Jurassic mammals were picky eaters.

New analyses of tiny fossil mammals from Glamorgan, South Wales are shedding light on the function and diets of our earliest ancestors, a team including researchers from the University of Southampton report today in the journal Nature. Mammals and their immediate ancestors from the Jurassic period (201-145 million years ago) developed new characteristics — such as better hearing and teeth capable of precise chewing.

By analysing jaw mechanics and fossil teeth, the team were able to determine that two of the earliest shrew-sized mammals, Morganucodon and Kuehneotherium, were not generalised insectivores but had already evolved specialised diets, feeding on distinct types of insects.

Morganucodon and Kuehneotherium. Credit: Pamela Gill

Morganucodon and Kuehneotherium.
Credit: Pamela Gill

Lead author, Dr Pamela Gill of the University of Bristol, said: “None of the fossils of the earliest mammals have the sort of exceptional preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth. Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology.”

The team used synchrotron X-rays and CT scanning to reveal in unprecedented detail the internal anatomy of these tiny jaws, which are only 2cm in length. As the jaws are in many pieces, the scans were ‘stitched together’ to make a complete digital reconstruction. Finite element modelling, the same technique used to design hip joints and bridges, was used to perform a computational analysis of the strength of the jaws. This showed that Kuehneotherium and Morganucodon had very different abilities for catching and chewing prey.

Study co-author, Dr Neil Gostling from the University of Southampton, said: “The improvement in CT scanning, both in the instrumentation, at Light Source at the Paul Scherrer Institute in Switzerland where we scanned or even the µ-VIS Centre at Southampton, along with access for research of this kind, allows us to make inroads into understanding the biology and the ecology of animals long dead. The questions asked of the technology do not produce ‘speculation’, rather the results show a clearly defined answer based on direct comparison to living mammals. This would not be possible without the computational techniques we have used here.”

Using an analysis previously carried out on the teeth of present-day, insect-eating bats, the researchers found that the teeth of Morganucodon and Kuehneotherium had very different patterns of microscopic pits and scratches, known as ‘microwear’. This indicated they were eating different things with Morganucodon favouring harder, crunchier food items such as beetles while Kuehneotherium selected softer foods such as scorpion flies which were common at the time.

Team leader, Professor Emily Rayfield from the University of Bristol, added: “This study is important as it shows for the first time that the features that make us unique as mammals, such as having only one set of replacement teeth and a specialised jaw joint and hearing apparatus, were associated with the very earliest mammals beginning to specialise their teeth and jaws to eat different things.”

Courtesy: University of Southampton. “Jurassic mammals were picky eaters, new study finds.” ScienceDaily. ScienceDaily, 20 August 2014.

Prehistoric crocodilian diversity depends on sea temperature

The ancestors of today’s crocodiles colonised the seas during warm phases and became extinct during cold phases, according to a new Anglo-French study which establishes a link between marine crocodilian diversity and the evolution of sea temperature over a period of more than 140 million years.

The research, led by Dr Jeremy Martin from the Université de Lyon, France and formerly from the University of Bristol, UK is published this week in Nature Communications.

Today, crocodiles are ‘cold-blooded’ animals that mainly live in fresh waters but two notable exceptions, Crocodylus porosus and Crocodylus acutus venture occasionally into the sea. Crocodiles occur in tropical climates, and they are frequently used as markers of warm conditions when they are found as fossils.

This is a marine crocodilian, here a dyrosaurid, swimming in the warm surface waters during the end of the Cretaceous period. Credit: Guillaume Suan

This is a marine crocodilian, here a dyrosaurid, swimming in the warm surface waters during the end of the Cretaceous period.
Credit: Guillaume Suan

While only 23 species of crocodiles exist today, there were hundreds of species in the past. On four occasions in the past 200 million years, major crocodile groups entered the seas, and then became extinct. It is a mystery why they made these moves, and equally why they all eventually went extinct. This new study suggests that crocodiles repeatedly colonized the oceans at times of global warming.

Lead author of the report, Dr Jeremy Martin said: “We thought each of these evolutionary events might have had a different cause. However, there seems to be a common pattern.”

Dr Martin, with a team of paleontologists and geochemists from the Université de Lyon and the University of Bristol, compared the evolution of the number of marine crocodilian fossil species to the sea temperature curve during the past 200 million years. This temperature curve, established using an isotopic thermometer, is widely applied for reconstruction of past environmental conditions and in this case, is based on the isotopic composition of the oxygen contained in the fossilised remains of fossil marine fish (bone, teeth, scales).

Co-author, Christophe Lécuyer explained: “According to this method, it is possible to calculate the temperature of the water in which these fish lived by applying an equation linking the isotopic composition of the fossilised remains to the temperature of mineralisation of their skeleton. The seawater temperatures derived from the composition of fish skeleton thus corresponds to the temperature of water in which the marine crocodiles also lived.”

The results show that colonisation of the marine environment about 180 million years ago was accompanied by a period of global warming of the oceans. These first marine crocodilians became extinct about 25 million years later, during a period of global freezing. Then, another crocodilian lineage appeared and colonised the marine environment during another period of global warming.

The evolution of marine crocodilians is therefore closely tied to the temperature of their medium, and shows that their evolution and their lifestyle, as in modern crocodilians, are constrained by environmental temperatures.

Nevertheless, one fossil lineage does not appear to follow this trend. Jurassic metriorhynchoids did not go extinct during the cold spells of the early Cretaceous, unlike the teleosaurids, another group of marine crocodilians. Quite surprisingly, metriorhynchoids only disappeared a few million years later. This exception will certainly provide grounds for new research, particularly into how the biology of this group adapted to life in the pelagic environment.

Professor Michael Benton from the University of Bristol, another co-author of the study, said: “This work illustrates a case of the impact of climate change on the evolution of animal biodiversity, and shows that for crocodilians, warming phases of our earth’s history constitute ideal opportunities to colonise new environments.”

Source:Jeremy E. Martin, Romain Amiot, Christophe Lécuyer, Michael J. Benton. Sea surface temperature contributes to marine crocodylomorph evolution. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5658

Caiuajara dobruskii:New pterosaur species found

A flying reptile whose head was topped with a big bony crest shaped like the sail of a yacht swooped through the skies over Brazil roughly 90 million years ago.

Scientists announced on Wednesday the remarkable discovery of about 50 fossilized skeletons of a creature called Caiuajara dobruskii, a type of flying reptile known as a pterosaur that lived alongside the dinosaurs, at a site in southern Brazil.

These pterosaurs, whose wingspans measured up to nearly 2.35 meters, inhabited a lakeside oasis in a large desert region during the Cretaceous Period, living in vibrant colonies with others of the same species of all ages, they said.

“This helps us to have a glimpse on the anatomical variation achieved by this species from young to old,” said Alexander Kellner, a paleontologist with Brazil’s National Museum at the Federal University of Rio de Janeiro, who led the study.

Many pterosaurs, especially the later ones, boasted elaborate and sometimes large head crests. Caiuajara’s head was topped with a big triangular crest that looked like “a bony sail,” according to Kellner. “It looks bizarre,” he said.

There is no indication that the crest was limited to either males or females, but it appears to have become ever larger relative to the rest of the body as the pterosaur matured.

“The size of the crest was small in young animals and very large in older ones,” Kellner added.

Pterosaurs were Earth’s first flying vertebrates, with birds and bats making their appearances much later. They thrived from about 220 million years ago to 65 million years ago, when they were wiped out by the asteroid that also doomed the dinosaurs.

The new pterosaur Caiuajara dobruskii had a sail-like crest that became larger relative to the rest of the body as the pterosaur matured. (Maurilio Oliveira/Museu Nacional-UFRJ)

The new pterosaur Caiuajara dobruskii had a sail-like crest that became larger relative to the rest of the body as the pterosaur matured. (Maurilio Oliveira/Museu Nacional-UFRJ)

The researchers described 47 skeletons in their study published in the scientific journal PLOS ONE and said they have identified 10 more not described in the paper. They said this species lived about 80 to 90 million years ago.

Caiuajara was toothless and most likely a fruit eater, Kellner said. The skeletons of the juveniles strongly suggested they could fly at a very young age, Kellner added.

Knowledge about pterosaurs has been spotty, with their fragile skeletons not lending themselves well to fossilization. The sheer number of Caiuajara individuals discovered and their variety of ages have made it one of the best understood pterosaurs ever found, the researchers said.

Chinese scientists in June said they had unearthed no fewer than 40 adult individuals of another newly identified pterosaur species as well as five pterosaur eggs — very rare indeed — preserved beautifully in three dimensions.

No eggs of Caiuajara have been found at the site in Brazil. “Not yet. But one is allowed to dream, correct?” said Kellner.

New species of pterosaur found in mass grave

A rare stash of thousands of ancient bones found in Brazil has turned in a magnificent find: over 47 skeletons of a single, new species of Upper Cretaceous pterosaur.

Discovered in an old lake deposit on the outskirts of Cruzeiro do Oeste in the southern state of Parana, the bones are unusual for two reasons: firstly, that pterosaur bones had never been found in the southern part of Brazil, with all other pterosaur material found in the northeast.

As for how the grave came to be, evidence suggests that the site — an oasis — was a habitat for the pterosaurs for a very long time, and they did not all die simultaneously.

“Episodic events (e.g., desert storms) likely carried the disarticulated and partially articulated skeletons to the bottom of the lake where they got eventually preserved. The presence of three main levels of accumulation in a section of less than one meter suggests that this region was home to pterosaur populations for an extended period of time,” the paper reads.

“It is also plausible that Caiuajara was a migratory pterosaur that visited this area from time to time, although the first possibility is favoured here. The causes of death remain unknown, although similarities with dinosaur drought-related mortality are striking. However, it is also possible that desert storms could have been responsible for the occasional demise of these pterosaurs.”

Secondly, the size of the cache, found over a space of about 20 square metres, is deeply impressive. Pterosaurs seem to have lived on the coast, and recovered remains are usually limited to fragments of a single specimen. Although the researchers confirmed 47 individuals, they estimate the actual number to be well into the hundreds.

“Most pterosaurs are known from ancient coastal or shallow marine deposits and the number of species that lived deep inside the continents is limited, particularly from desert environments,” the research paper, published in the journal PLOS One, reads.

The new species has been named Caiuajara dobruskii, and the cache contained bones from several stages of development, from young to adult, with wingspans ranging from 0.65 metres to 2.35 metres. The pterosaurs’ heads are also adorned with a large crest, which grew in prominence as the animals matured. The size of the grave suggests that they were a social species, living and flying in colonies, developing flight from a very young age.

As for how the grave came to be, evidence suggests that the site — an oasis — was a habitat for the pterosaurs for a very long time, and they did not all die simultaneously.

“Episodic events (e.g., desert storms) likely carried the disarticulated and partially articulated skeletons to the bottom of the lake where they got eventually preserved. The presence of three main levels of accumulation in a section of less than one meter suggests that this region was home to pterosaur populations for an extended period of time,” the paper reads.

“It is also plausible that Caiuajara was a migratory pterosaur that visited this area from time to time, although the first possibility is favoured here. The causes of death remain unknown, although similarities with dinosaur drought-related mortality are striking. However, it is also possible that desert storms could have been responsible for the occasional demise of these pterosaurs.”

Amber offers new views of a lost world

Scientists are searching through a massive collection of 20-million-year-old amber found in the Dominican Republic more than 50 years ago, and the effort is yielding fresh insights into ancient tropical insects and the world they inhabited.

When the collection is fully curated, a task that will take many years, it will be the largest unbiased Dominican amber collection in the world, the researchers report.

Sir David Attenborough narrates and appears in a video about the digital curation of a 20-million-year-old amber collection at the Illinois Natural History Survey at Illinois. (See link to video in paragraph 9.) - IMAGE and VIDEO by Kaitlin and Kevin Southworth

Sir David Attenborough narrates and appears in a video about the digital curation of a 20-million-year-old amber collection at the Illinois Natural History Survey at Illinois. IMAGE and VIDEO by Kaitlin and Kevin Southworth

Perhaps the most striking discovery thus far is that of a pygmy locust, a tiny grasshopper the size of a rose thorn that lived 18- to 20-million years ago and fed on moss, algae and fungi. The specimen is remarkable because it represents an intermediate stage of evolution in the life of its subfamily of locusts (known as the Cladonotinae). The most ancient representatives of this group had wings, while modern counterparts do not. The newly discovered locust has what appear to be vestigial wings – remnant structures that had already lost their primary function.

The discovery is reported in the journal ZooKeys.

“Grasshoppers are very rare in amber and this specimen is extraordinarily well-preserved,” said Sam Heads, a paleontologist at the Illinois Natural History Survey, a division of the Prairie Research Institute at the University of Illinois.

Heads, laboratory technician Jared Thomas and study co-author Yinan Wang found the new specimen a few months after the start of their project to screen more than 160 pounds of Dominican amber collected in the late 1950s by former INHS entomologist Milton Sanderson. Sanderson described several specimens from the collection in a paper in Science in 1960, a report that inspired a generation of scientists to seek out and study Dominican amber, Heads said.

Heads has named the new pygmy locust Electrotettix attenboroughi, the genus name a combination of electrum (Latin from Greek, meaning “amber”) and tettix (Greek, meaning “grasshopper”). The species is named for Sir David Attenborough, a British naturalist and filmmaker (not to be confused with Richard Attenborough, David’s actor brother who appeared in the movie “Jurassic Park”).

“Sir David has a personal interest in amber, and also he was one of my childhood heroes and still is one of my heroes and so I decided to name the species in his honor — with his permission of course,” Heads said. (Attenborough narrates and appears in a new video about the Sanderson collection and the specimen that bears his name.)

The process of screening the amber is slow and painstaking. Much of the amber is clouded with oxidation, and the researchers must carefully cut and polish “windows” in it to get a good look at what’s inside. In addition to the pygmy locust, Heads and his colleagues have found mating flies, stingless bees, gall midges, Azteca ants, wasps, bark beetles, mites, spiders, plant parts and even a mammal hair.

The pygmy locust was found in a fragment that also contained wasps, ants, midges, plant remnants and fungi. Such associations are rich in information, Heads said, offering clues about the creatures’ physiological needs and the nature of their habitat.

“Fossil insects can provide lots of insight into the evolution of specific traits and behaviors, and they also tell us about the history of the time period,” Heads said. “They’re a tremendous resource for understanding the ancient world, ancient ecosystems and the ancient climate – better even, perhaps, than dinosaur bones.”

Note: This story has been adapted from a news release issued by the University of Illinois at Urbana-Champaign

Kulindadromeus zabaikalicus suggest all dinosaurs could have been feathered

The first ever example of a plant-eating dinosaur with feathers and scales has been discovered in Russia. Previously only flesh-eating dinosaurs were known to have had feathers, so this new find raises the possibility that all dinosaurs could have been feathered.

The new dinosaur, named Kulindadromeus zabaikalicus as it comes from a site called Kulinda on the banks of the Olov River in Siberia, is described in a paper recently published in Science.

Kulindadromeus shows epidermal scales on its tail and shins, and short bristles on its head and back. The most astonishing discovery, however, is that it also has complex, compound feathers associated with its arms and legs.

Kulindadromeus zabaikalicus in its lacustrine environment. Credit: Andrey Atuchin

Kulindadromeus zabaikalicus in its lacustrine environment.
Credit: Andrey Atuchin

Birds arose from dinosaurs over 150 million years ago so it was no surprise when dinosaurs with feathers were found in China in 1996. But all those feathered dinosaurs were theropods, flesh-eating dinosaurs that include the direct ancestors of birds.

Lead author Dr Pascal Godefroit from the Royal Belgian Institute of Natural History in Brussels said: “I was really amazed when I saw this. We knew that some of the plant-eating ornithischian dinosaurs had simple bristles, and we couldn’t be sure whether these were the same kinds of structures as bird and theropod feathers. Our new find clinches it: all dinosaurs had feathers, or at least the potential to sprout feathers.”

The Kulinda site was found in summer 2010 by Professor Dr Sofia Sinitsa from the Institute of Natural Resources, Ecology and Cryology SB RAS in Chita, Russia. In 2013, the Russian-Belgian team excavated many dinosaur fossils, as well as plant and insect fossils.

The feathers were studied by Dr Maria McNamara (University of Bristol and University College, Cork) and Professor Michael Benton (University of Bristol), who has also worked on the feathers of Chinese dinosaurs, and Professor Danielle Dhouailly (Université Joseph Fourier in Grenoble, France) who is a specialist on the development of feathers and scales in modern reptiles and birds.

Dr McNamara said: “These feathers are really very well preserved. We can see each filament and how they are joined together at the base, making a compound structure of six or seven filaments, each up to 15mm long.”

Professor Dhouailly said: “Developmental experiments in modern chickens suggest that avian scales are aborted feathers, an idea that explains why birds have scaly legs. The astonishing discovery is that the molecular mechanisms needed for this switch might have been so clearly related to the appearance of the first feathers in the earliest dinosaurs.”

Kulindadromeus was a small plant-eater, only about 1m long. It had long hind legs and short arms, with five strong fingers. Its snout was short, and its teeth show clear adaptations to plant eating. In evolutionary terms, it sits low in the evolutionary tree of ornithischian dinosaurs. There are six skulls and several hundred partial skeletons of this new dinosaur at the Kulinda locality.

This discovery suggests that feather-like structures were likely widespread in dinosaurs, possibly even in the earliest members of the group. Feathers probably arose during the Triassic, more than 220 million years ago, for purposes of insulation and signalling, and were only later co-opted for flight. Smaller dinosaurs were probably covered in feathers, mostly with colourful patterns, and feathers may have been lost as dinosaurs grew up and became larger.

Source: Bristol University. “Fossils found in Siberia suggest all dinosaurs could have been feathered.” ScienceDaily. ScienceDaily, 30 July 2014. <www.sciencedaily.com/releases/2014/07/140730050516.htm>.

New way to study ground fractures

Boise State University geophysics researchers have created a new way to study fractures by producing elastic waves, or vibrations, through using high-intensity light focused directly on the fracture itself. The new technique developed in the Physical Acoustics Lab at Boise State may help determine if there is a fluid, such as magma or water, or natural gas inside fractures in the Earth.

Typically, scientists create sound waves at the surface to listen for echoes from fractures in the ground, but this new technique could provide more accurate information about the cracks because sound does not have to travel to the fracture and back again. The new technique aims to enhance scientists’ abilities to image faults in the Earth, including those human-made through the process of hydraulic fracturing, or fracking.

The new method is explained in a paper that appears online in the journal Physical Review Letters.

“These concepts are of great importance in earthquake dynamics, but also in exploration of hydrocarbons,” said study coauthor Thomas Blum, a Boise State doctoral student. “If we can understand, for example, the microscopic structure of fracture points using this technique, we might be able to learn how, exactly, earthquakes happen. Scientists do not yet fully understand the structure of the faults, so if we could remotely sense the structure of faults, we might be able to learn more.”

Boise State University geophysics researchers have created a new way to study fractures by producing elastic waves, or vibrations, through using high-intensity light focused directly on the fracture itself. Credit: Image courtesy of Boise State University

Boise State University geophysics researchers have created a new way to study fractures by producing elastic waves, or vibrations, through using high-intensity light focused directly on the fracture itself.
Credit: Image courtesy of Boise State University

Blum and Kasper van Wijk, associate professor of geosciences at Boise State, came up with the new technique by focusing laser light directly onto a fracture inside a transparent sample to create elastic waves. The researchers proved that laser-based ultrasonic techniques can “excite,” or cause vibrations, in the fracture. The result — jointly obtained with scientists at Colorado School of Mines and ConocoPhillips — opens up the possibility of measuring variations in the fracture and diagnosing the mechanical properties of fractures by directly exciting them.

Source:Thomas Blum, Kasper van Wijk, Roel Snieder, Mark Willis. Laser Excitation of a Fracture Source for Elastic Waves. Physical Review Letters, 2011; 107 (27) DOI: 10.1103/PhysRevLett.107.275501.

Mammoth and mastodon behavior was less roam

Their scruffy beards weren’t ironic, but there are reasons mammoths and mastodons could have been the hipsters of the Ice Age.

According to research from the University of Cincinnati, the famously fuzzy relatives of elephants liked living in Greater Cincinnati long before it was trendy – at the end of the last ice age. A study led by Brooke Crowley, an assistant professor of geology and anthropology, shows the ancient proboscideans enjoyed the area so much they likely were year-round residents and not nomadic migrants as previously thought.

They even had their own preferred hangouts. Crowley’s findings indicate each species kept to separate areas based on availability of favored foods here at the southern edge of the Last Glacial Maximum’s major ice sheet.

“I suspect that this was a pretty nice place to live, relatively speaking,” Crowley says. “Our data suggest that animals probably had what they needed to survive here year-round.”

Crowley’s research with co-author and recent UC graduate Eric Baumann, “Stable Isotopes Reveal Ecological Differences Among Now-Extinct Proboscideans from the Cincinnati Region, USA,” was recently published in Boreas, an international academic research journal.

Learning more about the different behaviors of these prehistoric creatures could benefit their modern-day cousins, African and Asian elephants. Both types are on the World Wildlife Fund’s endangered species list. Studying how variable different types of elephants might have been in the past, Crowley says, might help ongoing efforts to protect these largest of land mammals from continued threats such as poaching and habitat destruction.

“There are regionally different stories going on,” Crowley says. “There’s not one overarching theme that we can say about a mammoth or a mastodon. And that’s becoming more obvious in studies people are doing in different places. A mammoth in Florida did not behave the same as one in New York, Wyoming, California, Mexico or Ohio.”

Research led by the University of Cincinnati's Brooke Crowley, posing with this mammoth mandible, has uncovered some interesting ideas about mammoth and mastodon behavior. - Dottie Stover, University of Cincinnati

Research led by the University of Cincinnati’s Brooke Crowley, posing with this mammoth mandible, has uncovered some interesting ideas about mammoth and mastodon behavior. – Dottie Stover, University of Cincinnati

For their research, Crowley and Baumann looked to the wisdom in teeth – specifically museum specimens of molars from four mastodons and eight mammoths from Southwestern Ohio and Northwestern Kentucky. Much can be revealed by carefully drilling a tooth’s surface and analyzing the stable carbon, oxygen and strontium isotopic signatures in the powdered enamel.

Each element tells a different story. Carbon provides insight into an animal’s diet, oxygen relates to overall climatic conditions of an animal’s environment and strontium indicates how much an animal may have traveled at the time its tooth was forming.

“Strontium reflects the bedrock geology of a location,” Crowley says. “So if a local animal grows its tooth and mineralizes it locally and dies locally, the strontium isotope ratio in its tooth will reflect the place where it lived and died. If an animal grows its tooth in one place and then moves elsewhere, the strontium in its tooth is going to reflect where it came from, not where it died.”

Their analysis allowed them to determine several things:

Mammoths ate more grasses and sedges than mastodons, which favored leaves from trees or shrubs.

  • Strontium from all of the animals (except one mastodon) matched local water samples, meaning they likely were less mobile and migratory than previously thought.
  • Differences in strontium and carbon between mammoths and mastodons suggest they didn’t inhabit the same localities.
  • Mammoths preferred to be closer to the retreating ice sheet where grasses were more abundant, whereas mastodons fed farther from the ice sheet in more forested habitat.

“As a geologist, questioning the past is one of the most interesting and exciting things to do,” says Baumann, an environmental geologist with a contractor for the U.S. Environmental Protection Agency. “Based on our data, mammoths and mastodons seemed to have different diets and lived in different areas during their lives. This is important because it allows us to understand how species in the past lived and interacted. And the past is the key to the present.”

Crowley of the McMicken College of Arts and Sciences plans further research into how strontium isotopes can be used to explore megafauna, including other projects dealing with mammoths and mastodons.

Note: This story has been adapted from a news release issued by the University of Cincinnati

Giant earthquakes help predict volcanic eruptions

Researchers at the Institut des Sciences de la Terre (CNRS/Université Joseph Fourier/Université de Savoie/IRD/IFSTTAR) and the Institut de Physique du Globe de Paris (CNRS/Université Paris Diderot/IPGP), working in collaboration with Japanese researchers, have for the first time observed the response of Japanese volcanoes to seismic waves produced by the giant Tohoku-oki earthquake of 2011. Their conclusions, published in Science on July 4, 2014, reveal how earthquakes can impact volcanoes and should help to assess the risk of massive volcanic eruptions worldwide.

Until the early 2000s, seismic noise* was systematically removed from seismological analyses. This background noise is in fact associated with seismic waves caused by ocean swell. These waves, which can be compared to permanent, continuous microseisms, can be used by seismologists instead of earthquakes (which are highly localized over a limited time period) to image Earth’s interior and its evolution over time, rather like an ultrasound scan on a global scale.

Imaging seismic susceptibility makes it possible to detect regions affected by high-pressure volcanic fluids. The image in the background is catalogued as 'Red Fuji' (Katsushika Hokusai, 1830). Credit: Copyright Florent Brenguier

Imaging seismic susceptibility makes it possible to detect regions affected by high-pressure volcanic fluids. The image in the background is catalogued as ‘Red Fuji’ (Katsushika Hokusai, 1830).
Credit: Copyright Florent Brenguier

Now, seismic noise has been used for the continuous measurement of perturbations of the mechanical properties of Earth’s crust. Researchers at the Institut des Sciences de la Terre (CNRS/Université Joseph Fourier/Université de Savoie/IRD/IFSTTAR) and the Institut de Physique du Globe de Paris (CNRS/Université Paris Diderot/IPGP) have applied this novel method while working in collaboration with Japanese colleagues using the Hi-net network, which is the world’s densest seismic network (comprising more than 800 seismic detectors throughout Japan).

After the giant Tohoku-oki earthquake of 2011, the researchers analyzed over 70 terabytes of seismic data from the network. For the first time, they showed that the regions where the perturbations of Earth’s crust were the greatest were not those where the shocks were the strongest. They were in fact localized under volcanic regions, especially under Mount Fuji. The new method thus enabled the scientists to observe the anomalies caused by the perturbations from the earthquake in volcanic regions under pressure. Mount Fuji, which exhibits the greatest anomaly, is probably under great pressure, although no eruption has yet followed the Tohoku-oki earthquake. The 6.4-magnitude seism that occurred four days after the 2011 quake confirms the critical state of the volcano in terms of pressure. These findings lend support to theories that the last eruption of Mount Fuji in 1707 was probably triggered by the giant 8.7-magnitude Hoei earthquake, which took place 49 days before the eruption.

More generally, the results show how regions affected by high-pressure volcanic fluids can be characterized using seismic data from dense seismic detector networks. This should help to anticipate the risk of major volcanic eruptions worldwide.

*Seismic noise includes all the unwanted components affecting an analysis, such as the noise produced by the measuring device itself or external perturbations inadvertently picked up by the measuring devices.