the eastern region of New Zealand—from the Chatham Island archipelago to the eastern coast of the South Island, where other most ancient penguin fossils have been found, 800km away.
University of Canterbury adjunct Professor Scofield, Senior Curator of Natural History at the Canterbury Museum in Christchurch, says the paper provides further support for the theory that penguins rapidly evolved shortly after the period when dinosaurs still walked the land and giant marine reptiles swam in the sea.
“We think it’s likely that the ancestors of penguins diverged from the lineage leading to their closest living relatives—such as albatross and petrels—during the Late Cretaceous period, and then many different species sprang up after the dinosaurs were wiped out,” Professor Scofield says
“It’s not impossible that penguins lost the ability to fly and gained the ability to swim after the extinction event of 66 million years ago, implying the birds underwent huge changes in a very short time. If we ever find a penguin fossil from the Cretaceous period, we’ll know for sure.”
Reference:
Chatham Island Paleocene fossils provide insight into the palaeobiology, evolution, and diversity of early penguins (Aves, Sphenisciformes) , Palaeontologia Electronica 22.3.78 1-92 doi.org/10.26879/1009
Note: The above post is reprinted from materials provided by Flinders University.
Unlike regular earthquakes, which can cause visible damage, slow earthquakes cannot be felt at the Earth’s surface. Credit: Pixabay/ marcellomigliosi1956, licensed under pixabay license
Earthquakes are sudden and their shaking can be devastating. But about 20 years ago, a new type of earthquake was discovered. We cannot feel them, and geologists still know very little about them, such as how often they occur.
Regular earthquakes occur when rock underground breaks along a fault—a crack in the Earth’s crust that commonly forms a boundary between tectonic plates—and slips at a speed of about a metre per second.
Previously, it was thought that unless there’s an earthquake, faults move very slowly, at fingernail growth rate. Then, better earthquake-detection instruments revealed that there is a whole range of slip speeds in between. These are known as slow earthquakes and can last days, months or sometimes even years.
“Earth movement accelerates but it doesn’t accelerate to the point where it makes an earthquake that can be felt on the surface,” said Dr. Ake Fagereng, a geologist at Cardiff University in the UK.
There are still many questions to be answered about slow earthquakes though. How they happen, for example, still isn’t clear, as well as what the repercussions might be.
Dr. Fagereng and his colleagues are especially interested in slow earthquakes’ relationship to regular ones and the conditions that give rise to these events, which they are investigating as part of a project called MICA. “If we can figure that out, then we can hopefully also get at whether those conditions can change so that an earthquake speeds up,” said Dr. Fagereng.
In addition to drilling into an offshore area in New Zealand that experiences slow earthquakes, the team has been visiting regions in Japan, Namibia, Cyprus and the UK that would have experienced them in the past. Since they occur deep below the surface of the Earth, which is hard to study, the researchers have chosen areas that were once at the appropriate depths and conditions but have been brought to the surface over time due to erosion and uplift.
“We are looking for structures that formed (as a result of slow earthquakes) and what they tell us about how the rocks accommodated that slip,” said Dr. Fagereng.
Creep
Their theory is that slow earthquakes occur when creep—tiny, continuous movements in a fault—accelerates throughout the fault zone, which can be several kilometres thick. Their field observations showed that a fault can be made up of different rock types of varying strength, such as solid basalt and granite and weaker clay-rich sediment. They suspected that stronger rocks start to fracture as creep speeds up due to weaker rocks moving around them but couldn’t explain exactly why.
Using information from their fieldwork, they’ve now developed a mathematical model to reproduce their theory and describe some of the physics behind it. A mixture of rocks with different deformation styles—such as breaking or bending—seems to be key. A proportion of creeping weak rock is required, as well as locally high enough pressure to cause some rock to rupture.
“A possibility for these slow earthquakes is that you have a thick creeping zone with embedded stronger (rock) bits,” said Dr. Fagereng.
The team is planning to follow up with more field observations to refine their model. They still can’t explain why slow earthquakes occur at particular locations, for example, and why they are much more predictable than regular earthquakes, often occurring at set intervals.
Dr. Fagereng thinks that findings from the project could help improve earthquake and tsunami forecasting. Last year, researchers found the first evidence of a slow earthquake preceding a regular earthquake in an area west of Fairbanks, Alaska, in the US. But the link between the two types of tremors isn’t well understood. In some cases, slow earthquakes could also alleviate stress that would otherwise build up and cause a larger earthquake.
“We’re hoping to get somewhere on what the relation is between slow earthquakes and regular earthquakes,” said Dr. Fagereng. “And then that could potentially feed into models for what size earthquake you can get in different regions.”
Lab experiments could also shed light on the physics of slow earthquakes. Dr. Nicolas Brantut from University College London in the UK and his colleagues are using bespoke machines that can deform rock samples at high pressures and temperatures to mimic conditions deep below the surface of the Earth.
Brittle-plastic transition
His team is particularly interested in the brittle-plastic transition, a region about 10 to 15 kilometres below the surface where the behaviour of rocks changes. Above this zone they are brittle, whereas beneath it they flow due to the high temperature and pressure which increase with depth. “The brittle part is where you have earthquakes,” said Dr. Brantut.
However, slow earthquakes seem to occur in the brittle-plastic zone, based on seismological observations. In many cases, they also take place at the same temperature and pressure conditions found in this region. But so far, slow slip events have typically been modelled based on the frictional forces at a fault without taking into account the peculiarities of the brittle-plastic transition zone where rocks start to flow.
“The interactions between friction mechanisms and plastic flow mechanisms are not understood well enough to rule them out as mechanisms for slow earthquakes,” said Dr. Brantut.
As part of the RockDEaF project, Dr. Brantut and his team are investigating the motion of rocks at the brittle-plastic transition. They are replicating the conditions in this region on pieces of rock centimetres long to see whether they fracture or flow. “We want to understand how these mechanisms compete with each other,” said Dr. Brantut.
Simulating
So far, the team has examined the brittle-plastic transition by simulating a fault in the Earth’s crust in a block of marble. They investigated the behaviour of the rock at different pressures and were expecting to find a sharp transition between brittle and plastic behaviour.
However, they were surprised to find that both behaviours occurred simultaneously under a wide range of pressure conditions. “This is something that I think nobody has realised before,” said Dr. Brantut. “The fact that we can have both friction and deformation in a continuum at the same time.”
Dr. Brantut thinks that results from the project could help pin down where slow earthquakes could occur by determining the conditions and properties of rock that are required.
But they could also provide new clues about the depths at which regular earthquakes originate. Temperature below the surface of the Earth increases as a function of depth, which is typically an increase of 10°C to 40°C per kilometre in the crust. An earthquake’s lowest point of origin is thought to coincide with depths that reach 600°C, since rocks become supple when they surpass this temperature and therefore can’t fracture and generate an earthquake. However better understanding of the transition in rock behaviour should help determine if temperature is the deciding factor.
“We should understand more about what really controls how deep we can expect earthquakes to propagate,” said Dr. Brantut.
Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia
Earthquakes can have devastating impacts on communities all around the world. They strike without warning, often resulting in large fatalities. Since the aftershocks that follow the initial earthquake often prove to be more catastrophic than the mainshock, being able to accurately predict the intensity of future aftershocks can help to save lives. Associate Professor Jiancang Zhuang and Emeritus Professor Yosihiko Ogata from The Institute of Statistical Mathematics (ISM) in Japan, in collaboration with colleagues, have developed a method that can forecast the probability of when and where aftershocks are likely to occur, and how strong the largest of these will be.
Their findings were published on September 6th, 2019 in Nature Communications.
Earthquakes can trigger movement within the Earth’s crust, causing instability that can result in more powerful tremors. An earthquake is seldom an isolated event, but rather accompanied with a sequence of events, often referred to as clusters. Each sequence is typically dominated by an event that has a larger magnitude than all the other events within the sequence. This event is known as the mainshock, while the events that precede and/or follow are known as foreshocks and aftershocks respectively. Aftershocks occur in the same region as the mainshock but are of smaller magnitude. When an aftershock is larger than the mainshock, the original mainshock is redesignated as a foreshock, and the larger aftershock is recognized as the mainshock.
“Many strong earthquakes are followed by a subsequent large earthquake, of magnitude similar to the initial quake or even stronger. Repeating earthquakes cause accumulated damage on already weakened buildings and infrastructures; therefore, forecasting their occurrence is a challenging task from the viewpoint of civil protection to prevent the continuous loss of lives,” said the authors. “The probabilities of the largest earthquake following a large earthquake can be evaluated by learning from other earthquake sequences—a statistical method known as Bayesian inference—and from a very short record of the earthquake sequence,” Zhuang explained.
The authors have introduced a new method for predicting the magnitude of the largest aftershock within a future time interval, in real-time, from the history of the earthquake sequence. This method analyzes the data patterns from the particular earthquake by combining two statistical methods (Bayesian statistics and extreme value theory) and incorporating the data into the Epidemic Type Aftershock-Sequence (ETAS) model—a point process representing the time-related activity of earthquakes in a certain geophysical region—in order to quickly and accurately compute and forecast the probability and severity of aftershocks. The method, which was successfully used to analyze the earthquake sequences from the 2016 earthquake in Kumamoto, Japan, and retrospectively predicted the likelihood of large subsequent earthquakes following the mainshock, provides a useful tool for mitigating earthquake hazard.
“We understand that it is impossible to make precise predictions of when and where a damaging earthquake will occur due to the inherent randomness in earthquake occurrence and our limited observations of the underground process. But earthquake occurrence is not completely random either,” said Zhuang. “This work is done by making use of our understanding of earthquake clustering, which is the most predictable component in seismicity. Our goal is to find as many predictable components in the earthquake process as possible so that we can reduce the randomness in our forecasts.”
This research follows on from a related research result co-authored by Ogata that was published in Scientific Reports in 2013, which used the Omori formula to forecast large aftershocks within one day after the main shock.
“The difference between the two papers,” says Zhuang, “is that the former is based on the Omori formula, which only applies in the case of a single mainshock, and implies the frequency of aftershocks decreases quickly with time. Whereas our paper is based on the ETAS model, a more advanced model that applies to multiple major earthquakes, such as in the Kumamoto case,” he said. “The model used in the 2013 study aims to correct the biases caused by missing data, while the new model helps to obtain stable results as quickly as possible by using prior knowledge.”
Furthermore, the model described in the 2013 paper “forecasts the rate of earthquake in the future, and only considers the largest magnitude in a fixed time interval in the future,” said Zhuang, adding: “The results of the two papers compensate each other rather than conflict one another. It is difficult to compare them directly through their outputs.”
“One of the important advantages of the implemented method is that it fully incorporates the uncertainties of the model parameters into the analysis and the clustering structure of seismicity,” the authors write, concluding that “complex triggering including foreshocks and/or higher-order aftershocks cannot be neglected for purposes of earthquake/aftershock forecasting.”
According to Zhuang, the next step is to be able to compute this in real-time, so that once the record of earthquakes is updated, the probability forecast is updated immediately.
Reference:
Robert Shcherbakov et al, Forecasting the magnitude of the largest expected earthquake, Nature Communications (2019). DOI: 10.1038/s41467-019-11958-4
New research is shedding light on how and where ancient flying reptiles called pterosaurs lived. Credit: Julius Csotonyi
Ancient flying reptiles known as pterosaurs were much more diverse than originally thought, according to a new study by an international group of paleontologists.
The research—conducted by scientists at the University of Alberta and the Museu Nacional in Rio de Janeiro, Brazil—reveals an ancient and extremely well-preserved pterosaur specimen originally discovered in a private limestone quarry in Lebanon more than 15 years ago.
“The diversity of these ancient animals was much greater than we could ever have guessed at, and is likely orders of magnitude more diverse than we will ever be able to discover from the fossil record,” said U of A paleontologist Michael Caldwell, who was a co-author on the study.
Results also suggest that this particular type of pterosaur likely fed on crustaceans, flying on long, narrow wings and catching its prey at the surface of shallow waters, as do modern seabirds like the albatross and frigatebird.
“Pterosaur specimens, the first vertebrates to achieve powered flight, are still quite rare in the African continent,” said Alexander Kellner of the Museu Nacional and professor at the Federal University of Rio de Janeiro. “Here we describe the best preserved material of this group of flying reptiles known from this continent so far, shedding new and much-needed light on the evolutionary history of these creatures.”
The newly identified pterosaur lived 95 million years ago in the middle of what is now called the Tethys Seaway—a vast expanse of shallow marine waters filled with reefs and lagoons, separating Europe from Africa and stretching all the way to Southeast Asia. The researchers found that the pterosaurs living in the Tethys Seaway are related to those from China.
“This means that this Lebanese pterodactyloid was part of a radiation of flying reptiles living in and around and across the ancient Tethys Seaway, from China to a great reef system in what is today Lebanon,” explained Caldwell.
The specimen is now housed in the Mineralogy Museum at Saint Joseph University in Beirut, and a cast of the specimen resides at the U of A.
The research was conducted with Kellner and Roy Nohra of Saint Joseph University, and in collaboration with the ICP Catalan Institute of Palaeontology Miquel Crusafont in Barcelona, Spain, and Expo Haqel in Haqel, Lebanon.
The study, “First Complete Pterosaur From the Afro-Arabian Continent: Insight Into Pterodactyloid Diversity,” is published in Scientific Reports.
Reference:
Alexander W. A. Kellner et al. First complete pterosaur from the Afro-Arabian continent: insight into pterodactyloid diversity, Scientific Reports (2019). DOI: 10.1038/s41598-019-54042-z
A representation of a plesiosaur – living reconstruction (representation: Kai Caspar)
In the Mesozoic era, about 250 to 65 million years ago a large number of reptiles populated the oceans. The most successful were the plesiosaurs, which existed for about the same time as the dinosaurs. Enlarged red blood cells ensured their survival. This was discovered by paleontologists at Bonn University and zoologist Kai R. Caspar from Duisburg-Essen University (UDE). The results can be read in the international bioscientific online journal PeerJ.
Why did the size of the red blood cells increase? The scientists explain this with the environment of the marine animals. “Obviously, the plesiosaur firstly developed in the open sea after their ancestors had migrated from the shallow coastal waters to the high seas. The processes in their bodies adapted accordingly,” says Kai Caspar. The enlarged red blood cells were advantageous for their longer, repeated dives in the open sea. “The larger they are, the more oxygen can be bound per cell,” says the biologist.
For their investigation, the scientists created microscopically thin sections of fossil bones of the plesiosaurs, large (ancient) marine reptiles, and compared them with those of coastal ancestors. “The pattern found is unequivocal: By moving to the high seas, the blood cell size of these marine animals increased rapidly,” summarises the UDE-scientist.
From an evolutionary perspective, this change is obviously still useful. Today`s whales, seals and penguins also have unusually large red blood cells, but their close relatives on land and in freshwater do not. “This supports our assumption that this is a significant adaption of warm-blooded marine life,” says Kai Caspar.
Reference:
Corinna V. Fleischle et al. Hematological convergence between Mesozoic marine reptiles (Sauropterygia) and extant aquatic amniotes elucidates diving adaptations in plesiosaurs, PeerJ (2019). DOI: 10.7717/peerj.8022
Margaret Mangan didn’t sleep well in the weeks following the Ridgecrest, Calif., earthquakes. The July shaking triggered a swarm of smaller tremors in the nearby Coso Volcanic Field, a cluster of lava domes and cinder cones at the northern end of the Mojave Desert. And it was Mangan’s job to watch for a possible eruption.
“We were pretty much on 24-7 vigilance,” said Mangan, the longtime scientist-in-charge of the U.S. Geological Survey’s California Volcano Observatory.
For several weeks, she personally monitored thousands of quakes via an automated alert system that pinged her phone at all hours. Occasionally, she had to wake a colleague in the middle of the night to make sure the shaking pattern didn’t point to rising magma.
California is famous for its catastrophic earthquakes and wildfires, but they are not the state’s only natural hazards. As head of the observatory, or CalVO, Mangan has drawn attention to the state’s more overlooked threats: a dozen restive volcanoes that stretch from Medicine Lake near the Oregon border to the Salton Buttes in the Coachella Valley.
“Most people are surprised that there are any volcanoes in California,” said Kari Cooper, a geologist at the University of California, Davis. “It’s just really not on people’s radar.”
It should be. According to a report Mangan and her colleagues released this year, the risk of a small-to-moderate eruption somewhere in the state over the next 30 years is 16% – about the same as for a magnitude 6.7 or greater earthquake along the San Andreas Fault.
Those odds are “not something to ignore,” she said.
For Mangan, the threat of a volcanic crisis is not merely hypothetical.
She began her career at the USGS’ Hawaii Volcano Observatory in 1990, just as Mount Kilauea began to pave over the town of Kalapana on the Big Island. It was the first time she had seen an eruption with her own eyes.
“For a volcanologist,” she said, it was “almost a religious experience.”
The event also drove home the degree of devastation a volcano can cause—and made her realize how important it is for people living in volcanically active areas to know what could happen. “I’ve seen what it can do to communities,” she said, “and the psyche of people that are faced with these things.”
Mangan came to California in the late 1990s to work at what was then called the Long Valley Volcanic Observatory.
Long Valley lies on the east side of the Sierra Nevada—the mountains themselves the roots of ancient volcanoes—and it drew scientists for good reason: In 1980, just a few days after Mount St. Helens blew its top, Mammoth Mountain started to show signs of unrest. (It eventually settled down, damaging nothing more than real estate values.)
The Long Valley research team also monitored the area’s other volcanoes, which were equally—if not more—concerning. That included the relatively young Mono Craters, which last erupted in the middle ages, and the Long Valley Caldera, which produced a supereruption that splattered ash across the southwestern U.S. 760,000 years ago.
Mangan took over the observatory in 2009. She and her staff used seismometers to listen for magma rumbling up through the crust and tracked the elevation of the ground, which can swell when magma begins to pool beneath a volcano. They also measured volcanic gases seeping through vents for clues about what was happening underground. (The answer is still not much.)
The eastern Sierra isn’t the only volcanically active region in the state. Seven other volcanoes made the most recent USGS watch list, including Mount Lassen and Mount Shasta in the north (very high-risk volcanoes); the Medicine Lake volcano, the Clearlake Volcanic Field near Napa and the Salton Buttes (high risk); and Death Valley’s Ubehebe Craters and the Coso Volcanic Field (moderate risk).
Mangan proposed bringing them all together under a unified California Volcano Observatory, and she took charge when CalVO opened in 2012.
In that role, she tried to alert people to the dangers of volcanoes while sharing her fascination with them.
“One of the reasons the state is so gorgeous is that there are volcanoes here,” she said.
In 2010, the Icelandic volcano Eyjafjallajokull produced a modest eruption. It released a quarter as much ash as Mount St. Helens, causing zero deaths and minimal damage.
But the eruption brought European air traffic to a halt for a week, stranding millions of passengers, including the mother of an employee at the California Governor’s Office of Emergency Services. It prompted the agency to realize that the same thing could happen in California—and that the state wasn’t prepared.
When CalOES asked for help, Mangan was thrilled. It was exactly the kind of thing she created CalVO to do.
Over the next few years, she led a team that assessed California’s volcanoes and the hazards they pose. The analysis contained some sobering results.
Roughly 200,000 people live in or visit the state’s volcanic hazard zones every day, and 45,000 of them are close enough to be exposed to threats like deadly blasts of hot gas and rock, lava flows, and volcanic mudslides.
Unlike earthquakes, which are over in a matter of seconds, volcanic eruptions can drag on, said Marcus Bursik, a geologist at the University of Buffalo who has worked extensively in California. “They persist for quite a long time—over years if not decades.”
As with Eyjafjallajokull, even a small paroxysm could snarl air travel. Planes regularly fly over California’s volcanoes, ferrying up to 300,000 passengers to, from and along the West Coast every day. Each year, millions more people drive through the Mount Shasta hazard zone on Interstate 5 between Redding and the Oregon border.
The indirect effects of an eruption could spread ever farther, Mangan and her colleagues found.
Thousands of miles of high-voltage power lines bound for major population centers cross through hazard zones, particularly in the northern part of the state. These could short out if covered in wet ash, leaving consumers in the dark for weeks.
A natural gas pipeline snakes between Shasta, Lassen and Medicine Lake, supplying 4.2 million homes. And many of the state’s water reservoirs lie within the ash fall zones of various volcanoes, the report noted.
“Even a small eruption in the wrong place could take out large swaths of California’s infrastructure and really cause problems for people who are hundreds of miles away,” Cooper said.
California’s Office of Emergency Services is now developing volcano response plans for the state and its vulnerable cities and counties.
“A lot of it is getting out of the way,” said Kevin Miller, manager of the earthquake, tsunami and volcano program at CalOES.
Many communities are already working on evacuation procedures for wildfires, and these could be put to use in a volcanic crisis, emergency managers say. For instance, Siskiyou County—home to Mount Shasta—has coordinated with the California Highway Patrol on a plan to commandeer both directions of I-5 if necessary.
CalOES is adding volcanoes to its MyHazards website, which allows residents to enter their address and get information about local threats, along with advice on how to deal with them.
Communities can also increase their resilience by fortifying critical equipment, like electrical substations, with protective shields and closing air intakes to keep ash out of buildings.
These efforts build on the groundwork Mangan laid over the last few years. She has crisscrossed the state, meeting with local officials to help them grasp what an eruption in their backyard would really mean.
At one stop, she persuaded Frank Frievalt to consider stronger safeguards for Mammoth Lakes, where he’s the chief of the fire protection district.
Since ash damages electronics and interferes with radio signals, Frievalt realized a top priority would be to bring in extra repeaters. “That happens all the time on wildfires,” he said. “In this case, we’d have to figure out a way to make them more resilient to an ash environment.”
Mangan has also worked with the Federal Emergency Management Agency to develop a California-specific version of its volcano crisis awareness training that includes a mock eruption exercise.
In 2015, Mangan coordinated an exchange between scientists, emergency responders and land managers in California and Chile, so they could learn from one another about the challenges of living in the shadow of active volcanoes. On their trip, the Californians witnessed the aftermath of an eruption in the town of Chaiten, where a volcano roared to life in 2008 and unleashed a mudflow that buried homes up to their windowsills.
“I’ve never been to a place that was totally decimated,” said Carolyn Napper, a ranger at the Shasta-Trinity National Forest who participated in the program.
Jim Richardson, the superintendent of Lassen Volcanic National Park, knew he was in good hands with Mangan keeping watch over his territory. (Lassen last erupted in the early 1900s, sending a slurry of melted snow and mud racing down a nearby river valley and lofting ash all the way to Elko, Nev.)
One Saturday afternoon last year, Richardson was sitting on his couch when he felt the house rattle. “That was an earthquake!” he said to his wife.
As he was checking the USGS website, he got a phone call from Mangan. There was nothing to worry about, she assured him. It was just the volcano talking in its sleep.
Richardson had come to rely on her not only for her technical expertise, but her ability to translate it into useful guidance for managers like him. “She has been our No. 1 go-to in-person person,” he said.
Starting Sunday, it will no longer be Mangan calling when a volcano shudders. She is retiring after 36 years with the USGS, including seven at the helm of CalVO.
“I’ve raised the awareness,” said Mangan, 65. Now it will be up to her successor and the state to get prepared.
Note: The above post is reprinted from materials provided by Los Angeles Times Distributed by Tribune Content Agency, LLC.
New research in Science Advances is uncovering the vital role that Precambrian-eon microbes may have played in two of the early Earth’s biggest mysteries.
University of British Columbia (UBC) researchers, and collaborators from the universities of Alberta, Tübingen, Autònoma de Barcelona and the Georgia Institute of Technology, found that ancestors of modern bacteria cultured from an iron-rich lake in Democratic Republic of Congo could have been key to keeping Earth’s dimly lit early climate warm, and in forming the world’s largest iron ore deposits billions of years ago.
The bacteria have special chemical and physical features that in the complete absence of oxygen allow them to convert energy from sunlight into rusty iron minerals and into cellular biomass. The biomass ultimately causes the production of the potent greenhouse gas methane by other microbes.
“Using modern geomicrobiological techniques, we found that certain bacteria have surfaces which allow them to expel iron minerals, making it possible for them to export these minerals to the seafloor to make ore deposits,” said Katharine Thompson, lead author of the study and PhD student in the department of microbiology and immunology.
“Separated from their rusty mineral products, these bacteria then go on to feed other microbes that make methane. That methane is what likely kept Earth’s early atmosphere warm, even though the sun was much less bright than today.”
This is a possible explanation to the ‘faint-young-sun’ paradox, originated by astronomer Carl Sagan. The paradox is that there were liquid oceans on early Earth, yet heat budgets calculated from the early Sun’s luminosity and modern atmospheric chemistry imply Earth should have been entirely frozen. A frozen Earth would not have supported very much life. A methane-rich atmosphere formed in connection to large-scale iron ore deposits and life was initially proposed by University of Michigan atmospheric scientist James Walker in 1987. The new study provides strong physical evidence to support the theory and finds that microscale bacterial-mineral interactions were likely responsible.
“The fundamental knowledge we’re gaining from studies using modern geomicrobiological tools and techniques is transforming our view of Earth’s early history and the processes that led to a planet habitable by complex life including humans,” said senior author of the paper, Sean Crowe, Canada Research Chair in Geomicrobiology and associate professor at UBC.
“This knowledge of the chemical and physical processes through which bacteria interact with their surroundings can also be used to develop and design new processes for resource recovery, novel building and construction materials, and new approaches to treating disease.”
In the future, such geo-microbiological information will likely be invaluable to large-scale geoengineering efforts that might be used to remove from CO2 from the atmosphere for carbon capture and storage, and again influence climate through bacterial mineral interactions.
Reference:
Katharine J. Thompson, Paul A. Kenward, Kohen W. Bauer, Tyler Warchola, Tina Gauger, Raul Martinez, Rachel L. Simister, Céline C. Michiels, Marc Llirós, Christopher T. Reinhard, Andreas Kappler, Kurt O. Konhauser, Sean A. Crowe. Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans. Science Advances, 2019; 5 (11): eaav2869 DOI: 10.1126/sciadv.aav2869
Microscopic structures created in the lab. Credit: Sean McMahon
The search for evidence of life on Mars could be helped by fresh insights into ancient rocks on Earth.
Research which suggests that structures previously thought to be fossils may, in fact, be mineral deposits could save future Mars missions valuable time and resources.
Microscopic tubes and filaments that resemble the remains of tiny creatures may have been formed by chemical reactions involving iron-rich minerals, the study shows.
Previous research had suggested that such structures were among the oldest fossils on Earth.
The new findings could aid the search for extraterrestrial life during future missions to Mars by making it easier to distinguish between fossils and non-biological structures.
The discovery was made by a scientist from the University of Edinburgh who is developing techniques to seek evidence that life once existed on Mars.
Astrobiologist Sean McMahon created tiny formations in the lab that closely mimic the shape and chemical composition of iron-rich structures commonly found in Mars-like rocks on Earth, where some examples are thought to be around four billion years old.
Dr McMahon created the complex structures by mixing iron-rich particles with alkaline liquids containing the chemicals silicate or carbonate.
This process — known as chemical gardening — is thought to occur naturally where these chemicals abound. It can occur in hydrothermal vents on the seabed and when deep groundwater circulates through pores and fractures in rocks.
His findings suggest that structure alone is not sufficient to confirm whether or not microscopic life-like formations are fossils. More research will be needed to say exactly how they were formed.
The study, published in the journal Proceedings of the Royal Society B, was funded by the European Union’s Horizon 2020 programme.
Dr Sean McMahon said: “Chemical reactions like these have been studied for hundreds of years but they had not previously been shown to mimic these tiny iron-rich structures inside rocks. These results call for a re-examination of many ancient real-world examples to see if they are more likely to be fossils or non-biological mineral deposits.”
Reference:
Sean McMahon. Earth’s earliest and deepest purported fossils may be iron-mineralized chemical gardens. Proceedings of the Royal Society B: Biological Sciences, 2019; 286 (1916): 20192410 DOI: 10.1098/rspb.2019.2410
This figure illustrates how inorganic carbon cycles through the mantle more quickly than organic carbon, which contains very little of the isotope carbon-13. Both inorganic and organic carbon are drawn into Earth’s mantle at subduction zones (top left). Due to different chemical behaviors, inorganic carbon tends to return through eruptions at arc volcanoes above the subduction zone (center). Organic carbon follows a longer route, as it is drawn deep into the mantle (bottom) and returns through ocean island volcanos (right). The differences in recycling times, in combination with increased volcanism, can explain isotopic carbon signatures from rocks that are associated with both the Great Oxidation Event, about 2.4 billion years ago, and the Lomagundi Event that followed. Credit: J. Eguchi/University of California, Riverside
Earth’s breathable atmosphere is key for life, and a new study suggests that the first burst of oxygen was added by a spate of volcanic eruptions brought about by tectonics.
The study by geoscientists at Rice University offers a new theory to help explain the appearance of significant concentrations of oxygen in Earth’s atmosphere about 2.5 billion years ago, something scientists call the Great Oxidation Event (GOE). The research appears this week in Nature Geoscience.
“What makes this unique is that it’s not just trying to explain the rise of oxygen,” said study lead author James Eguchi, a NASA postdoctoral fellow at the University of California, Riverside who conducted the work for his Ph.D. dissertation at Rice. “It’s also trying to explain some closely associated surface geochemistry, a change in the composition of carbon isotopes, that is observed in the carbonate rock record a relatively short time after the oxidation event. We’re trying explain each of those with a single mechanism that involves the deep Earth interior, tectonics and enhanced degassing of carbon dioxide from volcanoes.”
Eguchi’s co-authors are Rajdeep Dasgupta, an experimental and theoretical geochemist and professor in Rice’s Department of Earth, Environmental and Planetary Sciences, and Johnny Seales, a Rice graduate student who helped with the model calculations that validated the new theory.
Scientists have long pointed to photosynthesis—a process that produces waste oxygen—as a likely source for increased oxygen during the GOE. Dasgupta said the new theory doesn’t discount the role that the first photosynthetic organisms, cyanobacteria, played in the GOE.
“Most people think the rise of oxygen was linked to cyanobacteria, and they are not wrong,” he said. “The emergence of photosynthetic organisms could release oxygen. But the most important question is whether the timing of that emergence lines up with the timing of the Great Oxidation Event. As it turns out, they do not.”
Cyanobacteria were alive on Earth as much as 500 million years before the GOE. While a number of theories have been offered to explain why it might have taken that long for oxygen to show up in the atmosphere, Dasgupta said he’s not aware of any that have simultaneously tried to explain a marked change in the ratio of carbon isotopes in carbonate minerals that began about 100 million years after the GOE. Geologists refer to this as the Lomagundi Event, and it lasted several hundred million years.
One in a hundred carbon atoms are the isotope carbon-13, and the other 99 are carbon-12. This 1-to-99 ratio is well documented in carbonates that formed before and after Lomagundi, but those formed during the event have about 10% more carbon-13.
Eguchi said the explosion in cyanobacteria associated with the GOE has long been viewed as playing a role in Lomagundi.
“Cyanobacteria prefer to take carbon-12 relative to carbon-13,” he said. “So when you start producing more organic carbon, or cyanobacteria, then the reservoir from which the carbonates are being produced is depleted in carbon-12.”
Eguchi said people tried using this to explain Lomagundi, but timing was again a problem.
“When you actually look at the geologic record, the increase in the carbon-13-to-carbon-12 ratio actually occurs up to 10s of millions of years after oxygen rose,” he said. “So then it becomes difficult to explain these two events through a change in the ratio of organic carbon to carbonate.”
The scenario Eguchi, Dasgupta and Seales arrived at to explain all of these factors is:
A dramatic increase in tectonic activity led to the formation of hundreds of volcanoes that spewed carbon dioxide into the atmosphere.
The climate warmed, increasing rainfall, which in turn increased “weathering,” the chemical breakdown of rocky minerals on Earth’s barren continents.
Weathering produced a mineral-rich runoff that poured into the oceans, supporting a boom in both cyanobacteria and carbonates.
The organic and inorganic carbon from these wound up on the seafloor and was eventually recycled back into Earth’s mantle at subduction zones, where oceanic plates are dragged beneath continents.
When sediments remelted into the mantle, inorganic carbon, hosted in carbonates, tended to be released early, re-entering the atmosphere through arc volcanoes directly above subduction zones.
Organic carbon, which contained very little carbon-13, was drawn deep into the mantle and emerged hundreds of millions of years later as carbon dioxide from island hotspot volcanoes like Hawaii.
“It’s kind of a big cyclic process,” Eguchi said. “We do think the amount of cyanobacteria increased around 2.4 billion years ago. So that would drive our oxygen increase. But the increase of cyanobacteria is balanced by the increase of carbonates. So that carbon-12-to-carbon-13 ratio doesn’t change until both the carbonates and organic carbon, from cyanobacteria, get subducted deep into the Earth. When they do, geochemistry comes into play, causing these two forms of carbon to reside in the mantle for different periods of time. Carbonates are much more easily released in magmas and are released back to the surface at a very short period. Lomagundi starts when the first carbon-13-enriched carbon from carbonates returns to the surface, and it ends when the carbon-12-enriched organic carbon returns much later, rebalancing the ratio.”
Eguchi said the study emphasizes the importance of the role that deep Earth processes can play in the evolution of life at the surface.
“We’re proposing that carbon dioxide emissions were very important to this proliferation of life,” he said. “It’s really trying to tie in how these deeper processes have affected surface life on our planet in the past.”
Dasgupta is also the principal investigator on a NASA-funded effort called CLEVER Planets that is exploring how life-essential elements might come together on distant exoplanets. He said better understanding how Earth became habitable is important for studying habitability and its evolution on distant worlds.
“It looks like Earth’s history is calling for tectonics to play a big role in habitability, but that doesn’t necessarily mean that tectonics is absolutely necessary for oxygen build up,” he said. “There might be other ways of building and sustaining oxygen, and exploring those is one of the things we’re trying to do in CLEVER Planets.”
Reference:
Great Oxidation and Lomagundi events linked by deep cycling and enhanced degassing of carbon, Nature Geoscience (2019). DOI: 10.1038/s41561-019-0492-6
Distribution of springtails on termite and ant hosts within ~ 16 Ma old Dominican amber. Credit: N. Robin, C. D’Haese and P. Barden
When trying to better the odds for survival, a major dilemma that many animals face is dispersal — being able to pick up and leave to occupy new lands, find fresh resources and mates, and avoid intraspecies competition in times of overpopulation.
For birds, butterflies and other winged creatures, covering long distances may be as easy as the breeze they travel on. But for soil-dwellers of the crawling variety, the hurdle remains: How do they reach new, far-off habitats?
For one group of tiny arthropods called springtails (Collembola), a recent fossil discovery now suggests their answer to this question has been to piggyback on the dispersal abilities of others, literally.
In findings published in BMC Evolutionary Biology, researchers at the New Jersey Institute of Technology (NJIT) and Museum national d’Histoire naturelle have detailed the discovery of an ancient interaction preserved in 16-million-year-old amber from the Dominican Republic: 25 springtails attached to, and nearby, a large winged termite and ant from the days of the early Miocene.
The fossil exhibits a number of springtails still attached to the wings and legs of their hosts, while others are preserved as if gradually floating away from their hosts within the amber. Researchers say the discovery highlights the existence of a new type of hitchhiking behavior among wingless soil-dwelling arthropods, and could be key to explaining how symphypleonan springtails successfully achieved dispersal worldwide.
“The existence of this hitchhiking behavior is especially exciting given the fact that modern springtails are rarely described as having any interspecfic association with surrounding animals,” said Ninon Robin, the paper’s first author whose postdoctoral research at NJIT’s Department of Biological Sciences was funded by the Fulbright Program of the French-American Commission. “This finding underscores how important fossils are for telling us about unsuspected ancient ecologies as well as still ongoing behaviors that were so far simply overlooked.”
Today, springtails are among the most common arthropods found in moist habitats around the world. Most springtails possess a specialized appendage under their abdomen they use to “spring” away in flee-like fashion to avoid predation. However this organ is not sufficient for traversing long distances, especially since most springtails are unable to survive long in dry areas.
The hitchhikers the researchers identified belong to a lineage of springtails found today on every continent, known as Symphypleona,which they say may have been “pre-adapted” to grasping on to other arthropods through prehensile antennae.
Because springtails would have encountered such winged termites and ants frequently due to their high abundance during the time of the preservation, these social insects may have been their preferred hosts for transportation.
“Symphypleonan springtails are unusual compared to other Collembola in that they have specialized antennae that are used in mating courtship,” said Phillip Barden, assistant professor of biology at NJIT and the study’s principal investigator. “This antennal anatomy may have provided an evolutionary pathway for grasping onto other arthropods. In this particular fossil, we see these specialized antennae wrapping around the wings and legs of both an ant and termite. Some winged ants and termites are known to travel significant distances, which would greatly aid in dispersal.”
Barden says that the discovery joins other reports from the Caribbean and Europe of fossil springtails attached to a beetle, a mayfly and a harvestman in amber, which together suggest that this behavior may still exist today.
Barden notes that evidence of springtail hitchhiking may not have been captured in such high numbers until now due to the rarity of such a fossilized interaction, as well as the nature of modern sampling methods for insects, which typically involves submersion in ethanol for preservation.
“Because it appears that springtails reflexively detach from their hosts when in danger, evidenced by the detached individuals in the amber, ethanol would effectively erase the link between hitchhiker and host,” said Barden. “Amber derives from fossilized sticky tree resin and is viscous enough that it would retain the interaction. … Meaning, sometimes you have to turn to 16-million-year-old amber fossils to find out what might be happening in your backyard.”
Researchers employed 20 kilometers (pink) of a 51-kilometer undersea fiber-optic cable, normally used to communicate with an off-shore science node (MARS, Monterey Accelerated Research System), as a seismic array to study the fault zones under Monterey Bay. During the four-day test, the scientists detected a magnitude 3.5 earthquake 45 kilometers away in Gilroy, and mapped previously uncharted fault zones (yellow circle). Credit: Nate Lindsey, UC Berkeley
Fiber-optic cables that constitute a global undersea telecommunications network could one day help scientists study offshore earthquakes and the geologic structures hidden deep beneath the ocean surface.
In a paper appearing this week in the journal Science, researchers from the University of California, Berkeley, Lawrence Berkeley National Laboratory (Berkeley Lab), Monterey Bay Aquarium Research Institute (MBARI) and Rice University describe an experiment that turned 20 kilometers of undersea fiber-optic cable into the equivalent of 10,000 seismic stations along the ocean floor. During their four-day experiment in Monterey Bay, they recorded a 3.5 magnitude quake and seismic scattering from underwater fault zones.
Their technique, which they had previously tested with fiber-optic cables on land, could provide much-needed data on quakes that occur under the sea, where few seismic stations exist, leaving 70% of Earth’s surface without earthquake detectors.
“There is a huge need for seafloor seismology. Any instrumentation you get out into the ocean, even if it is only for the first 50 kilometers from shore, will be very useful,” said Nate Lindsey, a UC Berkeley graduate student and lead author of the paper.
Lindsey and Jonathan Ajo-Franklin, a geophysics professor at Rice University in Houston and a visiting faculty scientist at Berkeley Lab, led the experiment with the assistance of Craig Dawe of MBARI, which owns the fiber-optic cable. The cable stretches 52 kilometers offshore to the first seismic station ever placed on the floor of the Pacific Ocean, put there 17 years ago by MBARI and Barbara Romanowicz, a UC Berkeley Professor of the Graduate School in the Department of Earth and Planetary Science. A permanent cable to the Monterey Accelerated Research System (MARS) node was laid in 2009, 20 kilometers of which were used in this test while off-line for yearly maintenance in March 2018.
“This is really a study on the frontier of seismology, the first time anyone has used offshore fiber-optic cables for looking at these types of oceanographic signals or for imaging fault structures,” said Ajo-Franklin. “One of the blank spots in the seismographic network worldwide is in the oceans.”
The ultimate goal of the researchers’ efforts, he said, is to use the dense fiber-optic networks around the world—probably more than 10 million kilometers in all, on both land and under the sea—as sensitive measures of Earth’s movement, allowing earthquake monitoring in regions that don’t have expensive ground stations like those that dot much of earthquake-prone California and the Pacific Coast.
“The existing seismic network tends to have high-precision instruments, but is relatively sparse, whereas this gives you access to a much denser array,” said Ajo-Franklin.
Photonic seismology
The technique the researchers use is Distributed Acoustic Sensing, which employs a photonic device that sends short pulses of laser light down the cable and detects the backscattering created by strain in the cable that is caused by stretching. With interferometry, they can measure the backscatter every 2 meters (6 feet), effectively turning a 20-kilometer cable into 10,000 individual motion sensors.
“These systems are sensitive to changes of nanometers to hundreds of picometers for every meter of length,” Ajo-Franklin said. “That is a one-part-in-a-billion change.”
Earlier this year, they reported the results of a six-month trial on land using 22 kilometers of cable near Sacramento emplaced by the Department of Energy as part of its 13,000-mile ESnet Dark Fiber Testbed. Dark fiber refers to optical cables laid underground, but unused or leased out for short-term use, in contrast to the actively used “lit” internet. The researchers were able to monitor seismic activity and environmental noise and obtain subsurface images at a higher resolution and larger scale than would have been possible with a traditional sensor network.
“The beauty of fiber-optic seismology is that you can use existing telecommunications cables without having to put out 10,000 seismometers,” Lindsey said. “You just walk out to the site and connect the instrument to the end of the fiber.”
During the underwater test, they were able to measure a broad range of frequencies of seismic waves from a magnitude 3.4 earthquake that occurred 45 kilometers inland near Gilroy, California, and map multiple known and previously unmapped submarine fault zones, part of the San Gregorio Fault system. They also were able to detect steady-state ocean waves—so-called ocean microseisms—as well as storm waves, all of which matched buoy and land seismic measurements.
“We have huge knowledge gaps about processes on the ocean floor and the structure of the oceanic crust because it is challenging to put instruments like seismometers at the bottom of the sea,” said Michael Manga, a UC Berkeley professor of earth and planetary science. “This research shows the promise of using existing fiber-optic cables as arrays of sensors to image in new ways. Here, they’ve identified previously hypothesized waves that had not been detected before.”
According to Lindsey, there’s rising interest among seismologists to record Earth’s ambient noise field caused by interactions between the ocean and the continental land: essentially, waves sloshing around near coastlines.
“By using these coastal fiber optic cables, we can basically watch the waves we are used to seeing from shore mapped onto the seafloor, and the way these ocean waves couple into the Earth to create seismic waves,” he said.
To make use of the world’s lit fiber-optic cables, Lindsey and Ajo-Franklin need to show that they can ping laser pulses through one channel without interfering with other channels in the fiber that carry independent data packets. They’re conducting experiments now with lit fibers, while also planning fiber-optic monitoring of seismic events in a geothermal area south of Southern California’s Salton Sea, in the Brawley seismic zone.
Reference:
N.J. Lindsey at University of California, Berkeley in Berkeley, CA el al., “Illuminating seafloor faults and ocean dynamics with dark fiber distributed acoustic sensing,” Science (2019). science.sciencemag.org/cgi/doi … 1126/science.aay5881
Russian and Italian scientists have recently come closer to understanding volcanic eruptions by studying Monte Nuovo near Naples as a basis. Lava, the molten rock that forms and then solidifies on the Earth’s surface, contains information that can not only reveal the causes of eruptions, but also unravel the mysteries of the planet’s past and future.
The study of Italian volcanoes has advanced thanks to the new physical methods of Professor Sultan Dabagov’s laboratory at MEPhI and INFN (National Institute of Nuclear Physics in Italy). The latest advances in physics were used in the research, which has allowed scientists to obtain the information “recorded” in the remains of an eruption.
“Our work is a detailed study of the active phase in the planet’s life, which manifests itself in the form of volcanic eruptions. Eruptions are complex phenomena, and finding the correlations between their many variables is a step toward understanding and prediction. We used powerful sources of X-ray radiation capable of penetrating deep into the studied samples without destroying them,” Sultan Dabagov, the research director, professor at the Institute of Nanotechnology in Electronics, Spintronics and Photonics at MEPhI, told Sputnik.
According to the scientist, in the first stage, they studied volcanic samples using multi-capillary optics based on X-rays. Then, to confirm the results, they examined the samples using more powerful synchrotron radiation. This made it possible to obtain X-rays and tomograms of the samples, recreate the internal features of various rocks and obtain high-resolution three-dimensional models.
The researchers believe that analyzing these models in comparison to samples of other eruptions will lead to conclusions about historically known eruptions and the eruptions of active and passive volcanoes.
“The data obtained using computed tomography and synchrotron radiation can be integrated into the general environment of feature-finding methods used in geology. We can better understand the impact of micro- and nanoporosity of the studied rocks on their permeability in order to answer many important questions on the formation and the future development of the planet,” Sultan Dabagov said.
The work of the Russian and Italian scientists is aimed at creating a tool that allows for detailed tomographic analysis in a lab using a low-power X-ray tube. This is possible with multi-capillary optics.
The new tool will allow for the continuous study of volcanic samples since it is smaller and cheaper than synchrotron sources (this will help equip almost any geological research center). According to experts, the use of multi-capillary optics with small-sized sources and radiation detectors can form the basis for creating compact portable devices for analyzing various rocks on the ground, without moving samples.
Reference:
A. Liedl et al. A 3D imaging textural characterization of pyroclastic products from the 1538 AD Monte Nuovo eruption (Campi Flegrei, Italy), Lithos (2019). DOI: 10.1016/j.lithos.2019.05.010
Spherules in the Barberton greenstone belt in the Kaapvaal craton, South Africa. Credit: Lowe et al., 2014.
When — and how — Earth’s surface evolved from a hot, primordial mush into a rocky planet continually resurfaced by plate tectonics remain some of the biggest unanswered questions in earth science research. Now a new study, published in Geology, suggests this earthly transition may in fact have been triggered by extra-terrestrial impacts.
“We tend to think of the Earth as an isolated system, where only internal processes matter,” says Craig O’Neill, director of Macquarie University’s Planetary Research Centre. “Increasingly, though, we’re seeing the effect of solar system dynamics on how the Earth behaves.”
Modelling simulations and comparisons with lunar impact studies have revealed that following Earth’s accretion about 4.6 billion years ago, Earth-shattering impacts continued to shape the planet for hundreds of millions of years. Although these events appear to have tapered off over time, spherule beds — distinctive layers of round particles condensed from rock vaporized during an extra-terrestrial impact — found in South Africa and Australia suggest the Earth experienced a period of intense bombardment about 3.2 billion years ago, roughly the same time the first indications of plate tectonics appear in the rock record.
This coincidence caused O’Neill and co-authors Simone Marchi, William Bottke, and Roger Fu to wonder whether these circumstances could be related. “Modelling studies of the earliest Earth suggest that very large impacts — more than 300 km in diameter — could generate a significant thermal anomaly in the mantle,” says O’Neill. This appears to have altered the mantle’s buoyancy enough to create upwellings that, according to O’Neill, “could directly drive tectonics.”
But the sparse evidence found to date from the Archaean — the period of time spanning 4.0 to 2.5 billion years ago — suggests that mostly smaller impacts less than 100 km in diameter occurred during this interval. To determine whether these more modest collisions were still large and frequent enough to initiate global tectonics, the researchers used existing techniques to expand the Middle Archaean impact record and then developed numerical simulations to model the thermal effects of these impacts on Earth’s mantle.
The results indicate that during the Middle Archaean, 100-kilometer-wide impacts (about 30 km wider than the much younger Chixculub crater) were capable of weakening Earth’s rigid, outermost layer. This, says O’Neill, could have acted as a trigger for tectonic processes, especially if Earth’s exterior was already “primed” for subduction.
“If the lithosphere were the same thickness everywhere, such impacts would have little effect,” states O’Neill. But during the Middle Archean, he says, the planet had cooled enough for the mantle to thicken in some spots and thin in others. The modelling showed that if an impact were to happen in an area where these differences existed, it would create a point of weakness in a system that already had a large contrast in buoyancy — and ultimately trigger modern tectonic processes.
“Our work shows there is a physical link between impact history and tectonic response at around the time when plate tectonics was suggested to have started,” says O’Neill. “Processes that are fairly marginal today — such as impacting, or, to a lesser extent, volcanism — actively drove tectonic systems on the early Earth,” he says. “By examining the implications of these processes, we can start exploring how the modern habitable Earth came to be.”
Reference:
C. O’Neill, S. Marchi, W. Bottke, R. Fu. The role of impacts on Archaean tectonics. Geology, 2019; DOI: 10.1130/G46533.1
Oblique view of the risk map for lava flow inundation on the flanks of Mt. Etna for the next 50 years. Colors represent different levels of risk and indicate the probability of damage. The lava flow risk map constitutes a powerful instrument to promptly evaluate the real cost of living in areas near Mt. Etna and provide a tool both for the management of the eruptive emergencies and the long-term planning of the territory. In addition, the risk assessment approach developed by researchers of the TecnoLab at the INGV in Catania allows a fast update of the risk map including new data as soon as they are available. Credit: Del Negro and colleagues
On Mt. Etna volcano, inhabited areas have been inundated repeatedly by lava flows in historical times. The increasing exposure of a larger population, which has almost tripled in the area around Mt. Etna during the last 150 years, has resulted from on a poor assessment of the volcanic hazard and risk, allowing inappropriate land use in vulnerable areas. Thus, the researchers of the Laboratory of Technologies for Volcanology (TecnoLab) at the INGV in Catania assessed and mapped hazard, exposure, and risk for providing a basic broad overview of the potential effusive eruption impacts on the flanks of Mt. Etna.
Despite our knowledge of volcanic hazards and our capability to monitor volcanic activity, the possibility that effusive eruptions of Etna volcano could harm people, properties and services is greater today than ever before. A 2013 analysis of lava flow hazards and their distribution around the Etna volcano showed them to be far more dangerous than previously expected. There is no compelling evidence to think that rates and magnitudes of volcanism are changing, but, as a consequence of rising population densities, increasingly sophisticated facilities, and expanding complex social and economic infrastructure, all communities around Mt. Etna are becoming more vulnerable to experiencing heavy consequences from volcanic hazard activity.
The researchers of the TecnoLab assessed the lava flow risk on the flanks of Mt. Etna by using a GIS-based approach that combines simply the hazard with the exposure of elements at stake (the vulnerability was not considered). The hazard, showing the long-term probability related to lava flow inundation, was obtained by combining three different kinds of information: the spatiotemporal probability of the future opening of new flank eruptive vents, the event probability associated with classes of expected eruptions, and the overlapping of lava flow paths simulated by the MAGFLOW model. Data including all exposed elements were gathered from institutional web portals and high-resolution satellite imagery, and organized in four thematic layers: population, buildings, service networks, and land use. The total exposure is given by a weighted linear combination of the four thematic layers, where weights are calculated using the Analytic Hierarchy Process (AHP).
The resulting risk map shows the likely damage caused by a lava flow eruption, allowing rapid visualization of the areas in which there would be the greatest losses if a flank eruption occurred on Mt. Etna. The highest hazard levels were obtained within the uninhabited Valle del Bove and along the upper portions of the South and North-East Rifts. Instead, higher exposure levels were found near the eastern coast where the population is highly concentrated and, as a consequence, there are wider urban areas and critical infrastructures. By combining the location of the main population centers on Etna with those where the hazard is high, we identified the south-eastern flank as the sector with the highest overall level of risk due to effusive eruptions from vents located on the volcano flanks.
Reference:
Ciro Del Negro et al. Living at the edge of an active volcano: Risk from lava flows on Mt. Etna, GSA Bulletin (2019). DOI: 10.1130/B35290.1
Anak Krakatoa eruption. Credit: Dr Mohammad Heidarzadeh
The deadly volcanic eruption of Anak Krakatoa in 2018 unleashed a wave at least 100m high that could have caused widespread devastation had it been travelling in another direction, new research shows.
Over 400 people lost their lives in December 2018 when Anak Krakatoa erupted and partially collapsed into the sea, sending a wave westward towards the Indonesian island of Sumatra that was between 5 and 13 metres high when it made landfall less than an hour later.
However, new analysis from researchers at Brunel University London and the University of Tokyo has shown that the disaster wreaked could have been significantly worse had the wave—which started between 100m and 150m high—been travelling towards closer shores.
“When volcanic materials fall into the sea they cause displacement of the water surface,” said Dr. Mohammad Heidarzadeh, an assistant professor of civil engineering at Brunel, who led the study. “Similar to throwing a stone into a bathtub—it causes waves and displaces the water.
“In the case of Anak Krakatoa, the height of the water displacement caused by the volcano materials was over 100m.”
Although the height of the wave quickly shrunk, thanks mainly to the joint effects of gravity pulling the mass of water downward and the friction generated between the tsunami wave and the seafloor, it was still over 80m high when it hit an uninhabited island just a few kilometres away.
“Fortunately, nobody was living on that island,” said Dr. Heidarzadeh. “However, if there was a coastal community close to the volcano—say, within 5km—the tsunami height would have been between 50m and 70m when it hit the coast.”
For context, Dr. Heidarzadeh gives the example of the 1883 eruption of Krakatoa, which generated a tsunami that struck land at a maximum height of 42m, causing at least 36,000 deaths at a time when the coastal areas were less populated.
The new research is important for coastal communities living near volcanos all over the world, said Dr. Heidarzadeh, as it’s the first to show that such a huge wave could be generated by the December 2018 Anak Krakatoa volcanic eruption.
The new analysis, published in the journal Ocean Engineering, used sea-level data from five locations near Anak Krakatoa to validate computer models which simulated the tsunami’s movement from the collapse of the volcano to landfall.
“The measurements were done by wave gauges operated by the government of Indonesia,” Dr. Heidarzadeh said.
“We used that real data to make sure that our simulations are consistent with reality—it’s extremely important to validate computer simulations with real-world data.”
Indonesia, one of the most earthquake and tsunami prone areas of the world, was struck by two deadly waves in 2018—one unleashed by Anak Krakatoa, and one by a landslide off the coast of Sulawesi, which killed over 2000 people.
Dr. Heidarzadeh will now be working with the Indonesian Institute of Sciences (LIPI) and Agency for the Assessment & Application of Technology (BPPT) to map the country’s eastern seafloor and develop a new tsunami resilience plan – a project funded by £500,000 from The Royal Society.
Reference:
Mohammad Heidarzadeh et al. Numerical modeling of the subaerial landslide source of the 22 December 2018 Anak Krakatoa volcanic tsunami, Indonesia, Ocean Engineering (2019). DOI: 10.1016/j.oceaneng.2019.106733
