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Oklahoma earthquakes linked to oil and gas drilling

Large volumes of highly saline water extracted along with oil and gas from some producing formations gets injected into a deep disposal zone, the Arbuckle Formation, which sits directly upon crystalline basement rocks. Rising pore pressure in the Arbuckle Formation can penetrate already-stressed basement faults and trigger earthquakes. Credit: Steven Than/Stanford University

Stanford geophysicists have identified the triggering mechanism responsible for the recent spike of earthquakes in parts of Oklahoma — a crucial first step in eventually stopping them.

In a new study published in the June 19 issue of the journal Science Advances, Professor Mark Zoback and PhD student Rall Walsh show that the state’s rising number of earthquakes coincided with dramatic increases in the disposal of salty wastewater into the Arbuckle formation, a 7,000-foot-deep, sedimentary formation under Oklahoma.

In addition, the pair showed that the primary source of the quake-triggering wastewater is not so-called “flow back water” generated after hydraulic fracturing operations. Rather, the culprit is “produced water”-brackish water that naturally coexists with oil and gas within the Earth. Companies separate produced water from extracted oil and gas and typically reinject it into deeper disposal wells.

“What we’ve learned in this study is that the fluid injection responsible for most of the recent quakes in Oklahoma is due to production and subsequent injection of massive amounts of wastewater, and is unrelated to hydraulic fracturing,” said Zoback, the Benjamin M. Page Professor in the School of Earth, Energy & Environmental Sciences.

The Stanford study results were a major contributing factor in the recent decision by the Oklahoma Geological Survey (OGS) to issue a statement that said it was “very likely” that most of the state’s recent earthquakes are due to the injection of produced water into disposal wells that extend down to, or even beyond, the Arbuckle formation.

Recent increases in seismicity

Before 2008, Oklahoma experienced one or two magnitude 4 earthquakes per decade, but in 2014 alone, the state experienced 24 such seismic events. Although the earthquakes are felt throughout much of the state, they pose little danger to the public, but scientists say that the possibility of triggering larger, potentially damaging earthquakes cannot be discounted.

In the study, Zoback and Walsh looked at three study areas-centered around the towns of Cherokee, Perry and Jones-in Oklahoma that have experienced the greatest number of earthquakes in recent years. All three areas showed clear increases in quakes following increases in wastetwater disposal. Three nearby control areas that did not have much wastewater disposal did not experience increases in the number of quakes.

Because the pair were also able to review data about the total amount of wastewater injected at wells, as well as the total amount of hydraulic fracturing happening in each study area, they were able to conclude that the bulk of the injected water was produced water generated using conventional oil extraction techniques, not during hydraulic fracturing.

“We know that some of the produced water came from wells that were hydraulically fractured, but in the three areas of most seismicity, over 95 percent of the wastewater disposal is produced water, not hydraulic fracturing flowback water,” said Zoback, who is also a senior fellow at Stanford’s Precourt Institute for Energy and director of the university’s recently launched Natural Gas Initiative, which is focused on ensuring that natural gas is developed and used in ways that are economically, environmentally, and societally optimal.

Time delay explained

The three study areas in Oklahoma that Zoback and Walsh looked at all showed a time delay between peak injection rate and the onset of seismicity, as well as spatial separations between the epicenter of the quakes and the injection well sites. Some of the quakes occurred months or even years after injection rates peaked and in locations that were sometimes located miles away from any wells.

These discrepancies had previously puzzled scientists, and had even been used by some to argue against a link between wastewater disposal and triggered earthquakes, but Zoback said they are easily explained by a simple conceptual model for Oklahoma’s seismicity that his team has developed.

According to this model, wastewater disposal is increasing the pore pressure in the Arbuckle formation, the disposal zone that sits directly above the crystalline basement, the rock layer where earthquake faults lie. Pore pressure is the pressure of the fluids within the fractures and pore spaces of rocks at depth. The earth’s crust contains many pre-existing faults, some of which are geologically active today. Shear stress builds up slowly on these faults over the course of geologic time, until it finally overcomes the frictional strength that keeps the two sides of a fault clamped together. When this happens, the fault slips, and energy is released as an earthquake.

Active faults in Oklahoma might trigger an earthquake every few thousand years. However, by increasing the fluid pressure through disposal of wastewater into the Arbuckle formation in the three areas of concentrated seismicity-from about 20 million barrels per year in 1997 to about 400 million barrels per year in 2013-humans have sped up this process dramatically. “The earthquakes in Oklahoma would have happened eventually,” Walsh said. “But by injecting water into the faults and pressurizing them, we’ve advanced the clock and made them occur today.”

Moreover, because pressure from the wastewater injection is spreading throughout the Arbuckle formation, it can affect faults located far from well sites, creating the observed time delay. “You can easily imagine that if a fault wasn’t located directly beneath a well, but several miles away, it would take time for the fluid pressure to propagate,” Walsh said.

Possible solutions

Now that the source of the recent quakes in Oklahoma is known, scientists and regulators can work on ways to stop them. One possible solution, Zoback said, would be cease injection of produced water into the Arbuckle formation entirely, and instead inject it back into producing formations such as the Mississippian Lime, an oil-rich limestone layer where much of the produced water in Oklahoma comes from in the first place.

Some companies already reinject water back into reservoirs in order to displace remaining oil and make it easier to recover. The Stanford study found that this technique, called enhanced oil recovery, does not result in increased earthquakes.

Even if companies opt to use producing formations to store wastewater, however, the quakes won’t cease immediately. “They’ve already injected so much water that the pressure is still spreading throughout the Arbuckle formation,” Zoback said. “The earthquakes won’t stop overnight, but they should subside over time.”

Reference:
F. Rall Walsh III and Mark D. Zoback. Oklahoma’s recent earthquakes and saltwater disposal. Science Advances, 2015 DOI: 10.1126/sciadv.1500195

Note: The above post is reprinted from materials provided by Stanford’s School of Earth, Energy & Environmental Sciences. The original item was written by Ker Than.

US mid-continent seismicity linked to high-rate injection wells

A new study ties high-rate injection wells like this salt water disposal well in Colorado to enormous earthquake increase. Credit: Bill Ellsworth, USGS

A dramatic increase in the rate of earthquakes in the central and eastern U.S. since 2009 is associated with fluid injection wells used in oil and gas development, says a new study by the University of Colorado Boulder and the U.S. Geological Survey.
The number of earthquakes associated with injection wells has skyrocketed from a handful per year in the 1970s to more than 650 in 2014, according to CU-Boulder doctoral student Matthew Weingarten, who led the study. The increase included several damaging quakes in 2011 and 2012 ranging between magnitudes 4.7 and 5.6 in Prague, Oklahoma; Trinidad, Colorado; Timpson, Texas; and Guy, Arkansas.

“This is the first study to look at correlations between injection wells and earthquakes on a broad, nearly national scale,” said Weingarten of CU-Boulder’s geological sciences department. “We saw an enormous increase in earthquakes associated with these high-rate injection wells, especially since 2009, and we think the evidence is convincing that the earthquakes we are seeing near injection sites are induced by oil and gas activity.”

A paper on the subject appears in the June 18 issue of Science.

The researchers found that “high-rate” injection wells — those pumping more than 300,000 barrels of wastewater a month into the ground — were much more likely to be associated with earthquakes than lower-rate injection wells. Injections are conducted either for enhanced oil recovery, which involves the pumping of fluid into depleted oil reservoirs to increase oil production, or for the disposal of salty fluids produced by oil and gas activity, said Weingarten.

Co-authors on the study include CU-Boulder Professor Shemin Ge of the geological sciences department and Jonathan Godt, Barbara Bekins and Justin Rubinstein of the U.S. Geological Survey (USGS). Godt is based in Denver and Bekins and Rubenstein are based in Menlo Park, California.

The team assembled a database of roughly 180,000 injection wells in the study area, which ranged from Colorado to the East Coast. More than 18,000 wells were associated with earthquakes — primarily in Oklahoma and Texas — and 77 percent of associated injection wells remain active, according to the study authors.

Of the wells associated with earthquakes, 66 percent were oil recovery wells, said Ge. But active saltwater disposal wells were 1.5 times as likely as oil recovery wells to be associated with earthquakes. “Oil recovery wells involve an input of fluid to ‘sweep’ oil toward a second well for removal, while wastewater injection wells only put fluid into the system, producing a larger pressure change in the reservoir,” Ge said.

Enhanced oil recovery wells differ from hydraulic fracturing, or fracking wells, in that they usually inject for years or decades and are operated in tandem with conventional oil production wells, said Weingarten. In contrast, fracking wells typically inject for just hours or days.

The team noted that thousands of injection wells have operated during the last few decades in the central and eastern U.S. without a ramp-up in seismic events. “It’s really the wells that have been operating for a relatively short period of time and injecting fluids at high rates that are strongly associated with earthquakes,” said Weingarten.

In addition to looking at injection rates of individual wells over the study area, the team also looked at other aspects of well operations including a well’s cumulative injected volume of fluid over time, the monthly injection pressure at individual wellheads, the injection depth, and their proximity to “basement rock” where earthquake faults may lie. None showed significant statistical correlation to seismic activity at a national level, according to the study.

Oklahoma had the most seismic activity of any state associated with wastewater injection wells. But parts of Colorado, west Texas, central Arkansas and southern Illinois also showed concentrations of earthquakes associated with such wells, said Weingarten.

In Colorado, the areas most affected by earthquakes associated with injection wells were the Raton Basin in the southern part of the state and near Greeley north of Denver.

“People can’t control the geology of a region or the scale of seismic stress,” Weingarten said. “But managing rates of fluid injection may help decrease the likelihood of induced earthquakes in the future.”

The study was supported by the USGS John Wesley Powell Center for Analysis and Synthesis, which provides opportunities for collaboration between government, academic and private sector scientists.

Video

Reference:
M. Weingarten, S. Ge, J. W. Godt, B. A. Bekins, J. L. Rubinstein. High-rate injection is associated with the increase in U.S. mid-continent seismicity. Science, 2015 DOI: 10.1126/science.aab1345

Note: The above post is reprinted from materials provided by University of Colorado at Boulder.

Five amazing extinct creatures that aren’t dinosaurs

Jumping the shark. Credit: Dmitry Bogdanov, CC BY-SA

The release of Jurassic World has reignited our love for palaeontology. Many of us share a longing to understand the dinosaurs that roamed the Earth long before we arrived. But palaeontology is a discipline much broader than this.

Dinosaurs dominated the land for 135 million years, but what happened during the rest of the Earth’s 4.6 billion-year history? The role of palaeontologists past and present has been to unravel the mysteries of life on Earth, and in doing so they’ve found a lot more than just dinosaur bones.

1. The spiky-backed ocean dweller

Right side up? Credit: Natural Math/flickr, CC BY-SA


Hallucigenia was discovered when a 508 million year old fossil was found in 1911 in the world-famous Burgess Shale fossil site in Canada. Since then, our understanding of this ocean-dwelling creature has changed dramatically.

Its age means it falls into the geological Cambrian period, a pivotal moment for all life on Earth when complex lifeforms started to rapidly evolve. When originally described, Hallucigenia was first thought to have walked along the ocean floor on spiny legs and used tentacles on its back to catch food. Palaeontologists also argued over which end was its head.

But when a similar fossil was found in China, Hallucigenia was re-examined. Palaeontologists then discovered that its “legs” were actually protective spines on its back, and the tentacles formed two rows on its underside enabling it to “walk”. Researchers are still debating many of the features of Hallucigenia today, more than 100 years after it was discovered.

2. (Almost) the first fish out of water

Best foot forward. Credit: Nobu Tamura, CC BY-SA

100 million years on from Hallucigenia, aquatic habitats were thriving, but life on land was still in its earliest stages. Tiktaalik, part fish, part four-legged animal, is believed to be the first creature to develop characteristics that would help animals move out of the water and on to land.

It had gills, fins and scales like a fish, but also evolved features such as a flexible neck and a reptile-like head and lungs, beneficial for life on the ground. Fossils also show Tiktaalik had long fins that acted as legs, meaning it could “walk” along riverbeds as well as swim.

3. The giant Scottish scorpion

Sting in the tail. Credit: Nobu Tamura, CC BY

Pulmonoscorpius kirktonensis, a 70cm-long scorpion, lived in what we now know as Scotland 340 million years ago. At a length greater than that of the average pet cat, this terrifying creature used its tail to catch and kill its prey.

Pulmonoscorpius also had unusually large eyes compared to its modern relatives, so most likely hunted during daylight hours. Scorpions shed their skin as they grow, so fossils of both the skin and the animal itself have been found.

4. The spiral-lipped shark

Jumping the shark. Credit: Dmitry Bogdanov, CC BY-SA

Helicoprion, a shark-like fish alive during the Permian (290 million years ago), had a rather unique dental structure. With a face that baffled palaeontologists for years, this creature had a lower jaw made up of a spiral of teeth, known as a tooth-whorl.

Modern sharks are able to lose and replace their teeth, but Helicoprion kept them all, with older teeth hidden within the inner layers of the tooth-whorl. When it caught its prey (most likely relatives of the squid), it would close its mouth and rotate its tooth-whorl to shred its catch.

5. A tiny, drunk horse

Gone to that big horsey ring in the sky. Credit: Daderot

The Messel Oil Shale, once a volcanic lake in Germany, has plenty to offer the world of palaeontology. Eurohippus messelensis, was a miniature horse (the size of a modern day fox) originally thought to have died from eating fermented berries and in a drunken stupor, fallen into the lake. It’s now believed the 47 million year old horse actually died from inhaling toxic gas occasionally released from the depths of the lake.

But the misfortune continues, as it was later discovered that the horse was pregnant. Palaeontologists used high-resolution microscopes to identify the bones of a foal within the adult Eurohippus, improving our understanding of foetal development in these animals.

Palaeontology is a career firmly seated on many childhood wish-lists alongside movie stars and astronauts, and rightly so. But it’s important to remember there’s a lot more to palaeontology than the dinosaurs. This list is just the start.

Note: The above post is reprinted from materials provided by The Conversation.
This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives).

Fossil of large walking bat discovered in New Zealand

Teeth of a 16-million-year-old bat discovered in New Zealand. Credit: Rod Morris

Fossilised remains of a new bat species, which lived 16 million years ago, walked on four limbs and was three times larger than today’s average bat, have been discovered in New Zealand.

The fossils were found near Central Otago on South Island, in sediment left over from a vast prehistoric body of water known as Lake Manuherikia, which was part of warmer subtropical rainforest during the early Miocene era, between 16 and 19-million-years-ago.

The new species, Mystacina miocenalis, was described today in the journal PLOS ONE, and is related to another bat, Mystacina tuberculata, which still lives in New Zealand’s old growth forests.

“Our discovery shows for the first time that Mystacina bats have been present in New Zealand for upwards of 16 million years, residing in habitats with very similar plant life and food sources,” says lead author and vertebrate palaeontologist, Associate Professor Suzanne Hand from the University of New South Wales (UNSW) in Australia.

New Zealand’s only native terrestrial mammals are three species of bat, including two belonging to the Mystacina genus – one of which was last sighted in the 1960s. They are known as burrowing bats because they forage on the ground under leaf-litter and snow, as well as in the air, scuttling on their wrists and backward-facing feet, while keeping their wings tightly furled.

These bats were believed to have an ancient history in New Zealand, but until now, the oldest fossil of a Mystacina bat in New Zealand was from a cave in South Island, dating to 17,500 years ago. This latest discovery forces a rethink of when these peculiar, walking bats first crossed the ditch, arriving from what is present-day Australia.

“This helps us understand the capacity of bats to establish populations on islands and the climatic conditions required for this to happen,” says Associate Professor Hand.

“Bats are important pollinators and seed dispersers that keep forests healthy. Understanding the connectivity between the bat faunas of different landmasses is important for evaluating biosecurity threats and conservation priorities for fragile island ecosystems.”

The new species has similar teeth to its contemporary relative, suggesting a broad diet that included nectar, pollen and fruit, as well as insects and spiders. Limb bones found in the deposit also showed similar structures specialised for walking.

Where they differ is body size: at an estimated 40 grams, the fossil bat is roughly three times heavier than its living cousin, and the average weight of more than 900 living bat species.

“The size of bats is physically constrained by the demands of flight and echolocation, as you need to be small, quick and accurate to chase insects in the dark,” explains Associate Professor Hand. “The unusually large size of this bat suggests it was doing less in-flight hunting and was taking heavier prey from the ground, and larger fruit than even its living cousin.”

The team also found a diverse array of plant, animal and insect fossils at the site, which shows that the 16-million-year-old subtropical ecosystem bore resemblance to the more temperate one that exists today.

“Remarkably, the Miocene ecosystems associated with the fossil bat contain the kinds of trees used today by Mystacina for its colonial roosts,” says Associate Professor Hand. “Most of its food plants are also represented, as are terrestrial arthropods including a variety of beetles, ants and spiders, which these bats continue to hunt on the ground.”

The Lake Manuherikia site has been a treasure trove for palaeontologists over the years, producing New Zealand’s oldest frogs, lizards and land birds, as well as its only crocodiles and terrestrial turtles.

Reference:
Suzanne J. Hand, Daphne E. Lee, Trevor H. Worthy, Michael Archer, Jennifer P. Worthy, Alan J. D. Tennyson, Steven W. Salisbury, R. Paul Scofield, Dallas C. Mildenhall, Elizabeth M. Kennedy, Jon K. Lindqvist. Miocene Fossils Reveal Ancient Roots for New Zealand’s Endemic Mystacina (Chiroptera) and Its Rainforest Habitat. PLOS ONE, 17 Jun 2015 DOI: 10.1371/journal.pone.0128871

Note: The above post is reprinted from materials provided by University of New South Wales.

First sensor of Earth’s magnetic field in an animal

Inside the head of the worm C. elegans, the TV antenna-like structure at the tip of the AFD neuron (green) is the first identified sensor for Earth’s magnetic field. Credit: Illustration by Andres Vidal-Gadea.

A team of scientists and engineers at The University of Texas at Austin has identified the first sensor of Earth’s magnetic field in an animal, finding in the brain of a tiny worm a big clue to a long-held mystery about how animals’ internal compasses work.
Animals as diverse as migrating geese, sea turtles and wolves are known to navigate using Earth’s magnetic field. But until now, no one has pinpointed quite how they do it. The sensor, found in worms called C. elegans, is a microscopic structure at the end of a neuron that other animals probably share, given similarities in brain structure across species. The sensor looks like a nano-scale TV antenna, and the worms use it to navigate underground.

“Chances are that the same molecules will be used by cuter animals like butterflies and birds,” said Jon Pierce-Shimomura, assistant professor of neuroscience in the College of Natural Sciences and member of the research team. “This gives us a first foothold in understanding magnetosensation in other animals.”

The researchers discovered that hungry worms in gelatin-filled tubes tend to move down, a strategy they might use when searching for food.

When the researchers brought worms into the lab from other parts of the world, the worms didn’t all move down. Depending on where they were from — Hawaii, England or Australia, for example — they moved at a precise angle to the magnetic field that would have corresponded to down if they had been back home. For instance, Australian worms moved upward in tubes. The magnetic field’s orientation varies from spot to spot on Earth, and each worm’s magnetic field sensor system is finely tuned to its local environment, allowing it to tell up from down.

The research is published today in the journal eLife.

The study’s lead author is Andrés Vidal-Gadea, a former postdoctoral researcher in the College of Natural Sciences at UT Austin, now a faculty member at Illinois State University. He noted that C. elegans is just one of myriad species living in the soil, many of which are known to migrate vertically.

“I’m fascinated by the prospect that magnetic detection could be widespread across soil dwelling organisms,” said Vidal-Gadea.

The neuroscientists and engineers, who use C. elegans in their research into Alzheimer’s disease and addiction, had previously discovered the worm’s ability to sense humidity. That work led them to ask what else the worms might be able to sense, such as magnetic fields.

In 2012, scientists from Baylor College of Medicine announced the discovery of brain cells in pigeons that process information about magnetic fields, but they did not discover which part of the body senses the fields. That team and others have proposed a magnetosensor in the birds’ inner ear.

“It’s been a competitive race to find the first magnetosensory neuron,” said Pierce-Shimomura. “And we think we’ve won with worms, which is a big surprise because no one suspected that worms could sense the Earth’s magnetic field.”

The neuron sporting a magnetic field sensor, called an AFD neuron, was already known to sense carbon dioxide levels and temperature.

The researchers discovered the worms’ magnetosensory abilities by altering the magnetic field around them with a special magnetic coil system and then observing changes in behavior. They also showed that worms which were genetically engineered to have a broken AFD neuron did not orient themselves up and down as do normal worms. Finally, the researchers used a technique called calcium imaging to demonstrate that changes in the magnetic field cause the AFD neuron to activate.

Pierce-Shimomura suggested this research might open up the possibility of manipulating magnetic fields to protect agricultural crops from harmful pests.Other members of the research team from the College of Natural Sciences are Joshua Russell, a former graduate student who completed his Ph.D.; Kristi Ward, a former undergraduate; and Celia Beron, a current undergraduate. Research team members from the Cockrell School of Engineering are: Dr. Adela Ben-Yakar, associate professor of mechanical engineering; Navid Ghorashian, a former graduate student who completed his Ph.D.; and Sertan Gokce, a current graduate student.

Support for this research came from the National Institutes of Health and the National Institute of Neurological Disorders and Stroke.

Reference:
Andrés Vidal-Gadea, Kristi Ward, Celia Beron, Navid Ghorashian, Sertan Gokce, Joshua Russell, Nicholas Truong, Adhishri Parikh, Otilia Gadea, Adela Ben-Yakar, Jonathan Pierce-Shimomura. Magnetosensitive neurons mediate geomagnetic orientation inCaenorhabditis elegans. eLife, 2015; 4 DOI: 10.7554/eLife.07493

Note: The above post is reprinted from materials provided by University of Texas at Austin.

‘Dead Zone’ for Gulf of Mexico was predicted

Less oxygen dissolved in the water is often referred to as a “dead zone” (in red above) because most marine life either dies, or, if they are mobile such as fish, leave the area. Habitats that would normally be teeming with life become, essentially, biological deserts. Credit: NOAA

Scientists are expecting a very large “dead zone” in the Gulf of Mexico and a smaller than average hypoxic level in the Chesapeake Bay this year, based on several NOAA-supported forecast models.
NOAA-supported modelers at the University of Michigan, Louisiana State University, and the  Louisiana Universities Marine Consortium are forecasting that this year’s Gulf of Mexico hypoxic “dead” zone will be between 7,286 and 8,561 square miles which could place it among the ten largest recorded. That would range from an area the size of Connecticut, Rhode Island and the District of Columbia combined on the low end to the New Jersey on the upper end. The high estimate would exceed the largest ever reported 8,481 square miles in 2002 .

Hypoxic (very low oxygen) and anoxic (no oxygen) zones are caused by excessive nutrient pollution, often from human activities such as agriculture, which results in insufficient oxygen to support most marine life in near-bottom waters. Aspects of weather, including wind speed, wind direction, precipitation and temperature, also impact the size of dead zones.

The Gulf estimate is based on the assumption of no significant tropical storms in the two weeks preceding or during the official measurement survey cruise scheduled from July 25-August 3 2013.  If a storm does occur the size estimate could drop to a low of 5344 square miles, slightly smaller than the size of Connecticut.

This year’s prediction for the Gulf reflect flood conditions in the Midwest that caused large amounts of nutrients to be transported from the Mississippi watershed to the Gulf. Last year’s dead zone in the Gulf of Mexico was the fourth smallest on record due to drought conditions, covering an area of approximately 2,889 square miles, an area slightly larger than the state of Delaware. The overall average between 1995-2012 is 5,960 square miles, an area about the size of Connecticut.

A second NOAA-funded forecast, for the Chesapeake Bay, calls for a smaller than average dead zone in the nation’s largest estuary. The forecasts from researchers at the University of Maryland Center for Environmental Science  and the University of Michigan has three parts: a prediction for the mid-summer volume of the low-oxygen hypoxic zone, one for the mid-summer oxygen-free anoxic zone, and a third that is an average value for the entire summer season.

The forecasts call for a mid-summer hypoxic zone of 1.46 cubic miles, a mid-summer anoxic zone of 0.26 to 0.38 cubic miles, and a summer average hypoxia of  1.108 cubic miles, all at the low end of previously recorded zones.  Last year the final mid-summer hypoxic zone was 1.45 cubic miles.

This is the seventh year for the Bay outlook which, because of the shallow nature of large areas of the estuary, focuses on water volume or cubic miles, instead of square mileage as used in the Gulf. The history of hypoxia in the Chesapeake Bay since 1985 can be found at the EcoCheck website.

Both forecasts are based on nutrient run-off and river stream data from the U.S. Geological Survey (USGS), with the Chesapeake data funded with a cooperative agreement between USGS and the Maryland Department of Natural Resources.  Those numbers are then inserted into models developed by funding from the National Ocean Service’s National Centers for Coastal Ocean Science (NCCOS).

“Monitoring the health and vitality of our nation’s oceans, waterways, and watersheds is critical as we work to preserve and protect coastal ecosystems,” said Kathryn D. Sullivan, Ph.D., acting under secretary of commerce for oceans and atmosphere and acting NOAA administrator.  “These ecological forecasts are good examples of the critical environmental intelligence products and tools that help shape a healthier coast, one that is so inextricably linked to the vitality of our communities and our livelihoods.”

The dead zone in the Gulf of Mexico affects nationally important commercial and recreational fisheries, and threatens the region’s economy. The Chesapeake dead zones, which have been highly variable in recent years, threaten a multi-year effort to restore the Bay’s water quality and enhance its production of crabs, oysters, and other important fisheries.

During May 2013, stream flows in the Mississippi and Atchafalaya rivers were above normal resulting in more nutrients flowing into the Gulf. According to USGS estimates, 153,000 metric tons of nutrients flowed down the rivers to the northern Gulf of Mexico in May, an increase of 94,900 metric tons over last year’s 58,100 metric tons, when the region was suffering through drought. The 2013 input is an increase of 16 percent above the average nutrient load estimated over the past 34 years.

For the Chesapeake Bay, USGS estimates 36,600 metric tons of nutrients entered the estuary from the Susquehanna and Potomac rivers between January and May, which is 30 percent below the average loads estimated from1990 to 2013.

“Long-term nutrient monitoring and modeling is key to tracking how nutrient conditions are changing in response to floods and droughts and nutrient management actions,” said Lori Caramanian, deputy assistant secretary of the interior for water and science. “Understanding the sources and transport of nutrients is key to developing effective nutrient management strategies needed to reduce the size of hypoxia zones in the Gulf, Bay and other U.S. waters where hypoxia is an on-going problem.”

“Coastal hypoxia is proliferating around the world,” said Donald Boesch, Ph.D., president of the University of Maryland Center for Environmental Science. “It is important that we have excellent abilities to predict and control the largest dead zones in the United States. The whole world is watching.”

The confirmed size of the 2013 Gulf hypoxic zone will be released in August, following a monitoring survey led by the Louisiana Universities Marine Consortium beginning in late July, and the result will be used to improve future forecasts. The final measurement in the Chesapeake will come in October following surveys by the Chesapeake Bay Program’s partners from the Maryland Department of Natural Resources and the Virginia Department of Environmental Quality.

Despite the Mississippi River/Gulf of Mexico Nutrient Task Force’s goal to reduce the dead zone to less than 2,000 square miles, it has averaged 5,600 square miles over the last five years. Demonstrating the link between the dead zone and nutrients from the Mississippi River, this annual forecast continues to provide guidance to federal and state agencies as they work on the 11 implementation actions outlined by the Task Force in 2008 for mitigating nutrient pollution.

NOAA’s National Ocean Service has been funding investigations and forecast development for the dead zone in the Gulf of Mexico since 1990, and oversees national hypoxia research programs which include the Chesapeake Bay and other affected bodies of water.

USGS operates more than 3,000 real-time stream gages and collects water quality data at numerous long-term stations throughout the Mississippi River basin  and the Chesapeake Bay to track how nutrient loads are changing over time.

Video

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

New research shows Earth’s core contains 90 percent of Earth’s sulfur

earth-magmaH.jpg

So perhaps there is some truth in the old legends of the underworld reeking of brimstone (or sulphur, as it is now called)? New research confirms that the Earth’s core does in fact contain vast amounts of sulphur, estimated to be up to 8.5 x 1018 tonnes. This is about 10 times the amount of sulphur in the rest of the Earth, based on the most recent estimates (and for comparison, around 10% of the total mass of the Moon). This is the first time that scientists have conclusive geochemical evidence for sulphur in the Earth’s core, lending weight to the theory that the Moon was formed by a planet-sized body colliding with the Earth. This work is reported in the peer-reviewed journal, Geochemical Perspectives Letters.

The Earth’s core begins 2900km beneath our feet, so it is impossible to investigate directly. However, an international group of researchers have been able to develop indirect geochemical methods to show core composition.

As lead researcher Dr Paul Savage (Department of Earth Sciences, Durham University, UK) said:

“Scientists have suspected that there is sulphur in the core for some time, but this is the first time we have solid geochemical evidence to support the idea.”

For a long time it has been known that the Earth’s core is too light to be made only of iron and nickel, and it had been assumed that the core contained other lighter elements, such as sulphur, silicon, oxygen and carbon. However, given the depth of the core, this has been impossible to confirm directly. Fortunately, a cataclysmic event in the distant past – when the Earth collided with a large, planet-sized body, tearing off the part which became our Moon – left a fingerprint, which has been used to confirm the core content.

The researchers believe that the impact of the collision melted the Earth’s mantle, allowing a sulphur-rich liquid to form in Earth’s mantle, the vast middle layer between the core and the crust; some was probably lost into space, but some remained and sunk into the core. The key to confirming this lay in measuring the isotope ratios of elements (isotopes are atoms of the same element with slightly different masses) in the mantle, and comparing these to certain meteorites, which are believed to be the best match to the Earth’s original composition.

Because of variability in mantle composition, it is difficult to draw firm conclusions from measuring sulphur directly, so the researchers chose to analyse copper from the Earth’s mantle and crust – copper is often bound to sulphur. “We chose copper, because it is a chalcophile element, which means it prefers to be in sulphide-rich material – so is a good element to trace the fate of sulphur on Earth,” said senior author Professor Frédéric Moynier (Institut de Physique du Globe, Paris). “Generally, where there is copper, there is sulphur; copper gives us a proxy measurement for sulphur.”

The work comprised 3 distinct stages:

  • Firstly, the researchers had to estimate the isotopic composition of copper in the Earth’s mantle and crust.
  • Secondly, they had to estimate the isotopic composition of copper in the Earth before it formed a core, and was bombarded by giant impactors. Direct measurement is of course impossible, so they used meteorites, which are regarded as the best analogue.
  • Finally, they had to simulate which copper isotopic signature would be generated by the removal of sulphur-rich liquid after the ‘giant impact’.

Using the state-of-the-art mass spectroscopes at the Washington University in St. Louis and the Institut de Physique du Globe, Paris, they were able to confirm that there was a difference of 0.025% in the copper isotopic ratios between the Earth mantle samples, and the meteorite samples. Because the isotopes of copper divide unevenly between a sulphur-rich liquid and the rest of Earth’s mantle, this shows that a large amount of sulphur must have been removed from the mantle.

Paul Savage said:

“This study is the first to show clear geochemical evidence that a sulphide liquid must have separated from the mantle early on in Earth’s history – which most likely entered the core. We estimate that the quantity of sulphur in the core is vast, around 8.5 x 1018 tonnes, which to give an idea of scale, is around 10% of the mass of the Moon. In addition, the work adds weight to the theory that the Moon was formed via a collision between the Earth and another body.

“In a way, we can also say that we have life imitating art. For millennia, tales have been told of the underworld being awash with fire and brimstone. Now at least, we can be sure of the brimstone.”

Commenting, Executive Co-Editor of Geochemical Perspectives Letters, Professor Graham Pearson (University of Alberta) said:

“The presence and identity of other elements in the Earth’s core has been one of the most enduring problems in geochemistry. Savage and colleagues provide very elegant evidence, using isotopes of copper as a tracer, of the stripping of vast amounts of sulphur from the Earth’s early mantle into the core. So the core turns out to be a good place to hide quite substantial amounts of elements other than iron and nickel. This study will surely encourage others to persist in the search for evidence of other elements in the core – data that is critically needed to complete our understanding of how the Earth formed and what the geochemical mass balance is in the Earth.”

Reference:
Copper isotope evidence for large-scale sulphide fractionation during Earth’s differentiation, Geochemical Perspectives Letters, v1, n1 , DOI: 10.7185/geochemlet.1506

The above post is reprinted from materials provided by European Association of Geochemistry.

‘Unprecedented’ earthquake evidence in Africa discovered

A geological fault near Galula in Tanzania

A discovery by James Cook University researchers means evidence from the past could be used to help predict the danger of earthquakes in less-developed countries.
Lead researcher Hannah Hilbert-Wolf and supervisor Dr Eric Roberts used innovative methods to examine the ground around Mbeya in Tanzania where a large earthquake occurred some 25,000 years ago.

They found evidence of fluidisation (where soil behaves like quicksand) and upward displacement of material unprecedented in a continental setting, raising questions of how resilient the rapidly growing cities of the region would be in a major shake.

“We can now use this to evaluate how the ground would deform in a modern earthquake,” said Dr Roberts. “This is important because the approach is inexpensive and can be used to model how structures might be affected by future events, providing a valuable tool in hazard assessment.”

Ms Hilbert-Wolf said the team found evidence of massive ground deformation and previously unknown styles of liquefaction and fluidisation, caused by past earthquakes. “This could be a major concern for the growing urban population of East Africa, which has similar tectonic settings and surface conditions,” she said.

The study comes on the back of a series of damaging earthquakes already this year, including in Nepal and Papua New Guinea and the study may be of much use in predicting the effects of earthquakes in those countries.

“What we have shown is that in developing countries in particular, which may lack extensive seismic monitoring, the rock record can be used to not only investigate the timing and frequency of past events, but also provide important insights into how the ground will behave in certain areas to seismic shock,” said Ms Hilbert-Wolf.

In 1910, 7.5 million people lived in Tanzania when the most powerful earthquake in Africa of the twentieth century struck, collapsing houses and triggering liquefaction and fluidisation. By 2050 it is estimated that around 130 million people will live in Tanzania, mostly in constructed urban settings that are more susceptible to earthquake damage and surface deformation than traditionally fabricated buildings.

Reference:
Hannah Louise Hilbert-Wolf, Eric M. Roberts. Giant Seismites and Megablock Uplift in the East African Rift: Evidence for Late Pleistocene Large Magnitude Earthquakes. PLOS ONE, 2015; 10 (6): e0129051 DOI: 10.1371/journal.pone.0129051

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

A third of the world’s biggest groundwater basins are in distress

UC Irvine researchers used NASA satellites to show aquifer depletion worldwide. They are trying to raise awareness about the lack of information about remaining groundwater supplies on Earth Credit: UC Irvine / NASA

Two new studies led by UC Irvine using data from NASA Gravity Recovery and Climate Experiment satellites show that civilization is rapidly draining some of its largest groundwater basins, yet there is little to no accurate data about how much water remains in them.
The result is that significant segments of Earth’s population are consuming groundwater quickly without knowing when it might run out, the researchers conclude. The findings appear today in Water Resources Research.

“Available physical and chemical measurements are simply insufficient,” said UCI professor and principal investigator Jay Famiglietti, who is also the senior water scientist at NASA’s Jet Propulsion Laboratory. “Given how quickly we are consuming the world’s groundwater reserves, we need a coordinated global effort to determine how much is left.”

The studies are the first to characterize groundwater losses via data from space, using readings generated by NASA’s twin GRACE satellites that measure dips and bumps in Earth’s gravity, which is affected by the weight of water.

For the first paper, researchers examined the planet’s 37 largest aquifers between 2003 and 2013. The eight worst off were classified as overstressed, with nearly no natural replenishment to offset usage. Another five aquifers were found, in descending order, to be extremely or highly stressed, depending upon the level of replenishment in each — still in trouble but with some water flowing back into them.

The most overburdened are in the world’s driest areas, which draw heavily on underground water. Climate change and population growth are expected to intensify the problem.

“What happens when a highly stressed aquifer is located in a region with socioeconomic or political tensions that can’t supplement declining water supplies fast enough?” asked the lead author on both studies, Alexandra Richey, who conducted the research as a UCI doctoral student. “We’re trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods.”

The research team — which included co-authors from NASA, the National Center for Atmospheric Research, National Taiwan University and UC Santa Barbara — found that the Arabian Aquifer System, an important water source for more than 60 million people, is the most overstressed in the world.

The Indus Basin aquifer of northwestern India and Pakistan is the second-most overstressed, and the Murzuk-Djado Basin in northern Africa is third. California’s Central Valley, utilized heavily for agriculture and suffering rapid depletion, was slightly better off but still labeled highly stressed in the first study.

“As we’re seeing in California right now, we rely much more heavily on groundwater during drought,” Famiglietti said. “When examining the sustainability of a region’s water resources, we absolutely must account for that dependence.”

In a companion paper published today in the same journal, the scientists conclude that the total remaining volume of the world’s usable groundwater is poorly known, with often widely varying estimates, but is likely far less than rudimentary estimates made decades ago.

By comparing their satellite-derived groundwater loss rates to what little data exists on groundwater availability, they found major discrepancies in projected “time to depletion.” In the overstressed Northwest Sahara Aquifer System, for example, this fluctuated between 10 and 21,000 years.

“We don’t actually know how much is stored in each of these aquifers. Estimates of remaining storage might vary from decades to millennia,” Richey said. “In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly.”

The study notes that the dearth of groundwater is already leading to significant ecological damage, including depleted rivers, declining water quality and subsiding land.

Groundwater aquifers are typically located in soil or deeper rock layers beneath Earth’s surface. The depth and thickness of many make it tough and costly to drill to or otherwise reach bedrock and learn where the moisture bottoms out. But it has to be done, according to the authors.

“I believe we need to explore the world’s aquifers as if they had the same value as oil reserves,” Famiglietti said. “We need to drill for water the same way that we drill for other resources.”

References:

  • Alexandra S. Richey, Brian F. Thomas, Min-Hui Lo, James S. Famiglietti, Sean Swenson, Matthew Rodell. Uncertainty in global groundwater storage estimates in a total groundwater stress framework. Water Resources Research, 2015; DOI: 10.1002/2015WR017351
  • Alexandra S. Richey, Brian F. Thomas, Min-Hui Lo, John T. Reager, James S. Famiglietti, Katalyn Voss, Sean Swenson, Matthew Rodell. Quantifying renewable groundwater stress with GRACE. Water Resources Research, 2015; DOI: 10.1002/2015WR017349

Note: The above post is reprinted from materials provided by University of California, Irvine.

Scientists find methane in Mars meteorites

Scientists found methane gas in samples taken from Martian meteorites. Credit: Image by Michael Helfenbein

An international team of researchers has discovered traces of methane in Martian meteorites, a possible clue in the search for life on the Red Planet.
The researchers examined samples from six meteorites of volcanic rock that originated on Mars. The meteorites contain gases in the same proportion and with the same isotopic composition as the Martian atmosphere. All six samples also contained methane, which was measured by crushing the rocks and running the emerging gas through a mass spectrometer. The team also examined two non-Martian meteorites, which contained lesser amounts of methane.

The discovery hints at the possibility that methane could be used as a food source by rudimentary forms of life beneath the Martian surface. On Earth, microbes do this in a range of environments.

“Other researchers will be keen to replicate these findings using alternative measurement tools and techniques,” said co-author Sean McMahon, a Yale University postdoctoral associate in the Department of Geology and Geophysics. “Our findings will likely be used by astrobiologists in models and experiments aimed at understanding whether life could survive below the surface of Mars today.”

The discovery was part of a joint research project led by the University of Aberdeen, in collaboration with the Scottish Universities Environmental Research Centre, the University of Glasgow, Brock University in Ontario, and the University of Western Ontario.

“One of the most exciting developments in the exploration of Mars has been the suggestion of methane in the Martian atmosphere,” said University of Aberdeen professor John Parnell, who directed the research. “Recent and forthcoming missions by NASA and the European Space Agency, respectively, are looking at this, however, it is so far unclear where the methane comes from, and even whether it is really there. However, our research provides a strong indication that rocks on Mars contain a large reservoir of methane.”

Co-author Nigel Blamey, of Brock University, said the team plans to expand its research by analyzing additional meteorites.

Yale’s McMahon noted that the team’s approach may prove helpful in future Mars rover experiments. “Even if Martian methane does not directly feed microbes, it may signal the presence of a warm, wet, chemically reactive environment where life could thrive,” McMahon said.

Reference:
Nigel J. F. Blamey, John Parnell, Sean McMahon, Darren F. Mark, Tim Tomkinson, Martin Lee, Jared Shivak, Matthew R. M. Izawa, Neil R. Banerjee, Roberta L. Flemming. Evidence for methane in Martian meteorites. Nature Communications, 2015; 6: 7399 DOI: 10.1038/ncomms8399

Note: The above post is reprinted from materials provided by Yale University. The original item was written by Jim Shelton.

Bacteria could help clean groundwater contaminated by uranium ore processing

Sign at shuttered uranium mill in Rifle, Colorado, warns onlookers of hazards that remain from Cold War era nuclear weapons production. Credit: Bill Gillette, U.S. National Archives and Records Administration

A strain of bacteria that “breathes” uranium may hold the key to cleaning up polluted groundwater at sites where uranium ore was processed to make nuclear weapons.
A team of Rutgers University scientists and collaborators discovered the bacteria in soil at an old uranium ore mill in Rifle, Colorado, almost 200 miles west of Denver. The site is one of nine such mills in Colorado used during the heyday of nuclear weapons production.

The research is part of a U.S. Department of Energy program to see if microorganisms can lock up uranium that leached into the soil years ago and now makes well water in the area unsafe to drink.

The team’s discovery, published in the April 13, 2015 issue of PLOS ONE, is the first known instance where scientists have found a bacterium from a common class known as betaproteobacteria that breathes uranium. This bacterium can breathe either oxygen or uranium to drive the chemical reactions that provide life-giving energy.

“After the newly discovered bacteria interact with uranium compounds in water, the uranium becomes immobile,” said Lee Kerkhof, a professor of marine and coastal sciences in the School of Environmental and Biological Sciences. “It is no longer dissolved in the groundwater and therefore can’t contaminate drinking water brought to the surface.”

Kerkhof leads the Rutgers team that works with U.S. Department of Energy researchers.

Breathing uranium is rather rare in the microbial world. Most examples of bacteria which can respire uranium cannot breathe oxygen but often breathe compounds based on metals – typically forms of solid iron. Scientists had previously witnessed decreasing concentrations of uranium in groundwater when iron-breathing bacteria were active, but they have yet to show that those iron-breathing bacteria were directly respiring the uranium.

While the chemical reaction that the bacteria perform on uranium is a common process known as “reduction,” or the act of accepting electrons, Kerkhof said it’s still a mystery how the reduced uranium produced by this microorganism ultimately behaves in the subsurface environment.

“It appears that they form uranium nanoparticles,” he said, but the mineralogy is still not well known and will be the subject of ongoing research.

The Rutgers team was able to isolate the uranium-breathing bacterium in the lab by recognizing that uranium in samples from the Rifle site could be toxic to microorganisms as well as humans. The researchers looked for signs of bacterial activity when they gradually added small amounts of dissolved uranium at the right concentration back to the samples where uranium had become immobilized. Once they found the optimal uranium concentrations, they were able to isolate the novel strain.

Exactly how the strain evolved, Kerkhof said, “we are not sure.” But, he explained, bacteria have the ability to pass genes to each other. So just like bacteria pick up resistance to things like antibiotics and heavy metal toxicity, this bacterium “picked up a genetic element that’s now allowing it to detoxify uranium, to actually grow on uranium.” His research team has completed sequencing its genome to support future research into the genetic elements that allow the bacterium to grow on uranium.

What Kerkhof is optimistic about is the potential for these bacteria to mitigate the specific groundwater pollution problem in Rifle. Scientists at first expected the groundwater to flush into the Colorado River and carry the dissolved uranium with it, where it would get diluted to safer levels. But that hasn’t happened. Other potential methods of remediation, such as digging up the contaminated soil or treating it with harsh chemicals, are thought to be too expensive or hazardous.

“Biology is a way to solve this contamination problem, especially in situations like this where the radionuclides are highly diluted but still present at levels deemed hazardous,” said Kerkhof. If the approach is successful, it could be considered for other sites where uranium was processed for nuclear arsenals or power plant fuel. While the problem isn’t widespread, he said there’s potentially a lot of water to be concerned about. And the problem could spread beyond traditional places such as ore processing sites.

“There is depleted uranium in a lot of armor-piercing munitions,” he said, “so places like the Middle East that are experiencing war could be exposed to high levels of uranium in the groundwater.”

Reference:
Nicole M. Koribanics, Steven J. Tuorto,Nora Lopez-Chiaffarelli, Lora R. McGuinness,Max M. Häggblom, Kenneth H. Williams, Philip E. Long,Lee J. Kerkhof. Spatial Distribution of an Uranium-Respiring Betaproteobacterium at the Rifle, CO Field Research Site. DOI: 10.1371/journal.pone.0123378

Note : The above story is based on materials provided by Rutgers University.

New study favors cold, icy early Mars

This is a conceptual rendition of the competing warm and cold scenarios for early Mars. Credit: Robin D. Wordsworth

The high seas of Mars may never have existed, according to a new study that looks at two opposite climate scenarios of early Mars and suggests that a cold and icy planet billions of years ago better explains water drainage and erosion features seen on the planet today.
For decades, researchers have debated the climate history of Mars and how the planet’s early climate led to the many water-carved channels seen today. The idea that 3 to 4 billion years ago Mars was once warm, wet and Earth-like with a northern sea — conditions that could have led to life — is generally more popular than that of a frigid, icy planet where water is locked in ice most of the time and life would be hard put to evolve.

To see which early Mars better explains the modern features of the planet, researcher Robin Wordsworth of the Harvard Paulson School of Engineering and Applied Sciences and his colleagues used a 3-dimensional atmospheric circulation model to compare a water cycle on Mars under different scenarios 3 to 4 billion years ago, during what’s called the late Noachian and early Hesperian periods. One scenario looked at Mars as a warm and wet planet with an average global temperature of 10 degrees Celsius (50 degrees Fahrenheit) and the other as a cold and icy world with an average global temperature of minus 48 degrees Celsius (minus 54 degrees Fahrenheit).

The study’s authors found that the cold scenario was more likely to have occurred than the warm scenario, based on what is known about the history of the Sun and the tilt of Mars’s axis 3 to 4 billion years ago. The cold model also did a better job explaining the water erosion features that have been left behind on the Martian surface, and which have puzzled and intrigued scientists since they were first discovered by the Viking orbiters in the 1970s.

A paper presenting the results has been accepted for publication in AGU’s Journal of Geophysical Research – Planets.

The colder scenario was more straightforward to model, Wordsworth explained, because Mars only gets 43 percent of the solar energy of Earth, and early Mars was lit by a younger Sun believed to have been 25 percent dimmer than it is today. That makes it very likely early Mars was cold and icy, he said.

An extreme tilt of the Martian axis would have pointed the planet’s poles at the Sun and driven polar ice to the equator, where water drainage and erosion features are seen today. More importantly, under a thicker atmosphere that likely existed under the colder scenario, highland regions at the equator get colder and northern low-lying regions get warmer – the so-called ‘icy highlands effect’ that is responsible for making the peaks of mountains snow-covered on Earth today. Despite a number of warming factors – including a thicker atmosphere filled with climate-warming carbon dioxide — Mars still would have been quite cold, Wordsworth added.

Creating a warm/wet Mars took more work, Wordsworth said. Previous studies have shown that even when the effects of climate-warming clouds, dust and carbon dioxide are taken into account, climate models still don’t show early Mars developing any warm and wet periods, he said.

But the conditions on early Mars may have been different than scientists’ thought, Wordsworth said. The study’s authors added to their model different climate effects to force Mars into a warmer, wet state.

Even then, however, the warm/wet early Mars does not explain the patchwork of Martian water erosion features and valley networks observed on the planet today, and why these features tend to be concentrated near the planet’s equator, Wordsworth said.

Under the warm/wet model, rainfall rates varied a lot with longitude and latitude. The warm/wet model predicts that on early Mars rain was greatest in an area called Arabia and around the Hellas basin, including in the west and southeast areas of the basin, where few water drainage features are found today. At the same time, several regions with many water-carved valleys, such as Margaritifer Sinus, received one-tenth to one-twentieth as much rain as Arabia and the Hellas basin under the warm/wet scenario.

In the warm/wet scenario, mountains also created rain shadows, like those that wring water from clouds to create deserts on Earth. On Mars, the bulge of Tharsis would have caused more rain to fall on the windward western side of the volcanic plateau, where few water features are seen today. To the east, downwind of the bulge, drier air would flow over Margaritifer Sinus, causing less rain to fall there – a situation that doesn’t match the drainage features observed there.

The cold/icy scenario isn’t perfect but it’s a better fit to the observations in general, Wordsworth said. While this scenario accumulates frozen water closer to the drainage features observed today on Mars, something had to have melted the ice which carved the valleys, he said. In this scenario, the climate is cool most of the time, and short-lived events like meteor impacts and volcanic eruptions likely caused the necessary melting, he said.

“I’m still trying to keep an open mind about this,” said Wordsworth. “There is lots of work to be done. But our results show that the cold/icy scenario matches the surface distribution of erosion features more closely. This strongly suggests that early Mars was generally cold, and water was supplied to the highland regions as snow, not as rain.”

Proving that a cold climate on early Mars led to the features seen on the planet today is a “big question”, said Bethany Ehlmann, a planetary scientist at California Institute of Technology and NASA’s Jet Propulsion Laboratory in Pasadena, California, who was not involved in the new study.

The new paper answers part of that question by showing that locations with snow accumulation in the cold and icy scenario roughly correspond to valley network locations seen today, she said. Further, the model of the cold and icy early Mars shows that some melting of ice would occur, she said.

“We know from rover- and orbiter-based data that there were lakes on ancient Mars,” she said. “Key questions are: how long did they persist? Were they episodic or persistent? And does the feeder valley network demand rain or is snow and ice melt sufficient?”

The 3-D climate modeling used in the new study begins to address these questions with a new level of sophistication by investigating how specific locations might have accumulated rain or snow, she said.

Reference:
Robin D. Wordsworth, Laura Kerber, Raymond T. Pierrehumbert, Francois Forget, James W. Head. Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3D climate model. DOI: 10.1002/2015JE004787

Note : The above story is based on materials provided by American Geophysical Union.

Why big dinosaurs steered clear of the tropics

212 million years ago in what is now northern New Mexico, the landscape was dry and hot with common wildfires. Early dinosaurs such as the carnivorous dinosaur in background were small and rare, whereas other reptiles such as the long-snouted phytosaurs and armored aetosaurs were quite common. Credit: Victor Leshyk

For more than 30 million years after dinosaurs first appeared, they remained inexplicably rare near the equator, where only a few small-bodied meat-eating dinosaurs eked out a living. The age-long absence of big plant-eaters at low latitudes is one of the great, unanswered questions about the rise of the dinosaurs.
And now the mystery has a solution, according to an international team of scientists who pieced together a remarkably detailed picture of the climate and ecology more than 200 million years ago at Ghost Ranch in northern New Mexico, a site rich with fossils from the Late Triassic Period.

The new findings show that the tropical climate swung wildly with extremes of drought and intense heat. Wildfires swept the landscape during arid regimes and continually reshaped the vegetation available for plant-eating animals.

“Our data suggest it was not a fun place,” says study co-author Randall Irmis, curator of paleontology at the Natural History Museum of Utah and assistant professor at the University of Utah. “It was a time of climate extremes that went back and forth unpredictably and large, warm-blooded dinosaurian herbivores weren’t able to exist nearer to the equator — there was not enough dependable plant food.”

The study, led by geochemist Jessica Whiteside, lecturer at the University of Southampton, is the first to provide a detailed look at the climate and ecology during the emergence of the dinosaurs. The results are important, also, for understanding human-caused climate change. Atmospheric carbon dioxide levels during the Late Triassic were four to six times current levels. “If we continue along our present course, similar conditions in a high-CO2 world may develop, and suppress low-latitude ecosystems,” Irmis says.

The other authors are Sofie Lindström, Ian Glasspool, Morgan Schaller, Maria Dunlavey, Sterling Nesbitt, Nathan Smith and Alan Turner. They report the findings today in the Proceedings of the National Academy of Sciences.

Reconstructing the deep past

The earliest known dinosaur fossils, found in Argentina, date from around 230 million years ago. Within 15 million years, multitudes of species with different diets and body sizes had evolved and were abundant beyond the tropical latitudes. In the tropics, the only dinosaurs present were small carnivores. This pattern persisted for 30 million years after the first dinosaurs appeared.

In the new study, the authors focused on Chinle Formation rocks, which were deposited by rivers and streams between 205 and 215 million years ago at Ghost Ranch (better known to many outside of paleontology as the place where artist Georgia O’Keeffe lived and painted for much of her career). The multi-colored rocks of the Chinle Formation are a common sight on the Colorado Plateau at places such as the Painted Desert at Petrified Forest National Park in Arizona. During the Late Triassic, North America and other land masses of the world were bound together in the supercontinent Pangea. The Ghost Ranch site stood close to the equator at roughly the same latitude as present-day southern India.

The researchers reconstructed the deep past by analyzing several kinds of data: fossils, charcoal left by ancient wildfires, and stable isotopes from organic matter and carbonate nodules that formed in ancient soils. “Each dataset complements the others, and they all point towards similar conditions,” Whiteside says. “I think this is one of the major strengths of our study.”

Fossilized bones, pollen grains and fern spores revealed the types of animals and plants living at different times, marked by layers of sediment. Dinosaurs remained rare among the fossils, accounting for less than 15 percent of vertebrate animal remains. They were outnumbered in diversity, abundance and body size by the reptiles known as Pseudosuchian archosaurs, the lineage that gave rise to crocodiles and alligators.

The sparse dinosaurs consisted mostly of small, carnivorous theropods. Big, long-necked dinosaurs, or sauropodomorphs — already the dominant plant-eaters at higher latitudes — did not exist at the study site or any other low-latitude site in Triassic Pangaea, as far as the fossil record shows.

Abrupt changes in climate left a record in the shifting abundance of different types of pollen and fern spores between sediment layers. Fossilized organic matter from decaying plants provided another window on climate shifts. Changes in the ratio of stable isotopes of carbon in the organic matter bookmarked times when plant productivity declined during extended droughts.

Drought and fire

Wildfire burn temperatures varied drastically, the researchers found, consistent with a fluctuating environment in which the amount of combustible plant matter rose and fell over time. The researchers estimated the intensity of wildfires using bits of charcoal recovered in the sediment layers. The amount of light reflected from the fossil charcoal under a light microscope relates directly to the burn temperature of the wood. The overall picture, the authors say, is that of a climate punctuated by extreme shifts in precipitation in which plant die-offs fueled hotter fires, which in turn killed more plants, damaged soils and increased erosion.

Atmospheric carbon dioxide levels, calculated from stable isotope analyses of soil carbonate and preserved organic matter, rose from about 1,200 parts per million at the base of the section, to about 2,400 parts per million near the top. At these high CO2 concentrations, climate models predict more frequent and more extreme weather fluctuations consistent with the fossil and charcoal evidence.

Continuing shifts between extremes of dry and wet likely prevented the establishment of dinosaur-dominated communities found in the fossil record at higher-latitudes across South America, Europe and southern Africa, where aridity and temperatures were less extreme and humidity was consistently higher. Resource-limited conditions could not support a diverse community of fast-growing, warm-blooded, large dinosaurs, which require a productive and stable environment to thrive.

“The conditions would have been something similar to the arid western United States today, although there would have been trees and smaller plants near streams and rivers and forests during humid times,” says Whiteside. “The fluctuating and harsh climate with widespread wild fires meant that only small two-legged carnivorous dinosaurs, such as Coelophysis, could survive.”

Reference:
Jessica H. Whiteside, Sofie Lindström, Randall B. Irmis, Ian J. Glasspool, Morgan F. Schaller, Maria Dunlavey, Sterling J. Nesbitt, Nathan D. Smith, and Alan H. Turner. Extreme ecosystem instability suppressed tropical dinosaur dominance for 30 million years. PNAS, 2015 DOI: 10.1073/pnas.1505252112

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

Cave study reveals 3000 years of climate variation

Roaring Cave in Scotland. A study of its limestone has produced a unique 3000-year-long record of climatic variations that may have influenced historical events including the fall of the Roman Empire and the Viking Age of expansion. Credit: Courtesy of UNSW

Research on limestone formations in a remote Scottish cave has produced a unique 3000-year-long record of climatic variations that may have influenced historical events including the fall of the Roman Empire and the Viking Age of expansion.
The UNSW-led study of five stalagmites in Roaring Cave north of Ullapool in north-west Scotland is the first to use a compilation of cave measurements to track changes in a climate phenomenon called the North Atlantic Oscillation.

“Our results also provide the longest annual record of this important phenomenon, which has a big impact on the climate in Europe,” says study leader, UNSW Professor Andy Baker.

“It confirms that the during the Medieval Warm Period between 1080 and 1430 the oscillation index was in an unusually prolonged positive phase, which brings increased rain to Scotland and drier conditions in the western Mediterranean,” says Professor Baker, of the UNSW Connected Waters Initiative Research Centre.

“Our results also reveal there was another persistent positive phase between 290 and 550, which coincides with the decline of Rome and a period of intensified human migration in southern Europe during the Dark Ages.

“This was followed by a persistent negative phase between 600 and 900 which may have provided warm and dry conditions in north-western Europe that made it suitable for westward expansion by the Vikings, although the precise timing of this event is contested.”

The study is published in the journal Scientific Reports.

The North Atlantic Oscillation climate index measures the air pressure difference between Iceland and the Azores islands off the Portuguese coast, and is a record of the strength of the westerly winds in the North Atlantic.

Roaring Cave, or Uamh an Tartair, in north-west Scotland, is a shallow cave beneath a blanket of peat that has accumulated during the past 4000 years.

Rainfall levels in this region closely correspond with the strength of the oscillation index in winter, with higher precipitation when it is positive. And the upward rate of growth of stalagmites in the cave is very sensitive to rainfall – the more water in the peat, the more slowly the stalagmites grow.

“We painstakingly measured the thickness of each annual growth ring in five stalagmites taken from the cave, including one that provides a continuous annual record spanning more than 1800 years,” says Professor Baker.

By overlapping the five stalagmites they obtained a proxy record of the climate at the cave during a 3000-year period from about 1000 BC to 2000 AD.

“Our research provides a climate context for some of the big human migration events in Europe and allows us to start building hypotheses about the impact of environment on societal change,” says Professor Baker.

The team includes researcher from UNSW, the University of Lausanne in Switzerland and the University of Arizona in the US.

Reference:
Andy Baker, John C. Hellstrom, Bryce F. J. Kelly, Gregoire Mariethoz, Valerie Trouet. A composite annual-resolution stalagmite record of North Atlantic climate over the last three millennia. Scientific Reports, 2015; 5: 10307 DOI: 10.1038/srep10307

Note: The above post is reprinted from materials provided by University of New South Wales.

Mount Everest, moved three centimetres due to Nepal earthquake

Everest Base Camp shown on April 26, 2015, a day after an avalanche triggered by an earthquake caused the death of 18 people Credit: AFP Photo/Roberto Schmidt

The world’s tallest peak, Mount Everest, moved three centimetres (1.2 inches) to the southwest because of the Nepal earthquake that devastated the country in April, Chinese state media reported Tuesday.
The 7.8-magnitude quake reversed the gradual northeasterly course of the mountain, according to a report in the state-run China Daily, citing the National Administration of Surveying, Mapping and Geoinformation.

Before the quake, Everest had moved 40 centimetres to the northeast over the past decade at a speed of four centimetres a year, the report said. The mountain also rose three centimetres over the same time period.

The earthquake caused an avalanche on Everest, killing 18 people and leaving its climbing base camp in ruins. It prompted authorities in both China and Nepal to cancel all climbs for this year.

The mountain straddles the border between the two countries.

Two earthquakes, on April 25 and May 12, killed more than 8,700 people in Nepal, triggered landslides and destroyed half a million homes, leaving thousands without shelter just weeks ahead of monsoon rains.

The second quake, which had a magnitude of 7.3, did not move the mountain, China Daily said.

Note : The above story is based on materials provided by AFP.

New Study: Origins of Red Sea’s mysterious ‘cannon earthquakes’ revealed

Annotated view of the Nile and Red Sea, with a dust storm Credit: NASA

For many generations, Bedouin people living in the Abu Dabbab area on the Egyptian Red Sea coast have heard distinct noises—like the rumbling of a quarry blast or cannon shot—accompanying small earthquakes in the region. Now, a new study published in the Bulletin of the Seismological Society of America offers an explanation for this uniquely noisy seismic event.
Seismic activity in the area of the Egyptian seaside resort Abu Dabbab may be caused by an active fault that lays below a 10-kilometer thick block of old, now rigid igneous rock. The surface of the block slides along the active parts of the fault, lubricated by fluids from the Red Sea that have penetrated the crust, according to Sami El Khrepy of King Saud University in Riyadh, Saudi Arabia and colleagues.

The researchers think this large and rigid block of igneous crust acts as a sort of broadcaster, allowing the full sounds of seismic movement to rise through the rock with little weakening of the acoustic signal. The high-frequency sounds of earthquakes can then be heard by humans at the surface.

Earlier studies had suggested that the Abu Dabbab earthquakes were caused by magma rising through the crust, but the new report “found that a volcanic origin of the seismicity is unlikely, and the area is not expected to be subjected to volcanic hazard,” said El Khrepy.

Earthquake swarms are frequent in this area of the northern Red Sea near Abu Dabbab, but most of the earthquakes are weak, ranging in magnitude from 0.3 to 3.5. The largest well-documented earthquakes, measuring magnitude 6.1 and magnitude 5.1, occurred in 1955 and 1984, respectively.

El Khrepy and colleagues decided to take a closer look at the structure of the Abu Dabbab crust, to determine the origin of this seismicity. To peer into the crust, they combined data from local earthquake monitoring with a new set of local and regional earthquake data collected by the National Seismic Network of Egypt (ENSN), which was completed in 2002. They then applied a technique called seismic tomography, which uses data on the speed of seismic waves traveling through different rock types to develop a 3-D map of some of the subsurface geological features in the area.

“This study is the first detailed look at the seismic tomography in this region of Abu Dabbab’s cannon earthquakes,” said El Khrepy, “It was not possible to do this work without ENSN deployment.”

The researchers determined that the earthquakes at Abu Dabbab extend in a line from the coast into the Red Sea, “and the seismicity pattern is arc-shaped in depth, confined to the dome-like structure of the rigid igneous body that formed during the Precambrian era” above an active fault, El Khrepy said.

The strike-slip and thrust movements of the fault may drive water from the Red Sea in between the fault and the surface of the igneous block, allowing the two to slip past each other, the scientists suggest.

“Based on the new results and also the historical data,” El Khrepy concluded, “we report that the confined seismicity in this zone is of tectonic, and not volcanic, origin.”

Reference:
I. Koulakov, S. El Khrepy, N. Al-Arifi, P. Kuznetsov, E. Kasatkina. Structural cause of a missed eruption in the Harrat Lunayyir basaltic field (Saudi Arabia) in 2009. Geology, 2015; 43 (5): 395 DOI: 10.1130/G36271.1

Note : The above story is based on materials provided by Seismological Society of America.

Understanding the softness in Earth’s lithosphere

This figure shows a photo-micrograph of a thin section of a rock from the lithosphere, on which records of seismic waves are superimposed. Regions with different colors show minerals with different orientations.

Yale researchers have proposed a new model to explain the drop in elastic stiffness in the middle of the Earth’s continental lithosphere.
Lithosphere is the stiff layer of rock that lies atop the slow-motion convection of Earth’s solid, yet ductile, interior. It is the “plate” of plate tectonics, the system of interlocking fragments that explains earthquakes, volcanoes, and even the long-term variation of carbon dioxide in the atmosphere.

A softening in the middle of the continental lithosphere was discovered when seismologists studied the structure of the United States. This same softening was observed in other continents as well, at a depth of 80 to 150 km. Researchers found the phenomenon puzzling, because softening detected by seismology is usually linked to softening that occurs over millions of years (also known as geologic time). If that were the case, the continental lithosphere would have a weak layer in it, and it would be difficult to explain the continents’ long-term stability.

Yale geophysicists Shun-ichiro Karato, Tolulope Olugboji (a former Yale student, now at the University of Maryland), and Jeffrey Park may have found the answer.

In a study published June 15 in the journal Nature Geoscience, they present a new model to describe the phenomenon. They say the softening is a natural consequence of the way rocks deform as temperatures rise below the melting point. The key is that this softening occurs in a second or less (the seismic time scale), rather than over millions of years.

Rocks are composed of strong mineral crystals separated by grain boundaries, where atoms are disordered and weaker. As temperature increases, the mineral grains remain strong, but grain boundaries weaken and allow sliding to occur. As a consequence of this sliding, the overall stiffness of a rock is reduced at the seismic time scale, but not the geological time scale.

“Our model is consistent with a stable continent, because the weakness of grain-boundary sliding is limited to deformation of the lithosphere in approximately one second, not its long-term deformation,” Karato said.

Reference:
Mechanisms and geologic significance of the mid-lithosphere discontinuity in the continents, DOI: 10.1038/ngeo2462

Note : The above story is based on materials provided by Yale University.

Accelerated warming of continental shelf off northeast coast of U.S.

A new study shows that water temperatures in this continental shelf region have been trending upward, with unprecedented warming occurring over the last 13 years. The research is based upon temperature data from the waters off the northeast coast of the U.S. that were collected in collaborative effort between scientists and the operators of the container ship Oleander, which routinely travels between Bermuda and New Jersey (green line). The mean surface circulation in the northwestern North Atlantic is shown. Credit: Forsyth, et al

A couple of unexplained large scale changes in the waters off the northeast coast of the U.S. have oceanographers perplexed: an accelerated rate of sea level rise compared to most other parts of the world; and the disturbing signs of collapsing fisheries in the region.
A new study by physical oceanographers at Woods Hole Oceanographic Institution (WHOI), published in the Journal of Geophysical Research, shows that water temperatures in this continental shelf region have been trending upward, with unprecedented warming occurring over the last 13 years. The study also suggests a connection between sea level anomalies and water temperature along the continental shelf.

“The warming rate since 2002 is 15 times faster than from the previous 100 years,” says co-author Glen Gawarkiewicz, a WHOI senior scientist. “There’s just been this incredible acceleration to the warming, and we don’t know if its decadal variability, or if this trend will continue.”

The scientists compared their findings with a study of surface waters using data collected by Nantucket Light ship, and other light ships up and down the East Coast between 1880 and 2004, previously analyzed by Steve Lentz of WHOI and Kipp Shearman of Oregon State University. The new study shows that recent accelerated warming is not confined to the surface waters, but extends throughout the water column.

“Others have reported on the temperature increase in this region,” says Gawarkiewicz’s colleague, WHOI assistant scientist Magdalena Andres, “but they’ve been confined to looking at the surface temperatures from satellites or buoys.” And Gawarkiewicz and Andres wanted to understand how deep the warming went.

The research is based upon a rare collection of temperature data from the waters off the northeast coast of the U.S. that were collected in collaborative effort between scientists and the operators of the container ship Oleander, which routinely travels between Bermuda and New Jersey. The effort, which began in the late 1970s with funding from NOAA/NMFS, involved launching bathythermographs along the ship’s track to collect temperature data approximately 14 times each year. Later the program was funded through the National Science Foundation and the University of Rhode Island and Stony Brook University. The bulk of the prior analysis has been on velocity data also collected by the Oleander.

“The Oleander data is special, because it goes through the whole water column on the shelf. And if you’re a fish living on the bottom, you care more about that,” says Andres. “It was this trove of shelf temperature data that we could use to help us address these questions.”

That’s where Jacob Forsyth, lead author of the study, came into the picture. In 2014, Forsyth had just begun an 11-week summer student fellowship at WHOI, with Andres and Gawarkiewicz as his co-advisors. “On a lark, we had Jacob look at the data, not knowing if it would pan out,” says Andres. “But it was a super data set, and Jacob did a great job analyzing the data,” she added.

A physics and economics major at Bowdoin College, Forsyth had taken just one college oceanography course but had a passion for the ocean and for science. Early into his fellowship, Forsyth found himself at WHOI immersed in the academic literature, quality controlling nearly 40 years’ worth of data, and teaching himself MatLab to begin looking at this database no one had really assembled before.

The bulk of the data were collected by volunteer observers who rode the Oleander from New Jersey to Bermuda at monthly intervals deploying the bathythermographs, a probe that is dropped from a ship to measure the temperature as it falls through the water. Two very small wires transmit the temperature data to the ship where it is recorded for later analysis. Because water temperature can vary by layer, it was important to obtain information on the temperature structure of the ocean to depths of up to 700 meters. More recently an automated data collection system has been used which was developed by Dave Fratantoni, formerly of WHOI.

The researchers looked at the temperatures for a given year and averaged them across the shelf, to get a temperature index for the year. Their work showed that temperature has been steadily increasing, and most recently, it’s been getting warmer, faster. Superimposed on that, they found a lot of year-to-year variability.

Andres says, “what’s controlling the trends may be different than what’s controlling the year to year changes.” She notes, “There are two questions: What are the mechanisms for the slow, sustained warming? And what is it for the inter-annual variability? Those don’t have to be the same thing.”

What the researchers did determine is that the slow, sustained warming is not just due to warming of the atmosphere, but that it’s something related to dynamics of the shelf break, where the shallow continental shelf abuts the deeper continental slope.

“The warming more recently seems to be at the edge of the continental shelf, which would indicate there might be a Gulf Stream role or a slope water role in the warming,” says Gawarkiewicz, “and that’s different than if it was all from the atmosphere over the last 12 years, because that would be uniform and near the surface.” Investigating the exact cause is among their next steps.

In addition to analyzing the warming trend, Forsyth, who will enter the MIT-WHOI Joint Program in Oceanography this summer, used the data to search for a relationship between sea levels and temperatures. He found, in fact, there is a very strong relationship between the two, where sea level anomalies may serve as a predictor of shelf temperature. Forsyth determined the lag between the two indicators was approximately two years — enough time to give environmental monitors a chance to respond.

The researchers underscore the importance of a long, continuous set of measurements, and that they are hard to come by due to the limitations of funding. The Oleander program and the newly installed Pioneer Array, a part of a larger NSF-funded network of observatories in the Atlantic and Pacific called the Ocean Observatories Initiative, which is positioned along the shelf break, will collect continuous measurements, so critical in understanding the dynamics of the region. Because it’s a productive fishing ground, the warming at lower depths can have a big impact on the distribution and abundance of fish in the area.

Reference:
Jacob Samuel Tse Forsyth, Magdalena Andres, Glen G. Gawarkiewicz. Recent accelerated warming of the continental shelf off New Jersey: Observations from the CMVOleander expendable bathythermograph line. Journal of Geophysical Research: Oceans, 2015; 120 (3): 2370 DOI: 10.1002/2014JC010516

Note: The above post is reprinted from materials provided by Woods Hole Oceanographic Institution.

Sarychev Volcano Eruption snapped from Space, June 12, 2009

A fortuitous orbit of the International Space Station allowed the astronauts this striking view of Sarychev Volcano (Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Sarychev Peak is one of the most active volcanoes in the Kuril Island chain, and it is located on the northwestern end of Matua Island.

Video Copyright © NASA

Fossils explain how life coped during snowball Earth

A close-up of one of wart-like bumps on the putative fossilized red algae. Credit: Cohen et al

Researchers have discovered what they think are fossils of a unique red algae species that lived about 650 million years ago during a brief respite between some of the most extreme ice ages the world has ever known. The fossils could speak to how life coped in the aptly named Cryogenian period, when glaciers held most of Earth in a frozen grip.
“The reason we were looking at these samples in the first place is that they come from a really interesting time period in Earth’s history, right between two major global glaciations called Snowball Earth events,” said Phoebe Cohen, the study’s lead author and an assistant professor of geosciences at Williams College, in Williamstown, Mass. “We want to understand how these glaciations affected the evolution of life.”

Learning how life on our planet changed under the extreme conditions of back-to-back Snowball Earths—separated by just 10 million years, a relatively short gap in geological time—should shed light on how extraterrestrial life deals with the vicissitudes of nature.

“We are fundamentally interested in the co-evolution between our planet and the life that inhabits it,” said Cohen. “We want to know: What can this teach us about how life might evolve on other planets?”

The new study appeared in the March issue of the journal Palaios and was funded by grants from the NASA Astrobiology Institute element and the Exobiology & Evolutionary Biology element of the NASA Astrobiology Program.

Identifying what once was

The fossils, uncovered within layered rocks in southwestern Mongolia, consist of thin, flat sheets with bumpy protuberances on one side. “These samples look like weird scraps of stiff slime with tiny warts on them,” said Cohen.

The fossil sheets are only between 50 and 350 micrometers, or millionths of a meter, in thickness. (For comparison, a human hair is about 100 micrometers in girth.) Tiny, round bumps as tall as 230 or so micrometers rise and here from the sheets, whose undersides are featurelessly smooth.

The tops of the bumps have a small depression in them, much like the warts that grow on human skin caused by viruses. Ridges of material, meanwhile, skirt the bumps and intersect or split in places, forming structures that look like flaps.

Compared to most organism remains, both before and after the emergence of these warty sheets, these fossils have a superficial resemblance to “biofilms.” These films are composed of bacteria that join together and secrete a gooey, protective substance. The fossils also bear a resemblance to groups of microbes, such as amoebas, that similarly link up to form so-called slime molds.

A scanning elecgtron microscope image of a sample of the top surface fossilized warty sheets, with evident bumps and ridges. Credit: Cohen et al

But the best match given all of the fossils’ features is red algae. This group of creatures includes many seaweeds and other types of marine plants.

A telltale identifier is the bumps, which Cohen and her colleagues think served as reproductive structures. “They are similar in a lot of ways to reproductive structures in modern red algal groups,” said Cohen.

The function of the ridges on the wart-like mounds, however, remains a conundrum.

“We aren’t sure what they are,” said Cohen, “but the fact that they don’t have a modern comparison, frankly, is not surprising to me at all.”

As Cohen pointed out, the organisms preserved as warty sheets have been extinct for hundreds of millions of years. “So much evolution has happened within the red algae since then,” Cohen said. “Some things stay the same, or similar, like reproductive structures, but other things, like these ridges, may have once had a function that we don’t yet understand.”

One theory is that the ridges provided some sort of structural support to the organism, “like corrugated cardboard,” Cohen said. Even so, any strong claims about the ridges’ ultimate purpose are difficult to make given the small amount of fossil material to work with and a limited knowledge of the environment where the wart-shaped microbes went about their daily lives.

An eon of red algae?

Notably, the new red algae fossils—if that is indeed what they are—fill a gap in the fossil record documenting the rise of this marine plant group. The oldest known sample of red algae goes back about a billion years. Fossils reckoned to belong to the same lineage then do not appear again until about 600 million years, well after the glaciers of the second Snowball Earth had receded.

Neither the red algae fossils from a billion years ago, nor those from shortly after the Cryogenian period’s end, possess the ridge and flaplike structures of the newfound fossils. “In this case, we’re seeing a new morphology show up in between these two Snowball Earth events,” said Cohen.

The “why” remains unknown, but future finds could provide clues.

“New fossils always give us more information about how groups of organisms evolved, and potentially why as well,” said Cohen. “So adding more fossils to the record of red algae helps us get a better picture of how this major group of algae evolved, and in what context.”

Life’s steadfastness

Red algae as a branch in the tree of life seems to have weathered the storm of two globe-spanning glaciations. “We know red algae are around before the first Snowball Earth event, in between the two, and after,” said Cohen. “In my opinion, that’s an impressive feat, and it makes predictions about what these events were like.”

For instance, in order for life like algae to have survived, water must have remained unfrozen in at least some pockets on the planet. Overall, Cohen is encouraged by what the findings show of the resiliency of life in a broader, astrobiological perspective. “Once life gets going, it seems pretty hard to extinguish,” said Cohen “You can freeze it, throw giant meteors at it, change the air it has to breath, and it keeps on evolving and adapting and expanding.”

“Hopefully, what is true for life on Earth will also be true for life elsewhere,” Cohen added, “and that persistence will increase the likelihood of us identifying life elsewhere in the Universe.”

Note : The above story is based on materials provided by Astrobio.net
This story is republished courtesy of NASA’s Astrobiology Magazine. Explore the Earth and beyond at www.astrobio.net .

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