The Giant’s Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic eruption. It is also known as Clochán an Aifir or Clochán na bhFomhórach in Irish and tha Giant’s Causey in Ulster-Scots.
It is located in County Antrim on the northeast coast of Northern Ireland, about three miles (4.8 km) northeast of the town of Bushmills. It was declared a World Heritage Site by UNESCO in 1986, and a national nature reserve in 1987 by the Department of the Environment for Northern Ireland.
In a 2005 poll of Radio Times readers, the Giant’s Causeway was named as the fourth greatest natural wonder in the United Kingdom. The tops of the columns form stepping stones that lead from the cliff foot and disappear under the sea. Most of the columns are hexagonal, although there are also some with four, five, seven or eight sides. The tallest are about 12 metres (39 ft) high, and the solidified lava in the cliffs is 28 metres (92 ft) thick in places.
Much of the Giant’s Causeway and Causeway Coast World Heritage Site is today owned and managed by the National Trust and it is one of the most popular tourist attractions in Northern Ireland. The remainder of the site is owned by the Crown Estate and a number of private landowners.
There may be more than a quadrillion tons of diamond hidden in the Earth’s interior, according to a new study from MIT and other universities. But the new results are unlikely to set off a diamond rush. The scientists estimate the precious minerals are buried more than 100 miles below the surface, far deeper than any drilling expedition has ever reached.
The ultradeep cache may be scattered within cratonic roots — the oldest and most immovable sections of rock that lie beneath the center of most continental tectonic plates. Shaped like inverted mountains, cratons can stretch as deep as 200 miles through the Earth’s crust and into its mantle; geologists refer to their deepest sections as “roots.”
In the new study, scientists estimate that cratonic roots may contain 1 to 2 percent diamond. Considering the total volume of cratonic roots in the Earth, the team figures that about a quadrillion (1016) tons of diamond are scattered within these ancient rocks, 90 to 150 miles below the surface.
“This shows that diamond is not perhaps this exotic mineral, but on the [geological] scale of things, it’s relatively common,” says Ulrich Faul, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “We can’t get at them, but still, there is much more diamond there than we have ever thought before.”
Faul’s co-authors include scientists from the University of California at Santa Barbara, the Institut de Physique du Globe de Paris, the University of California at Berkeley, Ecole Polytechnique, the Carnegie Institution of Washington, Harvard University, the University of Science and Technology of China, the University of Bayreuth, the University of Melbourne, and University College London.
A sound glitch
Faul and his colleagues came to their conclusion after puzzling over an anomaly in seismic data. For the past few decades, agencies such as the United States Geological Survey have kept global records of seismic activity — essentially, sound waves traveling through the Earth that are triggered by earthquakes, tsunamis, explosions, and other ground-shaking sources. Seismic receivers around the world pick up sound waves from such sources, at various speeds and intensities, which seismologists can use to determine where, for example, an earthquake originated.
Scientists can also use this seismic data to construct an image of what the Earth’s interior might look like. Sound waves move at various speeds through the Earth, depending on the temperature, density, and composition of the rocks through which they travel. Scientists have used this relationship between seismic velocity and rock composition to estimate the types of rocks that make up the Earth’s crust and parts of the upper mantle, also known as the lithosphere.
However, in using seismic data to map the Earth’s interior, scientists have been unable to explain a curious anomaly: Sound waves tend to speed up significantly when passing through the roots of ancient cratons. Cratons are known to be colder and less dense than the surrounding mantle, which would in turn yield slightly faster sound waves, but not quite as fast as what has been measured.
“The velocities that are measured are faster than what we think we can reproduce with reasonable assumptions about what is there,” Faul says. “Then we have to say, ‘There is a problem.’ That’s how this project started.”
Diamonds in the deep
The team aimed to identify the composition of cratonic roots that might explain the spikes in seismic speeds. To do this, seismologists on the team first used seismic data from the USGS and other sources to generate a three-dimensional model of the velocities of seismic waves traveling through the Earth’s major cratons.
Next, Faul and others, who in the past have measured sound speeds through many different types of minerals in the laboratory, used this knowledge to assemble virtual rocks, made from various combinations of minerals. Then the team calculated how fast sound waves would travel through each virtual rock, and found only one type of rock that produced the same velocities as what the seismologists measured: one that contains 1 to 2 percent diamond, in addition to peridotite (the predominant rock type of the Earth’s upper mantle) and minor amounts of eclogite (representing subducted oceanic crust). This scenario represents at least 1,000 times more diamond than people had previously expected.
“Diamond in many ways is special,” Faul says. “One of its special properties is, the sound velocity in diamond is more than twice as fast as in the dominant mineral in upper mantle rocks, olivine.”
The researchers found that a rock composition of 1 to 2 percent diamond would be just enough to produce the higher sound velocities that the seismologists measured. This small fraction of diamond would also not change the overall density of a craton, which is naturally less dense than the surrounding mantle.
“They are like pieces of wood, floating on water,” Faul says. “Cratons are a tiny bit less dense than their surroundings, so they don’t get subducted back into the Earth but stay floating on the surface. This is how they preserve the oldest rocks. So we found that you just need 1 to 2 percent diamond for cratons to be stable and not sink.”
In a way, Faul says cratonic roots made partly of diamond makes sense. Diamonds are forged in the high-pressure, high-temperature environment of the deep Earth and only make it close to the surface through volcanic eruptions that occur every few tens of millions of years. These eruptions carve out geologic “pipes” made of a type of rock called kimberlite (named after the town of Kimberley, South Africa, where the first diamonds in this type of rock were found). Diamond, along with magma from deep in the Earth, can spew out through kimberlite pipes, onto the surface of the Earth.
For the most part, kimberlite pipes have been found at the edges of cratonic roots, such as in certain parts of Canada, Siberia, Australia, and South Africa. It would make sense, then, that cratonic roots should contain some diamond in their makeup.
“It’s circumstantial evidence, but we’ve pieced it all together,” Faul says. “We went through all the different possibilities, from every angle, and this is the only one that’s left as a reasonable explanation.”
This research was supported, in part, by the National Science Foundation.
Reference:
Joshua M. Garber, Satish Maurya, Jean-Alexis Hernandez, Megan S. Duncan, Li Zeng, Hongluo L. Zhang, Ulrich Faul, Catherine McCammon, Jean-Paul Montagner, Louis Moresi, Barbara A. Romanowicz, Roberta L. Rudnick, Lars Stixrude. Multidisciplinary Constraints on the Abundance of Diamond and Eclogite in the Cratonic Lithosphere. Geochemistry, Geophysics, Geosystems, 2018; DOI: 10.1029/2018GC007534
Southern Japan on Feb. 3rd, 2011, showing the active cones of Kirishima (Shinmoedake) and Aira caldera (Sakurajima) volcanoes. While Kirishima is erupting very strongly, Aira’s activity is relatively low. Credit: NASA
Scientists have confirmed for the first time that radical changes of one volcano in southern Japan was the direct result of an erupting volcano 22 kilometers (13.7 miles) away. The observations from the two volcanos—Aira caldera and Kirishima—show that the two were connected through a common subterranean magma source in the months leading up to the 2011 eruption of Kirishima.
The Japanese cities of Kirishima and Kagoshima lie directly on the border of the Aira caldera, one of the most active, hazardous, and closely monitored volcanoes in southern Japan. Identifying how volcanoes interact is critical to determine if and how an eruption can influence the activity of a distant volcano or raise the threat of a new strong explosive event.
The research team from the University of Miami’s (UM) Rosenstiel School of Marine and Atmospheric Science and Florida International University analyzed deformation data from 32 permanent GPS stations in the region to identify the existence of a common magma reservoir that connected the two volcanoes.
Leading up to the eruption of Kirishima, which is located in the densely-populated Kagoshima region, the Aira caldera stopped inflating, which experts took as a sign that the volcano was at rest. The results from this new study, however, indicated that the opposite was happening—the magma chamber inside Aira began to deflate temporarily while Kirishima was erupting and resumed shortly after the activity at Kirishima stopped.
“We observed a radical change in the behavior of Aira before and after the eruption of its neighbor Kirishima,” said Elodie Brothelande, a postdoctoral researcher at the UM Rosenstiel School and lead author of the study. “The only way to explain this interaction is the existence of a connection between the two plumbing systems of the volcanoes at depth.”
Prior to this new study, scientists had geological records of volcanoes erupting or collapsing at the same time, but this is the first example of an unambiguous connection between volcanoes that allowed scientists to study the underlying mechanisms involved. The findings confirm that volcanoes with no distinct connection at the surface can be part of a giant magmatic system at depth.
“To what extend magmatic systems are connected is an important question in terms of the hazards,” said Falk Amelung, professor of geophysics at the UM Rosenstiel School and coauthor of the study. “Is there a lot of magma underground and can one eruption trigger another volcano? Up until now there was little or no evidence of distinct connections.”
“Eruption forecasting is crucial, especially in densely populated volcanic areas,” said Brothelande. “Now, we know that a change in behavior can be the direct consequence of the activity of its neighbor Kirishima.”
The findings also illustrate that large volcanic systems such as Aira caldera can respond to smaller eruptions at nearby volcanoes if fed from a common deep reservoir but not all the time, since magma pathways open and close periodically.
“Now, we have to look whether this connnection is particular for these volcanoes in southeastern Japan or are widespread and occurr around the world,” said Amelung.
The study, titled “Geodetic evidence for interconnectivity between Aira and Kirishima magmatic systems, Japan,” was published June 28 in the journal Scientific Reports.
Reference:
E. Brothelande et al, Geodetic evidence for interconnectivity between Aira and Kirishima magmatic systems, Japan, Scientific Reports (2018). DOI: 10.1038/s41598-018-28026-4
Fingal’s Cave is a sea cave on the uninhabited island of Staffa, in the Inner Hebrides of Scotland, known for its natural acoustics. The National Trust for Scotland owns the cave as part of a National Nature Reserve. It became known as Fingal’s Cave after the eponymous hero of an epic poem by 18th-century Scots poet-historian James Macpherson.
Formation
Fingal’s Cave is formed entirely from hexagonally jointed basalt columns within a Paleocene lava flow, similar in structure to the Giant’s Causeway in Northern Ireland and those of nearby Ulva.
In all these cases, cooling on the upper and lower surfaces of the solidified lava resulted in contraction and fracturing, starting in a blocky tetragonal pattern and transitioning to a regular hexagonal fracture pattern with fractures perpendicular to the cooling surfaces. As cooling continued these cracks gradually extended toward the centre of the flow, forming the long hexagonal columns we see in the wave-eroded cross-section today. Similar hexagonal fracture patterns are found in desiccation cracks in mud where contraction is due to loss of water instead of cooling.
Scientists have measured the nutritional value of herbivore dinosaurs’ diet by growing their food in atmospheric conditions similar to those found roughly 150 million years ago.
Previously, many scientists believed that plants grown in an atmosphere with high carbon dioxide levels had low nutritional value. But a new experimental approach led by Dr. Fiona Gill at the University of Leeds has shown this is not necessarily true.
The team grew dinosaur food plants, such as horsetail and ginkgo, under high levels of carbon dioxide mimicking atmospheric conditions similar to when sauropod dinosaurs, the largest animals ever to roam Earth, would have been widespread.
An artificial fermentation system was used to simulate digestion of the plant leaves in the sauropods’ stomachs, allowing the researchers to determine the leaves’ nutritional value. The findings, published in Palaeontology, showed many of the plants had significantly higher energy and nutrient levels than previously believed.
This suggests that the megaherbivores would have needed to eat much less per day and the ecosystem could potentially have supported a significantly higher dinosaur population density, possibly as much as 20% greater than previously estimated.
Dr. Gill, a palaeontologist and geochemist from the School of Earth and Environment at Leeds, said: “The climate was very different in the Mesozoic era—when the huge brachiosaurus and diplodocus lived—with possibly much higher carbon dioxide levels. There has been the assumption that as plants grow faster and/or bigger under higher CO2 levels, their nutritional value decreases. Our results show this isn’t the case for all plant species.
“The large body size of sauropods at that time would suggest they needed huge quantities of energy to sustain them. When the available food source has higher nutrient and energy levels it means less food needs to be consumed to provide sufficient energy, which in turn can affect population size and density.
“Our research doesn’t give the whole picture of dinosaur diet or cover the breadth of the plants that existed at this time, but a clearer understanding of how the dinosaurs ate can help scientists understand how they lived.”
“The exciting thing about our approach to growing plants in prehistoric atmospheric conditions is that it can used to simulate other ecosystems and diets of other ancient megaherbivores, such as Miocene mammals—the ancestors of many modern mammals.”
Reference:
Fiona L. Gill et al, Diets of giants: the nutritional value of sauropod diet during the Mesozoic, Palaeontology (2018). DOI: 10.1111/pala.12385
Note: The above post is reprinted from materials provided by University of Leeds.
Earth’s youngest banded iron formation in western China. Credit: Zhiquan Li
The banded iron formation, located in western China, has been conclusively dated as Cambrian in age. Approximately 527 million years old, this formation is young by comparison to the majority of discoveries to date. The deposition of banded iron formations, which began approximately 3.8 billion years ago, had long been thought to terminate before the beginning of the Cambrian Period at 540 million years ago.
“This is critical, as it is the first observation of a Precambrian-like banded iron formation that is Early Cambrian in age. This offers the most conclusive evidence for the presence of widespread iron-rich conditions at a time, confirming what has recently been suggested from geochemical proxies,” said Kurt Konhauser, professor in the Department of Earth and Atmospheric Sciences and co-author. Konhauser supervised the research that was led by Zhiquan Li, a PhD candidate from Beijing while on exchange at UAlberta.
The Early Cambrian is known for the rise of animals, so the level of oxygen in seawater should have been closer to near modern levels. “This is important as the availability of oxygen has long been thought to be a handbrake on the evolution of complex life, and one that should have been alleviated by the Early Cambrian,” says Leslie Robbins, a PhD candidate in Konhauser’s lab and a co-author on the paper.
The researchers compared the geological characteristics and geochemistry to ancient and modern samples to find an analogue for their deposition. The team relied on the use of rare earth element patterns to demonstrate that the deposit formed in, or near, a chemocline in a stratified iron-rich basin.
“Future studies will aim to quantify the full extent of these Cambrian banded iron formations in China and whether similar deposits can be found elsewhere,” says Kurt Konhauser.
Reference:
Zhiquan Li et al. Earth’s youngest banded iron formation implies ferruginous conditions in the Early Cambrian ocean. Scientific Reports, 2018 DOI: 10.103841598-018-28187-2
This handout picture released on July 12, 2018 by the National History Museum of Toulouse (Musee d’Histoire Naturelle de Toulouse) and taken in September 2017 shows the skull of a mastodon from the Pyrenees, an extinct ‘relative of elephant’, found by a farmer, according to the head of the museum.
A French farmer kept quiet for years after stumbling across the skull of an extinct ancestor of the elephant near the Pyrenees mountains, the Natural History Museum of Toulouse has told AFP.
The farmer discovered the first-ever skull of a Pyrenean mastodon in 2014 while doing work on his land near the village of L’Isle-en-Dodon, about 70 kilometres (44 miles) southwest of Toulouse.
Worried that the farm would be overrun by hordes of amateur paleontologists he kept the find a secret for two years before eventually contacting the museum.
“It was only when we went there, in 2017, that we realised the significance of the discovery,” the museum’s management said.
The gomphoterium pyrenaicum was “a kind of elephant with four tusks measuring around 80 centimetres, two on the upper jaw and two on the lower jaw,” museum director Francis Duranthon told AFP on Wednesday.
Before that the only evidence that the giant herbivores had roamed the area millions of years ago were four teeth found in the same area in 1857.
“Now we have a full skull which will allow us to get a clearer picture of the anatomy of this species,” Duranthon said.
“We’re putting a face on a species which had become almost mythical,” the museum’s curator Pierre Dalous added.
The skull has been unearthed and brought to a laboratory partly encased in rock.
“Now we have to chip away, centimetre by centimetre, to reveal the rest of the skull,” Dalous said, adding that experts were halfway through the work which is expected to be completed within six to nine months.
Note: The above post is reprinted from materials provided by AFP.
Biogeochemistry Lab Manager Janet Hope from the ANU Research School of Earth Sciences holds a vial of pink colored porphyrins representing the oldest intact pigments in the world. Credit: The Australian National University
Scientists from The Australian National University (ANU) and overseas have discovered the oldest colours in the geological record, 1.1 billion-year-old bright pink pigments extracted from rocks deep beneath the Sahara desert in Africa.
Dr Nur Gueneli from ANU said the pigments taken from marine black shales of the Taoudeni Basin in Mauritania, West Africa, were more than half a billion years older than previous pigment discoveries. Dr Gueneli discovered the molecules as part of her PhD studies.
“The bright pink pigments are the molecular fossils of chlorophyll that were produced by ancient photosynthetic organisms inhabiting an ancient ocean that has long since vanished,” said Dr Gueneli from the ANU Research School of Earth Sciences.
The fossils range from blood red to deep purple in their concentrated form, and bright pink when diluted.
ANU led the research with support from Geoscience Australia and researchers in the United States and Japan.
The researchers crushed the billion-year-old rocks to powder, before extracting and analysing molecules of ancient organisms from them.
“The precise analysis of the ancient pigments confirmed that tiny cyanobacteria dominated the base of the food chain in the oceans a billion years ago, which helps to explain why animals did not exist at the time,” Dr Gueneli said.
Senior lead researcher Associate Professor Jochen Brocks from ANU said that the emergence of large, active organisms was likely to have been restrained by a limited supply of larger food particles, such as algae.
“Algae, although still microscopic, are a thousand times larger in volume than cyanobacteria, and are a much richer food source,” said Dr Brocks from the ANU Research School of Earth Sciences.
“The cyanobacterial oceans started to vanish about 650 million years ago, when algae began to rapidly spread to provide the burst of energy needed for the evolution of complex ecosystems, where large animals, including humans, could thrive on Earth.”
Reference:
N. Gueneli, A. M. McKenna, N. Ohkouchi, C. J. Boreham, J. Beghin, E. J. Javaux, and J. J. Brocks. 1.1-billion-year-old porphyrins establish a marine ecosystem dominated by bacterial primary producers. PNAS, 2018 DOI: 10.1073/pnas.1803866115
The Jeerinah Formation in Western Australia, where a UW-led team found a sudden shift in nitrogen isotopes. “Nitrogen isotopes tell a story about oxygenation of the surface ocean, and this oxygenation spans hundreds of kilometers across a marine basin and lasts for somewhere less than 50 million years,” said lead author Matt Koehler. Credit: Roger Buick / University of Washington
Earth’s oxygen levels rose and fell more than once hundreds of millions of years before the planetwide success of the Great Oxidation Event about 2.4 billion years ago, new research from the University of Washington shows.
The evidence comes from a new study that indicates a second and much earlier “whiff” of oxygen in Earth’s distant past — in the atmosphere and on the surface of a large stretch of ocean — showing that the oxygenation of the Earth was a complex process of repeated trying and failing over a vast stretch of time.
The finding also may have implications in the search for life beyond Earth. Coming years will bring powerful new ground- and space-based telescopes able to analyze the atmospheres of distant planets. This work could help keep astronomers from unduly ruling out “false negatives,” or inhabited planets that may not at first appear to be so due to undetectable oxygen levels.
“The production and destruction of oxygen in the ocean and atmosphere over time was a war with no evidence of a clear winner, until the Great Oxidation Event,” said Matt Koehler, a UW doctoral student in Earth and space sciences and lead author of a new paper published the week of July 9 in the Proceedings of the National Academy of Sciences.
“These transient oxygenation events were battles in the war, when the balance tipped more in favor of oxygenation.”
In 2007, co-author Roger Buick, UW professor of Earth and space sciences, was part of an international team of scientists that found evidence of an episode — a “whiff” — of oxygen some 50 million to 100 million years before the Great Oxidation Event. This they learned by drilling deep into sedimentary rock of the Mount McRae Shale in Western Australia and analyzing the samples for the trace metals molybdenum and rhenium, accumulation of which is dependent on oxygen in the environment.
Now, a team led by Koehler has confirmed a second such appearance of oxygen in Earth’s past, this time roughly 150 million years earlier — or about 2.66 billion years ago — and lasting for less than 50 million years. For this work they used two different proxies for oxygen — nitrogen isotopes and the element selenium — substances that, each in its way, also tell of the presence of oxygen.
“What we have in this paper is another detection, at high resolution, of a transient whiff of oxygen,” said Koehler. “Nitrogen isotopes tell a story about oxygenation of the surface ocean, and this oxygenation spans hundreds of kilometers across a marine basin and lasts for somewhere less than 50 million years.”
The team analyzed drill samples taken by Buick in 2012 at another site in the northwestern part of Western Australia called the Jeerinah Formation.
The researchers drilled two cores about 300 kilometers apart but through the same sedimentary rocks — one core samples sediments deposited in shallower waters, and the other samples sediments from deeper waters. Analyzing successive layers in the rocks years shows, Buick said, a “stepwise” change in nitrogen isotopes “and then back again to zero. This can only be interpreted as meaning that there is oxygen in the environment. It’s really cool — and it’s sudden.”
The nitrogen isotopes reveal the activity of certain marine microorganisms that use oxygen to form nitrate, and other microorganisms that use this nitrate for energy. The data collected from nitrogen isotopes sample the surface of the ocean, while selenium suggests oxygen in the air of ancient Earth. Koehler said the deep ocean was likely anoxic, or without oxygen, at the time.
The team found plentiful selenium in the shallow hole only, meaning that it came from the nearby land, not making it to deeper water. Selenium is held in sulfur minerals on land; higher atmospheric oxygen would cause more selenium to be leached from the land through oxidative weathering — “the rusting of rocks,” Buick said — and transported to sea.
“That selenium then accumulates in ocean sediments,” Koehler said. “So when we measure a spike in selenium abundances in ocean sediments, it could mean there was a temporary increase in atmospheric oxygen.”
The finding, Buick and Koehler said, also has relevance for detecting life on exoplanets, or those beyond the solar system.
“One of the strongest atmospheric biosignatures is thought to be oxygen, but this study confirms that during a planet’s transition to becoming permanently oxygenated, its surface environments may be oxic for intervals of only a few million years and then slip back into anoxia,” Buick said.
“So, if you fail to detect oxygen in a planet’s atmosphere, that doesn’t mean that the planet is uninhabited or even that it lacks photosynthetic life. Merely that it hasn’t built up enough sources of oxygen to overwhelm the ‘sinks’ for any longer than a short interval.
“In other words, lack of oxygen can easily be a ‘false negative’ for life.”
Koehler added: “You could be looking at a planet and not see any oxygen — but it could be teeming with microbial life.”
Reference:
Matthew C. Koehler, Roger Buick, Michael A. Kipp, Eva E. Stüeken, Jonathan Zaloumis. Transient surface ocean oxygenation recorded in the ∼2.66-Ga Jeerinah Formation, Australia. Proceedings of the National Academy of Sciences, 2018; 201720820 DOI: 10.1073/pnas.1720820115
Scientists have discovered fresh insights into the metallic core at the centre of our planet.
The findings could aid understanding of how Earth was formed from elements in space, some 10 billion years ago.
They could also shed light on the fundamental physical nature of nitrogen, one of the most abundant elements in the atmosphere.
An international team of researchers carried out sophisticated experiments to replicate conditions at Earth’s core.
Using high energy laser beams and optical sensors, they were able to observe how samples of nitrogen behaved at more than 1 million times normal atmospheric pressure and temperatures above 3,000C.
Their observations confirmed that, under such conditions, nitrogen exists as a liquid metal.
The findings give scientists valuable insight into how nitrogen behaves at extreme conditions, which could aid understanding of how the planets were formed.
It may help to explain why Earth is the only planet known to have an abundance of nitrogen in its atmosphere — where it exists as a gas. Nitrogen in the air could emerge from deeper within the planet, where, for example, it could mix with other liquid metal.
The findings could also shed light on how the planet’s atmosphere evolved and how it may develop in future.
Their study, carried out by the University of Edinburgh with researchers in China and the US, was published in Nature Communications. It was supported by the Engineering and Physical Science Research Council and the British Council.
Dr Stewart McWilliams, of the University of Edinburgh’s School of Physics and Astronomy, who took part in the study, said: “Earth’s atmosphere is the only one of all the planets where nitrogen is the main ingredient — greater even than oxygen. Our study shows this nitrogen could have emerged from deep inside the planet.”
Reference:
Shuqing Jiang, Nicholas Holtgrewe, Sergey S. Lobanov, Fuhai Su, Mohammad F. Mahmood, R. Stewart McWilliams, Alexander F. Goncharov. Metallization and molecular dissociation of dense fluid nitrogen. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05011-z
Distribution of 382 seismic stations used in this study. Red and pink beach balls denote focal mechanisms of the 2011 Tohoku-oki earthquake (Mw 9.0) and other megathrust earthquakes (Mw ? 7.0) during 1917 – 2017, respectively. The white line marks the downdip limit of interplate seismicity. Yellow dashed lines denote depth contours of the upper boundary of the subducting Pacific plate. (B) Tectonic settings of the study region (blue box). Black saw-tooth lines: oceanic trenches. Credit Credit: Copyright Dapeng Zhao
The earthquake, which registered with a moment magnitude (Mw) of 9.0, was the most powerful earthquake ever recorded in Japan, and the fourth most powerful earthquake in the world since modern record-keeping began in 1900. It triggered powerful tsunami waves causing over 18,000 causalities. The tsunami caused nuclear accidents at the Fukushima Daiichi Nuclear Power Plant, and subsequent evacuations affected hundreds of thousands of residents. This earthquake has attracted great interest among researchers, because few experts expected such a large earthquake would occur in that area.
In Northeast Japan (Tohoku), the Pacific plate is subducting northwestward beneath the Okhotsk plate, causing the 2011 Tohoku-oki earthquake. Subduction is a process where one of Earth’s tectonic plates sinks under another. To date, many researchers have investigated the causal mechanism of the Tohoku-oki earthquake, and a key question has arisen: Which plate controlled this huge earthquake? The upper Okhotsk plate or the lower Pacific plate? There have been conflicting results, because the detailed structure in and around the source zone is still unclear.
The Tohoku University team, comprising Dapeng Zhao and Xin Liu (now at Ocean University of China), applied a method of seismic tomography*1 to over 144,000 P-wave arrival-time data recorded by the dense Japanese seismic network to determine a high-resolution tomography beneath the Tohoku-oki region. They also used seafloor topography and gravity data to constrain the structure of the source zone.
Seismic tomography is an effective tool for investigating the three-dimensional (3-D) structure of the Earth’s interior, in particular, for clarifying the detailed structure of large earthquake source areas. Using this method, the team received clear 3-D images of the Tohoku-oki source zone, and showed that the 2011 Tohoku-oki earthquake occurred in an area with high seismic velocity in the Tohoku megathrust zone*2. This high-velocity area reflects a mechanically strong (hard) patch which was responsible for the 2011 Tohoku-oki earthquake. This hard patch results from both granitic batholiths*3 in the overriding Okhotsk plate and hard rocks atop the subducting Pacific plate.
These results indicate that structural anomalies in and around the Tohoku megathrust originate from both the upper Okhotsk plate and the lower Pacific plate, which controlled the generation and rupture processes of the 2011 Tohoku-oki earthquake. This huge earthquake was caused by collision of harder rocks in both the upper and lower plates. This work sheds new light on the causal mechanism of megathrust earthquakes. It also suggests that the location of a future great earthquake may be pinpointed by investigating the detailed structure of the megathrust zone.
*1 Seismic tomography: A method to image the three-dimensional structure of the Earth’s interior by inverting abundant seismic wave data generated by many earthquakes and recorded at many seismic stations.
*2 Megathrust: A great thrust fault where a tectonic plate subducts beneath another plate. The lower plate is called subducting plate, and the upper one is called overriding plate. In Tohoku, the upper and lower plates are the Okhotsk and Pacific plates, respectively.
*3 Granitic batholith: A batholith is a large mass of intrusive igneous rock, larger than 100 square kilometers in area, that forms from cooled magma deep in the Earth’s crust. Granitic batholiths are much harder than other rocks such as sedimentary materials.
Reference:
Xin Liu, Dapeng Zhao. Upper and lower plate controls on the great 2011 Tohoku-oki earthquake. Science Advances, 2018; 4 (6): eaat4396 DOI: 10.1126/sciadv.aat4396
This is the 3.32 million-year-old Australopithecus afarensis foot from Dikika, Ethiopia, superimposed over a footprint from a human toddler. Credit: Jeremy DeSilva
More than 3 million years ago, our ancient human ancestors, including their toddler-aged children, were standing on two feet and walking upright, according to a new study published in Science Advances.
“For the first time, we have an amazing window into what walking was like for a 2½-year-old, more than 3 million years ago,” says lead author, Jeremy DeSilva, an associate professor of anthropology at Dartmouth College, who is one of the world’s foremost authorities on the feet of our earliest ancestors. “This is the most complete foot of an ancient juvenile ever discovered.”
The tiny foot, about the size of a human thumb, is part of a nearly complete 3.32-million-year-old skeleton of a young female Australopithecus afarensis discovered in 2002 in the Dikika region of Ethiopia by Zeresenay (Zeray) Alemseged, a professor of organismal biology and anatomy at the University of Chicago and senior author of the study. Alemseged is internationally known as a leading paleontologist on the study of human origins and human evolution.
“Placed at a critical time and the cusp of being human, Australopithecus afarensis was more derived than Ardipithecus (a facultative biped) but not yet an obligate strider like Homo erectus. The Dikika foot adds to the wealth of knowledge on the mosaic nature of hominin skeletal evolution” explained Alemseged.
Given that the fossil of the tiny foot is the same species as the famous Lucy fossil and was found in the same vicinity, it is not surprising that the Dikika child was erroneously labeled “Lucy’s baby” by the popular press, though this youngster lived more than 200,000 years before Lucy.
In studying the fossil foot’s remarkably preserved anatomy, the research team strived to reconstruct what life would have been like years ago for this toddler and how our ancestors survived. They examined what the foot would have been used for, how it developed and what it tells us about human evolution. The fossil record indicates that these ancient ancestors were quite good at walking on two legs. “Walking on two legs is a hallmark of being human. But, walking poorly in a landscape full of predators is a recipe for extinction,” explained DeSilva.
At 2½ years old, the Dikika child was already walking on two legs, but there are hints in the fossil foot that she was still spending time in the trees, hanging on to her mother as she foraged for food. Based on the skeletal structure of the child’s foot, specifically, the base of the big toe, the kids probably spent more time in the trees than adults. “If you were living in Africa 3 million years ago without fire, without structures, and without any means of defense, you’d better be able get up in a tree when the sun goes down,” added DeSilva. “These findings are critical for understanding the dietary and ecological adaptation of these species and are consistent with our previous research on other parts of the skeleton especially, the shoulder blade,” Alemseged noted.
Reference:
Jeremy M. DeSilva, Corey M. Gill, Thomas C. Prang, Miriam A. Bredella, Zeresenay Alemseged. A nearly complete foot from Dikika, Ethiopia and its implications for the ontogeny and function of Australopithecus afarensis. Science Advances, 2018; 4 (7): eaar7723 DOI: 10.1126/sciadv.aar7723
Note: The above post is reprinted from materials provided by Dartmouth College.
C. kakwa were multituberculate mammals, meaning that their teeth have many cusps, or tubercles, arranged in rows. Credit: Jessica Theodor
The discovery of a new species of mammal in Alberta’s fossil record has shaken up some long-held beliefs about other species in its lineage.
The ancient Catopsalis kakwa (C. kakwa) was only about the size of a squirrel, and weighed between 400 and 600 grams. What it lacks in size, however, it makes up for in terms of its implications for previous research proposing the evolution of larger body mass in multituberculates, rodent-like mammals named for their teeth that have many cusps, or tubercles, arranged in rows.
Dr. Craig Scott, Ph.D., curator of fossil mammals at the Royal Tyrrell Museum, spent much of 2017 conducting fieldwork in Alberta—where C. kakwa was discovered. Scott, along with Dr. Anne Weil, Ph.D., of Oklahoma State University, and Dr. Jessica Theodor, Ph.D., professor in the Department of Biological Sciences, worked together to determine the identity and lineage of the fossilized species and analyze its tooth row to determine what it might have looked like. Their results were recently published in the Journal of Paleontology.
Novel use of classic research method reveals new piece of mammalian history
Through specialized research techniques, the researchers were able to determine that the fossilized tooth row was from a multituberculate mammal that was part of the Taeniolabidoidea, in the Catopsalis lineage.
“This particular group of multituberculates is one of the longest-lived lineages in terms of mammal evolution,” explains Theodor, who specializes in body size analysis in mammals. “They were around when the dinosaurs were here and survived long after they went extinct. That’s incredibly long-lived—about 165 million years.”
Over 200 species are known to have lived in their multi-million years of existence. They were among the most diverse mammals of the early Paleocene era (66 to 56 million years ago), having survived the catastrophic Cretaceous-Palaeogene mass extinction that exterminated dinosaurs. During the species’ long life span, they developed the increasingly specialized arrangement of multituberculate teeth.
It was the analysis of these teeth that helped Theodor, Scott, and Weil determine that the fossil specimen did, in fact, come from a never-before-seen species. C. kakwa is the smallest species of Catopsalis and the smallest Taeniolabidoidea ever discovered.
To reach these findings, Theodor used the biting surface area of the entire cheek tooth row as a starting point for size, instead of the surface area of the first lower molar—a process that works very well for large mammals and has traditionally been used for multituberculates.
“Typically for mammals, you use the size of one tooth in the tooth row to estimate body size. Because mammals process our food with our teeth, the surface area of the tooth is related to the amount of food we have to ingest. As a result, if we measure the size of the tooth and we have a data set of living mammals where we know the size of their teeth relative to their overall body mass, we can write a predictive equation of the body size range for a particular tooth size,” Theodor explains.
However, there’s some new work that’s been done in rodents where, instead of using one tooth, they use the entire tooth row.”
Theodor took the length of the chewing tooth row (which functions similarly to human pre-molars and molars) and compared it with rodents. C. kakwa’s body mass was estimated using that whole dimension rather than a single tooth.
Further, while it has long been believed that species in the Catopsalis lineage gradually increased in body size, the finding of C. kakwa imply that is not the case. Until the discovery of C. kakwa, the evolution of Catopsalis appeared to document increasing body size.
“Because the trend in these multituberculates seems to be getting bigger and bigger, this thing is so unexpected in that it’s quite small and temporally it’s quite late in the game,” Scott explains.
C. kakwa’s size—and the fact that it was alive in the late early Paleocene—complicates the evolutionary history of Taeniolabidoidea, and implies either a ghost lineage or an evolutionary reversal of characteristics, going from large to small body size. A ghost lineage is when there is an extensive part of the evolutionary record of an animal that is not currently recognized in the fossil record; in this case, the fossil history of the mysterious small-sized Catopsalis has not yet been found.
With this new piece of the evolutionary puzzle, next steps for the team include further study of C. kakwa to better understand the evolutionary history of C. kakwa and taeniolabidoid multituberculates, and determine whether a ghost lineage or a reversal of characteristics is more likely to have occurred.
Pieces of polished amber, a honey-coloured fossilised tree sap, on sale at a market in Danai, Kachin state
“Amber hunters” on a quest for a Jurassic Park-style discovery of dinosaur remains sift through mounds of the precious resin in Myanmar—a lucrative trade that captivates palaeontologists but also fuels a decades-long conflict in the far north.
The morning amber market on the outskirts of Myitkyina, the capital of Kachin state, throngs with traders using torches and magnifying glasses to scrutinise pieces of the honey-coloured fossilised tree sap.
Some sell rough-edged uncut chunks. Others tout finished products: pendants, necklaces and bracelets made from carefully polished pieces.
The trading takes place just a few dozen kilometres from the fighting between Myanmar’s army and ethnic Kachin rebels battling for autonomy, land, identity—and natural resources that help finance both sides.
The jade and ruby industries dwarf the largely artisanal amber trade, but the resin can still fetch big sums for whoever controls the mines.
In Myitkyina’s market there is money to be made, says trader Myo Swe.
His speciality is “inclusions”, sap that has trapped parts of plants, animals and even dinosaurs before hardening into amber—history suspended inside the resin.
Find the right buyer and he could pocket up to $100,000 a piece in a shady industry that sees most amber smuggled across the border to China.
“Even if it just contains an ant or a mosquito—every piece is interesting,” the 40-year-old told AFP. “I value every one of them.”
Dinosaur tales
Amber, historically coveted as jewellery by nobility from China to ancient Greece, enjoyed a revival in popular culture thanks to the 1990s hit movie “Jurassic Park”, set in a theme park where dinosaurs have been cloned by extracting DNA from mosquitos preserved in the resin.
However, most amber heralds not from the Jurassic but from the later Cretaceous Period, up to 100 million years ago.
The best preserved “inclusions” offer today’s scientists and collectors a three-dimensional fossil, with some creatures even frozen mid-movement.
There are amber deposits found all over the world but, for palaeontology, the mines of Kachin are “irreplaceable”, explains 36-year-old Lida Xing from the China University of Geosciences in Beijing.
“The amber mining area in Kachin is the only Cretaceous period amber mining site in the world that is still engaged in commercial mining,” he says. “There’s no better place than Myanmar.”
Lida Xing shot to fame among fellow palaeontologists in 2015 when he brought back part of a feathered dinosaur tail to China from Myanmar that dated back some 99 million years.
The excitement of his discovery, though, was tinged with disappointment when he returned to try to find the source.
“They said they did not know. They had probably already sold or smashed it. This dinosaur might have even been a complete one with a head,” he told AFP in Beijing.
‘Conflict amber’
Amateur amber hunters aside, the main challenge for traders and collectors is working in a conflict zone.
An upsurge in fighting between the army and the Kachin Independence Army (KIA) over recent years has left more than 100,000 people displaced in the region.
Leaflets dropped by army helicopters in June last year even warned people living around the mines to leave the area or be considered to be cooperating with the rebels, according to Human Rights Watch.
Now only the hardiest of amber hunters attempt to go there.
“We almost could not reach the mining area because it was very dangerous,” Lida Xing says of his 2015 trip. “We sneaked in when the situation eased quite a lot, but no scientist was able to go inside after that.”
“This is a severe problem because, for palaeontology, you obtain a lot of useful information from the geological conditions and strata -— but we were not able to do this.”
Amber, jade, timber and gold are also “major drivers” of the conflict in northern Myanmar, says Hanna Hindstrom from monitoring group Global Witness.
Without sourcing responsibly, any company trading Myanmar amber “could be causing or contributing to a range of harms including conflict and human rights abuses”, she adds.
Akbar Khan, a 52-year-old self-described “extreme fossil in amber hunter” who runs a streetside stall in downtown Bangkok shrugs off the risks and ethical questions.
He makes frequent visits to Kachin and explains the adrenaline rush he gets from finding dinosaur parts is like nothing else.
“You feel like you’re walking in clouds, in heaven,” he says.
“If people have a big diamond, so what? The world is full of big diamonds… but the world is not full of dinosaurs in amber.”
Note: The above post is reprinted from materials provided by AFP.
Scientists may have solved a long-standing puzzle over why conditions on Earth have remained stable enough for life to evolve over billions of years. The ‘Gaia’ hypothesis proposed that living things interacting with inorganic processes somehow keep the planet in a state where life can persist — despite threats such as a brightening sun, volcanoes and meteorite strikes.
The puzzle of how this might work has divided experts for decades, but a team led by scientists from the University of Exeter have proposed a solution. They say stability could come from “sequential selection” in which situations where life destabilises the environment tend to be short-lived and result in further change until a stable situation emerges, which then tends to persist.
Once this happens, the system has more time to acquire further traits that help to stabilise and maintain it — a process known as “selection by survival alone.”
“We can now explain how the Earth has accumulated stabilising mechanisms over the past 3.5 billion years of life on the planet,” said Professor Tim Lenton, of the University of Exeter.
“The central problem with the original Gaia hypothesis was that evolution via natural selection cannot explain how the whole planet came to have stabilising properties over geologic timescales.”
“Instead, we show that at least two simpler mechanisms work together to give our planet with life self-stabilising properties.”
He added: “Our findings can help explain how we came to be here to wonder about this question in the first place.”
Professor Dave Wilkinson, of the University of Lincoln, who was also involved in the research, added: “I have been involved in trying to figure out how
Gaia might work for over 20 years — finally it looks like a series of promising ideas are all coming together to provide the understanding I have been searching for.”
Dr James Dyke, of the University of Southampton, also an author on the paper, said: “As well as being important for helping to estimate the probability of complex life elsewhere in the universe, the mechanisms we identify may prove crucial in understanding how our home planet may respond to drivers such as human-produced climate change and extinction events.”
Creating transformative solutions to the global changes that humans are now causing is a key focus of the University of Exeter’s new Global Systems Institute, directed by Professor Lenton, who said: “We can learn some lessons from Gaia on how to create a flourishing, sustainable, stable future for 9-11 billion people this century.”
The Gaia hypothesis, first put forward by James Lovelock in the 1970s, was named after the deity who personified the Earth in Greek mythology.
Reference:
Timothy M. Lenton, Stuart J. Daines, James G. Dyke, Arwen E. Nicholson, David M. Wilkinson, Hywel T.P. Williams. Selection for Gaia across Multiple Scales. Trends in Ecology & Evolution, 2018; DOI: 10.1016/j.tree.2018.05.006
The animals, which look similar to small moose or deer in a paleoartist’s rendering, are being dubbed Theosodon arozquetai and Llullataruca shockeyi, ungulates native only to Bolivia Credit: Velizar Simeonovski
Researchers at Case Western Reserve University and two other universities have discovered the 13-million-year-old fossils of a pair of new species of extinct hoofed mammals known as “litopterns” from a site in Bolivia.
The animals, which look similar to small moose or deer in a paleoartist’s rendering, are being dubbed Theosodon arozquetai and Llullataruca shockeyi, ungulates native only to Bolivia. They lived in the latter part of the middle Miocene epoch, a time interval from which relatively few fossils have been collected in South America.
The discoveries, announced in the June edition of the Journal of Vertebrate Paleontology, are important not only because they document two species previously unknown to science, but also because they come from the tropical latitudes of South America. The northern half of South America harbors a rich diversity of living mammals, but is a difficult place to find fossils of them.
“Studying fossils from regions such as Bolivia, where few others have looked, has allowed us discover and describe a variety of new species that are changing our views about the history of South America’s mammals,” said Darin Croft, a biology professor at Case Western Reserve, who co-led the expeditions that recovered the fossils.
The lead author on the journal publication was one of Croft’s former students, Case Western Reserve graduate Andrew McGrath, who is now studying this group of animals for his PhD at the University of California-Santa Barbara.
“These new species hint at what might be hiding in the northern parts of South America,” McGrath said. “For example, close relatives of Llullataruca disappeared from southern South America around 20 million years ago, but based on our research, we now know they were able to persist some seven million years longer in Bolivia and northern South America than in Patagonia.”
Federico Anaya of Bolivia’s Universidad Autónoma “Tomas Frías” in Potosí also collaborated on the project. Croft and Anaya have been working together in Bolivia for more than 15 years.
Croft, who has a primary appointment in anatomy at the School of Medicine, is considered one of the world’s leaders in neotropical paleomammalogy, the study of South America’s prehistoric mammals. Since South America was geographically isolated for most of the past 66 million years, its rich fossil record makes it a perfect location to “investigate topics such as mammal adaptation, diversification, and community ecology,” according to his website.
Some of that work was covered in his 2016 book with Chicago-based artist Velizar Simeonovski, Horned Armadillos and Rafting Monkeys: The Fascinating Fossil Mammals of South America, which received an Independent Publisher Book Awards gold medal in science in 2017.
“South America was untouched by mammals from other continents for millions of years, so the solutions its native mammals came up with were often different from those developed by mammals elsewhere,” he said. “By comparing how mammals on different continents have evolved to deal with similar ecological situations, we are able to gauge which characteristics developed due to universal ecological principles and which were peculiar to a certain place and time.”
Recently, Croft and collaborators explored that question by digging further into the mysteries of how some 11 species of mammals known as “sparassodonts”-extinct weasel-to-jaguar-sized meat-eating marsupials-were able to co-exist during the early Miocene (about 18 million years ago) in southern Argentina.
The research has left Croft and others wrestling with what he calls a “carnivore conundrum.”
In short, they are being challenged by findings that suggest that either all ancient carnivorous sparassodonts were crammed into a very narrow meat-eating niche (think mountain lion) — or some were actually omnivores (think raccoon), but had teeth that did not reflect their varied diet.
That scenario “would challenge a fundamental principle of paleoecological reconstruction,” Croft said in a recent blog post summarizing what was detailed extensively in a paper earlier this year. “Could it be that their teeth are leading us astray?”
Reference:
Andrew J McGrath, Federico Anaya, Darin A. Croft. Two new macraucheniids (Mammalia: Litopterna) from the late middle Miocene (Laventan South American Land Mammal Age) of Quebrada Honda, Bolivia. Journal of Vertebrate Paleontology, 2018; e1461632 DOI: 10.1080/02724634.2018.1461632
This figure show the lower jaw of Stylolophus minor, holotype of the new species. C is 3-D model reconstructed from CT scans. It shows by transparency the teeth roots, and especially those of the anterior incisors that are enlarged and oriented (tilted) horizontally as in the early proboscidean Phosphatherium. Length of M1-3 series: 38.5 mm. Scale bar, 10 mm. Credit: Photographs by Philippe Loubry (MNHN). Drawing by Charlène Letenneur (MNHN)
Long before rhinoceros, giraffes, hippos, and antelopes roamed the African savannah, a group of large and highly specialized mammals known as embrithopods inhabited the continent. The most well known is Arsinoitherium, an animal that looked much like a rhinoceros but was in fact more closely related to elephants, sea cows, and hyraxes. Now, researchers reporting in Current Biology on June 28 offer a glimpse into this ancient past with the discovery of the earliest and most ancient embrithopod yet described.
The approximately 55-million-year-old fossilized dental remains found in the first lower Eocene levels of the Ouled Abdoun phosphate basin in Morocco represent two new species in the genus Stylolophus, the researchers report. The earliest embrithopods were previously known from 48-million-year-old fossils collected in Africa and Turkey.
“The embrithopods were large and strange extinct mammals that belonged, together with hyraxes and elephants, to the early megaherbivorous mammalian fauna that inhabited the island Africa, well before the arrival about 23 million years ago of the Eurasian ungulate lineages such as the artiodactyls, including giraffes, buffalos, hippopotamus, and antelopes, and the perissodactyls, including zebras and rhinoceros,” says Emmanuel Gheerbrant of CNRS-MNHN in Paris, France. “They belong to the old endemic African fauna.”
Gheerbrant said that the origins of embrithopods had been uncertain, with two known co-existing families: one in Africa and the other in Turkey and Romania. It’s been unclear what the exact relationships of the embrithopods were with respect to sea cows and elephants.
The new phylogenetic study of the two species of Stylolophus found in Morocco confirms that they are basal embrithopods. It also shows that the extinct Embrithopod order is ancient, predating the divergence of the sea cows and elephants.
“Comparative anatomy of the new Moroccan species shows that the highly specialized embrithopod teeth derived from the ancestral dental morphology of all paenungulates, a clade including elephants, sea cows, and hyraxes, with the W-crested molars seen in some of the oldest hyracoids,” the group including hyraxes, Gheerbrant says. “The specialized design of the teeth with two transverse ridges, known in the most advanced forms such as Arsinoitherium, is a convergence of the embrithopods and the extant group of tethytheres, including manatees and elephants, towards leaf eating, which was favored by the ancient herbivorous niches available on the African island.”
The new species S. minor — which was unusually small at about the size of a sheep — is also the first to show the presence in embrithopods of enlarged and anteriorly inclined incisors, in the form of incipient tusks, as seen in the early ancestors of the group including elephants.
The early age and primitive state of Stylolophus, together with the high-level relationships (paenungulate and afrotherian), all support an African origin of the order Embrithopoda, the researchers say. The findings suggest that the Paleoamasiidae family found in Turkey arrived on the Eurasian shores of the Tethys Ocean (an ocean during much of the Mesozoic Era and the Paleogene period located between the ancient continents of Gondwana and Laurasia), after an early dispersal of an African ancestor resembling Stylolophus across the sea.
The researchers say that they’ll continue to search for paleontological evidence elucidating the evolutionary history and relationships of African ungulate-like mammals and insectivore-like afrotherian mammals, including golden moles, elephant shrews, tenrecs, aardvarks, and hyraxes. They’ll also continue the search for the enigmatic early roots of all placental mammals in Africa, going back even further in time to the Cretaceous Period.
Reference:
Emmanuel Gheerbrant, Arnaud Schmitt, László Kocsis. Early African Fossils Elucidate the Origin of Embrithopod Mammals. Current Biology, 2018; DOI: 10.1016/j.cub.2018.05.032
Note: The above post is reprinted from materials provided by Cell Press.
Ornella’s research on the brain evolution of mammals involves developing 3D models of an endocast, which is the imprint of the brain inside the cranium. Credit: University of Toronto Scarborough
A new U of T Scarborough study has found that the ancestor of the modern day mountain beaver had a larger relative brain size.
The research, which is published in the journal Palaeontology, offers a rare case of an animal’s brain becoming smaller relative to its body size, likely due to a change in its lifestyle over time.
The mountain beaver (Aplodontia rufa) is a rodent that’s adapted to burrowing, meaning it lives mostly underground in tunnels dug deep into the soil. But fossil records show that its 30-million-year old ancestor was better adapted to living in trees, similar to squirrels.
“Early squirrels and the mountain beaver’s ancestor had a similar, relative brain size,” says Ornella Bertrand, a postdoctoral fellow in the Department of Anthropology at U of T Scarborough and lead author of the study.
But something happened over time. While the mountain beaver can climb trees like its ancestor and squirrels — albeit likely not as well — they rarely travel too far from their burrows and are mostly nocturnal. As a result of mostly living underground and being less reliant on their vision, it appears an area of the neocortex responsible for sight may have shrunk over time.
“The brain is metabolically expensive, meaning it needs a lot of food energy to function,” says Bertrand, whose research focuses on the brain evolution of mammals. “So the parts of the brain that are not crucial for survival might have been selected against.”
Bertrand and her team compared virtual endocasts — the imprint the brain makes against the inner part of the cranium — and found that it may have been the part of the brain related to sight specifically that shrunk over time.
“There appears to be a relationship between being arboreal — that is living in trees — the size of the neocortex and strong vision,” says Bertrand. She adds that over time as the modern mountain beaver relied less on its vision, its neocortex decreased in size as a result.
While the modern mountain beaver actually has a larger overall brain size compared to its ancestor, it has a smaller brain relative to its body size, notes Bertrand.
An evolutionary decrease in brain size has been observed in domesticated animals like chickens, pigs and dogs, but this is a rare example of a decrease in brain size due to a specific shift in where the animal spends most of its time, says Bertrand.
As for when this change began to take place, it’s likely too hard to tell at this point. “It’s difficult to pinpoint when the relative size of the brain started to decrease since we only have three specimens to go by,” she adds.
Mountain beavers are native to the northwestern U.S. and parts of southern British Columbia, particularly in the Cascade Mountains. Large by rodent standards — averaging about 500 to 900 g and between 30 to 50 cm in length — they’re not closely related to the North American beaver.
In fact, despite superficial similarities in facial appearance and the fact they prefer moist habitats and eat tree seedlings, unlike North American beavers they have small, stumpy tails, and they don’t chop down trees, build dams or live in lodges. The mountain beaver is also considered a vulnerable species because its habitat in many places has been reduced.
Reference:
Ornella C. Bertrand, Farrah Amador-Mughal, Madlen M. Lang, Mary T. Silcox. Virtual endocasts of fossil Sciuroidea: brain size reduction in the evolution of fossoriality. Palaeontology, 2018; DOI: 10.1111/pala.12378
Ocean. Some 520-540 million years ago, animal life evolved in the ocean and began breaking down organic material on the seafloor, leading to more carbon dioxide and less oxygen in the atmosphere. Credit: Copyright Michele Hogan
The evolution of Earth’s first animals more than 500 million years ago caused global warming, new research shows.
Some 520-540 million years ago, animal life evolved in the ocean and began breaking down organic material on the seafloor, leading to more carbon dioxide and less oxygen in the atmosphere.
In the 100 million years that followed, conditions for these earliest animals became much harsher, as ocean oxygen levels fell and carbon dioxide caused global warming.
The research, published in Nature Communications, is from the Universities of Exeter, Leeds and Antwerp, and the Vrije Universiteit Brussel.
“Like worms in a garden, tiny creatures on the seabed disturb, mix and recycle dead organic material — a process known as bioturbation,” said Professor Tim Lenton, from the University of Exeter.
“Because the effect of animals burrowing is so big, you would expect to see big changes in the environment when the whole ocean floor changes from an undisturbed state to a bioturbated state.”
“We did indeed see a decrease in oxygen levels in the ocean around 520 million years ago,” said Professor Filip Meysman, from the University of Antwerp.
“But evidence from the rock record showed sediment was only a little disturbed.”
Professor Simon Poulton, from the University of Leeds, said: “This meant that the animals living in the seafloor at that time were not very active, and did not move very deep into the seabed.
“At first sight, these two observations did not seem to add up.”
Lead author Dr Sebastiaan van de Velde, of the Vrije Universiteit Brussel, explained: “The critical factor was to realise that the biggest changes happen at the lowest levels of animal activity.
“This meant that the first bioturbators had a massive impact.”
The researchers said this realisation was the “missing piece of the puzzle,” and allowed them to construct a mathematical model of Earth around that time to look to the changes caused by these early life forms.
Dr Benjamin Mills, also from the University of Leeds, who led this part of the research, said: “When we ran our model, we were surprised by what we saw.
“The evolution of these small animals did indeed decrease the oxygen in the ocean and atmosphere, but also increased atmospheric carbon dioxide levels to such an extent that it caused a global warming event.
“We knew that warming occurred at this point in Earth history, but did not realise it could be driven by animals.”
This process made conditions worse for these animals, which possibly contributed to a number of mass extinction events during the first 100 million years of animal evolution.
“There is an interesting parallel between the earliest animals changing their world in a way that was bad for them, and what we human animals are doing to the planet now,” said Professor Lenton, director of Exeter’s new Global Systems Institute, which aims to develop transformative solutions to the challenges facing the world today.
“We are creating a hotter world with expanding ocean anoxia (oxygen deficiency) which is bad for us and a lot of other creatures we share the planet with.”
Reference:
Sebastiaan van de Velde, Benjamin J. W. Mills, Filip J. R. Meysman, Timothy M. Lenton, Simon W. Poulton. Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-04973-4
Note: The above post is reprinted from materials provided by University of Exeter.
The central portion of Osuga Valles, which has a total length of 164 km. In some places, it is 20 km wide and plunges to a depth of 900 m. Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO
The surface of Mars bears imprints of structures that resemble fluvial steam networks on Earth. Scientists therefore assume that there must have been once enough water on the red planet to feed water streams that incised their path into the soil. For years, however, scientists have been debating the source from which this water must have originated: was it rainwater that caused streams and rivers to swell? Or did water ice in the soil melt due to volcanic activity, and seep out to form rivers? Each of these scenarios leads to a completely different conclusion about the climatic history of the red planet.
A new study now suggests that the branching structure of the former river networks on Mars has striking similarities with terrestrial arid landscapes. This has been demonstrated in a recent paper published in Science Advances by physicist Hansjörg Seybold from the group of James Kirchner, ETH professor at the Institute for Terrestrial Ecosystems, and planetary specialist Edwin Kite from the University of Chicago.
Valleys eroded mainly by rainwater
Using statistics from all mapped river valleys on Mars, the researchers conclude that the contours still visible today must have been created by superficial run-off of (rain)water. Consequently, the influence of groundwater seepage from the soil can be excluded as a dominant process for shaping these features.
The distribution of the branching angles of the valleys on Mars is very similar to those found in arid landscapes on Earth. According to lead author Seybold, this implies that there must have been a similar hydrological environment with sporadic heavy rainfall events on Mars over a prolonged period of time and that this rainwater may have run off quickly over the surface shaping the valley networks. This is how river valleys develop in arid regions on Earth. For example, in Arizona, researchers observed the same valley network patterns in a landscape where astronauts are training for future Mars missions. Valleys in arid regions fork at a narrow angle.
The branching angles on Mars are comparatively low. Seybold therefore rules out the influence of groundwater sapping as the major channel forming process on Mars. River networks that are formed by re-emerging groundwater, as found, for example, in Florida, tend to have much wider branching angles between the two tributaries and do not match the narrow angles of streams in arid areas.
Conditions such as those found in terrestrial arid landscapes today probably prevailed on Mars for only a relatively short period about 3.6 to 3.8 billion years ago. In that period, the atmosphere on Mars may have been much denser than it is today. “Recent research shows that there must have been much more water on Mars than previously assumed,” says Seybold.
Evaporation made it rain
One hypothesis suggests that the northern third of Mars was covered by an ocean at that time. Water evaporated, condensed around the high volcanoes of the highlands to the south of the ocean and led to heavy precipitation. As a result, rivers formed, which left traces that can still be observed on Mars today.
The big question is where the water has disappeared to over time. “It’s likely that most of it evaporated into space. But it could still be found in the vicinity of Mars,” says the physicist., ” but this is a question for a future space mission.”
Reference:
Hansjoerg J. Seybold, Edwin Kite, James W. Kirchner. Branching geometry of valley networks on Mars and Earth and its implications for early Martian climate. Science Advances, 2018; 4 (6): eaar6692 DOI: 10.1126/sciadv.aar6692
Note: The above post is reprinted from materials provided by ETH Zurich. Original written by Peter Rüegg.
