Why rocks flow slowly in Earth’s middle mantle

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

For decades, researchers have studied the interior of the Earth using seismic waves from earthquakes. Now a recent study, led by Arizona State University’s School of Earth and Space Exploration Associate Professor Dan Shim, has re-created in the laboratory the conditions found deep in the Earth, and used this to discover an important property of the dominant mineral in Earth’s mantle, a region lying far below our feet.

Shim and his research team combined X-ray techniques in the synchrotron radiation facility at the U.S. Department of Energy’s National Labs and atomic resolution electron microscopy at ASU to determine what causes unusual flow patterns in rocks that lie 600 miles and more deep within the Earth. Their results have been published in the Proceedings of the National Academy of Sciences.

As slabs of Earth's crust decend into the mantle, they encounter a zone about 1,100 kilometers down where the mantle rock abruptly becomes stiffer, flowing less easily. Similarly, rising plumes of molten rock encounter the same layer and have difficulty punching through from below. Credit: Dan Shim

As slabs of Earth’s crust decend into the mantle, they encounter a zone about 1,100 kilometers down where the mantle rock abruptly becomes stiffer, flowing less easily. Similarly, rising plumes of molten rock encounter the same layer and have difficulty punching through from below.
Credit: Dan Shim

Slow flow, down deep

Planet Earth is built of layers. These include the crust at the surface, the mantle and the core. Heat from the core drives a slow churning motion of the mantle’s solid silicate rocks, like slow-boiling fudge on a stove burner. This conveyor-belt motion causes the crust’s tectonic plates at the surface to jostle against each other, a process that has continued for at least half of Earth’s 4.5 billion-year history.

Shim’s team focused on a puzzling part of this cycle: Why does the churning pattern abruptly slow at depths of about 600 to 900 miles below the surface?

“Recent geophysical studies have suggested that the pattern changes because the mantle rocks flow less easily at that depth,” Shim said. “But why? Does the rock composition change there? Or do rocks suddenly become more viscous at that depth and pressure? No one knows.”

To investigate the question in the lab, Shim’s team studied bridgmanite, an iron-containing mineral that previous work has shown is the dominant component in the mantle.

“We discovered that changes occur in bridgmanite at the pressures expected for 1,000 to 1,500 km depths,” Shim said. “These changes can cause an increase in bridgmanite’s viscosity — its resistance to flow.”

The team synthesized samples of bridgmanite in the laboratory and subjected them to the high-pressure conditions found at different depths in the mantle.

Mineral key to the mantle

The experiments showed the team that, above a depth of 1,000 kilometers and below a depth of 1,700 km, bridgmanite contains nearly equal amounts of oxidized and reduced forms of iron. But at pressures found between those two depths, bridgmanite undergoes chemical changes that end up significantly lowering the concentration of iron it contains.

The process starts with driving oxidized iron out of the bridgmanite. The oxidized iron then consumes the small amounts of metallic iron that are scattered through the mantle like poppy seeds in a cake. This reaction removes the metallic iron and results in making more reduced iron in the critical layer.

Where does the reduced iron go? The answer, said Shim’s team, is that it goes into another mineral present in the mantle, ferropericlase, which is chemically prone to absorbing reduced iron.

“Thus the bridgmanite in the deep layer ends up with less iron,” explained Shim, noting that this is the key to why this layer behaves the way it does.

“As it loses iron, bridgmanite becomes more viscous,” Shim said. “This can explain the seismic observations of slowed mantle flow at that depth.”


@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

Antarctic ice rift close to calving, after growing 17km in 6 days, latest data from ice shelf shows

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

The rift in the Larsen C ice shelf in Antarctica has grown by 17km in the last few days and is now only 13km from the ice front, indicating that calving of an iceberg is probably very close, Swansea University researchers revealed after studying the latest satellite data.

The rift in Larsen C is likely to lead to one of the largest icebergs ever recorded. It is being monitored by researchers from the UK’s Project Midas, led by Swansea University.

This is the ice flow velocities of Larsen C in April/May 2017, from ESA Sentinel-1 data. Credit: A. Luckman, MIDAS, Swansea University, with Copernicus Sentinel data

This is the ice flow velocities of Larsen C in April/May 2017, from ESA Sentinel-1 data.
Credit: A. Luckman, MIDAS, Swansea University, with Copernicus Sentinel data

Professor Adrian Luckman of Swansea University College of Science, head of Project Midas, described the latest findings:

“In the largest jump since January, the rift in the Larsen C Ice Shelf has grown an additional 17 km (11 miles) between May 25 and May 31 2017. This has moved the rift tip to within 13 km (8 miles) of breaking all the way through to the ice front, producing one of the largest ever recorded icebergs.

The rift tip appears also to have turned significantly towards the ice front, indicating that the time of calving is probably very close.

The rift has now fully breached the zone of soft ‘suture’ ice originating at the Cole Peninsula and there appears to be very little to prevent the iceberg from breaking away completely.”

Researchers say the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up.

Larsen C is approximately 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.

Professor Luckman added, “When it calves, the Larsen C Ice Shelf will lose more than 10% of its area to leave the ice front at its most retreated position ever recorded; this event will fundamentally change the landscape of the Antarctic Peninsula.

We have previously shown that the new configuration will be less stable than it was prior to the rift, and that Larsen C may eventually follow the example of its neighbour Larsen B, which disintegrated in 2002 following a similar rift-induced calving event.

The MIDAS Project will continue to monitor the development of the rift and assess its ongoing impact on the ice shelf.

The team say they have no evidence to link the growth of this rift, and the eventual calving, to climate change. However, it is widely accepted that warming ocean and atmospheric temperatures have been a factor in earlier disintegrations of ice shelves elsewhere on the Antarctic Peninsula, most notably Larsen A (1995) and Larsen B (2002).

They point out that this is one of the fastest warming places on Earth, a feature which will certainly not have hindered the development of the rift in Larsen C.

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

Extreme geothermal activity discovered beneath New Zealand’s Southern Alps

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

An international team, including University of Southampton scientists, has found unusually high temperatures, greater than 100°C, close to Earth’s surface in New Zealand — a phenomenon typically only seen in volcanic areas such as Iceland or Yellowstone, USA.

The researchers made the discovery while boring almost a kilometre into the Alpine Fault, the major tectonic boundary between the Australian and Pacific plates -running the length of the country’s South Island. The team was working to better understand what happens at a tectonic plate boundary in the build-up to a large earthquake.

The Deep Fault Drilling Project (DFDP) borehole, was drilled at Whataroa to the north of Franz Josef Glacier and discovered extremely hot, highly pressured groundwater flowing near to the fault line. Water at temperatures of more than 100°C is normally only found at depths of over three kilometres, but in this case was encountered at just over 600m depth.

The Deep Fault Drilling Project borehole. Credit: John Townend, Victoria University, NZ

The Deep Fault Drilling Project borehole.
Credit: John Townend, Victoria University, NZ

In an article published in the international journal Nature, computer models are used show these high temperatures result from a combination of the uplift of hot rocks along the tectonic plate boundary and groundwater flow caused by high mountains close to the Alpine Fault.

Professor Damon Teagle, who leads the Southampton group involved in the project, says: “The Alpine Fault extends over such a massive distance, it is visible from space. It is potentially New Zealand’s greatest geohazard, failing in the form of large earthquakes about every 300 years. With the last event occurring in 1717 AD, there is a high probability of a major (magnitude 7 to 8) earthquake in the next 50 years — making research into its behaviour all the more important.”

Thermal and hydrological computer modelling pre-drilling by University of Southampton PhD student Jamie Coussens, supervisor Dr Nick Woodman and other colleagues, helped predict the high temperatures and borehole fluid pressures to enable the safe drilling of this borehole. Their models, now calibrated against real sub-surface observations, explain how such high temperatures occur at shallow depths.

“The Southern Alps receive a lot of rain and snow — about ten times more than the UK. Much of this water flows into the ground, down beneath the high mountain ridges, before being heated and returning to the surface in valleys,” says Jamie Coussens. “The rocks that this water flows through are being moved upwards at about 10 mm a year on the Alpine Fault. This slip is very fast in geological terms and has carried up hot rocks from 30 km depth, faster than they can cool.”

Although warm springs are common in the region most of the hot groundwater flows up into, or near, the gravely beds of large rivers and becomes diluted at the surface by cooler river waters.

The result has implications for our understanding of the strength of the Alpine Fault and fault zones in general, as failure properties of fault rocks are influenced by temperature and geothermal fluids.

Professor Teagle comments: “The temperature profile of the DFDP borehole is really exciting. These very high shallow temperatures prove early theoretical models of rapid tectonic uplift first suggested in the 1980s for the Southern Alps by profound thinkers such as Peter Koons and Rick Allis. I was inspired by these theories as an undergraduate at the University of Otago in southern New Zealand — it is wonderful to see these early conceptual predictions proven with borehole observations.”

Source:University of Southampton

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

Why the Sumatra earthquake was so severe…..

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

An international team of scientists has found evidence suggesting the dehydration of minerals deep below the ocean floor influenced the severity of the Sumatra earthquake, which took place on December 26, 2004.

The earthquake, measuring magnitude 9.2, and the subsequent tsunami, devastated coastal communities of the Indian Ocean, killing over 250,000 people.

A 'free-fall funnel', part of the drilling process. Credit: Tim Fulton, IODP / JRSO

A ‘free-fall funnel’, part of the drilling process.
Credit: Tim Fulton, IODP / JRSO

Research into the earthquake was conducted during a scientific ocean drilling expedition to the region in 2016, as part of the International Ocean Discovery Program (IODP), led by scientists from the University of Southampton and Colorado School of Mines.

During the expedition on board the research vessel JOIDES Resolution, the researchers sampled, for the first time, sediments and rocks from the oceanic tectonic plate which feeds the Sumatra subduction zone. A subduction zone is an area where two of the Earth’s tectonic plates converge, one sliding beneath the other, generating the largest earthquakes on Earth, many with destructive tsunamis.

Findings of a study on sediment samples found far below the seabed are now detailed in a new paper led by Dr Andre Hüpers of the MARUM-Center for Marine Environmental Sciences at University of Bremen – published in the journal Science.

Expedition co-leader Professor Lisa McNeill, of the University of Southampton, says: “The 2004 Indian Ocean tsunami was triggered by an unusually strong earthquake with an extensive rupture area. We wanted to find out what caused such a large earthquake and tsunami and what this might mean for other regions with similar geological properties.”

The scientists concentrated their research on a process of dehydration of sedimentary minerals deep below the ground, which usually occurs within the subduction zone. It is believed this dehydration process, which is influenced by the temperature and composition of the sediments, normally controls the location and extent of slip between the plates, and therefore the severity of an earthquake.

In Sumatra, the team used the latest advances in ocean drilling to extract samples from 1.5 km below the seabed. They then took measurements of sediment composition and chemical, thermal, and physical properties and ran simulations to calculate how the sediments and rock would behave once they had travelled 250 km to the east towards the subduction zone, and been buried significantly deeper, reaching higher temperatures.

The researchers found that the sediments on the ocean floor, eroded from the Himalayan mountain range and Tibetan Plateau and transported thousands of kilometres by rivers on land and in the ocean, are thick enough to reach high temperatures and to drive the dehydration process to completion before the sediments reach the subduction zone. This creates unusually strong material, allowing earthquake slip at the subduction fault surface to shallower depths and over a larger fault area – causing the exceptionally strong earthquake seen in 2004.

Dr Andre Hüpers of the University of Bremen says: “Our findings explain the extent of the large rupture area, which was a feature of the 2004 earthquake, and suggest that other subduction zones with thick and hotter sediment and rocks, could also experience this phenomenon.

“This will be particularly important for subduction zones with limited or no historic subduction earthquakes, where the hazard potential is not well known. Subduction zone earthquakes typically have a return time of a few hundred to a thousand years. Therefore our knowledge of previous earthquakes in some subduction zones can be very limited.”

Similar subduction zones exist in the Caribbean (Lesser Antilles), off Iran and Pakistan (Makran), and off western USA and Canada (Cascadia). The team will continue research on the samples and data obtained from the Sumatra drilling expedition over the next few years, including laboratory experiments and further numerical simulations, and they will use their results to assess the potential future hazards both in Sumatra and at these comparable subduction zones.

Source- Sciencedaily

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

WFS News: Hard rocks from Himalaya raise flood risk for millions

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

Scientists have shown how earthquakes and storms in the Himalaya can increase the impact of deadly floods in one of Earth’s most densely populated areas.

Large volumes of hard rock dumped into rivers by landslides can increase flood risk up to hundreds of kilometres downstream, potentially affecting millions of people, researchers say.

The findings could help researchers improve flood risk maps for the Ganga Plain, a low-lying region covering parts of India, Nepal and Pakistan. They could also provide fresh insight into the long-term impacts of earthquakes and storms in the region.

Until now, little was known about how landslides in the Himalaya could affect flood risk downstream on the Ganga Plain.

For the first time, scientists at the University of Edinburgh have traced the path of rocks washed down from the Himalayan mountains onto the Plain.

They found that large landslides in the southern, lower elevation ranges of the Himalaya are more likely to increase flood risk than those in the high mountains further north.

Rocks in the south are extremely hard and travel only a short distance — less than 20 km — to reach the Plain. This means much of this rock — such as quartzite — reaches the Plain as gravel or pebbles, which can build up in rivers, altering the natural path of the water, the team says.

This is an image of the Modi Khola river, Nepal. Credit: Henry Pinder

 This is an image of the Modi Khola river, Nepal.Credit: Henry Pinder

Rocks from more northerly regions of the Himalaya tend to be softer, and the team found they often travel at least 100 km to reach the Plain. These types of rock — including limestone and gneiss — are gradually broken down into sand which, unlike gravel and pebbles, is dispersed widely as it travels downstream.

Understanding whether landslides will produce vast quantities of gravel or sand is crucial for predicting how rivers on the Ganga Plain will be affected, researchers say.

The study is published in the journal Nature. The research was funded by the Natural Environment Research Council.

Elizabeth Dingle, PhD student in the University of Edinburgh’s School of GeoSciences, who led the study, said: “Our findings help to explain how events in the Himalaya can have drastic effects on rivers downstream and on the people who live there. Knowing where landslides take place in the mountains could help us better predict whether or not large deposits of gravel will reach the Ganga Plain and increase flood risk.”

Citation:University of Edinburgh. “Hard rocks from Himalaya raise flood risk for millions.” ScienceDaily. ScienceDaily, 26 April 2017. <www.sciencedaily.com/releases/2017/04/170426131003.htm>.

Journal Reference:Elizabeth H. Dingle, Mikaël Attal, Hugh D. Sinclair. Abrasion-set limits on Himalayan gravel flux. Nature, 2017; 544 (7651): 471 DOI: 10.1038/nature22039

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

Just how old are animals?

The origin of animals was one of the most important events in the history of Earth. Beautifully preserved fossil embryos suggest that our oldest ancestors might have existed a little more than half a billion years ago.

Yet, fossils are rare, difficult to interpret, and new, older fossils are constantly discovered.

An alternative approach to date the ‘tree of life’ is the molecular clock, introduced in the early 1960s by twice Nobel Laureate Linus Pauling, which uses genetic information.

Early molecular clock studies assumed that mutation accumulated at a fixed rate across all species and concluded that our oldest ancestor might have existed around 1.5 billions of years ago, a date that is almost three-times as old as the oldest fossil evidence of animal life.

Detail from an embryo of the scalidophoran Markuelia from the Middle Cambrian of Australia. Credit: Philip Donoghue - University of Bristol

Detail from an embryo of the scalidophoran Markuelia from the Middle Cambrian of Australia.
Credit: Philip Donoghue – University of Bristol

These results sparked heated, scientific debates that only eased off in the last decade when a new generation of more realistic “relaxed” clock methods, that do not assume constancy of the mutation rate, started to close the gap between molecules and fossils indicating that animals are unlikely to be older than around 850 million of years.

However, using a recently developed relaxed molecular clock method called RelTime, a team of scientists at Oakland (Michigan) and Temple (Philadelphia) dated the origin of animals at approximately 1.2 billion years ago reviving the debate on the age of the animals.

Puzzled by the results of the American team, researchers from the University of Bristol and Queen Mary University of London decided to take a closer look at RelTime and found that it failed to relax the clock. Their findings are published in the journal Genome Biology and Evolution.

Professor Philip Donoghue from the University of Bristol’s School of Earth Sciences, said: “What caught our attention was that results obtained using RelTime were in strong disagreement with a diversity of different studies, from different research groups and that used different software and data, all of which broadly agreed that animals are unlikely to be older than approximately 850 million years.”

Dr Mario dos Reis, a co-author from London, added: “Generally scientists use Bayesian methods to relax the clock. These methods use explicit probability models to account for the uncertainty in the fossil record and in the mutation rate.

“Bayesian methods borrow tools from financial mathematics to model variation in mutation rate in a way that is similar to that used to model the stochastic variation in stock prices with time.

“By applying these sophisticated mathematical tools, Bayesian methods relax the clock and estimate divergence times. However, RelTime is not a Bayesian method.”

Dr Jesus Lozano-Fernandez, also from the University of Bristol, added: “Estimating divergence times is difficult and different relaxed molecular clock methods use different approaches to do so. However, we discovered that the RelTime algorithm failed to relax the clock along the deepest branches of the animal tree of life.”

Bristol’s Professor Davide Pisani concluded: “Current Bayesian methods date the last common animal ancestor to less than approximately 850 millions of years ago, in relatively good agreement with the fossil record.

“RelTime suggested that animals are much older but it turned out that it suffers from the same problems of the early clock methods.

“This clearly indicates that older ideas suggesting that animals might be twice or three times as old as the oldest animal fossil are erroneous and only emerge when changes in mutation rate are incorrectly estimated.

“RelTime results sounded like a blast from the past, but their provably erroneous nature ended up blasting these same old ideas that they were trying to revive.”

Source – Sciencedaily

WFS News: Palaeontologist William Fox’s dinosaur fossil finds displayed

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

Rev William Fox had four dinosaurs named after him

Rev William Fox had four dinosaurs named after him

Fossils discovered by a Victorian clergyman who had four dinosaurs named after him are being exhibited on the Isle of Wight.

Among Rev William Fox’s finds was one of the first, almost complete dinosaur fossils – a partial skeleton of a plant-eating Hypsilophodon foxii.Some of his fossils are being displayed at Sandown’s Dinosaur Isle Museum.

A walking trail of routes in Brighstone that Fox used when making his discoveries has also been launched.

Dr Martin Munt, curator of the museum, said it was “an opportunity for island residents to learn more about our wonderful heritage”.

The events have been funded by the Royal Society’s Local Heroes scheme, which provides cash for exhibitions and events that reveal stories of “scientific brilliance”, Isle of Wight Council said.

The authority said prior to this recognition “a barely marked grave” and an “improvised plaque” were all that remained to mark Fox’s life.

The four dinosaurs named after Fox:

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

  • Polacanthus foxii, 1865 – a 5m (16ft)-long armoured dinosaur
  • Polacanthus foxii

    Polacanthus foxii

  • @WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev
  • Hypsilophodon foxii, 1869 – a 2m (6.5ft)-long small ornithopod
  • Hypsilophodon foxii

    Hypsilophodon foxii

  • @WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev
  • Eucamerotus foxii, 1872 – a sauropod dinosaur of uncertain size
  • Eucamerotus foxii

                      Eucamerotus foxii

  • @WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev
  • Calamospondylus foxii, 1889 – a small carnivorous dinosaur about 3.5m (11ft)-long
  • Calamospondylus foxii

    Calamospondylus foxii

Copies of the Fox walking trail map are available as free downloads from the Dinosaur Isle Museum website.

Source:Article in BBC News

@WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

How X-rays Helped to Solve Mystery of Floating Rocks

It’s true—some rocks can float on water for years at a time. And now scientists know how they do it, and what causes them to eventually sink.

X-ray studies at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have helped scientists to solve this mystery by scanning inside samples of lightweight, glassy, and porous volcanic rocks known as pumice stones. The X-ray experiments were performed at Berkeley Lab’s Advanced Light Source (ALS), an X-ray source known as a synchrotron.

The surprisingly long-lived buoyancy of these rocks—which can form miles-long debris patches on the ocean known as pumice rafts that can travel for thousands of miles—can help scientists discover underwater volcano eruptions.

In this 2006 satellite image, a large “raft” of floating pumice stones (beige) appears following a volcanic eruption in the Tonga Islands. (Credit: Jesse Alan/NASA Earth Observatory, Goddard Space Flight Center)

In this 2006 satellite image, a large “raft” of floating pumice stones (beige) appears following a volcanic eruption in the Tonga Islands. (Credit: Jesse Alan/NASA Earth Observatory, Goddard Space Flight Center)

And, beyond that, learning about its flotation can help us understand how it spreads species around the planet; pumice is nutrient rich and readily serves as a seafaring carrier of plant life and other organisms. Floating pumice can also be a hazard for boats, as the ashy mixture of ground-up pumice can clog engines.

“The question of floating pumice has been around the literature for a long time, and it hadn’t been resolved,” said Kristen E. Fauria, a UC Berkeley graduate student who led the study, published in Earth and Planetary Science Letters.

While scientists have known that pumice can float because of pockets of gas in its pores, it was unknown how those gases remain trapped inside the pumice for prolonged periods. If you soak up enough water in a sponge, for example, it will sink.

“It was originally thought that the pumice’s porosity is essentially sealed,” Fauria said, like a corked bottle floating in the sea. But pumice’s pores are actually largely open and connected—more like an uncorked bottle. “If you leave the cap off and it still floats … what’s going on?”

Some pumice stones have even been observed to “bob” in the laboratory—sinking during the evening and surfacing during the day.

To understand what’s at work in these rocks, the team used wax to coat bits of water-exposed pumice sampled from Medicine Lake Volcano near Mount Shasta in Northern California and Santa María Volcano in Guatemala.

They then used an X-ray imaging technique at the ALS known as microtomography to study concentrations of water and gas—in detail measured in microns, or thousandths of a millimeter—within preheated and room-temperature pumice samples.

The detailed 3-D images produced by the technique are very data-intensive, which posed a challenge in quickly identifying the concentrations of gas and water present in the pumice samples’ pores.

To tackle this problem, Zihan Wei, a visiting undergraduate researcher from Peking University, used a data-analysis software tool that incorporates machine learning to automatically identify the gas and water components in the images.

Concentrations of liquid and gas in samples of pumice stones are labeled in these images, produced by X-ray microtomography at Berkeley Lab’s Advanced Light Source. The images assisted researchers in identifying the mechanisms that enable pumice to float for prolonged periods. Heated pumice (shown in images at the top right and bottom right) samples contain a smaller volume of trapped gas than room-temperature samples. (Credit: UC Berkeley, Berkeley Lab)

Concentrations of liquid and gas in samples of pumice stones are labeled in these images, produced by X-ray microtomography at Berkeley Lab’s Advanced Light Source. The images assisted researchers in identifying the mechanisms that enable pumice to float for prolonged periods. Heated pumice (shown in images at the top right and bottom right) samples contain a smaller volume of trapped gas than room-temperature samples. (Credit: UC Berkeley, Berkeley Lab)

Researchers found that the gas-trapping processes that are in play in the pumice stones relates to “surface tension,” a chemical interaction between the water’s surface and the air above it that acts like a thin skin—this allows some creatures, including insects and lizards, to actually walk on water.

“The process that’s controlling this floating happens on the scale of human hair,” Fauria said. “Many of the pores are really, really small, like thin straws all wound up together. So surface tension really dominates.”

The team also found that a mathematical formulation known as percolation theory, which helps to understand how a liquid enters a porous material, provides a good fit for the gas-trapping process in pumice. And gas diffusion—which describes how gas molecules seek areas of lower concentration—explains the eventual loss of these gases that causes the stones to sink.

Individual gas bubbles trapped in two pumice samples (labeled “ML01” and “SM01”) are shaded with different colors. The size and connectedness of the bubbles can vary widely within a sample. (Credit: UC Berkeley, Berkeley Lab)

Individual gas bubbles trapped in two pumice samples (labeled “ML01” and “SM01”) are shaded with different colors. The size and connectedness of the bubbles can vary widely within a sample. (Credit: UC Berkeley, Berkeley Lab)

Michael Manga, a staff scientist in Berkeley Lab’s Energy Geosciences Division and a professor in the Department of Earth and Planetary Science at UC Berkeley who participated in the study, said, “There are two different processes: one that lets pumice float and one that makes it sink,” and the X-ray studies helped to quantify these processes for the first time. The study showed that previous estimates for flotation time were in some cases off by several orders of magnitude.

“Kristen had the idea that in hindsight is obvious,” Manga said, “that water is filling up only some of the pore space.” The water surrounds and traps gases in the pumice, forming bubbles that make the stones buoyant. Surface tension serves to keep these bubbles locked inside for prolonged periods. The bobbing observed in laboratory experiments of pumice floatation is explained by trapped gas expanding during the heat of day, which causes the stones to temporarily float until the temperature drops.

The X-ray work at the ALS, coupled with studies of small pieces of pumice floating in water in Manga’s UC Berkeley lab, helped researchers to develop a formula for predicting how long a pumice stone will typically float based on its size. Manga has also used an X-ray technique at the ALS called microdiffraction, which is useful for studying the origins of crystals in volcanic rocks.

Dula Parkinson, a research scientist at Berkeley Lab’s ALS who assisted with the team’s microtomography experiments, said, “I’m always amazed at how much information Michael Manga and his collaborators are able to extract from the images they collect at ALS, and how they’re able to join that information with other pieces to solve really complicated puzzles.”

These 3-D printed models show a magnified sample of pumice (black) and a large concentration of gas (white) filling interconnected pores within that pumice sample. (Credit: Berkeley Lab)

These 3-D printed models show a magnified sample of pumice (black) and a large concentration of gas (white) filling interconnected pores within that pumice sample. (Credit: Berkeley Lab)

The recent study triggered more questions about floating pumice, Fauria said, such as how pumice, ejected from deep underwater volcanoes, finds its way to the surface. Her research team has also conducted X-ray experiments at the ALS to study samples from so-called “giant” pumice that measured more than a meter long.

That stone was recovered from the sea floor in the area of an active underwater volcano by a 2015 research expedition that Fauria and Manga participated in. The expedition, to a site hundreds of miles north of New Zealand, was co-led by Rebecca Carey, a scientist formerly affiliated with the Lab’s ALS.

Underwater volcano eruptions are not as easy to track down as eruptions on land, and floating pumice spotted by a passenger on a commercial aircraft actually helped researchers track down the source of a major underwater eruption that occurred in 2012 and motivated the research expedition. Pumice stones spewed from underwater volcano eruptions vary widely in size but can typically be about the size of an apple, while pumice stones from volcanoes on land tend to be smaller than a golf ball.

“We’re trying to understand how this giant pumice rock was made,” Manga said. “We don’t understand well how submarine eruptions work. This volcano erupted completely different than we hypothesized. Our hope is that we can use this one example to understand the process.”

Fauria agreed that there is much to learn from underwater volcano studies, and she noted that X-ray studies at the ALS will play an ongoing role in her team’s work.

The Advanced Light Source is a DOE Office of Science User Facility. This work was supported by the U.S. National Science Foundation.

Whales only recently evolved into giants!!!

The blue whale, which uses baleen to filter its prey from ocean water and can reach lengths of over 100 feet, is the largest vertebrate animal that has ever lived. On the list of the planet’s most massive living creatures, the blue whale shares the top ranks with most other species of baleen whales alive today. According to new research from scientists at the Smithsonian’s National Museum of Natural History, however, it was only recently in whale’s evolutionary past that they became so enormous.

In a study reported May 24 in Proceedings of the Royal Society B, Nicholas Pyenson, the museum’s curator of fossil marine mammals, and collaborators Graham Slater at the University of Chicago and Jeremy Goldbogen at Stanford University, traced the evolution of whale size through more than 30 million years of history and found that very large whales appeared along several branches of the family tree about 2 to 3 million years ago. Increasing ice sheets in the Northern Hemisphere during this period likely altered the way whales’ food was distributed in the oceans and enhanced the benefits of a large body size, the scientists say.

Blue whale surface feeding. Credit: © michaelpeak / Fotolia

Blue whale surface feeding.
Credit: © michaelpeak / Fotolia

How and why whales got so big has remained a mystery until now, in part because of the challenges of interpreting an incomplete fossil record. “We haven’t had the right data,” Pyenson said. “How do you measure the total length of a whale that’s represented by a chunk of fossil?” Recently, however, Pyenson established that the width of a whale’s skull is a good indicator of its overall body size. With that advance, the time was right to address the long-standing question.

The Smithsonian holds the largest and richest skull collections for both living and extinct baleen whales, and the museum was one of the few places that housed a collection that could provide the raw data needed to examine the evolutionary relationships between whales of different sizes. Pyenson and his colleagues measured a wide range of fossil skulls from the National Museum of Natural History’s collections and used those measurements, along with published data on additional specimens, to estimate the length of 63 extinct whale species. The fossils included in the analysis represented species dating back to the earliest baleen whales, which lived more than 30 million years ago. The team used the fossil data, together with data on 13 species of modern whales, to examine the evolutionary relationships between whales of different sizes. Their data clearly showed that the large whales that exist today were not present for most of whales’ history. “We live in a time of giants,” Goldbogen said. “Baleen whales have never been this big, ever.”

The research team traced the discrepancy back to a shift in the way body size evolved that occurred about 4.5 million years ago. Not only did whales with bodies longer than 10 meters (approximately 33 feet) begin to evolve around this time, but smaller species of whales also began to disappear. Pyenson notes that larger whales appeared in several different lineages around the same time, suggesting that massive size was somehow advantageous during that timeframe.

“We might imagine that whales just gradually got bigger over time, as if by chance, and perhaps that could explain how these whales became so massive,” said Slater, a former Peter Buck postdoctoral fellow at the museum. “But our analyses show that this idea doesn’t hold up — the only way that you can explain baleen whales becoming the giants they are today is if something changed in the recent past that created an incentive to be a giant and made it disadvantageous to be small.”

This evolutionary shift, which took place at the beginning of the Ice Ages, corresponds to climatic changes that would have reshaped whales’ food supply in the world’s oceans. Before ice sheets began to cover the Northern Hemisphere, food resources would have been fairly evenly distributed throughout the oceans, Pyenson said. But when glaciation began, run off from the new ice caps would have washed nutrients into coastal waters at certain times of the year, seasonally boosting food supplies.

At the time of this transition, baleen whales, which filter small prey, like krill, out of seawater, were well equipped to take advantage of these dense patches of food. Goldbogen, whose studies of modern whale foraging behavior have demonstrated that filter-feeding is particularly efficient when whales have access to very dense aggregations of prey, said the foraging strategy becomes even more efficient as body size increases.

What’s more, large whales can migrate thousands of miles to take advantage of seasonally abundant food supplies. So, the scientists said, baleen whales’ filter-feeding systems, which evolved about 30 million years ago, appear to have set the stage for major size increases once rich sources of prey became concentrated in particular locations and times of year.

“An animal’s size determines so much about its ecological role,” Pyenson said. “Our research sheds light on why today’s oceans and climate can support Earth’s most massive vertebrates. But today’s oceans and climate are changing at geological scales in the course of human lifetimes. With these rapid changes, does the ocean have the capacity to sustain several billion people and the world’s largest whales? The clues to answer this question lie in our ability to learn from Earth’s deep past — the crucible of our present world — embedded in the fossil record.”

Funding for this study was provided by the Smithsonian’s Remington Kellogg Fund and with support from the Basis Foundation.

Source: sciencedaily

Key: WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

WFS News: New species of bus-sized fossil marine reptile unearthed in Russia

Key: WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

A new species of a fossil pliosaur (large predatory marine reptile from the ‘age of dinosaur’) has been found in Russia and profoundly change how we understand the evolution of the group, says an international team of scientists.

Spanning more than 135 Ma during the ‘Age of Dinosaurs’, plesiosaur marine reptiles represent one of longest-lived radiations of aquatic tetrapods and certainly the most diverse one. Plesiosaurs possess an unusual body shape not seen in other marine vertebrates with four large flippers, a stiff trunk, and a highly varying neck length. Pliosaurs are a special kind of plesiosaur that are characterized by a large, 2m long skull, enormous teeth and extremely powerful jaws, making them the top predators of oceans during the ‘Age of Dinosaurs’.

This is an artistic reconstruction of Luskhan itilensis. Credit: Copyright Andrey Atuchin, 2017

This is an artistic reconstruction of Luskhan itilensis. Credit: Copyright Andrey Atuchin, 2017

In a new study to be published today in the journal Current Biology, the team reports a new, exceptionally well-preserved and highly unusual pliosaur from the Cretaceous of Russia (about 130 million years ago). It has been found in Autumn 2002 on right bank of the Volga River, close to the city of Ulyanovsk, by Gleb N. Uspensky (Ulyanovsk State University), one of the co-authors of the paper. The skull of the new species, dubbed “Luskhan itilensis,” meaning the Master Spirit from the Volga river, is 1.5m in length, indicating a large animal. But its rostrum is extremely slender, resembling that of fish-eating aquatic animals such as gharials or some species of river dolphins. “This is the most striking feature, as it suggests that pliosaurs colonized a much wider range of ecological niches than previously assumed” said Valentin Fischer, lecturer at the Université de Liège (Belgium) and lead author of the study.

By analysing two new and comprehensive datasets that describe the anatomy and ecomorphology of plesiosaurs with cutting edge techniques, the team revealed that several evolutionary convergences (a biological phenomenon where distantly related species evolve and resemble one another because they occupy similar roles, for example similar feeding strategies and prey types in an ecosystem) took place during the evolution of plesiosaurs, notably after an important extinction event at the end of the Jurassic (145 million years ago). The new findings have also ramifications in the final extinction of pliosaurs, which took place several tens of million years before that of all dinosaurs (except some bird lineages). Indeed, the new results suggest that pliosaurs were able to bounce back after the latest Jurassic extinction, but then faced another extinction that would — this time — wipe them off the depths of ancient oceans, forever.

Journal Reference:

  1. Fischer Valentin, Benson Roger B J, Zverkov Nikolai G, Soul Laura C, Arkhangelsky Maxim S, Lambert Olivier, Stenshin Ilya M, Uspensky Gleb N & Druckenmiller Patrick S. Plasticity and convergence in the evolution of short-necked plesiosaurs. Current Biology, 2017 DOI: 10.1016/j.cub.2017.04.052
University of Liege. “New species of bus-sized fossil marine reptile unearthed in Russia.” ScienceDaily. ScienceDaily, 25 May 2017. <www.sciencedaily.com/releases/2017/05/170525125617.htm>.
Key: WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev