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Fossilized marine plankton tell the tale of the end Permian mass extinction

Artist’s impression of the Siberian Traps at the time of the Permian mass extinction. Credit: José-Luis Olivares/MIT

The worst mass extinction the Earth has ever seen occurred 252 million years ago. The boundary of the Permian and Triassic geological periods marked the demise of around 90 percent of marine species and 70 percent of land species.
Solving the intricate puzzles of mass extinctions is vital when it comes to understanding the external factors that could hinder life on other planets. Several theories have been proposed to explain this mass extinction, but scientists believe that the most likely trigger for this mass extinction was one of the largest volcanic eruptions ever recorded.

A paper by Qinglai Feng and Thomas Algeo entitled “Evolution of oceanic redox conditions during the Permo-Triassic transition: Evidence from deepwater radiolarian facies,” recently accepted in the journal Earth-Science Reviews details how tiny marine plankton known as radiolarians are shedding light on the sequence of events that led to this mass extinction.

In this scenario, a mantle plume rose from deep within the Earth and burst through the crust at Siberia. It didn’t just form one volcano, rather it was an event known as a flood basalt eruption. Lava poured from fissures over an area the size of Europe and this period of volcanic activity lasted between one and two million years. Today this area is known as the Siberian Traps.

Depletion of oxygen in the oceans

The gases and ash that spewed out caused catastrophic changes to the environment by initiating a greenhouse effect. The extra carbon dioxide, methane and water vapor in the atmosphere retained more radiation from the Sun, and global temperatures rose by between 10 to 15 degrees Celsius (18 to 27 degrees Fahrenheit). This increase in temperature ultimately caused the oxygen levels in the oceans to become dangerously low, a condition known as anoxia. There are several factors that contributed to the widespread ocean anoxia that exterminated so many species during the transition from the Permian to the Triassic.

The rising temperatures were a major factor as oxygen becomes less soluble in water as temperatures increase. The increased heat also warmed the surface waters more than usual. As warmer water is lower in density than cold water, the density difference between the deep layers and the surface increased. This hindered the layers of water from mixing, and thus contributed to the depletion in oxygen.

In the atmosphere, the volcanic gases mixed with water to form acid rain, which decimated forests and left the soil with no roots to keep it in place. Intensified weathering then washed this soil, along with extra nutrients, into the ocean. The additional nutrients in the water encouraged the growth of algae, which increased the amount of organic matter that sank into the ocean depths. The decay process of this organic matter consumed oxygen, and depleted the oxygen faster than it could be replenished.

Radiolarians

Understanding the sequence of events that took place in a mass extinction hundreds of millions of years ago is no easy task. One way to learn how oxygen levels impacted ancient life is to study the fossils of marine plankton known as radiolarians.

Radiolarians are marine plankton that are widespread throughout the oceans and have persisted from the Cambrian period (540 million years ago) to modern times. The distribution of these single-celled floating organisms is controlled by the conditions in the ocean, such as temperature, depth, and the amount of oxygen.

The skeletons of radiolarians are well preserved, even in deep water sediments. Different orders of radiolarians thrive at different depths in the ocean, so they make a good study subject in investigations on how extinctions were related to the depth of the water.

The level of oxygen in the prehistoric oceans can be measured from the mineralogy of the rocks in which the fossils are found. When the radiolarians were abundant during the Permian, the rocks were red in color due to the presence of hematite. Hematite is an iron oxide and an indicator that oxygen was plentiful in the ocean at this time. Later in the Permian, the rocks become gray or black in color. The hematite was replaced with pyrite, which is a mineral deposited in an anoxic environment.

Multiple mass extinctions

The varying diversity of radiolarians found in fossils shows that the mass extinction occurred in several stages. The rocks also showed that anoxic events likely occurred after major ash fall events. Multiple anoxic events were recorded in rocks in different regions around the globe throughout the late Permian and early Triassic. Each event coincided with enhanced extinction rates that resulted in sudden drops in the level of diversity, creating a “stepwise” mass extinction.

Fossils discovered in southern China reveal that the number of shallow water species of radiolarians increased from 85 to 125, known as a species radiation event. The cause of this radiation event is uncertain, but may be due to an increase in the diversity of suitable environments for the radiolarians to thrive.

Soon after this irradiation of species, the first extinction occurred. This was a precursor to the main mass extinction that wiped out most marine species. The number of species of radiolarians found in the Chinese rocks dwindled from 125 to 15. This precursor extinction annihilated species, rather than entire genera, although some of the remaining genera only had one surviving species.

“One characteristic of such volcanic systems is that they tend to have a short ‘lead-in’ time of activity prior to the main eruption, followed by a period of pulsed eruptive activity one to two million years following the main eruption,” says Thomas Algeo. “This pattern seems to fit observations for the Permian-Triassic crisis, and there is increasing evidence of intensification of marine environmental stresses prior to the main extinction event.”

When the main eruption occurred, more species were lost, but this time the extinction rates were also large at the genus level. Anoxia spread through the Panthalassa Ocean that once surrounded the supercontinent of Pangea, as well as the Paleo-Tethys ocean, which was nestled within the C-shaped Pangea. Oxygen was severely depleted at low and intermediate depths, particularly at low latitudes.

Shallow waters were only briefly subjected to anoxic conditions and some shallow waters, particularly those at mid to high latitudes, would have been a refuge for marine life. Evidence for this lies in the fact that radiolarians had a greater survival rate at higher latitudes.

Dead clade walking

After the main extinction at the end of the Permian, the number of radiolarians had been dramatically depleted on a global scale. The widespread anoxia that marked the end of the Permian persisted for a short time after the main extinction, and further anoxic events occurred intermittently for the next two million years. These additional anoxic events meant that the mass extinctions were not yet over for the radiolarians, and more genera disappeared during the early Triassic .Groups that had survived the main mass extinction were then annihilated, a phenomenon known as “dead clade walking.”

Later in the Triassic, oxic conditions returned to the oceans and the radiolarians and other marine species recovered. New groups of radiolarians evolved, and they spread out to reclaim both shallow and deep waters of the oceans.

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 .

São Francisco River

The São Francisco (Portuguese pronunciation: [sɐ̃w fɾɐ̃ˈsiʃku]) is a river in Brazil. With a length of 2,914 kilometres (1,811 mi), it is the longest river that runs entirely in Brazilian territory, and the fourth longest in South America and overall in Brazil (after the Amazon, the Paraná and the Madeira). It used to be known as the Opara by the indigenous people before colonisation, and is today also known as Velho Chico (“Old Frank”).

São Francisco river basin

The São Francisco originates in the Canastra mountain range in the central-western part of the state of Minas Gerais. It runs generally north in the states of Minas Gerais and Bahia, behind the coastal range, draining an area of over 630,000 square kilometres (240,000 sq mi), before turning east to form the border between Bahia on the right bank and the states of Pernambuco and Alagoas on the left one. After that, it forms the boundary between the states of Alagoas and Sergipe and washes into the Atlantic Ocean. In addition to the five states which the São Francisco directly traverses or borders, its drainage basin also includes tributaries from the state of Goiás and the Federal District.

It is an important river for Brazil, called “the river of national integration” because it unites diverse climes and regions of the country, in particular the Southeast with the Northeast. It is navigable between the cities of Pirapora (Minas Gerais) and Juazeiro (Bahia), as well as between Piranhas (Alagoas) and the mouth on the ocean, but traditional passenger navigation has all but disappeared in recent years due to changes in the river flow.

Discovery

The river was first discovered by Europeans on 4 October 1501 (by the Florentine discoverer Amerigo Vespucci, who named it after Saint Francis of Assisi, whose feast day falls on 4 October).

In 1865 the British explorer and diplomat Richard Francis Burton was transferred to Santos in Brazil. He explored the central highlands, canoeing down the São Francisco river from its source to the falls of Paulo Afonso.

The four parts of the São Francisco River

The course of the river, running through five states, may be divided into four parts, as follows:

  1. The high part, from its source to Pirapora in Minas Gerais
  2. The upper middle part, from Pirapora, where the navigable part begins, up to Remanso (Bahia) and the Sobradinho Dam
  3. The lower middle part, from the Sobradinho dam to Paulo Afonso, also in Bahia (bordering on Alagoas), and ending at the Itaparica Dam
  4. The low part, from Paulo Afonso to the river’s mouth on the Atlantic Ocean

Tributaries

The river obtains water from 168 rivers and streams, of which 90 are on the right bank and 78 on the left bank. The main tributaries are:

  • Paraopeba River
  • Abaeté River
  • Das Velhas River
  • Jequitaí River
  • Paracatu River
  • Urucuia River
  • Verde Grande River
  • Carinhanha River
  • Corrente River
  • Grande River

Note : The above story is based on materials provided by Wikipedia

Study of Chilean quake shows potential for future earthquake

The Iquique earthquake took place on the northern portion of the subduction zone formed when the Nazca tectonic plate slides under the South American plate. Credit: USGS

Near real-time analysis of the April 1 earthquake in Iquique, Chile, showed that the 8.2 event occurred in a gap on the fault unruptured since 1877 and that the April event was not what the scientists had expected, according to an international team of geologists.
“We assumed that the area of the 1877 earthquake would eventually rupture, but all indications are that this 8.2 event was not the 8.8 event we were looking for,” said Kevin P. Furlong, professor of geophysics, Penn State. “We looked at it to see if this was the big one.”

But according to the researchers, it was not. Seismologists expect that areas of faults will react the same way over and over. However, the April earthquake was about nine times less energetic than the one in 1877 and was incapable of releasing all the stress on the fault, leaving open the possibility of another earthquake.

The Iquique earthquake took place on the northern portion of the subduction zone formed when the Nazca tectonic plate slides under the South American plate. This is one of the longest uninterrupted plate boundaries on the planet and the site of many earthquakes and volcanos. The 8.2 earthquake was foreshadowed by a systematic sequence of foreshocks recorded at 6.0, 6.5, 6.7 and 6.2 with each foreshock triggering the next until the main earthquake occurred.

These earthquakes relieved the stresses on some parts of the fault. Then the 8.2 earthquake relieved more stress, followed by a series of aftershocks in the range of 7.7. While the aftershocks did fill in some of the gaps left by the 8.2 earthquake, the large earthquake and aftershocks could not fill in the entire gap where the fault had not ruptured in a very long time. That area is unruptured and still under stress.

The foreshocks eased some of the built up stress on 60 to 100 miles of fault, and the main shock released stress on about 155 miles, but about 155 miles of fault remain unchanged, the researchers report today (Aug. 13) in Nature.

“There can still be a big earthquake there,” said Furlong. “It didn’t release the total hazard, but it told us something about this large earthquake area. That an 8.8 rupture doesn’t always happen.”

The researchers were able to do this analysis in near real time because of the availability of large computing power and previously laid groundwork.

The computing power allowed researchers to model the fault more accurately. In the past, subduction zones were modeled as if they were on a plane, but the plate that is subducting curves underneath the other plate creating a 3-dimensional fault line. The researchers used a model that accounted for this curving and so more accurately recreated the stresses on the real geology at the fault.

“One of the things the U.S. Geological Survey and we have been doing is characterizing the major tectonic settings,” said Furlong. “So when an earthquake is imminent, we don’t need a lot of time for the background.”

In essence, they are creating a library of information about earthquake faults and have completed the first level, a general set of information on areas such as Japan, South America and the Caribbean. Now they are creating the levels of north and south Japan or Chile, Peru and Ecuador.

Knowing where the old earthquake occurred, how large it was and how long ago it happened, the researchers could look at the foreshocks, see how much stress they relieved and anticipate, at least in a small way, what would happen.

“This is what we need to do in the future in near real time for decision makers,” said Furlong.

Note : The above story is based on materials provided by Penn State. The original article was written by A’ndrea Elyse Messer.

South-west diversity still a mystery but comparison lends clues

WA’s south-west has higher species richness but fewer genera than the south-east of Australia. Credit: Arthur Chapman

A WA botanist says detailed fossil records and the development of phylogenetic trees could help experts understand why flora in Australia’s south-west is so diverse in comparison to the south-east.
Curator of WA Herbarium at the Department of Parks and Wildlife Kevin Thiele has confirmed in research that WA’s south-west has higher species richness but fewer genera than the south-east of Australia.

Dr Thiele says experts cannot yet explain the reasons for the special characteristics of the flora in the south-west, but more critical thinking and research will help to discriminate between possible explanations.

The collaborative research reviewed explanations behind south-west diversity, with one possibility being “supercharged speciation” that occurred in the south-west and not the south-east.

Alternatively, Dr Thiele says unlike the south-east, Australia’s south-west could have been environmentally stable for a long period of time.

“Even though the rate at which new species are generated in the south-west and south-east may be approximately equal, it may be that fewer species have gone extinct in the south-west over a long period of time,” he says.

However, Dr Thiele says the special nature of the flora in the south-west might not be historical and could be due to the soil of each area.

“The very richest parts of the south-west are areas that are on very nutrient-poor oligotrophic soils,” he says.

“These soils are a real challenge to grow on and it’s a common observation in many parts of the world that these types of very nutrient limited of sandy soils seem to have quite rich floras on them.”

Dr Thiele says developing phylogenies for flora in the two areas may help because particularly with molecular phylogenies, they can be dated to some extent.

“We might be able to see things like a difference in the phylogenetic patterns in the south-west and south-east,” he says.

Dr Thiele says there is not a good understanding of fossil history in the south-west of Australia however work done in south-east Australia has used fossil records of an old flora from before the ice ages.

He says the records show the flora was just as rich as the flora in south-western Australia, but much of it went extinct.

“That is beginning to suggest that perhaps there has been a greater extinction in the south-east,” he says.

However, Dr Thiele says even if there was great extinction during the ice ages, it doesn’t explain why the south-east is richer in genera.

More information: 
Dr Thiele describes the findings in a paper published in the Journal of the Royal Society of Western Australia, June 2014.

Note : The above story is based on materials provided by Science Network WA

Indus River

Satellite image of the Indus River basin in Pakistan, India, and China.

The Indus River is a major river in Asia which flows through Pakistan. It also has courses through western Tibet and Northern India. Originating in the Tibetan Plateau in the vicinity of Lake Mansarovar, the river runs a course through the Ladakh region of Jammu and Kashmir, towards Gilgit and Baltistan and then flows in a southerly direction along the entire length of Pakistan to merge into the Arabian Sea near the port city of Karachi in Sindh. The total length of the river is 3,180 km (1,980 mi). It is Pakistan’s longest river.
The river has a total drainage area exceeding 1,165,000 km2 (450,000 sq mi). Its estimated annual flow stands at around 207 km3 (50 cu mi), making it the twenty-first largest river in the world in terms of annual flow. The Zanskar is its left bank tributary in Ladakh. In the plains, its left bank tributary is the Chenab which itself has four major tributaries, namely, the Jhelum, the Ravi, the Beas and the Sutlej. Its principal right bank tributaries are the Shyok, the Gilgit, the Kabul, the Gomal and the Kurram. Beginning in a mountain spring from Nepal and fed with glaciers and rivers in the Himalayas, the river supports ecosystems of temperate forests, plains and arid countryside.

The Indus forms the delta of present-day Pakistan mentioned in the Vedic Rigveda as Sapta Sindhu and the Iranian Zend Avesta as Hapta Hindu (both terms meaning “seven rivers”). The river has been a source of wonder since the Classical Period, with King Darius of Persia sending Scylax of Caryanda to explore the river as early as 510 BC.

Description

The Indus River provides key water resources for the economy of Pakistan – especially the Breadbasket of Punjab province, which accounts for most of the nation’s agricultural production, and Sindh. The word Punjab means “land of five rivers” and the five rivers are Jhelum, Chenab, Ravi, Beas and Sutlej, all of which finally merge in Indus. The Indus also supports many heavy industries and provides the main supply of potable water in Pakistan.

The ultimate source of the Indus is in Tibet; it begins at the confluence of the Sengge and Gar rivers that drain the Nganglong Kangri and Gangdise Shan mountain ranges. The Indus then flows northwest through Ladakh and Baltistan into Gilgit, just south of the Karakoram range. The Shyok, Shigar and Gilgit rivers carry glacial waters into the main river. It gradually bends to the south, coming out of the hills between Peshawar and Rawalpindi. The Indus passes gigantic gorges 4,500–5,200 metres (15,000–17,000 feet) deep near the Nanga Parbat massif. It flows swiftly across Hazara and is dammed at the Tarbela Reservoir. The Kabul River joins it near Attock. The remainder of its route to the sea is in the plains of the Punjab and Sindh, where the flow of the river becomes slow and highly braided. It is joined by the Panjnad at Mithankot. Beyond this confluence, the river, at one time, was named the Satnad River (sat = “seven”, nadī = “river”), as the river was now carrying the waters of the Kabul River, the Indus River and the five Punjab rivers. Passing by Jamshoro, it ends in a large delta to the east of Thatta.

The Indus is one of the few rivers in the world to exhibit a tidal bore. The Indus system is largely fed by the snows and glaciers of the Himalayas, Karakoram and the Hindu Kush ranges of Tibet, the Indian state of Jammu and Kashmir and the Northern Areas of Pakistan respectively. The flow of the river is also determined by the seasons – it diminishes greatly in the winter, while flooding its banks in the monsoon months from July to September. There is also evidence of a steady shift in the course of the river since prehistoric times – it deviated westwards from flowing into the Rann of Kutch and adjoining Banni grasslands after the 1816 earthquake.

The traditional source of the river is the Senge Khabab or “Lion’s Mouth”, a perennial spring, not far from the sacred Mount Kailash, and is marked by a long low line of Tibetan chortens. There are several other tributaries nearby which may possibly form a longer stream than Senge Khabab, but unlike the Senger Khabab, are all dependent on snowmelt. The Zanskar River which flows into the Indus in Ladakh has a greater volume of water than the Indus itself before that point.

“That night in the tent [next to Senge Khabab] I ask Sonmatering which of the Indus tributaries which we crossed this morning is the longest. All of them, he says, start at least a day’s walk away from here. The Bukhar begins near the village of Yagra. The Lamolasay’s source is in a holy place: there is a monastery there. The Dorjungla is a very difficult and long walk, three days perhaps, and there are many sharp rocks; but it its water is clear and blue, hence the tributary’s other name, Zom-chu, which Karma Lama translates as ‘Blue Water’. The Rakmajang rises from a dark lake called the Black Sea.
One of the longest tributaries — and thus a candidate for the river’s technical source — is the Kla-chu, the river we crossed yesterday by bridge. Also known as the Lungdep Chu, it flows into the Indus from the south-east, and rises a day’s walk from Darchen. But Sonamtering insists that the Dorjungla is the longest of the ‘three types of water’ that fall into the Seng Tsanplo [‘Lion River’ or Indus].”

Geography

Tributaries

  • Nagar River
  • Astor River
  • Balram River
  • Dras River
  • Gar River
  • Ghizar River
  • Gilgit River
  • Gomal River
  • Kabul River
  • Kurram River
  • Panjnad River
  • Shigar River
  • Shyok River
  • Soan River
  • Tanubal River
  • Zanskar River
  • Jhelum River
  • Ravi River
  • Chenab River
  • Beas River
  • Satluj River

Geology

The Indus river feeds the Indus submarine fan, which is the second largest sediment body on the Earth at around 5 million cubic kilometres of material eroded from the mountains. Studies of the sediment in the modern river indicate that the Karakoram Mountains in northern Pakistan and India are the single most important source of material, with the Himalayas providing the next largest contribution, mostly via the large rivers of the Punjab (Jhelum, Ravi, Chenab, Beas and Sutlej). Analysis of sediments from the Arabian Sea has demonstrated that prior to five million years ago the Indus was not connected to these Punjab rivers which instead flowed east into the Ganges and were captured after that time. Earlier work showed that sand and silt from western Tibet was reaching the Arabian Sea by 45 million years ago, implying the existence of an ancient Indus River by that time. The delta of this proto-Indus river has subsequently been found in the Katawaz Basin, on the Afghan-Pakistan border.

In the Nanga Parbat region, the massive amounts of erosion due to the Indus river following the capture and rerouting through that area is thought to bring middle and lower crustal rocks to the surface.

Note : The above story is based on materials provided by Wikipedia

Midwestern Fault Zones Are Still Alive

Earthquakes occurring today in the New Madrid Seismic Zone (center of image; red dots denote quakes greater than magnitude 3 that have occurred since 1974) are not aftershocks of massive quakes that occurred in the winter of 1811 to 12, a new study suggests. Credit : U.S. Geological Survey

The occasional quakes rattling the New Madrid Seismic Zone, a series of midwestern faults named for a small town in the Missouri Bootheel, aren’t aftershocks of the massive quakes that rocked our fledgling nation more than 2 centuries ago, a new study suggests. The analysis reinvigorates a debate about the true level of seismic risk that those fault zones pose.
In the winter of 1811 to 1812, a series of colossal quakes—by some estimates among the strongest ever seen in what is today the continental United States—exploded beneath what is now the American Midwest. In a span of less than 2 months, four magnitude-7 or greater temblors struck along a zigzag set of faults centered near the river town of New Madrid, Missouri, the closest settlement to the destruction. Although the quakes were felt as far away as the East Coast, the area around the quake was sparsely populated, so devastation was limited. (The Greater St. Louis area, home to about 2.9 million people today but less than 6000 at the time the quakes occurred, is centered about 235 kilometers north of New Madrid.)

As with all major quakes, the New Madrid quakes spawned a lot of aftershocks, says Morgan Page, a geophysicist with the U.S. Geological Survey (USGS) in Pasadena, California. Indeed, one of the four largest quakes of that winter—one that occurred at about dawn on 16 December 1811—is considered to be an aftershock of the first quake in the series, which occurred about 5 hours earlier. One of seismology’s biggest debates, which bears on the amount of seismic risk in the area today, is how long those aftershocks continued. Some studies suggest that they’re still going on, which would support those who argue there is little chance of major quakes striking New Madrid in coming centuries.

A new analysis by Page and USGS colleague Susan Hough indicates that modern-day rumblings in the New Madrid Seismic Zone are not echoes of the 1811 to 1812 quakes, however. Instead, they are signs the seismic zone is still alive and kicking. The team’s analysis uses a model that simulates how series of aftershocks unfold—statistics that were first described by a Japanese seismologist in the 1890s. (According to that model, the number and size of aftershocks generally decrease over time in a predictable way.)

For the new study, Page and Hough considered three sets of data: the number and size of the original set of quakes, the number and spacing of magnitude-6 or larger aftershocks recorded in the years after the original group of temblors, and the number and size of magnitude-4 or larger quakes recorded by seismometers in the region today. Results of the team’s statistical analysis suggest that the long-verified, more-than-a-century-old model doesn’t fit the pattern of seismicity seen on the New Madrid Seismic Zone in the past 2 centuries, the researchers report online today in Science.

Specifically, the team found that if today’s magnitude-4 or larger quakes were truly aftershocks of the 1811 to 1812 quakes, then scientists should have seen about 135 magnitude-6 or larger temblors between 1812 and 2012. In fact, Page says, only two such quakes occurred. Conversely, a series of aftershocks that contains only two such moderate-sized aftershocks would also contain far fewer magnitude-4 or larger quakes than sensors actually record today. In other words, modern-day quakes are signs that the faults in the region are still accumulating stress—and sometimes releasing it as fresh rumblings.

But some scientists don’t find the team’s results convincing. For example, aftershock sequences for quakes that occur at faults far from a tectonic plate boundary—such as the New Madrid Seismic Zone—often last much longer than those triggered by quakes near plate boundaries, says Seth Stein, a geophysicist at Northwestern University in Evanston, Illinois. Because those faults behave differently, he contends, the new study doesn’t show that modern-day quakes aren’t aftershocks.

Stein and Mian Liu, a geophysicist at the University of Missouri, Columbia, find that GPS equipment installed throughout the region has failed to detect strain building up in Earth’s crust that would be required to trigger fresh quakes. That would suggest that the New Madrid threat is not growing, but the source of seismic stress in the region, far from any boundaries where tectonic plates jostle and scrape past each other, isn’t clear. Some scientists have argued that Earth’s crust in northern portions of North America is still slowly springing upward in response to the melting of the ice sheet that smothered the region during the last ice age. As that rebound slows, so should the buildup of stress in the crust underlying the Midwest, they say. For this reason, Stein and other scientists have in the past suggested that the New Madrid Seismic Zone is gradually dying.

But previous studies don’t show seismicity in the region to be slowing down, at least over the very long term. Indeed, groups of major quakes strike the New Madrid Seismic Zone with some regularity, Page says. Geologic evidence shows that other clusters of large quakes rumbled the region around 900 A.D. and around 1450, she notes. But that recent seismic history doesn’t help predict when the next set of “big ones” will occur, or how large they’ll be. “These things don’t go off on a regular basis,” she adds.

Based on previous analyses, USGS scientists have estimated the chance of having an earthquake similar to one of the 1811 to 1812 temblors in the next 50 years is about 7% to 10%, and the chance of having a magnitude-6 or larger earthquake in the next 50 years is 25% to 40%.

Note : The above story is based on materials provided by Sid Perkins ” American Association for the Advancement of Science “

New species of flying pterosaur

This is a reconstruction of three ontogenetic (growth) stages of the new pterosaur Caiuajara dobruskii. Credit: Maurilio Oliveira/Museu Nacional-UFRJ; CC-BY

Scientists discovered the bones of nearly 50 winged reptiles from a new species, Caiuajara dobruskii, that lived during the Cretaceous in southern Brazil, according to a study published August 13, 2014 in the open-access journal PLOS ONE by Paulo Manzig from Universidade do Contestado, Brazil, and colleagues.

The authors discovered the bones in a pterosaur bone bed in rocks from the Cretaceous period. They belonged to individuals ranging from young to adult, with wing spans ranging from 0.65-2.35m, allowing scientists to analyze how the bones fit into their clade, but also how the species developed as it matured. After the initial analysis, scientists determined that the bones represent a new pterosaur, Caiuajara dobruskii, which is the southernmost known occurrence of this particular clade.

Several features of the Caiuajara dobruskii head differ from all other members of this clade, including the presence of a bony expansion projecting inside the large opening in the skull in front of the eyes, and the rounded depressions in the outer surface of the jaw. Younger and older reptiles mainly varied in the size and angle of the bony crest on the top of the head. The crest appeared to change from small and inclined in juveniles, to large and steep in adults.

According to the authors, the bone analysis suggests this species was gregarious, lived in colonies and may have been able to fly at a very young age.

Journal Reference:
Manzig PC, Kellner AWA, Weinschutz LC, Fragoso CE, Vega CS, et al. Discovery of a Rare Pterosaur Bone Bed in a Cretaceous Desert with Insights on Ontogeny and Behavior of Flying Reptiles. PLOS ONE, 2014 DOI: 10.1371/journal.pone.0100005

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

Foreshock series controls earthquake rupture

GPS measurements of the displacement vectors. Credit: GFZ

A long lasting foreshock series controlled the rupture process of this year’s great earthquake near Iquique in northern Chile. The earthquake was heralded by a three quarter year long foreshock series of ever increasing magnitudes culminating in a Mw 6.7 event two weeks before the mainshock. The mainshock (magnitude 8.1) finally broke on April 1st a central piece out of the most important seismic gap along the South American subduction zone. An international research team under leadership of the GFZ German Research Centre for Geosciences now revealed that the Iquique earthquake occurred in a region where the two colliding tectonic plates where only partly locked.

The Pacific Nazca plate and the South American plate are colliding along South America’s western coast. While the Pacific sea floor submerges in an oceanic trench under the South American coast the plates get stressed until occasionally relieved by earthquakes. In about 150 years time the entire plate margin from Patagonia in the south to Panama in the north breaks once completely through in great earthquakes. This cycle is almost complete with the exception of a last segment — the seismic gap near Iquique in northern Chile. The last great earthquake in this gap occurred back in 1877. On initiative of the GFZ this gap was monitored in an international cooperation (GFZ, Institut de Physique du Globe Paris, Centro Sismologico National — Universidad de Chile, Universidad de Catolica del Norte, Antofagasta, Chile) by the Integrated Plate Boundary Observatory Chile (IPOC), with among other instruments seismographs and cont. GPS. This long and continuous monitoring effort makes the Iquique earthquake the best recorded subduction megathrust earthquake globally. The fact that data of IPOC is distributed to the scientific community in near real time, allowed this timely analysis.

Ruptures in Detail

The mainshock of magnitude 8.1 broke the 150 km long central piece of the seismic gap, leaving, however, two large segments north and south intact. GFZ scientist Bernd Schurr headed the newly published study that appeared in the lastest issue of Nature Advance Online Publication: “The foreshocks skirted around the central rupture patch of the mainshock, forming several clusters that propagated from south to north.” The long-term earthquake catalogue derived from IPOC data revealed that stresses were increasing along the plate boundary in the years before the earthquake. Hence, the plate boundary started to gradually unlock through the foreshock series under increasing stresses, until it finally broke in the Iquique earthquake. Schurr further states: “If we use the from GPS data derived locking map to calculate the convergence deficit assuming the ~6.7 cm/yr convergence rate and subtract the earthquakes known since 1877, this still adds up to a possible M 8.9 earthquake.” This applies if the entire seismic gap would break at once. However, the region of the Iquique earthquake might now form a barrier that makes it more likely that the unbroken regions north and south break in separate, smaller earthquakes.

International Field Campaign

Despite the fact that the IPOC instruments delivered continuous data before, during and after the earthquake, the GFZ HART (Hazard And Risk Team) group went into the field to meet with international colleagues to conduct additional investigations. More than a dozen researchers continue to measure on site deformation and record aftershocks in the aftermath of this great rupture. Because the seismic gap is still not closed, IPOC gets further developed. So far 20 multi-parameter stations have been deployed. These consist of seismic broadband and strong-motion sensors, continuous GPS receivers, magneto-telluric and climate sensors, as well as creepmeters, which transmit data in near real-time to Potsdam. The European Southern astronomical Observatory has also been integrated into the observation network.

Note : The above story is based on materials provided by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre.

Climate change and drought in ancient times

Samples taken from these sites: Top, left to right: Ghab Valley (western Syria), Iron Age settlement of Zincirli, Hatay Province (SE Turkey), and Hittite-era settlement of Nerik (near Samsun,Turkey); Middle, left to right: irrigation channel below Tel Halaf (northern Syria), barley growing near Zincirli, Hatay Province (SE Turkey), and a field in the same place after the harvest; Bottom, left to right: irrigation channel near Zincirli, fields near Zincirli and arid lands with field in Jabroud Region (SW Syria). Credit: Simone Riehl/University of Tübingen

The influence of climate on agriculture is believed to be a key factor in the rise and fall of societies in the Ancient Near East. Dr. Simone Riehl of Tübingen University’s Institute for Archaeological Science and the Senckenberg Center for Human Evolution and Palaeoenvironment has headed an investigation into archaeological finds of grain in order to find out what influence climate had on agriculture in early farming societies. Her findings are published in this week’s PNAS — Proceedings of the National Academy of Sciences.
She and her team analyzed grains of barley up to 12,000 years old from 33 locations across the Fertile Crescent to ascertain if they had had enough water while growing and ripening. Riehl found that periods of drought had had noticeable and widely differing effects on agriculture and societies in the Ancient Near East, with settlements finding a variety of ways to deal with the problem.

The 1,037 ancient samples were between 12,000 and 2,500 years old. They were compared with modern samples from 13 locations in the former Fertile Crescent. Dr. Riehl and her team measured the grains’ content of two stable carbon isotopes. When barley grass gets insufficient water while growing, the proportion of heavier carbon isotopes deposited in its cells will be higher than normal. The two isotopes 12C und 13C remain stable for thousands of years and can be measured precisely — giving Simone Riehl and her colleagues reliable information on the availability of water while the plants were growing.

They found that many settlements were affected by drought linked to major climate fluctuations. “Geographic factors and technologies introduced by humans played a big role and influenced societies’ options for development as well as their particular ways of dealing with drought,” says Riehl. Her findings indicate that harvests in coastal regions of the northern Levant were little affected by drought; but further inland, drought lead to the need for irrigation or, in extreme cases, abandonment of the settlement.

The findings give archaeologists clues as to how early agricultural societies dealt with climate fluctuations and differing local environments. “They can also help evaluate current conditions in regions with a high risk of crop failures,” Riehl adds. The study is part of a German Research Foundation-backed project looking into the conditions under which Ancient Near Eastern societies rose and fell.

Journal Reference:

S. Riehl, K. E. Pustovoytov, H. Weippert, S. Klett, F. Hole. Drought stress variability in ancient Near Eastern agricultural systems evidenced by  13C in barley grain. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1409516111

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

Wisconsin geologists go miles deep in quest to predict earthquakes

Crack in Bridge Street from the 2010 Canterbury earthquake ©Avenue

To understand earthquakes, scientists have hatched an audacious plan – go straight to the source.

That means drilling miles-deep into the earth, directly through faults where two plates of the earth’s crust come into contact.
Geologists at the University of Wisconsin-Madison are doing just that, as part of two experiments located at dangerous faults in New Zealand and Japan – faults that could rupture at any moment, causing massive earthquakes.

“These are the natural disasters that kill the most people on the planet. So we need to know as well as we can how they work and whether there are ways to mitigate their effects by early warning or detection,” said Harold Tobin, a professor in the department of geoscience at UW-Madison.

To understand the processes that trigger such massive quakes, the scientists will take samples of rock from the faults they drill, record the conditions in the borehole and, if they’re lucky, catch a quake in action.

Earthquakes are some of the most destructive and deadly natural disasters on the planet. They also are some of the least predictable. Scientists can say how likely a fault is to experience a quake, but only over the span of decades – not very helpful for people living in the area who need to take cover in the moments before.

Scientists don’t know how – or even if – it might be possible to predict earthquakes. Part of the problem is they know so little about how earthquakes start. The phenomenon begins deep below the surface of the earth, inaccessible to researchers.

Typically, earthquakes are studied by measuring the seismic waves that emanate from tremors within the earth. This information is useful, but it’s indirect. It’s sort of like trying to figure out what’s inside your Christmas present by shaking the box around – you’d know much more if you could unwrap it and look directly at what was inside.

This is why the scientists want to drill down to the fault. They will take cores as they drill, bringing up intact samples of rock in order to study their properties. And they will place instruments in the borehole to measure seismic tremors and other important characteristics of the fault zone, like the pressure, temperature, and stresses and strains on the rocks, as well as properties of groundwater in the area.

“If we want to understand earthquakes, it’s one of the few kind of direct ways we can get evidence about what faults are like,” said Clifford Thurber, a professor in the department of geoscience at UW-Madison.

Thurber and Tobin are part of an international group of scientists working on the Deep Fault Drilling Project, an experiment studying the Alpine Fault in New Zealand.

Fault due for quake

This fault has lain dormant since 1717, and it typically produces a major quake every 300 or 400 years. Scientists therefore think the fault is due, estimating a 28 percent chance of a quake in the next 50 years. Beginning in October, experimenters will drill nearly a mile deep into the Alpine Fault.

Drilling such holes, however, is no easy task – especially for faults that are underwater, as many of the most dangerous, tsunami-generating faults are.

As co-chief scientist of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) in Japan, Tobin spent seven weeks at sea last winter on a scientific drilling ship called the Chikyu, drilling into the Nankai Fault off the coast of southern Japan.

At times braving harsh winds and waves as high as 30 feet, Tobin and his fellow scientists took round-the-clock shifts analyzing the data and cores of rock that came out of the borehole. The hole is currently more than halfway to its planned depth of three miles below the seabed.

Instruments will remain in the boreholes of both experiments for decades, quietly collecting data, waiting for a quake that could strike at any time.

The UW researchers also were involved in an earlier experiment, the San Andreas Fault Observatory at Depth (SAFOD), completed in 2007. Scientists drilled a two-mile-deep hole that pierced the infamous San Andreas Fault in California.

The experiment recovered some of the first samples of rock from a fault at the depth where small earthquakes can originate.

However, scientists encountered many setbacks. Drilling was more expensive than expected, due to rising oil prices. And instruments placed in the borehole failed shortly after they were installed, due to the corrosive gases, crushing pressures and high temperatures they encountered at that depth.

“The whole thing is just like a cauldron down there,” Thurber said.

The lessons scientists learned through their struggles with SAFOD will be applied to the experiments in New Zealand and Japan.

These experiments won’t quite reach the depth where major quakes are initiated, but they will gain valuable information about how faults behave close to the source, and how earthquakes travel along the fault when it ruptures.

“We’re seeing rocks much closer to what they are like down where earthquakes do their thing,” Thurber said.

Note  : The above story is based on materials provided by ©2014 Milwaukee Journal Sentinel
Distributed by MCT Information Services

Foam favorable for oil extraction

Foam sent through a microfluidic model created at Rice University shows its ability to remove oil (pink) from low-permeability formations. Rice scientists conducted experiments to see how foam would compare with water, gas or combinations of the two for use in enhanced oil recovery. (Credit: Biswal Lab/Rice University)

HOUSTON – (Aug. 12, 2014) – A Rice University laboratory has provided proof that foam may be the right stuff to maximize enhanced oil recovery (EOR).

In tests, foam pumped into an experimental rig that mimicked the flow paths deep underground proved better at removing oil from formations with low permeability than common techniques involving water, gas, surfactants or combinations of the three.
The open-access paper led by Rice scientists Sibani Lisa Biswal and George Hirasaki was published online today by the Royal Society of Chemistry journal Lab on a Chip.

Oil rarely sits in a pool underground waiting to be pumped out to energy-hungry surface dwellers. Often, it lives in formations of rock and sand and hides in small cracks and crevices that have proved devilishly difficult to tap. Drillers pump various substances downhole to loosen and either push or carry oil to the surface.

Biswal’s lab has learned a great deal about how foam forms. Now, with an eye toward EOR, she and her colleagues created microfluidic models of formations — they look something like children’s ant farms — to see how well foam stacks up against other materials in removing as much oil as possible.

The formations are not much bigger than a postage stamp and include wide channels, large cracks and small cracks. By pushing various fluids, including foam, into test formations, the researchers can visualize the ways by which foam is able to remove oil from hard-to-reach places. They can also measure the fluid’s pressure gradient to see how it changes as it navigates the landscape.

The team determined the numbers are strongly in foam’s favor. Foam dislodged all but 25.1 percent of oil from low-permeability regions after four minutes of pushing it through a test rig, versus 53 percent for water and gas and 98.3 percent for water flooding; this demonstrated efficient use of injected fluid with foam to recover oil.

The less-viscous fluids appear to displace oil in high-permeability regions while blowing right by the smaller cracks that retain their treasure. But foam offers mobility control, which means a higher resistance to flow near large pores.

“The foam’s lamellae (the borders between individual bubbles) add extra resistance to the flow,” said Biswal, an associate professor of chemical and biomolecular engineering. “Water and gas don’t have that ability, so it’s easy for them to find paths of least resistance and move straight through. Because foam acts like a more viscous fluid, it’s better able to plug high-permeable regions and penetrate into less-permeable regions.”

Charles Conn, a Rice graduate student and lead author of the paper, said foam tends to dry out as it progresses through the model. “The bubbles don’t actually break. It’s more that the liquid drains away and leaves them behind,” he said.

Drying has two effects: It slows the progress of the foam even further and allows surfactant from the lamellae to drain into low-permeability zones, where it forces oil out. Foam may also cut the sheer amount of material that may have to be sent downhole.

One of the challenges will always be to get the foam to the underground formation intact. “It’s nice to know that foam can do these things, but if you can’t generate foam in the reservoir, then it’s not going to be useful,” Conn said. “If you lose the foam, it collapses into slugs of gas and liquid. You really want foam that can regenerate as it moves through the pores.”

The lab plans to test foam on core samples that more closely mimic the environment underground, Biswal said.

Kun Ma, a Rice alumnus, co-authored the paper. The Department of Energy, the Abu Dhabi National Oil Co., the Abu Dhabi Oil R&D Sub-Committee, the Abu Dhabi Co. for Onshore Oil Operations, the Zakum Development Co., the Abu Dhabi Marine Operating Co. and the Petroleum Institute of the United Arab Emirates supported the research.

Video:

Note  : The above story is based on materials provided by David Ruth , Mike Williams ” Copyright Rice University News & Media. “

Formation of Hydrocarbon Trap

Wilson Cycle

The Wilson cycle begins in Stage A with a
stable continental craton. A hot spot (not present in the drawings) rises up under the craton, heating it, causing it to swell upward, stretch and thin like taffy, crack, and finally split into two pieces. This process not only splits a continent in two it also creates a new divergent plate boundary.

Collision Mountain Ranges

Continental collision is a phenomenon of the plate tectonics of Earth that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produced, and two continents sutured together. Continental collision is known only from this planet and is an interesting example of how our different crusts, oceanic and continental, behave during subduction.

The Dawn of Plate Tectonics

Way back. A cliffside in Guam shows lava made during the formation of the Mariana Trench. On the left, a close-up of the cliff shows the same lavas in distinct pillowlike shapes. Credit: Dr. Mark Reagan

A journey to the Mariana Trench, the deepest crevice on Earth’s surface, reveals the great Pacific tectonic plate descending deep into the planet where it recycles back into mantle rock. This recycling of old tectonic plate, called subduction, drives plate tectonics and is nothing new to scientists, but exactly when the process got started is a hot debate. A new study may put that to rest by unmasking a sequence of 4.4-billion-year-old lavas as the remnants of the first subduction zone on Earth. If correct, the discovery marks the dawn of plate tectonics and thus several geological processes critical to Earth’s environment and perhaps even its life.

In 2008, scientists studying ancient lavas in northern Quebec, known to geologists as the Nuvvuagittuq greenstone belt, saw that they had the same geochemical signature as lavas from modern subduction zones like the Mariana. This meant that they must have mixed with briny fluids squeezed up through subduction zones and only there. The geochemistry of those rocks could be used as a sort of fingerprint to help identify subduction zone lavas.

Geologists Tracy Rushmer and Simon Turner of Macquarie University in Sydney, Australia, decided to take a closer look. They and their colleagues noticed a distinct chemical pattern to the layers in the lava, creating a unique sequence of rocks. The team thought this sequence could be similar to lava sequences made by modern subduction zones like the Mariana Trench. Mark Reagan, a geologist at the University of Iowa who has taken submersibles into the trench five times as deep as 6500 meters, confirmed Rushmer and Turner’s suspicions. “The whole sequence,” Rushmer says, “linked in with what Mark was seeing in the Mariana Trench.” The team says each rock layer in the sequences at the Mariana lavas and the Nuvvuagittuq lavas describes a step in the birth of a subduction zone.

The key is in how rocks and their chemistry change with each successive layer. As the oceanic slab descends, lavas begin rising up and erupt on the surface in layers atop one another, creating a rising sequence of igneous rocks. With increasing depth, heat and pressure begin squeezing different elements out of the slab in fluids. Over time, these fluids change the chemical composition of the lavas so that they become rich in rare earth elements like ytterbium, but poor in the element niobium. The first layer in the sequence erupts before the fluids can escape the slab, but the next layer in the sequence gets just enough fluid to make a partial signature. The final layer carries huge amounts of rare earth elements and very little niobium, together making the clarion mark of subduction zone lava.

The team realized not only do both rocks carry the same geochemical signature, but in comparing the Mariana and the Nuvvuagittuq, they also discovered the rocks and the geochemistry of both sequences change in the exact same way, they report in the current issue of Geology. This finding bolstered the theory that the Nuvvuagittuq sequence is an ancient subduction zone. “Seeing the evolving chemical signature,” Turner says, “was much more robust than just saying there is or isn’t niobium.”

Geochemist Julian Pearce of Cardiff University in the United Kingdom still isn’t completely convinced, though. He says the Nuvvuagittuq greenstone belt might just be too old and warped to have a reliable signal from 4.4 billion years ago. “The evidence would be compelling if the rocks were young, undeformed, and fresh,” Pearce says. As they are now, the Nuvvuagittuq rocks have been modified by intense heat and pressure “which can mask and modify geochemical signals” through contamination from nearby rocks. Furthermore, while Pearce believes a subduction zone is one place these geochemical signatures can be made, “it is not the only location.”

While those are legitimate concerns, geoscientist Norman Sleep of Stanford University in Palo Alto, California, isn’t too bothered. “It’s not fully sorted out yet,” Sleep says, but the Nuvvuagittuq rocks “really seem like modern arclike lavas” found at the Mariana. When it comes to the geochemical signature of subduction, Turner and the members of the team say that heat and pressure don’t alter the geochemical fingerprint much, and Sleep says this is reasonable. Despite all of the difficulties of studying such timeworn rocks, he says “the work done in this paper is very valuable.”

For one, everyone agrees subduction zones could sculpt ideal sanctuaries for the origin of life. Fluids released from subducting crust also transform mantle rocks into a mineral called serpentine. Those fluids go on to form hot springs on the ocean floor. “The serpentine provides an energy source,” Sleep says, which is one of three requirements for early life. The molecule RNA can satisfy the other two requirements by acting as both a catalyst helping other molecules form and a way to self-replicate. But RNA will fall apart without something to stabilize it. As luck would have it, these serpentine vents are bursting with boron, which acts as a stabilizing agent for RNA. This makes what could be the most ancient subduction zone on Earth, Pearce says, “a likely setting for life to start.”

Note : The above story is based on materials provided by Angus Chen “American Association for the Advancement of Science”

Reconstructions show how some of the earliest animals lived — and died

Palaeontological reconstruction of rangeomorph fronds from the Ediacaran Period (635-541 million years ago) built using computer models of rangeomorph growth and development. Credit: Jennifer Hoyal Cuthill

New three-dimensional reconstructions show how some of the earliest animals on Earth developed, and provide some answers as to why they went extinct.
A bizarre group of uniquely-shaped organisms known as rangeomorphs may have been some of the earliest animals to appear on Earth, uniquely suited to ocean conditions 575 million years ago.

A new model devised by researchers at the University of Cambridge has resolved many of the mysteries around the structure, evolution and extinction of these ‘proto animals’. The findings are reported today (11 August) in the journal Proceedings of the National Academy of Sciences.

Rangeomorphs were some of the earliest large organisms on Earth, existing during a time when most other forms of life were microscopic in size. Most rangeomorphs were about 10 centimetres high, although some were up to two metres in height.

These creatures were ocean dwellers which lived during the Ediacaran period, between 635 and 541 million years ago. Their bodies were made up of soft branches, each with many smaller side branches, forming a geometric shape known as a fractal, which can be seen in many familiar branching shapes such as fern leaves and even river networks.

Rangeomorphs were unlike any modern organism, which has made it difficult to determine how they fed, grew or reproduced, and therefore difficult to link them to any particular modern group. However, despite the fact that they looked like plants, evidence points to the fact that rangeomorphs were actually some of the earliest animals.

“We know that rangeomorphs lived too deep in the ocean for them to get their energy through photosynthesis as plants do,” said Dr Jennifer Hoyal Cuthill of Cambridge’s Department of Earth Sciences, who led the research. “It’s more likely that they absorbed nutrients directly from the sea water through the surface of their body. It would be difficult in the modern world for such large animals to survive only on dissolved nutrients.”

“The oceans during the Ediacaran period were more like a weak soup — full of nutrients such as organic carbon, whereas today suspended food particles are swiftly harvested by a myriad of animals,” said co-author Professor Simon Conway Morris.

Starting 541 million years ago, the conditions in the oceans changed quickly with the start of the Cambrian Explosion — a period of rapid evolution when most major animal groups first emerge in the fossil record and competition for nutrients increased dramatically.

Rangeomorphs have often been considered a ‘failed experiment’ of evolution as they died out so quickly once the Cambrian Explosion began in earnest, but this new analysis shows just how successful they once were.

Rangeomorphs almost completely filled the space surrounding them, with a massive total surface area. This made them very efficient feeders that were able to extract the maximum amount of nutrients from the ocean water.

“These creatures were remarkably well-adapted to their environment, as the oceans at the time were high in nutrients and low in competition,” said Dr Hoyal Cuthill. “Mathematically speaking, they filled their space in a nearly perfect way.”

Dr Hoyal Cuthill examined rangeomorph fossils from a number of locations worldwide, and used them to make the first computer reconstructions of the development and three-dimensional structure of these organisms, showing just how well-suited they were to their Ediacaran environment.

As the Cambrian Explosion began however, the rangeomorphs became ‘sitting ducks’, as they had no known means of defence from predators which were starting to evolve, and the changing chemical composition of the ocean meant that they could no longer get the nutrients they required to feed.

“As the Cambrian began, these Ediacaran specialists could no longer survive, and nothing quite like them has been seen again,” said Dr Hoyal Cuthill.

Note : The above story is based on materials provided by University of Cambridge. The original story is licensed under a Creative Commons Licence.

A global temperature conundrum: Cooling or warming climate?

A fisherman walks toward open water in the Antarctic ice sheet. Conflicting research on the heating and cooling of Earth has led to a global temperature conundrum, which climate scientists plan to address further this fall. Photo: iStock Photo

When the Intergovernmental Panel on Climate Change recently requested a figure for its annual report, to show global temperature trends over the last 10,000 years, the University of Wisconsin-Madison’s Zhengyu Liu knew that was going to be a problem.
“We have been building models and there are now robust contradictions,” says Liu, a professor in the UW-Madison Center for Climatic Research. “Data from observation says global cooling. The physical model says it has to be warming.”

Writing in the journal Proceedings of the National Academy of Sciences today, Liu and colleagues from Rutgers University, the National Center for Atmospheric Research, the Alfred Wegener Institute for Polar and Marine Research, the University of Hawaii, the University of Reading, the Chinese Academy of Sciences, and the University of Albany describe a consistent global warming trend over the course of the Holocene, our current geological epoch, counter to a study published last year that described a period of global cooling before human influence.

The scientists call this problem the Holocene temperature conundrum. It has important implications for understanding climate change and evaluating climate models, as well as for the benchmarks used to create climate models for the future. It does not, the authors emphasize, change the evidence of human impact on global climate beginning in the 20th century.

“The question is, ‘Who is right?'” says Liu. “Or, maybe none of us is completely right. It could be partly a data problem, since some of the data in last year’s study contradicts itself. It could partly be a model problem because of some missing physical mechanisms.”

Over the last 10,000 years, Liu says, we know atmospheric carbon dioxide rose by 20 parts per million before the 20th century, and the massive ice sheet of the Last Glacial Maximum has been retreating. These physical changes suggest that, globally, the annual mean global temperature should have continued to warm, even as regions of the world experienced cooling, such as during the Little Ice Age in Europe between the 16th and 19th centuries.

The three models Liu and colleagues generated took two years to complete. They ran simulations of climate influences that spanned from the intensity of sunlight on Earth to global greenhouse gases, ice sheet cover and meltwater changes. Each shows global warming over the last 10,000 years.

Yet, the bio- and geo-thermometers used last year in a study in the journal Science suggest a period of global cooling beginning about 7,000 years ago and continuing until humans began to leave a mark, the so-called “hockey stick” on the current climate model graph, which reflects a profound global warming trend.

In that study, the authors looked at data collected by other scientists from ice core samples, phytoplankton sediments and more at 73 sites around the world. The data they gathered sometimes conflicted, particularly in the Northern Hemisphere.

Because interpretation of these proxies is complicated, Liu and colleagues believe they may not adequately address the bigger picture. For instance, biological samples taken from a core deposited in the summer may be different from samples at the exact same site had they been taken from a winter sediment. It’s a limitation the authors of last year’s study recognize.

“In the Northern Atlantic, there is cooling and warming data the (climate change) community hasn’t been able to figure out,” says Liu.

With their current knowledge, Liu and colleagues don’t believe any physical forces over the last 10,000 years could have been strong enough to overwhelm the warming indicated by the increase in global greenhouse gases and the melting ice sheet, nor do the physical models in the study show that it’s possible.

“The fundamental laws of physics say that as the temperature goes up, it has to get warmer,” Liu says.

Caveats in the latest study include a lack of influence from volcanic activity in the models, which could lead to cooling — though the authors point out there is no evidence to suggest significant volcanic activity during the Holocene — and no dust or vegetation contributions, which could also cause cooling.

Liu says climate scientists plan to meet this fall to discuss the conundrum.

“Both communities have to look back critically and see what is missing,” he says. “I think it is a puzzle.”

The study was supported by grants from the (U.S.) National Science Foundation, the Chinese National Science Foundation, the U.S. Department of Energy, and the Chinese Ministry of Science and Technology.

Note : The above story is based on materials provided by University of Wisconsin-Madison. The original article was written by Kelly April Tyrrell.

Could Volcanoes Power the World?

That’s hot. Aerial photo of Iceland’s Viti explosive crater near the Krafla geothermal well field. W.Elders et al., Geothermics 49 (January 2014) © 2013 Elsevier Ltd.

Still searing from the formation of the solar system, the core of Earth is a nuclear reactor generating heat from the breakdown of radioactive elements like uranium, thorium, and potassium. Scientists have been harnessing that heat for decades by drilling deep wells to power turbines. But now researchers have been able to tap into even greater energy by drilling into volcanoes and exploiting the heat of molten rock. If current geothermal wells are replaced with the new technology, it could provide 30% more power than current renewable energy sources.

The idea of tapping the energy of magma came from a pair of accidents. In 1985, workers drilling for a geothermal well in Iceland ran into a sudden and uncontrollable blast of high-pressure steam. Scientists think the steam originated from a reservoir of water that’s under such pressure that as it begins to boil, the water cannot expand enough to become vapor and remains in a liquidlike state. Water in such a “supercritical state” contains enormous amounts of energy. Water reaches this state once it reaches 222 bars of pressure and 374°C or above, and flashes into steam when the pressure drops as the water rises to the surface.

For the next 2 decades, researchers dreamed of capturing superhot steam from supercritical fluids and turning it into electricity. Whereas a typical geothermal well produces 5 to 10 MW of electricity, geologist Wilfred Elders, an emeritus professor at the University of California, Riverside, says supercritical wells could potentially yield 10 times that much.

The second unexpected event happened in 2009. The Icelandic Deep Drilling Project (IDDP), a consortium of energy companies and scientists, including Elders, had begun drilling for the theorized supercritical fluid wells when they hit a pocket of magma. The molten rock ruined their equipment, but the team realized that the intense heat could actually boost the production capability of the well. The higher the temperature, the easier it becomes for water to enter a supercritical state, and the magma pouring into their well was hotter than 900°C. “There is an enormous energy potential, orders of magnitude greater than can be produced from conventional geothermal systems at 200 to 300°C,” Elders says.

To use the magma for energy, workers wouldn’t drill directly into it. Instead, they could either tap into superhot water in nearby magma-heated rock and use its steam to turn turbines, or make artificial steam by injecting water from the surface. In 2011, the researchers finished the well just above the magma, where the temperature didn’t quite reach 900°C. Even so, the well generated superheated steam and 35 MW of electricity at 500°C, Elders and his colleagues report in the current issue of Geothermics. For the first time, researchers proved it was possible to create supercritical geothermal wells enhanced by magma.

It isn’t so simple though. IDDP’s 2011 well suffered from mechanical failure after only 2 years of use, and tools are still being developed to withstand such extreme conditions. Location is a problem, too: Magma-heated systems require active volcanoes, and even there it’s exceedingly hard to find magma to drill into. It’s “a bit like finding a needle in a haystack,” says Bruce Marsh, a professor at Johns Hopkins University’s Department of Earth and Planetary Sciences, who wasn’t involved in the work. These types of wells won’t be easily replicable, but Marsh is hopeful. “Maybe after we find a few of these things, we’ll know how to look for them,” he says.

Power aside, Marsh says he is excited about the wells’ scientific value. Magma is hard to study, he notes. Researchers usually analyze it as solid rock that has come to the surface or as solid drill cores. But now scientists might be able to study it from where it is inside the crust and begin understanding what drives systems in Earth’s interior. “We’ve got a tiger by the tail,” Marsh says. “It’s the difference between studying something in the zoo and studying it in the wild.”

IDDP, meanwhile, is moving forward with other supercritical geothermal wells in Iceland soon, and similar projects are under way in New Zealand and Japan. “There’s enormous potential out there,” Marsh says.

Note : The above story is based on materials provided by Angus Chen ” American Association for the Advancement of Science. “

Rust villages of the deep: In Pele’s shadow, iron oxide, or rust, comes to life

Three-dimensional view of Loihi Seamount, with depths below the ocean surface in meters. Credit: Wikimedia Commons

Pele. Her name brings visions of fire, lightning, wind—and volcanoes. Of the ancient Hawaiian goddesses, Pele, the “lady in the red dress,” is the best known.
Locals believe that her powers formed Hawaii’s chain of volcanic islands. The word pele means molten lava in Hawaiian. Volcanic eruptions, or Pele’s tears, it’s said, are her way of expressing red-hot emotions.

Science may offer another explanation.

The island volcanoes of Hawaii are the most recent evidence, researchers say, of an ancient process that created the 3,700-mile-long Hawaiian-Emperor Seamount Chain.

It’s what goes on at the base of that chain, hidden in the depths of the Pacific Ocean, that interests marine ecologists David Emerson of the Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine, Craig Moyer of Western Washington University, and Clara Chan of the University of Delaware.

What the scientists found there is “Pele red” in color: Iron oxide, or rust, come to life.

Villages of rust in the sea’s depths

Along the Hawaiian-Emperor Seamount Chain at Loihi Seamount—an active submarine volcano 22 miles off the coast of the island of Hawaii and 3,000 feet below sea level—the biologists are conducting research on Zetaproteobacteria, life forms that use iron as an energy source. Zetaproteobacteria form iron-rich microbial mats on Loihi’s flanks.

Hydrothermal vents, seafloor geysers that support microbial oases, line Loihi’s summit. The hot fluids spewing from the vents contain high levels of iron, turning Loihi’s underwater slopes an unusual, and characteristic, orange-red.

This iron-rich cauldron is a perfect environment for Zetaproteobacteria.

“Iron is the fourth most abundant element in Earth’s crust,” says Emerson, “and is essential for life. For example, iron is the oxygen-carrying component of hemoglobin in blood.”

What’s less known about iron, he says, “is that it can support the growth of an array of microbes.”

Zetaproteobacteria are the dominant bacteria in Loihi’s iron-rich microbial mats. They’re rarely found in other deep-sea or marine habitats, suggesting that they might be restricted to niches where iron is abundant.

Recent discoveries have expanded their range, however, and that of their distant relatives to deep within the ocean crust, iron deposits in salt marshes, and to the corrosion on steel. “They’re more cosmopolitan than anyone realized,” says Emerson.

In freshwater, their kin are found in roadside ditches, slow-moving streams, wetlands, and on the roots of submerged plants.

“One indicator of their presence is a metallic sheen on the water, which is sometimes mistaken for an oil slick,” says Emerson.

A closer look reveals a mat of iron-oxidizing bacteria with linking, filament-like structures. They form an intricate miniature ecosystem, Emerson says.

It takes a village… of bacteria

“We don’t usually think of bacteria as villages,” he maintains. “For the Zetaproteobacteria that live at Loihi, that might be a good analogy, though. What they do with rust is remarkable.”

These undersea designers fashion “skyscrapers,” spires and highways of iron oxide filaments woven together.

“Zetaproteobacteria are the ultimate in sustainable architects,” says Chan. “They recycle rusty minerals into building blocks.”

With funding from the National Science Foundation (NSF), Emerson, Chan and Moyer are exploring the rust villages to learn the roles of their bacterial builders.

“These bacteria are a rare life form that derives energy out of iron oxidation, that is, they sustain themselves by turning iron into rust,” says Anton Post, program director in NSF’s Division of Ocean Sciences.

The scientists are also interested in other species that may live side-by-side with Zetaproteobacteria, how the inhabitants all work together, and how the interaction of life and minerals contributes to a rust village.

“One of the fates of the microbial mat ecosystems,” Emerson says, “is that they eventually turn into iron-rich stone.”

Another is that the iron oxides the bacteria produce are widely dispersed in the ocean, where they’re an iron source for plankton and other marine life.

Stalk-like structures unique to Zetaproteobacteria

The ability of Zetaproteobacteria to form iron oxide structures in sheaths or stalks is unique. These hallmarks, scientists say, are easily recognized under a microscope.

“Electron microscopy shows subtle differences that may be diagnostic of different populations of the bacteria,” says Emerson.

“Zetas” can produce huge amounts of iron oxides connected by sheaths; 100 cells might crank out as much as three feet of sheath in one day. This complex matrix shunts water and nutrient flow in the villages.

The microbes may also influence geochemical cycling and mineral deposition on larger scales.

Zetas to the rescue?

Zetaproteobacteria colonize steel exposed to seawater, where they foster the release of iron from the steel’s surface.

Water treatment managers view the bacteria’s relatives as nuisances that clog wells, foul and corrode pipelines, and lead to unsightly red water.

But now the Zetas’ and their freshwater cousins’ beneficial sides are coming to light.

The iron oxides they produce can act as filters, removing toxic metals like arsenic, lead and cadmium. The rust Zetas form also gets rid of organic pollutants such as pesticides, as well as nutrients like phosphorus that lead to overgrowth of algae in waterways, fast becoming a major problem in the Great Lakes and elsewhere.

The influence of Zetaproteobacteria and their clan may be far-reaching, spilling well beyond ocean depths.

Not so different from another architect who builds elaborate structures in shades of red: Pele herself.

Note : The above story is based on materials provided by National Science Foundation

Chilean earthquake causes icequakes in Antarctica

The HOWD Polenet seismic station is located near the northwest corner of the Antarctica’s Ellsworth Mountains. It was the station that showed the clearest indication of high-frequency signals following the 2010 Chilean earthquake. Credit: Eric Kendrick/Ohio State University

Seismic events aren’t rare occurrences on Antarctica, where sections of the frozen desert can experience hundreds of micro-earthquakes an hour due to ice deformation. Some scientists call them icequakes. But in March of 2010, the ice sheets in Antarctica vibrated a bit more than usual because of something more than 3,000 miles away: the 8.8-magnitude Chilean earthquake. A new Georgia Institute of Technology study published in Nature Geoscience is the first to indicate that Antarctica’s frozen ground is sensitive to seismic waves from distant earthquakes.
To study the quake’s impact on Antarctica, the Georgia Tech team looked at seismic data from 42 stations in the six hours before and after the 3:34 a.m. event. The researchers used the same technology that allowed them to “hear” the seismic response at large distances for the devastating 2011 magnitude 9 Japan earthquake as it rumbled through the earth. In other words, they simply removed the longer-period signals as the seismic waves spread from the distant epicenter to identify high-frequency signals from nearby sources. Nearly 30 percent (12 of the 42 stations) showed clear evidence of high-frequency seismic signals as the surface-wave arrived on Antarctica.

“We interpret these events as small icequakes, most of which were triggered during or immediately after the passing of long-period Rayleigh waves generated from the Chilean mainshock,” said Zhigang Peng, an associate professor in the School of Earth and Atmospheric Sciences who led the study. “This is somewhat different from the micro-earthquakes and tremor caused by both Love and Rayleigh-type surface waves that traditionally occur in other tectonically active regions thousands of miles from large earthquakes.

Peng says the subtle difference is that micro-earthquakes respond to both shearing and volumetric deformation from distant events. The newly found icequakes respond only to volumetric deformation.

“Such differences may be subtle, but they tell us that the mechanism of these triggered icequakes and small earthquakes are different,” Peng added. “One is more like cracking, while the other is like a shear slip event. It’s similar to two hands passing each other.”

Some of the icequakes were quick bursts and over in less than one second. Others were long duration, tremor-like signals up to 10 seconds. They occurred in various parts of the continent, including seismic stations along the coast and near the South Pole.

The researchers found the clearest indication of induced high-frequency signals at station HOWD near the northwest corner of the Ellsworth Mountains. Short bursts occurred when the P wave hit the station, then continued again when the Rayleigh wave arrived. The triggered icequakes had very similar high waveform patterns, which indicates repeated failure at a single location, possibly by the opening of cracks.

Peng says the source locations of the icequakes are difficult to determine because there isn’t an extensive seismic network coverage in Antarctica.

“But at least some of the icequakes themselves create surface waves, so they are probably formed very close to the ice surface,” he added. “While we cannot be certain, we suspect they simply reflect fracturing of ice in the near surface due to alternating volumetric compressions and expansions as the Rayleigh waves passed through Antarctica’s frozen ice.”

Antarctica was originally not on the research team’s target list. While examining seismic stations in the Southern Hemisphere, Peng “accidently” found the triggered icequakes at a few openly available stations. He and former Georgia Tech postdoctoral student Jake Walter (now a research scientist at the Institute for Geophysics at UT Austin) then reached out to other seismologists (the paper’s four co-authors) who were in charge of deploying more broadband seismometers in Antarctica.

Video :

High-frequency icequakes are shown at station HOWD in Antarctica during the distant waves of the 2010 magnitude 8.8 Chile earthquake. The triggered icequakes are indicated by the narrow vertical bands in the middle and lower sections of the graphic. They begin when the P wave arrives approximately 8 minutes (480 seconds) after the Chilean quake and continue through the arrival of the Rayleigh waves. The sound is generated by speeding up the HOWD’s seismic data 100 times. Credit: Georgia Tech

High-frequency icequakes are shown at station AGO (near the South Pole) in Antarctica during the distant waves of the 2010 magnitude 8.8 Chile earthquake. The triggered icequakes are indicated by the narrow vertical bands in the middle and lower sections of the graphic. They begin when the P wave arrives approximately 10 minutes (600 seconds) after the Chilean quake and continue through the arrival of the Rayleigh waves. The sound is generated by speeding up the AGO’s seismic data 100 times. Credit: Georgia Tech

More information:
Nature Geoscience, dx.doi.org/10.1038/ngeo2212

Note : The above story is based on materials provided by Georgia Institute of Technology

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