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How archaeologist created a prehistoric GPS for tracking ancient humans

Credit: Image courtesy of University of Florida
Credit: Image courtesy of University of Florida

Where’s the best place to start when retracing the life of a person who lived 4,000 years ago? Turns out, it’s simple — you start at the beginning.

Using a method known for helping forensic scientists solve cold cases, University of Florida doctoral student Ashley Sharpe created a map for determining the birthplace of ancient people and animals in Central America. Archaeologists will use the map to match lead found in bedrock from specific locations to a curious source: millennia-old teeth.

Pinpointing birth and death locations will help Sharpe and other archaeologists track the movement of prehistoric Maya and potentially solve mysteries surrounding the civilization’s origins and eventual demise.

Sharpe sampled lead isotope values found in rocks, which act as local signatures, from the Chicxulub crater in the Yucatán Peninsula–the site of the asteroid impact that wiped out the dinosaurs–and places in Belize, Guatemala and Honduras. Details of the new study are described in the November issue of PLOS ONE.

“If I find an ancient Maya individual buried on the Yucatan in Mexico, I can do a chemical analysis of the lead in their teeth and discover a very different story,” said Sharpe, who graduates from UF’s department of anthropology and the environmental archaeology program at the Florida Museum of Natural History on the UF campus this fall. “Maybe they originally came from Guatemala. This can change our view of everything.”

When our tooth enamel forms during childhood, it incorporates elements from the local environment, including the dust we breathe from rock layers beneath our feet. Bones, on the other hand, change every few years. And as we decompose, our bones soak up materials around the area we’re buried like a sponge.

As the hardest substance in the human body, tooth enamel is different. It offers a window into life histories.

Tracing the movement of individuals via their teeth can offer clues about marriage alliances and slavery practices. Building knowledge of individual lives helps archaeologists figure out which villages were enemies, which were allies, and how the Maya communicated and traveled between cities. This could lead to a better understanding of how communication networks developed between Maya states, Sharpe said.

Previously, UF forensic anthropologists used lead analysis to trace the birthplace of unidentified homicide victims. UF archaeologists have also used lead to track ancient humans in the Indus Valley Civilization.

UF forensic anthropologists are using lead analysis to trace the birthplace of unidentified homicide victims, which can help police investigators narrow their search for missing persons to a particular state, country or region. Other archaeologists at UF have included lead analysis in research used to track ancient humans from the Indus Valley Civilization.

“The anthropology department here at UF is becoming a hub for lead-based research,” Sharpe said. “In other words, we’re the place to go if you need to track the origins an ancient or modern skeleton.”

Researchers extract lead by first grinding up teeth, then inserting the particles into an inductively coupled plasma mass spectrometer. Temperatures inside the machine can be hotter than the sun, separating the lead.

Pollution makes using lead to identify the birthplace of modern people more complicated.

If someone unearthed the remains of a native Floridian 1,000 years from now, the lead in their teeth would probably be the same as someone from across the country because we all breathe similar pollution, which contaminates the lead, said study co-author John Krigbaum, a biological anthropologist at UF.

“Back in prehistoric times, people were a product of the lands that they grew up on, the foods that they ate and the air they breathed,” Krigbaum said. “That’s also the case today.”

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

Giant ‘great valley’ found on Mercury

Using colorized topography, Mercury's 'great valley' (dark blue) and Rembrandt impact basin (purple, upper right) are revealed in this high-resolution digital elevation model merged with an image mosaic obtained by NASA's MESSENGER spacecraft. Credit: NASA/JHUAPL/Carnegie Institution of Washington/DLR/Smithsonian Institution
Using colorized topography, Mercury’s ‘great valley’ (dark blue) and Rembrandt impact basin (purple, upper right) are revealed in this high-resolution digital elevation model merged with an image mosaic obtained by NASA’s MESSENGER spacecraft.
Credit: NASA/JHUAPL/Carnegie Institution of Washington/DLR/Smithsonian Institution

A newly discovered giant valley on the planet Mercury makes the Grand Canyon look tiny by comparison. Located by scientists at the University of Maryland, the Smithsonian Institution, the German Institute of Planetary Research and Moscow State University, the expansive valley holds an important key to the geologic history of the innermost planet in our solar system.

Discovered using stereo images from NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, the “great valley” lies in the planet’s southern hemisphere and overlaps the Rembrandt Basin–a large crater formed by a relatively recent impact from an asteroid or other such body. But the “great valley” formed in a much different way, according to a research paper published online November 16, 2016 in the journal Geophysical Research Letters.

Unlike Earth, which has a crust and upper mantle (collectively known as the lithosphere) divided into multiple tectonic plates, Mercury has a single, solid lithosphere that covers the entire planet. As the planet cooled and shrank early in its history, roughly 3-4 billion years ago, Mercury’s lithosphere buckled and folded to form the valley, much like the skin of a grape folds as it dries to become a raisin.

“This is a huge valley. There is no evidence of any geological formation on Earth that matches this scale,” said Laurent Montesi, an assistant professor of geology at UMD and a co-author of the research paper. “Mercury experienced a very different type of deformation than anything we have seen on Earth. This is the first evidence of large-scale buckling of a planet.”

The valley is about 250 miles wide and 600 miles long, with steep sides that dip as much as 2 miles below the surrounding terrain. To put this in perspective: if Mercury’s “great valley” existed on Earth, it would be almost twice as deep as the Grand Canyon and reach from Washington, D.C. to New York City, and as far west as Detroit.

More notable than its size, according to Montesi, is how the valley most likely formed and what that reveals about Mercury’s geologic history.

The valley’s walls appear to be two large, parallel fault scarps–step-like structures where one side of a fault moved vertically with respect to the other. Both scarps plunge steeply to the flat valley floor below. According to Montesi and his co-authors, the best explanation is that Mercury’s interior cooled rapidly, forming a strong, thick lithosphere. The entire floor of the newly discovered valley is one giant piece of this lithosphere that dropped between the two faults on either side.

This would make sense if, like most planets, Mercury has been steadily cooling since its formation. But Montesi notes that there are several clues to suggest that Mercury went through a more recent period of warming. This analysis, if true, would upend some time-tested assumptions about Mercury’s geologic past.

“Most features on Mercury’s surface are truly ancient, but there is evidence for recent volcanism and an active magnetic field. This evidence implies that the planet is warm inside,” Montesi said. “Everyone thought Mercury was a very cold planet–myself included. But it looks like Mercury might have heated significantly in recent planetary history.”

Reference:
“Fault-bound Valley Associated with the Rembrandt Basin on Mercury,” Thomas Watters, Laurent Montési, Ju?rgen Oberst, and Frank Preusker, was first published online November 16, 2016 in the journal Geophysical Research Letters. DOI: 10.1002/2016GL070205

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

Asteroid impacts could create niches for early life, suggests Chicxulub crater study

Recovered core from the Chicxulub impact crater. Credit: DSmith@ECORD
Recovered core from the Chicxulub impact crater. Credit: DSmith@ECORD

Scientists studying the Chicxulub crater have shown how large asteroid impacts deform rocks in a way that may produce habitats for early life.

Around 65 million years ago a massive asteroid crashed into the Gulf of Mexico causing an impact so huge that the blast and subsequent knock-on effects wiped out around 75 per cent of all life on Earth, including most of the dinosaurs. This is known as the Chicxulub impact.

In April and May 2016, an international team of scientists undertook an offshore expedition and drilled into part of the Chicxulub impact crater. Their mission was to retrieve samples from the rocky inner ridges of the crater — known as the ‘peak ring’ — drilling 506 to 1335 metres below the modern day sea floor to understand more about the ancient cataclysmic event.

Now, the researchers have carried out the first analysis of the core samples. They found that the impact millions of years ago deformed the peak ring rocks in such a way that it made them more porous, and less dense, than any models had previously predicted.

Porous rocks provide niches for simple organisms to take hold, and there would also be nutrients available in the pores, from circulating water that would have been heated inside the Earth’s crust. Early Earth was constantly bombarded by asteroids, and the team have inferred that this bombardment must have also created other rocks with similar physical properties. This may partly explain how life took hold on Earth.

The study, which is published today in the journal Science, also confirmed a model for how peak rings were formed in the Chicxulub crater, and how peak rings may be formed in craters on other planetary bodies.

The team’s new work has confirmed that the asteroid, which created the Chicxulub crater, hit the Earth’s surface with such a force that it pushed rocks, which at that time were ten kilometres beneath the surface, farther downwards and then outwards. These rocks then moved inwards again towards the impact zone and then up to the surface, before collapsing downwards and outwards again to form the peak ring. In total they moved an approximate total distance of 30 kilometres in a matter of a few minutes.

Professor Joanna Morgan, lead author of the study from the Department of Earth Science and Engineering, said: “It is hard to believe that the same forces that destroyed the dinosaurs may have also played a part, much earlier on in Earth’s history, in providing the first refuges for early life on the planet. We are hoping that further analyses of the core samples will provide more insights into how life can exist in these subterranean environments.”

The next steps will see the team acquiring a suite of detailed measurements from the recovered core samples to refine their numerical simulations. Ultimately, the team are looking for evidence of modern and ancient life in the peak-ring rocks. They also want to learn more about the first sediments that were deposited on top of the peak ring, which could tell the researchers if they were deposited by a giant tsunami, and provide them with insights into how life recovered, and when life actually returned to this sterilised zone after the impact.

Reference:
Joanna V. Morgan, Sean P. S. Gulick, Timothy Bralower, Elise Chenot, Gail Christeson, Philippe Claeys, Charles Cockell, Gareth S. Collins, Marco J. L. Coolen, Ludovic Ferrière, Catalina Gebhardt, Kazuhisa Goto, Heather Jones, David A. Kring, Erwan Le Ber, Johanna Lofi, Xiao Long, Christopher Lowery, Claire Mellett, Rubén Ocampo-Torres, Gordon R. Osinski, Ligia Perez-Cruz, Annemarie Pickersgill, Michael Poelchau, Auriol Rae, Cornelia Rasmussen, Mario Rebolledo-Vieyra, Ulrich Riller, Honami Sato, Douglas R. Schmitt, Jan Smit, Sonia Tikoo, Naotaka Tomioka, Jaime Urrutia-Fucugauchi, Michael Whalen, Axel Wittmann, Kosei E. Yamaguchi, William Zylberman. The formation of peak rings in large impact craters. Science, 2016 DOI: 10.1126/science.aah6561

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

Study finds Earth’s soils hosted life early

Abandoned pit at Mount Goldsworthy near Mount Grant in Western Australia Credit: Philip Schubert, Creative Commons
Abandoned pit at Mount Goldsworthy near Mount Grant in Western Australia
Credit: Philip Schubert, Creative Commons

Way before trees or lichens evolved, soils on Earth were alive, as revealed by a close examination of microfossils in the desert of northwestern Australia, reports a team of University of Oregon researchers.

These tiny fossils require a microscope to see and probably represent whole organisms. The 3,000 million-year-old Australian rocks have long been thought to be of marine origin. However, “a closer look at the dusty salt minerals of the rocks suggests they had to have experienced evaporation on land,” said UO paleontologist Gregory Retallack, lead author on a study in the December issue of the international journal Gondwana Research.

Other mineral and chemical tracers found in the rocks also required weathering in soils of the distant geological past, he said.

“Life was not only present but thriving in soils of the early Earth about two thirds of the way back to its formation from the solar nebula,” Retallack said. The origin of the solar system — and Earth — occurred some 4.6 billion years ago.

The study outlines a microbiome of at least five different kinds of microfossils recognized from their size, shape and isotopic compositions. The largest and most distinctive microfossils are spindle-shaped hollow structures of mold-like actinobacteria, still a mainly terrestrial group of decomposers that are responsible for the characteristic earthy smell of garden soil.

Other sphere-shaped fossils are similar to purple sulfur bacteria, which photosynthesize organic compounds in the absence of oxygen while leaving abundant sulfate minerals in the soil.

“With cell densities of over 1,000 per square millimeter and a diversity of producers and consumers, these microfossils represent a functioning terrestrial ecosystem, not just a few stray cells,” said Retallack, a professor in the Department of Earth Sciences and director of paleontology collections at the Museum of Natural and Cultural History. “They are evidence that life in soils was critical to the cycles of carbon, phosphorus, sulfur and nitrogen very early in the history of the planet.”

The new discoveries by the UO team are potentially controversial because many scientists have long pointed to stromatolites, a life form that emerged 3.7 billion years ago, and other marine life as evidence of life that evolved in the sea and found their way into intertidal rock formations.

Retallack referred to the memoir “Lab Girl” published this year by Hope Jahren, a geobiologist at the University of Hawaii, who wrote: “For several billion years, the whole of the Earth’s land surface was completely barren. Even after life had richly populated the oceans, there is no clear evidence for any life on land.”

“The newly recognized microfossils may have supplied some evidence at last,” Retallack said.

The ancient soils with sulfate salts and microfossils come from the Pilbara region of Western Australia. They are superficially similar to those found recently by the Mars rover Curiosity. “They may,” he said, “be useful as guides for the discovery of life on other planets.”

Critical to the new discoveries were advanced imaging and analyses performed with the cluster of instruments in the Center for Advanced Materials Characterization of Oregon, commonly known as CAMCOR, at the UO.

Reference:
Gregory J. Retallack, David H. Krinsley, Robert Fischer, Joshua J. Razink, Kurt A. Langworthy. Archean coastal-plain paleosols and life on land. Gondwana Research, 2016; 40: 1 DOI: 10.1016/j.gr.2016.08.003

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

Modelling Gondwana break-up

Credit: British Antarctic Survey
Credit: British Antarctic Survey

Gondwana break-up changed the global continental configuration, leading to the opening of major oceanic gateways, shifts in the climate system and significant impacts on the biosphere, hydrosphere and cryosphere.

Although of global importance, the earliest stages of the supercontinental fragmentation are poorly understood. Reconstructing the processes driving Gondwana break-up within the ice-covered Weddell Sea Rift System (WSRS) has proven particularly challenging. Here we present new compilations of airborne magnetic and airborne gravity data, together with digital enhancements and 2D models, enabling us to re-evaluate the crustal architecture of the WSRS and its tectonic and kinematic evolution.

Although geophysically favoured, our new model cannot easily be reconciled with geological and paleomagnetic interpretations, however, our model provides a simpler view of the WSRS as a broad Jurassic extensional/transtensional province within a distributed plate boundary between East and West Antarctica.

Reference:
T.A. Jordan et al. New geophysical compilations link crustal block motion to Jurassic extension and strike-slip faulting in the Weddell Sea Rift System of West Antarctica, Gondwana Research (2017). DOI: 10.1016/j.gr.2016.09.009

Note: The above post is reprinted from materials provided by British Antarctic Survey.

Seismologists warn of more quakes in New Zealand

People walking to a helicopter with their suitcases as hundreds of tourists were evacuated from Kaikoura, after an earthquake hit New Zealand
People walking to a helicopter with their suitcases as hundreds of tourists were evacuated from Kaikoura, after an earthquake hit New Zealand

Seismologists in New Zealand said Friday that this week’s 7.8 earthquake was one of the most complex ever recorded and warned there was a high likelihood of further powerful aftershocks.

As a massive clean-up continued following the tremor that claimed two lives early Monday, scientists were coming to grips with the “astonishing” scale of the seismic seizure.

The official GeoNet science agency said the land moved up to 11 metres (36 feet) along the many faultlines in the South Island disaster zone, permanently changing the region’s geography.

The quake also pushed up the seabed by as much as two metres along a 110 kilometre (70 mile) stretch of coastline that includes the tourist town of Kaikoura.

GeoNet said the quake ruptured at least four faults and was “clearly… one of the most complex earthquakes that has ever been observed”.

New Zealand is on the boundary of the Australian and Pacific tectonic plates, which form part of the so-called “Ring of Fire”, and experiences up to 15,000 tremors a year.

There have been well over 2,000 aftershocks since Monday and the agency said statistical analysis showed residents should prepare for more major shakes in the coming weeks.

The current probability of quakes of magnitude 6.0 and above hitting in the next month was “about 100 times larger than what we would normally expect”, it said.

The warning came as warships from the United States, Canada and Australia began delivering emergency supplies to Kaikoura, which bore the brunt of the tremor.

A convoy of New Zealand military vehicles also reached the town by land for the first time, travelling via a back road after huge landslides cut the main highway and rail lines.

About 1,000 tourists were evacuated from Kaikoura by air and sea in the days after the quake but some 2,000 locals still face difficult conditions.

The occupants of eight houses were ordered to flee their homes early Wednesday amid fears a cliff could fall on them following heavy rains.

Authorities also warned that some rain-swollen rivers had been blocked by quake debris, creating dangerous temporary dams.

“Landslide dams can break quickly, and release large volumes of water and sediment as a flood wave,” Civil Defence director Sarah Stuart-Black said.

The tremor was felt across the country, causing violent shaking in Wellington about 250 kilometres (155 miles) away.

Many buildings in the capital have been sealed off amid fears they have sustained structural damage, including an office block housing the defence department’s headquarters.

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

Study reveals two seismic processes by which hydraulic fracturing induces tremors

The researchers' image of seismic activity reveals a pre-existing but previously undetected fault system running parallel to two horizontally drilled wells. In one strand of the fault, hydraulic fracturing in both wells triggered small earthquakes by imposing mechanical stresses on the rock formations beneath the hydrocarbons-bearing zone — causing the fault to slip. However, in another strand of the fault — and more than two weeks after hydraulic fracturing injections had stopped — the magnitude 3.9 earthquake occurred at a calculated depth of just over four kilometres. This places the event within the upper levels of Precambrian basement rocks. Subsequent smaller seismic events persisted for a few months afterward, as the seismic activity migrated slowly from the basement back up toward the injection zone. Credit: University of Calgary
The researchers’ image of seismic activity reveals a pre-existing but previously undetected fault system running parallel to two horizontally drilled wells. In one strand of the fault, hydraulic fracturing in both wells triggered small earthquakes by imposing mechanical stresses on the rock formations beneath the hydrocarbons-bearing zone — causing the fault to slip. However, in another strand of the fault — and more than two weeks after hydraulic fracturing injections had stopped — the magnitude 3.9 earthquake occurred at a calculated depth of just over four kilometres. This places the event within the upper levels of Precambrian basement rocks. Subsequent smaller seismic events persisted for a few months afterward, as the seismic activity migrated slowly from the basement back up toward the injection zone.
Credit: University of Calgary

In some parts of western Canada, small-to-moderate earthquakes have been induced by oil and gas hydraulic fracturing operations. In Alberta, this type of induced seismicity is mainly concentrated within an area located about 30 kilometres west of the town of Fox Creek.

Although a correlation between hydraulic fracturing and seismic events has been documented for over four years, a detailed mechanism has not been clearly understood — until now.

Indirect evidence has pointed to activation of pre-existing faults as the underlying physical mechanism, but precise delineation of these features has been elusive. Without this deeper understanding, formulation of strong mitigation and prevention strategies has been a challenge for regulators and operating companies alike.

Now, a new University of Calgary study, “Fault Activation by Hydraulic Fracturing in Western Canada,” is reported in Science, one of the world’s leading academic journals. In the most detailed study of this phenomenon to date, Faculty of Science researchers in the Department of Geoscience have successfully imaged some of the pre-existing fault architecture near hydraulic fracturing operations and discovered that activation can occur through two distinct processes.

“This study has provided extraordinary new details about processes of fault activation by pore pressure increase or stress changes. We can now begin to address important questions — the ‘how’ and ‘why’ of seismicity induced by hydraulic fracturing — that previously were not discernible,” says David Eaton, professor of geophysics and co-author of the study, with former postdoctoral scholar Xuewei Bao.

The research holds promise for establishing new ways to assess risk and mitigate the hazards of earthquakes induced by hydraulic fracturing, and to help in developing science-informed regulations for such operations.

‘Exquisitely detailed’ picture

Eaton and Bao collected and analyzed seismic data going back to the winter of 2015, when the first seismic event exceeding magnitude 4 on the Richter scale, occurred in the Fox Creek area. They compiled data from private and public seismograph stations in the area, monitors they installed after the earthquake, and also a comprehensive database of hydraulic fracturing data from each well in the area.

Using state-of-the-art techniques, Bao and Eaton created a database of 905 distinct events, most of which were too small to be part of existing seismicity catalogues. They were able to link seismic events to specific operations at individual wells, thanks to Repsol Oil and Gas Canada Inc. and Canadian Discovery Ltd., which provided data for the study. This university-industry partnership is crucial for researchers to gain access to data and to understand the fundamental processes.

“The combination of precise micro-earthquake locations and uniquely comprehensive data gave us an exquisitely detailed picture of the timing and dynamics of rupture nucleation,” Eaton says.

Bao, who did the “painstakingly detailed” data analysis, has since joined the faculty at Zhejiang University in China.

Two distinct seismic processes revealed

Their image of seismic activity reveals a pre-existing but previously undetected fault system running parallel to two horizontally drilled wells. In one strand of the fault, hydraulic fracturing in both wells triggered small earthquakes by imposing mechanical stresses on the rock formations beneath the hydrocarbons-bearing zone — causing the fault to slip.

In this case, movement on the fault effectively terminated when hydraulic fracturing operations ceased, consistent with existing regulatory protocols to halt operations under certain conditions, Eaton notes.

However, in another strand of the fault — and more than two weeks after hydraulic fracturing injections had stopped — the magnitude 3.9 earthquake occurred at a calculated depth of just over four kilometres. This places the event within the upper levels of Precambrian basement rocks. Subsequent smaller seismic events persisted for a few months afterward, as the seismic activity migrated slowly from the basement back up toward the injection zone.

The researchers’ findings indicate that this persistent activity appears to be associated with infiltration of fracturing fluids into one strand of the fault.

Distinction between stress-induced and fluid-induced seismicity

“We didn’t expect to observe contrasting signatures for stress-induced and fluid-induced seismicity,” Eaton says. “This distinction may have important ramifications for hazard mitigation, depending on which process is inducing seismic activity.”

Reference:
X. Bao et al. Fault activation by hydraulic fracturing in western Canada, Science (2016). DOI: 10.1126/science.aag2583

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

Composite skeleton of Dodo bird to be auctioned

A staff member holds a brush as she poses for photographs with a Dodo skeleton, Raphus cucullatus, from Mauritius at Summers Place Auctions in Billingshurst, southern England, Thursday, Nov. 17, 2016. The skeleton from the species extinct since the 17th century is the first to come up for sale in 100 years and is estimated to fetch upto 500,000 pounds ($624,445 or 581,546 euro) in the "Evolution" sale on November 22. Credit: AP Photo/Matt Dunham
A staff member holds a brush as she poses for photographs with a Dodo skeleton, Raphus cucullatus, from Mauritius at Summers Place Auctions in Billingshurst, southern England, Thursday, Nov. 17, 2016. The skeleton from the species extinct since the 17th century is the first to come up for sale in 100 years and is estimated to fetch upto 500,000 pounds ($624,445 or 581,546 euro) in the “Evolution” sale on November 22.
Credit: AP Photo/Matt Dunham

A dodo skeleton is about to take flight—at least at an auction.

Summers Place Auctions is selling what it describes as a rare composite skeleton of a dodo bird, a creature once found on the island of Mauritius in the Indian Ocean.

Sailors hunted the dodo into extinction in the 17th century and it has come to symbolize the harsh impact man can have on the world’s ecosystem. The bird’s name recognition was enhanced by Lewis Carroll, who included a dodo in “Alice’s Adventures in Wonderland.”

Auction house director Rupert van der Werff says the guide price for the skeleton to be auctioned Tuesday in Billinghurst is estimated to be between 300,000-500,000 pounds ($373,630 to $622,780) and that interest is high.

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

Mount Etna spews lava & ash “2013”

Mount Etna, Europe’s most active volcano, erupted on Nov 2013. The eruption shot up a towering column of ash and fire to light up the night sky over much of eastern Sicily. Several inhabited villages dot the mountain’s slopes. The latest lava flow didn’t endanger any houses, and no evacuation was ordered. Etna erupts occasionally, its last major eruption occurred in 1992.

Climate change may prevent volcanoes from cooling the planet

During Mount St. Helens’ eruption on May 18th, 1980 a vigorous plume of ash erupted and remained for more than nine hours, eventually reaching 12 to 15 miles (20–25 kilometers) above sea level. Shown here is a close-up view of the May 18 ash plume. Credit: Wikipedia
During Mount St. Helens’ eruption on May 18th, 1980 a vigorous plume of ash erupted and remained for more than nine hours, eventually reaching 12 to 15 miles (20–25 kilometers) above sea level. Shown here is a close-up view of the May 18 ash plume.
Credit: Wikipedia

New UBC research shows that climate change may impede the cooling effect of volcanic eruptions.

When an eruption is powerful enough, volcanoes spew sulfur gasses high into the atmosphere, reaching a layer called the stratosphere, about 10 to 15 kilometres above Earth’s surface. Here, gasses react with water to form aerosol particles that linger in the stratosphere for one or two years, reflecting sunlight and heat from the sun, and cooling the planet. On average, there are anywhere from three to five eruptions that reach the stratosphere every year.

Previous research has shown that as the planet warms, the lower layers of the atmosphere will expand, making it much harder for the gasses to reach the stratosphere. At lower levels, in the troposphere, the gasses quickly get turned into aerosols and clouds and precipitate back down to earth as rain or snow.

“Volcanic eruptions tend to counteract global warming but as the planet heats up and our atmosphere changes, we’ve found that fewer eruptions will be able to reflect the sun’s radiation,” said Thomas Aubry, a PhD student studying climate and volcanoes. “It will be harder for the volcanic gasses to reach high enough into atmosphere to help cool the planet.”

Aubry notes that while the planet continues to warm, scientists have observed a slight decline in the rate of global warming over the last 10 to 15 years. Previous studies have shown that this is partially caused by the number of large eruptions over the last decade that have sent sulfur gasses high up into the stratosphere.

For this study, Aubry, who is a PhD student in professor Mark Jellinek’s lab in the department of earth, ocean and atmospheric sciences, used models of volcanic eruptions and global climate to calculate the impact on gasses released from volcanic eruptions.

According to climate model projections and global warming, Aubry and his co-authors found the amount of volcanic sulfur gasses in the stratosphere will decrease anywhere from two to twelve per cent in the next 100 years. Longer term, they predict anywhere from 12 to 25 per cent less sulfur gas in the stratosphere by the 22nd and 23rd centuries. They say the range is large because it is difficult to predict future eruptions and future greenhouse gas emissions.

To determine the precise impact on Earth’s surface temperature in the future will require further study. It also raises interesting questions about Earth’s history.

“Understanding this positive feedback loop has provocative implications for understanding climate variability in Earth’s past,” said Jellinek. “In particular, this mechanism may have contributed to Earth’s entry into a long period of global glaciation around 700 million years ago, a theory known as the Snowball Earth hypothesis.”

This study was published today in the journal Journal of Geophysical Research: Atmosphere. This research was funded UBC, the Natural Sciences and Engineering Research Council of Canada and the Swiss National Science Foundation.

Reference:
Thomas J. Aubry, A. Mark Jellinek, Wim Degruyter, Costanza Bonadonna, Valentina Radić, Margot Clyne, Adjoa Quainoo. Impact of global warming on the rise of volcanic plumes and implications for future volcanic aerosol forcing. Journal of Geophysical Research: Atmosphere, 2016; DOI: 10.1002/2016JD025405

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

Seeing under Antarctica’s ice

Representative Image: A Glacier cave on Perito Moreno Glacier, in Los Glaciares National Park, southern Argentina. Credit: Martin St-Amant/Wikipedia
Representative Image: A Glacier cave on Perito Moreno Glacier, in Los Glaciares National Park, southern Argentina.
Credit: Martin St-Amant/Wikipedia

Although scientists have been studying Antarctica for many years, most research has focused on the conditions of Antarctica as they currently are. Based on this information, scientists have been able to make predictions on both what caused these conditions and how they are likely evolve in the future. But because our understanding of the icy continent is essentially limited to what happened over the last 100 years, our overall knowledge is surprisingly limited. To truly understand Antarctica, scientists must ‘see’ the continent’s geological and climatic history dating back to the late Quaternary period – a history that is literally frozen from sight.

Due to the Antarctic Ice Sheet (AIS) that covers the continent, land-based observations into its geological past remain largely unknown. However, scientists from the COMANT (Comminution dating of glacio-marine sediments in Antarctica and the Southern Ocean) project discovered that this geological information can be retrieved by studying the origins and transport times of eroded materials found in the marine sediment cores surrounding Antarctica. With this information, researchers can reconstruct the history of continental weathering, sediment transport mechanisms and timescales.

‘This project uses an innovative approach called comminution dating to determine spatial and temporal changes in the transport time of fine clastic sediments produced by Antarctic subglacial erosion during the late Quaternary period, which can be seen in the flux of ice and sediment discharged into the Southern Ocean,’ explains Project Lead Adi Torfstein.

Determining the comminution age

The COMANT project builds on recent results coming from the Weddell Sea showing that, depending on glacial-interglacial timescales, sediment transport times range between tens to hundreds of thousands of years. ‘Building on these preliminary results, I studied the comminution ages of a large number of glacial-marine deposits at sites across the Southern Ocean,’ says Torfstein. ‘This in turn allowed me to conduct a comprehensive study of natural and analytical biases on the comminution dating approach.’

The project focused their efforts on U-series disequilibrium in detrital material, which is a measurement of weathering and transport time. Once a rock fragment is ground to a small particle of only a few microns in diameter, which is something that happens very quickly in glacial settings, one of the isotopes of uranium (234U) is continuously lost from the rim of the particle due to radioactive decaying. ‘This loss of 234U is measurable and depends, amongst other things, on the known decay rate of uranium isotopes,’ says Torfstein.

According to Torfstein, this change, or loss of 234U, is a geological clock that can be used to estimate the age of formation of a particle (rather than the age of formation of a rock or mineral). The time elapsed between the formation of the particle and the present is known as the ‘comminution age’.

Better understanding Earth’s history

Although the project is ongoing, researchers expect results to provide the first systematic and wide-scale study of comminution ages in the Southern Ocean. As such, the study will expand the possibilities of dating continental deposits, leading to a better understanding of the fundamental aspects of sedimentology, glaciology and landscape evolution.

‘This is important because the comminution age of a particle is controlled by the interplay between climate change, the tectonic evolution of the continents and the efficiency of transport mechanisms on the continents and in the oceans,’ adds Torfstein. ‘Thus, comminution ages reflect the cumulative impact of processes that govern the shaping of the Earth’s surface over time, and by reconstructing these ages, we can better understand its history.’

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

Cliff erosion rates in Sussex have accelerated ten-fold in the past 200 years

The erosion rates along Beachy Head and Seaford Head in Sussex had remained relatively stable for thousands of years. However, around 200 to 600 years ago the rates rapidly accelerated, increasing to between 22 and 32 centimetres each year. Credit: Image courtesy of Imperial College London
The erosion rates along Beachy Head and Seaford Head in Sussex had remained relatively stable for thousands of years. However, around 200 to 600 years ago the rates rapidly accelerated, increasing to between 22 and 32 centimetres each year.
Credit: Image courtesy of Imperial College London

The erosion rates of cliffs along the Sussex coast have rapidly sped up in the last 200 years, a new study has found.

The research shows that the erosion rates along Beachy Head and Seaford Head in Sussex had remained relatively stable, at around two to six centimetres each year, for thousands of years. However, around 200 to 600 years ago the rates rapidly accelerated, increasing to between 22 and 32 centimetres each year.

The authors suggest that rising sea levels and increasingly severe storms have rapidly eroded the Beachy Head and Seaford Head shorelines. The loss of beach means that the cliffs are exposed to the eroding wave action forces, which is causing them to collapse into the sea. The researchers suggest this erosion process is probably happening along other coastlines in the UK and elsewhere around the world, with implications for how coasts will respond to climate change and what we can do to manage the impact on important coastal infrastructure.

Dr Dylan Rood, co-author from the Department of Earth Science and Engineering at Imperial College London, said: “The coast is clearly eroding, and Britain has retreated fast. Our study on British coasts leaves no question that coastal cliff retreat accelerated in the recent past. A nearly ten-fold increase in retreat rates over a very short timescale, in geological terms, is remarkable. The UK cannot leave the issue of cliff erosion unresolved in the face of a warming world and rising sea levels. Cliff erosion is irreversible; once the cliffs retreat, they are gone for good.”

The scientists used a process called cosmogenic dating to learn how the chalk cliffs at Beachy Head and Seaford Head have eroded. Cosmogenic dating allows scientists to analyse the build-up of a rare isotope of beryllium (beryllium-10). This isotope is created when cosmic radiation reacts with oxygen atoms in the exposed flint rock, so by measuring its accumulation, it acts as a kind of ‘rock clock’ to show the rate of rock erosion.

Since the rate of accumulation has previously been relatively constant, measuring rock samples from across the shore platforms allowed researchers to build a record of how coastal erosion has proceeded over the last 7000 years or so.

Dr Rood added: “Cosmogenic isotopes including beryllium-10 are advancing the science of retreating coastlines in Great Britain and worldwide. These new tools provide a rare insight into how dramatically environmental change and human impact affected sensitive coastal landscapes. We still need to better understand how other rocky coastlines have responded in the past, and cosmogenic isotopes are the key to unlocking this mystery.”

The researchers now hope to use their observations to create a more accurate predictive model of how climate change will affect coastal erosion in the future, which could help authorities make more informed decisions about coastal management.

Reference:
Martin D. Hurst, Dylan H. Rood, Michael A. Ellis, Robert S. Anderson, Uwe Dornbusch. Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain. Proceedings of the National Academy of Sciences, 2016; 201613044 DOI: 10.1073/pnas.1613044113

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

Tooth wear patterns suggest Paranthropus early hominins had softer diets than expected

Well-preserved buccal microwear surfaces in which buccal striations could be measured. Credit: Martínez et al (2016)
Well-preserved buccal microwear surfaces in which buccal striations could be measured.
Credit: Martínez et al (2016)

Analysis of wear patterns on fossil teeth from East African hominins suggests the diets of Paranthropus aethiopicus and Paranthropus boisei were softer than had been thought, according to a study published November 16, 2016 in the open-access journal PLOS ONE by Laura Monica Martinez from Universitat de Barcelona, Spain, and colleagues.

Two species in the Paranthropus genus of early hominins, P. aethiopicus and P. boisei, co-existed for some time with early Homo species including H. ergaster, but seem to have had different diets. Previous isotopic analysis has supported the theory that while H. ergaster, which had relatively small jaws and teeth, consumed a lot of meat, Paranthropus species, which had massive lower jaws and molars with large chewing surfaces, may have specialized to eat a high proportion of fibrous, abrasive C4 plants.

However, examination of wear patterns on the grinding surfaces of hominin teeth has not supported this theory. The authors of the present study aimed to resolve this discrepancy by gathering additional tooth wear data. They examined microscopic scratches on the cheek surfaces of teeth from 167 fossil specimens of Paranthropus and early Homo species from sites in Ethiopia, Kenya and Tanzania.

The researchers found that, contrary to the previous isotopic evidence, the scratch patterns on cheek surfaces of P. aethiopicus and P. boisei teeth suggested that their dietary habits ‘did not involve chewing significant amounts of abrasive foods’. However, they note that these species might have eaten less abrasive, brittle C4 plants; which would be consistent with both the isotopic and the dental evidence.

Meanwhile, the scratch patterns found on H. ergaster teeth suggest that they ate more abrasive foods that had been expected, which could indicate that early Homo species also underwent a dietary shift to C4 plants as they evolved. This study provides valuable additional evidence concerning the evolution and composition of the diets of Paranthropus and Homo species over time.

Reference:
Laura Mónica Martínez, Ferran Estebaranz-Sánchez, Jordi Galbany, Alejandro Pérez-Pérez. Testing Dietary Hypotheses of East African Hominines Using Buccal Dental Microwear Data. PLOS ONE, 2016; 11 (11): e0165447 DOI: 10.1371/journal.pone.0165447

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

Geologists discover how a tectonic plate sank

Representative Image: HoloGlobe: Tectonic Plate Boundaries on a Globe Credit: NASA Scientific Visualization Studio
Representative Image: HoloGlobe: Tectonic Plate Boundaries on a Globe
Credit: NASA Scientific Visualization Studio

In a paper published in Proceedings of the National Academy of Sciences (PNAS) Saint Louis University researchers report new information about conditions that can cause Earth’s tectonic plates to sink.

John Encarnacion, Ph.D., professor of earth and atmospheric sciences at SLU, and Timothy Keenan, a graduate student, are experts in tectonics and hard rock geology, and use geochemistry and geochronology coupled with field observations to study tectonic plate movement.

“A plate, by definition, has a rigidity to it. It is stiff and behaves as a unit. We are on the North American Plate and so we’re moving roughly westward together about an inch a year,” Encarnacion said. “But when I think about what causes most plates to move, I think about a wet towel in a pool. Most plates are moving because they are sinking into Earth like a towel laid down on a pool will start to sink dragging the rest of the towel down into the water.”

Plates move, on average, an inch or two a year. The fastest plate moves at about four inches a year and the slowest isn’t moving much at all. Plate motions are the main cause of earthquakes, and seismologists and geologists study the details of plate motions to make more accurate predictions of their likelihood.

“Whenever scientists can show how something that is unexpected might have actually happened, it helps to paint a more accurate picture of how Earth behaves,” Encarnacion said. “And a more accurate picture of large-scale Earth processes can help us better understand earthquakes and volcanoes, as well as the origin and locations of mineral deposits, many of which are the effects and products of large-scale plate motions.”

Plate movement affects our lives in other ways, too: It recently was reported that Australia needs to redraw its maps due to plate motion. Australia is moving relatively quickly northwards, and so over many decades it has traveled several feet, causing GPS locations to be significantly misaligned.

Subduction, the process by which tectonic plates sink into Earth’s mantle, is a fundamental tectonic process on earth, and yet the question of where and how new subduction zones form remains a matter of debate. Subduction is the main reason tectonic plates move.

The SLU geologists’ research takes them out into the field to study rocks and sample them before taking them back to the lab to be studied in more detail.

Their work involves geological mapping: looking at rocks, identifying them, plotting them on a map and figuring out how they formed and what has happened to them after they form. Researchers date rock samples and look at their chemistry to learn about the specific conditions where an ancient rock formed, such as if a volcanic rock formed in a volcanic island like Hawaii or on the deep ocean floor.

In this study, Keenan and Encarnacion traveled to the Philippines to study plates in that region. They found that a divergent plate boundary, where two plates move apart, was forcefully and rapidly turned into a convergent boundary where one plate eventually began subducting.

This is surprising because although the plate material at a divergent boundary is weak, it is also buoyant and resists subduction. The research findings suggest that buoyant but weak plate material at a divergent boundary can be forced to converge until eventually older and denser plate material enters the nascent subduction zone, which then becomes self-sustaining.

“We think that the subduction zone we studied was actually forced to start because of the collision of India with Asia. India was once separated from Asia, but it slowly drifted northwards eventually colliding with Asia. The collision pushed out large chunks of Asia to the southeast. That push, we think, pushed all the way out into the ocean and triggered the start of a new subduction zone.”

Their finding supports a new model for how plates can begin to sink: “Places where plates move apart can be pushed together to start subduction.”

The SLU researchers now want to learn if their model applies to other tectonic plates.

“How common was this forced initiation of a subduction zone that we think happened in the Philippines?” Encarnacion said. “I would like to see work on other ancient subduction zones to see whether our model applies to them as well.”

Other researchers on the study include Robert Buchwaldt, Dan Fernandez, James Mattinson, Christine Rasoazanamparany, and P. Benjamin Luetkemeyer.

Saint Louis University’s Department of Earth and Atmospheric Sciences, combines strong classroom and field-based instruction with internationally recognized research across a broad spectrum of the physical sciences, including seismology, hydrology, geochemistry, meteorology, environmental science, and the study of modern and ancient climate change. Students also have the opportunity to work directly with faculty on their research and pursue internships through a growing network of contacts in the public and private sector.

Research centers include the Earthquake Center, the Cooperative Institute for Precipitation Systems, the Global Geodynamics Program, the Center for Environmental Sciences, and Quantum WeatherTM. The fusion of academic programs with world-class research provides students with an unparalleled opportunity to explore their interests and prepare for a wide variety of careers after graduation.

Reference:
Timothy E. Keenan, John Encarnación, Robert Buchwaldt, Dan Fernandez, James Mattinson, Christine Rasoazanamparany, P. Benjamin Luetkemeyer. Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology. Proceedings of the National Academy of Sciences, 2016; 201609999 DOI: 10.1073/pnas.1609999113

Note: The above post is reprinted from materials provided by Saint Louis University Medical Center.

Exploring gigantic volcanic eruptions that caused worldwide mass extinctions

This diagram shows the Pacific large igneous provinces included in a study by Virginia Tech Department of Geosciences researchers. Sections colored in red were visited by Esteban Gazel and his team, while the entire Pacific Large Low Shear Velocity Province is shown in yellow. The Pacific Large Low Shear Velocity Province is nearly 2,000 miles wide. Credit: Virginia Tech
This diagram shows the Pacific large igneous provinces included in a study by Virginia Tech Department of Geosciences researchers. Sections colored in red were visited by Esteban Gazel and his team, while the entire Pacific Large Low Shear Velocity Province is shown in yellow. The Pacific Large Low Shear Velocity Province is nearly 2,000 miles wide.
Credit: Virginia Tech

A paper published in Nature Communications by Virginia Tech researchers confirms a major feature in the formation of large igneous provinces — massive worldwide volcanic eruptions that created incredibly high volumes of lava and triggered environmental catastrophes and mass extinctions from 170 to 90 million years ago.

Heading the new research is Esteban Gazel, an assistant professor in the Department of Geosciences, part of the College of Science at Virginia Tech, and alumnae Pilar Madrigal, who graduated with a doctoral degree in geology from Virginia Tech in 2016 and is now an assistant professor at the University of Costa Rica.

“We confirmed an ongoing working hypothesis that in order to form these massive eruptions there has to be an input from deep mantle upwellings, as well as interaction with a shallow structure, like a mid-ocean ridge, to allow the outpouring of large volumes of lava,” said Madrigal.

“Our work also suggests that the deep upwellings of hot mantle material forming these large igneous provinces occurred in pulses of 10 million to 20 million years,” she added. “This hint of cyclicity is an interesting result suggesting that there may be deep mantle instabilities occurring every so often that we still don’t fully understand and that could potentially be related with core-mantle interactions.”

The hypothesis had been shown only in numerical and dynamical models until Gazel and Madrigal independently evaluated the geodynamical evidence with geochemical and petrological models they produced to find robust correlations indicating that this interaction was key in forming large igneous provinces. Large igneous provinces are massive formations of igneous rocks made of volcanic and intrusive materials, all formed from rapid production of magma. Large igneous provinces are scattered around the world in ocean basins bordering Siberia, Africa, India, and on the east coasts of North and South America. In this study, Gazel and Madrigal focused their attention on the Pacific Ocean locations.

“The generation of these igneous provinces correlates with some of the most devastating events in our planet’s history,” said Gazel, who spearheaded the study. “The geological record of these events contain crucial information to understand the inner dynamics of the Earth’s mantle. But also, every time they happened, they completely changed life on the planet.”

Gazel and Madrigal studied the geochemical composition and timing of the large igneous provinces that occurred in the Pacific Plate during the Mesozoic Period, in a time span of between 170 to 90 million years ago. They collected samples of underwater lava flows now exposed along the Pacific coast of Costa Rica. These lavas were formed in the Pacific and were brought to the surface by tectonic processes, said Gazel.

“The field work was very exciting because one can see these underwater formations that are now exposed on the surface” said Gazel, adding that their collection efforts included boat trips, swimming to outcrops, and hiking along the coast.

And Gazel knew the area well. He spent summers in the Nicoya Peninsula of Costa Rica. “These rocks and I go back a long way,” he said. “I used to spend the summers playing and getting in trouble on these pillow basalts during my childhood.”

In collaboration with Kennet Flores, assistant professor at Brooklyn College in New York, the team produced a series of kinematic models to calculate the Pacific’s paleotectonic configuration during the Cretaceous Period.

The study also included isotopic and age-dating data collected in collaboration with researchers Michael Bizimis and Brian Jicah from the University of South Carolina and the WiscAr Geochronology Laboratory at the University of Wisconsin-Madison, respectively.

The study findings suggest a relationship between eruption of these provinces and the location of paleo mid-ocean ridges, where normal oceanic crust forms in a steady-state fashion, and the position of the edges of the Pacific Large Low-Shear Velocity Province, a thermochemical anomaly roughly 1,860 miles wide between eastern Australia and the west coast of South America, located deep in the Earth at the mantle-core boundary.

This new discovery suggests interaction between deep, hot mantle upwelling and mid-ocean ridges enabling the formation of large igneous provinces.

Added Gazel, “This is an important breakthrough, as we can better explain why these events were so big. To put things into perspective, the pulse that happened 120 million years ago that formed the Ontong-Java, Manihiki, and Hukurangi large igneous provinces covered an area equivalent to about 40 percent of the continental U.S. in a very short time.”

Most of these magmatic provinces formed at the same time as an event known as the Cretaceous Normal Superchron, roughly 120 to 80 million years ago, when for millions of years the Earth’s core did not change its polarity, which was most likely caused by fluctuations of core-mantle heat flux, said Gazel.

He said there were many other extinction-level events throughout history, such as one nearly 300 million years ago that almost wiped out all life on the planet, from the eruption of the Siberian Traps, another large-igneous province. He added, “Understanding these processes is not only important to decode the deep puzzles of Earth but also to better understand the fragility and resilience of life on our planet.”

Research was supported by the National Science Foundation’s Petrology and Geochemistry and Tectonics Program.

Reference:
Pilar Madrigal, Esteban Gazel, Kennet E. Flores, Michael Bizimis, Brian Jicha. Record of massive upwellings from the Pacific large low shear velocity province. Nature Communications, 2016; 7: 13309 DOI: 10.1038/ncomms13309

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

Autism and human evolutionary success

Clues of autistic traits can be found in cave art. Credit: University of York
Clues of autistic traits can be found in cave art.
Credit: University of York

A subtle change occurred in our evolutionary history 100,000 years ago which allowed people who thought and behaved differently – such as individuals with autism – to be integrated into society, academics from the University of York have concluded.

The change happened with the emergence of collaborative morality – an investment in the well-being of everyone in the group – and meant people who displayed autistic traits would not only have been accepted but possibly respected for their unique skills.

It is likely our ancestors would have had autism, with genetics suggesting the condition has a long evolutionary history.

But rather than being left behind, or at best tolerated, the research team conclude that many would have played an important role in their social group because of their unique skills and talents.

“We are arguing that diversity, variation between people, was probably more significant in human evolutionary success than the characteristics of one person, “said Penny Spikins, senior lecturer in the archaeology of human origins, at the University of York.

“It was diversity between people which led to human success and it is particularly important as it gives you different specialised roles.

“We are arguing that it is the rise of collaborative morality that led to the possibility for widening the diversity of the human personality.”

Many people with autism have exceptional memory skills, heightened perception in realms of vision, taste and smell and enhanced understanding of natural systems such as animal behaviour.

The incorporation of some of these skills into a community would play a vital role in the development of specialists, the authors of the report, which is published in Time and Mind, suggest.

A previous ethnographic study in 2005 of an elderly reindeer herder from Siberia revealed a detailed memory of the parentage, medical history and character of each one of his 2,600 animals.

His vital knowledge would have made a significant contribution to their management and survival.

The grandfather was more comfortable in the company of the reindeer than of humans, but was much respected and had a wife and son and grandchildren.

Finding tangible evidence of autism in archaeological records has always been challenging for academics.

Dr Spikins said “The archaeological record doesn’t give us a skeletal record for autism, but what it does do is give us a record for other people who have various differences and how they have been integrated.”

Other clues can be found in cave art and other artefacts.

“There has been a long-standing debate about identifying traits of autism in Upper Palaeolithic cave art.

“We can’t say some of it was drawn by someone with autism, but there are traits that are identifiable to someone who has autism. It was also roughly at that time that we see collaborative morality emerging.”

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

Mississippi River could leave farmland stranded

Mississippi River floodwaters deposited many tons of sand on farmland and roads in Dogtooth Bend peninsula when the Len Small levee breached in January of 2016. The sand dunes left behind required graders and snow plows to open the road for local traffic. Credit: University of Illinois
Mississippi River floodwaters deposited many tons of sand on farmland and roads in Dogtooth Bend peninsula when the Len Small levee breached in January of 2016. The sand dunes left behind required graders and snow plows to open the road for local traffic.
Credit: University of Illinois

If the Mississippi River continues to go unchecked, the farmland on Dogtooth Bend peninsula may be only accessible by boat. According to a University of Illinois study, each successive flood carves a deeper channel across the narrow neck of the peninsula. This floodwater shortcut threatens to permanently reroute the Mississippi River, leaving Dogtooth Bend an island rather than a peninsula.

U of I researcher Ken Olson and his colleague from Iowa State University, Lois Wright Morton, have studied the seasonal Mississippi River flooding for over a decade. They’ve paid particularly close attention to the damages caused by major flooding events in 1993, 2011, and most recently in January 2016.

“Approximately 15,000 acres of farmland in the Dogtooth Bend area would no longer be accessible by road if the Mississippi River is allowed to realign naturally. In some cases the land use would likely shift from agriculture to other uses,” Olson explains.

Olson says climate scientists predict a continued pattern of extreme rainfall events in the upper Mississippi River region. This suggests that unexpected above-average rainfall events in the Ohio and Mississippi River basins will continue to increase the frequency of extreme flooding events.

“The 2016 Len Small levee breach was much more severe than 2011 because of its location,” says Olson. “The fast-moving river cut a 1-mile long breach in late December through early January, scouring out a crater lake and deep gullies info adjacent farmland. The southeast flow of the Mississippi River created a new channel connecting the old channel with the main stem of the river.”

Olson says Dogtooth Bend farmers and landowners, members and staff of the Len Small Levee and Drainage District, community and state-level leaders, and the U.S. Army Corps of Engineers have some difficult decisions ahead in repairing the current landscape and preparing for future flood events–decisions that affect future land uses, resource allocations, and the livelihoods of the people of southern Illinois.

The study suggests three remedies for the situation. One is to continue to repair the Len small levee when needed. Olson says this is only a short-term fix.

A second idea is to proactively construct a diversion channel with embankments on both sides where the old meander channel is currently located. “During high water periods, the channel would temporarily redirect excess Mississippi River floodwaters and allow the water to exit back into the river at mile marker 15,” Olson says. This would also require one or more bridges be built over the diversion channel to allow access to farmland, homes, and recreational hunting areas.

“A third alternative is to assist the Mississippi River realignment tendency and construct a sixth-tenths of a mile wide new river channel through the 3.5 miles shortcut between mile marker 34 and 15 where the Mississippi River is already cutting with each major flooding event,” Olson says. “The USACE could accelerate this process even more by making this channel between mile markers 34 and 15 the main stem river navigation channel.”

This last alternative fix would require thorough hydrologic, environmental, social, and economic assessments. And, as Olson reminds, “over time, the mighty Mississippi River will eventually win, as it always has in the past.”

Note: The above post is reprinted from materials provided by University of Illinois College of Agricultural, Consumer and Environmental Sciences.

Study links groundwater changes to fracking

A study done in northeastern Pennsylvania suggests that drinking water near hydraulic fracturing sites is undergoing chemical changes. Lead author Beizhan Yan checks out a site on a back road. Credit: Kevin Krajick/Lamont-Doherty Earth Observatory
A study done in northeastern Pennsylvania suggests that drinking water near hydraulic fracturing sites is undergoing chemical changes. Lead author Beizhan Yan checks out a site on a back road.
Credit: Kevin Krajick/Lamont-Doherty Earth Observatory

A new study has found heightened concentrations of some common substances in drinking water near sites where hydraulic fracturing has taken place. The substances are not at dangerous levels and their sources are unclear, but the researchers say the findings suggest underground disturbances that could be harbingers of eventual water-quality problems. The study may be the first of its kind to spot such broad trends.

The researchers, from Columbia University’s Lamont-Doherty Earth Observatory and other institutions, found that both distance and topography play a role. In lowland drinking wells within one kilometer (about six-tenths of a mile) of a drill site, they found higher levels of dissolved calcium, chlorine, sulfates and iron. In lowland wells more than a kilometer away, they found higher levels of methane, sodium and manganese compared with equally distant wells on higher ground. Upland wells within a kilometer of a drill site showed no specific trends.

Hydraulic fracturing, or fracking, involves injecting pressurized, chemical-laced water into deep rock layers to crack them open and release natural gas. The target layers are almost invariably far below drinking-water aquifers, leading industry to defend the practice as safe. Critics suspect it is not, but definitive proof either way has been lacking so far, and the issue has become highly politicized.

Lead author Beizhan Yan, a Lamont-Doherty geochemist, said, “The finding suggests increased mixing of different groundwater sources.” This could be due to several possibilities, he said. For one, the sudden, powerful pulses introduced by fracking might act like a pump, expanding and contracting subterranean spaces, and squeezing the contents around. This stress could propagate up to the surface and initiate mixing of groundwater, either from the sides or below, he said. The observations might also be due to leaky well casings at shallow depths, or spills of fracking fluids on the surface trickling down, he said.

Study coauthor Steven Chillrud, also a geochemist at Lamont-Doherty, said, “We don’t really know what the mechanism is, but this shows there’s an impact related to distance. It’s an intriguing signal that really needs to be followed up on.”

Fracking did not start up in northeastern Pennsylvania until 2007, but now the region has thousands of wells. Chillrud noted that pollutants can take years or decades to move into an aquifer. “If it’s from below, that could be an indicator that other, more problematic elements will be coming through at some point,” he said.

The team took about 60 water samples from private wells, but decided these were too few to spot any trends, so they also looked at some 1,850 samples taken by other researchers in industry and academia, which they reanalyzed.

Coauthor Reynold Panettieri, a physician who directs Rutgers University’s Institute for Translational Medicine and Science, said none of the substances seemed to be at hazardous levels. However, he said, the different water chemistry nearer the fracking sites “seems to be a fingerprint of drilling. It gives us a map of hotspots that could potentially concentrate toxicants in the future.”

The study adds fuel to the ongoing national controversy over the safety of fracking. The U.S. Environmental Protection Agency issued a draft report last year citing scattered instances where water had been contaminated, but finding no evidence of what it called “widespread, systemic impacts.” Separate studies in Texas and Pennsylvania have found that in the few instances closely studied, when water does get polluted, cracked well casings or spills, not the fracking process itself, have been to blame.

Critics have cried foul over the EPA report, pointing out that so little data exists to address so big a question. According to the EPA, between 2000 and 2013, some 6,800 public-drinking water supplies serving 8.6 million people were located within a mile of a fracking site. During the same period, some 9.4 million people lived within a mile of a fracking site, many probably using private wells. The number is probably much greater now, since some 25,000 to 30,000 sites are fracked each year.

Last year, Panettieri, Yan and others published a study showing that people living near fracking sites in the same general area surveyed by the new study suffer increased rates of hospitalization for strokes, neurological illnesses and skin ailments. But they could not connect this observation to any particular cause. There are only a handful of similar epidemiological studies. Recently, EPA issued a call for proposals to conduct water and health impacts associated with oil and gas development in Appalachia.

Paul Heisig, a hydrologist with the U.S. Geological Survey, said the study raises questions that merit further research, but that no firm conclusions could be drawn. He pointed out that the industry data used in the study lack controls including the depths of sampled drinking wells, and variations in nearby land usage aside from fracking that could affect water quality. “The study points out there may be some issues, but it really needs to be pursued with more data,” he said.

The study appears this week in the journal Science of the Total Environment. Other coauthors are: Martin Stute and James Ross, also of Lamont-Doherty; Matthew Neidel and Xinhua Liu of Columbia University’s Mailman School of Public Health; Brian Mailloux and Lissa Soares of Barnard College; and Marilyn Howarth and Pouné Saberi of the University of Pennsylvania.

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

How and why to date a dinosaur

An Archaeopteryx in a phylogenetic tree
An Archaeopteryx in a phylogenetic tree

You might think dating dinosaurs would be an easy task, but in reality it’s actually quite difficult. We date dinosaurs based on where we find their fossils, using the ages of the rocks that they’re found in. This means that the ‘ages’ of different dinosaurs is actually indirect and constrained by how well we’re able to date the rocks they were found in.

Ghosts in the machine

As well as this, we know that the occurrences of dinosaur fossils are not accurate representations of their age either. If we know one dinosaur species A was around 120 million years ago, and its closest relative species B known only 100 million years ago, then species B must have existed 120 million years earlier too as they must have shared an origination time due to the way speciation works – we just haven’t found any fossils of it during this 20 million year gap though. And we call these ghost ranges or lineages.

What these ghost ranges do, when combined with trees that illustrate the relationships between different organisms, is alter the timings or dates of important events based on exactly how we time-scale the trees and the ghost and true ranges of species.

Why date a dinosaur?

This uncertainty in dating and the methods we use actually has quite important implications for significant events in the evolutionary history of dinosaurs. A team led by Graeme Lloyd of Macquarie University, Australia, recently set out to investigate three questions:

  • What was the origination time for Dinosauria (all dinosaurs)?
  • When did the earliest birds originate?
  • When did crown birds (the group that includes all modern birds) originate?

They used a cadre of time-scaling methods on a brand new evolutionary tree for all dinosaurs, making this the best test of these questions so far. So what did they all discover?

Whence came thee, dinosaur

What was the first dinosaur? That’s a tough question, and the reality is we’ll probably never actually know. The fossil record preserves little fragments and snapshots of life through time, so while we may never find the first real dinosaur, we can have a good whack at what the earliest dinosaur species was based on what the fossil record yields to us.

As with all good things in palaeontology, this is still up for debate too. A reasonably new species to science called Nyasasaurus might be the earliest dinosaur we know of, or just outside the group and actually what we call a dinosauriform. Depending on this uncertainty, the origin of Dinosauria seems to have most likely occurred in the Early or Middle Triassic, much earlier than the oldest fossils might suggest.

As with the first dinosaurs, the contender for the earliest bird is still up for debate, with researchers unable to pick between Archaeopteryx and the more recently discovered Aurornis, which might be a troodontid. Irrespective of this, the origin of the earliest birds, the clade Avialae, seems to hone in on around a Middle to Late Jurassic age, so around 160-145 million years ago. This is fairly close to when we see the oldest potential bird fossils, and some of the oldest evidence of feathered dinosaurs.

Birds of a feather

The group that includes all modern birds, Aves, or Neornithes, is what we call the ‘crown group’ for birds. Other dinosaurs like Triceratops belong on the stem of this group, and can actually be considered as ‘stem birds’. The origin of Neornithes is the most uncertain of all three groups analysed, stretching from the end of the Cretaceous around 66 million years ago all the way until the middle Early Cretaceous, around 120 million years ago. The reason for this uncertainty is simply due to the state of the fossil record during the Late Cretaceous, in which the taxonomy of some species is quite difficult to assess.

Importantly, all of these new estimates seem to post-date traditional estimates for the origins of these groups that rely mostly on simple occurrence dates of the fossils, and don’t account for their evolutionary relationships.

This is important for evolutionary studies as it means that we can now more accurately assess the times of important steps in the global tree of life, and apply these to our large-scale understanding of the macroevolution of life on Earth.

Note: The above post is reprinted from materials provided by Public Library of Science.

Rip in Crust Drives Undersea Volcanism, Study Says

Fresh lava overlying the product of an older eruption on the Pacific seafloor. A new study says the later eruption was driven mainly by a rip in earth’s crust. Photo Credit: Dan Fornari/Woods Hole Oceanographic Institution
Fresh lava overlying the product of an older eruption on the Pacific seafloor. A new study says the later eruption was driven mainly by a rip in earth’s crust. Photo Credit: Dan Fornari/Woods Hole Oceanographic Institution

Scientists analyzing a volcanic eruption at a mid-ocean ridge under the Pacific have come up with a somewhat contrarian explanation for what initiated it. Many scientists say undersea volcanism is triggered mainly by upwelling magma that reaches a critical pressure and forces its way up. The new study says the dominant force, at least in this case, was the seafloor itself—basically that it ripped itself open, allowing the lava to spill out. The eruption took place on the East Pacific Rise, some 700 miles off Mexico.

“Mid-ocean ridges are commonly viewed as seafloor volcanoes, operating like volcanoes on land,” said the study’s lead author, Yen Joe Tan, a graduate student at Columbia University’s Lamont-Doherty Earth Observatory. “We’re saying they should actually be viewed as tears in the crust, where magma oozes out.” The study appears in the journal Nature this week.

The mid-ocean ridges are mountain chains that run continuously for more than 40,000 miles along the planet’s seafloors, like stitching on a baseball. From their centers, they pour out lava. This pushes the seafloor out in opposite directions from the ridges toward the continents. In many cases, the leading edge of the seafloor then dives under the land, or subducts, and is subsumed back into the deep earth. This process—the basic mechanism of plate tectonics—was defined in the 1960s and 1970s. Scientists have since debated exactly what drives ridge eruptions.

Many say magma pressure is the main factor, but it might not be the only one. A ridge might also get torn by what specialists call “plate pull”—the force exerted when the distant edge of seafloor subducts under a continent, slowly lugging the rest behind it. Stress might also develop because eruptions build symmetrical chains of mountains on either side of the ridge axis, as lava spills down the sides. This might weaken the center through sheer force of gravity, somewhat like what happens when one slices a hot dog lengthwise, and the two sides fall apart.

In an effort to resolve the relative roles of magma and stress, Tan and his coauthors analyzed an eruption thought to have taken place in 2005-2006, along a heavily studied segment of the East Pacific Rise. A team of researchers had earlier left underwater microphones and sea-bottom seismometers at the site, which recorded the eruption. They later retrieved the sound and seismic data, and mapped the fresh lava using underwater cameras. They also collected samples of the lava, and later analyses of it suggested that the eruption took place over seven to 10 months.

The authors of the new paper took another look after a 2015 eruption at an unconnected study site, at Axial Seamount, off the coast of Oregon. Unlike the earlier East Pacific Rise eruption, this one was studied in real time with an assortment of instruments. Among the data produced were recordings of violent popping noises that appeared related to the emergence of lava on the seafloor—possibly the result of exploding gas bubbles, or implosions of hardening lava.

In light of the Axial Seamount observations, the researchers reviewed the 2005-2006 data from the East Pacific Rise, and came up with a newly sharpened picture. Their reanalysis suggested that most of the eruption took place rapidly, not over months. Other researchers had already identified a series of conventional earthquakes of about magnitude 2 on Jan. 22, 2006, of the kind usually associated with the rupture of a rock boundary, along a 35-kilometer-long segment of the ridge. About 15 minutes later, the seismometers started picking up clusters of lower-frequency earthquakes, of a type usually associated with rising magma. Another hour or two on, popping sounds like those heard at Axial Seamount appeared, in four separate areas along the segment, each in an area about 5 kilometers long.

The team pinned down the locations of the sounds, and when they overlaid these with the earlier map of the fresh lava, they matched. Their interpretation: the first series of earthquakes signaled the rupture of a fault overlying the magma, with little or no help from magma pressure. Then, with a path now clear, the magma ascended. Magma pressure was probably not the initial trigger for the eruptions, say the authors, because they came simultaneously from four separate places along the apparent ruptured fault.

“It’s been a kind of chicken-and-egg question,” said coauthor Maya Tolstoy, a marine geophysicist at Lamont-Doherty. “You have these two different forces [magma vs. tectonics] that could play a role, and it’s hard to tell which triggers the eruption. Here, we can make the argument for one dominating, because we see this series of events, and then multiple magma chambers erupting at the same time.”

The authors say that according to their observations, about 85 percent of the lava emerged within two days, with remnants dribbling out over the course of a week. The eruptions produced some 22 million cubic meters of seafloor—about enough to cover 13 football fields 1,000 feet deep.

Cynthia Ebinger, a professor at the University of Rochester who studies eruptions at spreading sites both on land and under the ocean, said in an email that very few seafloor eruptions have been so directly observed. The study “adds a new factor to consider,” she said. “It shows that tectonic stresses can trigger large-volume intrusions and eruptions” to create new seafloor.

Michael Perfit, a professor at the University of Florida who also studies undersea eruptions, said the study “tells a remarkable story.” But, he said, the authors may have overstated the relative role of tectonic stress versus magma pressure. “I think it’s really got to be both,” he said. He cited a 2014 geochemical study he coauthored suggesting that the magma was replenished with new material from below about 6 weeks before the eruption. This suggests pressure could have played a more substantial role, he said.

Ebinger said it remained possible that either magma pressure or tectonic forces could be “the straw that breaks the camel’s back” in any specific eruption.

The paper was also coauthored by seismologist Felix Waldhauser of Lamont-Doherty and marine geophysicist William Wilcock of the University of Washington. The research was supported by the U.S. National Science Foundation.

The paper, “Dynamics of a seafloor spreading episode at the East Pacific Rise,” is available from the authors or from Nature.

Reference:
Dynamics of a seafloor-spreading episode at the East Pacific Rise, Nature, DOI:10.1038/nature20116

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

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