Rock soil droplets formed by heating most likely came from Stone Age house fires and not
from a disastrous cosmic impact 12,900 years ago, according to new research from the University of California, Davis. The study, of soil from Syria, is the latest to discredit the controversial theory that a cosmic impact triggered the Younger Dryas cold period.
The Younger Dryas lasted a thousand years and coincided with the extinction of mammoths and other great beasts and the disappearance of the Paleo-Indian Clovis people. In the 1980s, some researchers put forward the idea that the cool period, which fell between two major glaciations, began when a comet or meteorite struck North America.
In the new study, published online in the Journal of
The Younger Dryas, the period being studied by UC Davis and other earth scientists, coincided with the extinction of mammoths and other great beasts and the disappearance of the Paleo-Indian Clovis people. (Thinkstock image
Archaeological Science, scientists analyzed siliceous scoria droplets — porous granules associated with melting — from four sites in northern Syria dating back 10,000 to 13,000 years ago. They compared them to similar scoria droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas.
“For the Syria side, the impact theory is out,” said lead author Peter Thy, a project scientist in the UC Davis Department of Earth and Planetary Sciences. “There’s no way that can be done.”
The findings supporting that conclusion include:
The composition of the scoria droplets was related to the local soil, not to soil from other continents, as one would expect from an intercontinental impact.
The texture of the droplets, thermodynamic modeling and other analyses showed the droplets were formed by short-lived heating events of modest temperatures, and not by the intense, high temperatures expected from a large impact event.
And in a key finding, the samples collected from archaeological sites spanned 3,000 years. “If there was one cosmic impact,” Thy said, “they should be connected by one date and not a period of 3,000 years.”
So if not resulting from a cosmic impact, where did the scoria droplets come from? House fires. The study area of Syria was associated with early agricultural settlements along the Euphrates River. Most of the locations include mud-brick structures, some of which show signs of intense fire and melting. The study concludes that the scoria formed when fires ripped through buildings made of a mix of local soil and straw.
Reference:
P. Thy, G. Willcox, G.H. Barfod, D.Q. Fuller. Anthropogenic origin of siliceous scoria droplets from Pleistocene and Holocene archaeological sites in northern Syria. Journal of Archaeological Science, 2015; 54: 193 DOI: 10.1016/j.jas.2014.11.027
Dartmouth researchers and their BARREL (Balloon Array for Radiation belt Relativistic Electron Losses) colleagues launch instrument-laden balloons at lower altitudes above Antarctica to assess the fallout of electrons from the Earth’s radiation belts. Credit: Dartmouth College
In a new study that sheds light on space weather’s impact on Earth, Dartmouth researchers and their colleagues show for the first time that plasma waves buffeting the planet’s radiation belts are responsible for scattering charged particles into the atmosphere.
The study is the most detailed analysis so far of the link between these waves and the fallout of electrons from the planet’s radiation belts. The belts are impacted by fluctuations in “space weather” caused by solar activity that can disrupt GPS satellites, communication systems, power grids and manned space exploration.
The results appear in the journal Geophysical Research Letters. A PDF is available on request.
The Dartmouth space physicists are part of a NASA-sponsored team that studies the Van Allen radiation belts, which are donut-shaped belts of charged particles held in place by Earth’s magnetosphere, the magnetic field surrounding our planet. In a quest to better predict space weather, the Dartmouth researchers study the radiation belts from above and below in complementary approaches — through satellites (the twin NASA Van Allen Probes) high over Earth and through dozens of instrument-laden balloons (BARREL, or Balloon Array for Radiation belt Relativistic Electron Losses) at lower altitudes to assess the particles that rain down.
The Van Allen Probes measure particle, electric and magnetic fields, or basically everything in the radiation belt environment, including the electrons, which descend following Earth’s magnetic field lines that converge at the poles. This is why the balloons are launched from Antarctica, where some of the best observations can be made. As the falling electrons collide with the atmosphere, they produce X-rays and that is what the balloon instruments are actually recording.
“We are measuring those atmospheric losses and trying to understand how the particles are getting kicked into the atmosphere,” says co-author Robyn Millan, an associate professor in Dartmouth’s Department of Physics and Astronomy and the principal investigator of BARREL. “Our main focus has been really on the processes that are occurring out in space. Particles in the Van Allen belts never reach the ground, so they don’t constitute a health threat. Even the X-rays get absorbed, which is why we have to go to balloon altitudes to see them.”
In their new study, the BARREL researchers’ major objective was to obtain simultaneous measurements of the scattered particles and of ionoized gas called plasma out in space near Earth’s equator. They were particularly interested in simultaneous measurements of a particular kind of plasma wave called electromagnetic ion cyclotron waves and whether these waves were responsible for scattering the particles, which has been an open question for years.
The researchers obtained measurements in Antarctica in 2013 when the balloons and both the Geostationary Operational Environmental Satellite (GOES) and Van Allen Probe satellites were near the same magnetic field line. They put the satellite data into their model that tests the wave-particle interaction theory, and the results suggest the wave scattering was the cause of the particle fallout. “This is the first real quantitative test of the theory,” Millan says.
Reference:
Zan Li, Robyn M. Millan, Mary K. Hudson, Leslie A. Woodger, David M. Smith, Yue Chen, Reiner Friedel, Juan V. Rodriguez, Mark J. Engebretson, Jerry Goldstein, Joseph F. Fennell, Harlan E. Spence. Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations. Geophysical Research Letters, 2014; DOI: 10.1002/2014GL062273
Note : The above story is based on materials provided by Dartmouth College.
An aerial photo shows the quake-damaged Fukushima Dai-Ni nuclear power plant in the town of Naraha and Tomioka in the Futaba district of Fukushima prefecture on March 12, 2011
The earthquake that set off the tsunami which caused the Fukushima nuclear plant disaster was unleashed by a stealthy nine-year buildup of pressure on a plate boundary, scientists said Tuesday.
Part of a fault where two mighty plates on the Earth’s crust collide east of Japan was being quietly crushed and twisted for nearly a decade, they said.
It was this hard to detect activity which caused the fault eventually to rip open on March 11, 2011 and cause the catastrophe.
The deformation “increased the stress in the source region… and finally triggered the earthquake,” said study co-author Kazuki Koketsu of the University of Tokyo.
“It had an impact on the occurrence time of the earthquake,” Koketsu told AFP by email. “It advanced the time (of the quake) by about one year.”
The earthquake, occurring below the Pacific floor about 200 kilometres (120 miles) east of the east coast city of Sendai, was one of the biggest ever recorded, measuring 9.0 on the moment magnitude scale.
The sea bottom shifted by about 27 metres (88 feet), causing a massive tsunami that sparked the Fukushima disaster and left 18,000 people dead or missing.
The fault lies on the Japan Trench, where the Pacific plate dives beneath the North American plate on which the Japanese archipelago lies.
Subduction faults like these have been responsible for some of the world’s most devastating quakes.
But they are also notoriously difficult to monitor, given that events are as rare as they are massive. Centuries may elapse between occurrences, which means the danger could be undocumented.
Koketsu and colleague Yusuke Yokota looked at data supplied by the GeoNet network of Global Positioning System (GPS) stations dotted across Japan.
They used the data to build a map of ground movement in the Tohoku and Kanto districts from March 21, 1996 to March 8, 2011—a day before a 7.3-magnitude foreshock.
The team had to strip out seismic noise from relatively smaller earthquakes nearby in order to expose the background signals—the long, agonising deformation on the Japan Trench.
The research builds on previous initiatives to harness GeoNet data, which has millimetric accuracy of land motion.
“Our paper proved that a network of GPS stations can monitor a slow event which may lead to a great subduction earthquake,” said Koketsu.
But, he cautioned: “It has not yet been proven that a slow event always occurs prior to every great subduction earthquake.”
The paper appears in the journal Nature Communications.
Natural methane seeps off the U.S. coast may have been active for thousands of years. 2013 Northeast U.S. Canyons Expedition/NOAA Okeanos Explorer Program
Methane seeps—ever heard of them?
You might have this past summer. That’s when the national news media featured stories about a recent discovery of hundreds of methane seeps—where methane gas bubbles up from the sea floor—in the North Atlantic Ocean. The discussion about this scientific find typically turned to important questions about the methane’s impact on climate change, but there is another interesting question about methane seeps.
What are the creatures and ecosystems that exist there?
Researchers at Indiana State University have been studying methane seep ecosystems for a number of years, making trips underwater to investigate the unique association of organisms that live there. On their most recent trip to study seeps, Indiana State scientists made a big discovery regarding a tiny creature that lives in both seep and non-seep habitats.
In collaboration with Scripps Institute of Oceanography and California Institute of Technology, an Indiana State professor, graduate and undergraduate students embarked on a series of cruises to the methane seeps near Oregon and Costa Rica in 2010. With little previously known about the biological communities living in and around the rocks common in these deep-sea environments, researchers pursued a variety of investigations to learn more about the organisms and ecosystems at different seep habitats and nearby non-seep environments.
One investigation, led by Indiana State professor Tony Rathburn and doctoral student Ashley Burkett, stumbled upon an overabundance of a microscopic organism—a species of “benthic foraminifera”—that could change how scientists understand past environments.
“We found over 1,000 individuals of this specific species,” Burkett said. “The species is really interesting for us, and it’s used to figure out what the climate was like in the geologic past.”
Living on the sea floor, benthic foraminifera are microscopic creatures that produce an equally microscopic shell. The particular species of foraminifera that Rathburn and Burkett found was previously thought only to live in environments with high levels of dissolved oxygen. When scientists have found the shells of this creature in the fossil record, they have thought that the presence of the species indicated a well-oxygenated environment at a specific time in geologic history. With that idea in mind, scientists have developed a concept of what the ocean and climate was like in the past.
So, finding this species in abundance in both seep and non-seep environments where oxygen is limited was unexpected. Based on their research, Rathburn and Burkett speculate that it’s not the abundance of oxygen that determines where these creatures are located. It may simply be that they’re present where there are hard surfaces on the sea floor for them to live on.
“Scientists have used the presence of the species as an indicator of well-oxygenated environments,” Burkett said. “But this may not be the case. It may have been that there was an absence of nice rocks to colonize in the soupy sediments of poorly oxygenated environments.”
This important find was also just as unintended as it was unexpected. Rathburn and Burkett came upon these foraminifera while conducting a multifaceted seafloor experiment. Their original intent was to determine how long the tissue of foraminifera would remain on the sea floor after death. But to their delight, they got more than they asked for thanks to, of all things, plastic.
For their original experiment, they had placed test subjects inside a steel cage wrapped in plastic mesh, and this contraption was pushed half way into the sea floor sediment. Rathburn and Burkett chose the plastic mesh, because it was durable, easy to use and wouldn’t deteriorate quickly. But it turns out that the mesh was a foraminifera magnet – after a year on the sea floor, the creatures had colonized on the plastic.
“We pulled the cages up (from the sea floor), and I started to disassemble them. We were looking at the tops of the cages and commented that there was all this goo on them …. One of us said, ‘We should look at this.'”
And look she did. Using a microscope, Burkett examined the “goo” and discovered this unexpected creature. Many hours were spent painstakingly picking off all the foraminifera—about a thousand of them—from the cages, and examining the data.
Burkett presented her surprise findings this past October to the scientific community at a meeting of the Geologic Society of America in Vancouver, Canada. The response was positive.
“At this meeting, we shocked people with our results,” Rathburn said. “(Our research) will shake up our ideas about how to use these creatures in the interpretation of the environments of the past.”
Water (above) and sulfur (below) mass fractions found within the martian soil are mapped up to about 30-40 cm deep at hundreds of kilometer regional scales. Credit: Map courtesy of Suniti Karunatillake, Louisiana State University
A research team led by LSU Geology and Geophysics Assistant Professor Suniti Karunatillake reveals a spatial association between the presence of sulfur and hydrogen found in martian soil. The work by this multi-institutional team of researchers from Georgia Tech (James Wray), Stony Brook University (Scott McLennan and Deanne Rogers), CNRS/ Université Fédérale Toulouse Midi-Pyrénées (Olivier Gasnault), Cornell University (Steve Squyres), and University of Arizona (William Boynton) may in turn identify hydrous iron sulfates as key carriers of H2O in bulk martian soil.
The gamma spectral signature of hydrogen serves as a possible indicator of water, a primary driver of weathering and life processes on Earth. The analyzed elemental data from the Gamma Ray Spectrometer onboard the Mars Odyssey orbiter was published in Geophysical Research Letters on Nov. 22, 2014.
The study indicates that within the southern latitudes of Mars, sulfur compounds are a key hydrated phase. This is revealed in part by water-to-sulfur molar ratios that fall within expected ranges corresponding to hydrated sulfate compounds. Reinforcing the data, hydrogen and sulfur correlate compellingly in the southern latitudes. The molar ratios were observed over 80 percent of Mars’ southern hemisphere. Consequently, sulfate compounds, acting as primary contributors of H2O, may also influence modern water-driven processes on Mars.
“Sulfur variation plays an important role as a control on inferred fluid pH, alteration environments, and water activity while the variation in hydration state reinforces the compelling possibility of H2O bound primarily in sulfates in the southern hemisphere,” Karunatillake said. “This applies specifically to bulk soil at decimeter depths, including the possibility that geochemical processes of iron sulfate-rich Paso Robles soil in Gusev Crater may have been more common at regional scales in ancient martian terrain than previously appreciated.”
The team suggests that further observations by the Curiosity rover in Gale Crater could move forward models of aqueous processes on Mars. For example, recent analyses of “Rocknest” soil samples suggest complementary modes of soil hydration in the Gale Crater area.
Reference:
S. Karunatillake, J. J. Wray, O. Gasnault, S. M. McLennan, A. D. Rogers, S. W. Squyres, W. V. Boynton, J. R. Skok, L. Ojha, N. Olsen. Sulfates hydrating bulk soil in the Martian low and middle latitudes. Geophysical Research Letters, 2014; 41 (22): 7987 DOI: 10.1002/2014GL061136
Watkins Mountains in southern East Greenland, with Greenland’s highest peak, Gunbjörn Fjeld (3.7 km above sea level) in the background. The photo was taken at about 2 km above sea level, towards the 1.5 km high Watkins Escarpment cut into basalts erupted at the Paleocene-Eocene transition about 56 million years ago, much closer to sea level at that time. Credit: Peter Japsen, GEUS
The ice on Greenland could only form due to processes in the deep Earth interior. Large-scale glaciations in the Arctic only began about 2.7 million years ago; before that, the northern hemisphere was largely free of ice for more than 500 million years. Scientists at the German Research Centre for Geosciences GFZ, Utrecht University, the Geological Survey of Denmark and Greenland (GEUS) and the University of Oslo could now explain why the conditions for the glaciation of Greenland only developed so recently on a geological time scale.
The reason for that is the interaction of three tectonic processes. For one thing, Greenland had to be lifted up, such that the mountain peaks reached into sufficiently cold altitudes of the atmosphere. Secondly, Greenland needed to move sufficiently far northward, which led to reduced solar irradiation in winter. Thirdly, a shift of the Earth axis caused Greenland to move even further northward.
These glaciations began in the East of Greenland. The authors found hints in rock samples that the high mountains in the east of Greenland were only uplifted during the last ten million years, whereby this process happened especially fast since about 5 million years ago. At that time, Greenland was still largely free of ice. Seismological investigations indicate that hot rocks rise underneath Iceland from Earth’s deep mantle. These observations were used as input in computer models by main author Bernhard Steinberger at the German Research Centre for Geosciences GFZ. “These hot rocks flow northward beneath the lithosphere, that is, towards eastern Greenland,” Steinberger explains. “Because the upwelling beneath Iceland −the Iceland plume − sometimes gets stronger and sometimes weaker, uplift and subsidence can be explained.”
Greenland migrating
The seismological investigations also showed that the lithosphere in the East of Greenland is especially thin — only about 90 kilometers thick. Earth scientists Steinberger and colleagues reconstructed the position of the tectonic plates 60 to 30 million years ago, and found that the Iceland plume was exactly beneath this part of Greenland during that time. This explains why the lithosphere is so thin. For that reason, the eastern part of Greenland could also be more easily uplifted: Plume material can flow up to a depth of less than 100 km and therefore lift up the overlying lithosphere comparatively easily.
Whereas the Iceland plume remained in approximately the same position in Earth mantle, Greenland moved as a tectonic plate, with a northward component of six degrees of latitude during the past 60 Million years, towards cooler regions.
Shift of Earth axis
This northward motion was amplified through “True polar wander”: “Our computations show that Earth axis shifted about 12° towards Greeland during the last 60 million years” GFZ researcher Steinberger says. Therefore, in combination with the tectonic plate motion, Greenland moved about 18° northward. It was now sufficiently far north, and its mountain tops in the East were sufficiently high, such that glaciations could be initiated.
Reference:
Bernhard Steinberger, Wim Spakman, Peter Japsen, Trond H. Torsvik. The key role of global solid-Earth processes in preconditioning Greenland’s glaciation since the Pliocene. Terra Nova, 2014; DOI: 10.1111/ter.12133
Cyanobacteria: Such tiny organisms produced today’s proportion of about 20 percent oxygen in the atmosphere of the earth. Credit: Kappler, Swanner/University of Tübingen
Three billion years ago, Earth’s atmosphere contained less than 0.0001 percent oxygen. Today’s atmosphere has around 20 percent oxygen — and that is due to the work of tiny microorganisms in Earth’s primeval oceans. Cyanobacteria, which still exist in a similar form today, probably started using energy from sunlight to photosynthesize some of the carbon dioxide in the atmosphere into organic compounds. Oxygen gas was a byproduct of this process. After about two billion years, it enabled the evolution of the many higher organisms that respire on oxygen, including us.
Tübingen geomicrobiologists Dr. Elizabeth Swanner and Professor Andreas Kappler say that after evolution of the first cyanobacteria, one would expect a rapid and massive oxygen production, i.e. cyanobacteria could have produced much more oxygen much sooner. Working with colleagues from the Department of Geosciences at the University of Tübingen and geoscientists from the University of Alberta (Edmonton, Canada) they looked for factors which prevented early bacteria from multiplying faster. They found that soluble iron in the earliest oceans quickly combined with oxygen to form rust — forming reactive oxygen molecules, which damage biological tissue and make the cyananobacteria grow more slowly and produce less oxygen. Their findings are published in the latest Nature Geoscience.
Today’s seawater contains little iron. But more than three billion years ago, the oceans contained abundant reduced iron. This is partially because oxygen, which causes the iron to precipitate, had not yet entered the ocean to great depths, and also because the seafloor at that time contained abundant iron released by bursts of hydrothermal activity. “In these periods, we often find no indicators of oxygen release,” says Elizabeth Swanner, the study’s lead author. The researchers carried out lab experiments seeking a link between high concentrations of iron and low cyanobacteria growth. It appears that the iron — which the bacteria needed to live — hindered photosynthesis when it was present in high concentrations, thereby cutting off the bacteria’s energy supply. “Too much iron in the presence of oxygen was harmful. You could say the early cyanobacteria poisoned themselves,” Andreas Kappler says.
These new findings will help scientists to better understand the global cycles of carbon and oxygen in the periods of higher soluble iron concentration, also shedding light on the processes in which iron stopped being food and became poison for cyanobacteria and other photosynthesizing organisms. In addition, the connection between iron levels and oxygen production found here will help researchers to reconstruct the long-term processes behind the evolution of animals — which need high levels of oxygen.
Reference:
Elizabeth D. Swanner, Aleksandra M. Mloszewska, Olaf A. Cirpka, Ronny Schoenberg, Kurt O. Konhauser, Andreas Kappler. Modulation of oxygen production in Archaean oceans by episodes of Fe(II) toxicity. Nature Geoscience, 2015; DOI: 10.1038/ngeo2327
Rare Udachnaya diamondiferous peridotite. Credit: Larry Taylor
Diamonds are beautiful and enigmatic. Though chemical reactions that create the highly coveted sparkles still remain a mystery, a professor from the University of Tennessee, Knoxville, is studying a rare rock covered in diamonds that may hold clues to the gem’s origins.
The golf-ball sized chunk of rock contains more than 30,000 diamonds, each less than a millimeter in size (rendering them worthless), along with speckles of red and green garnet and other minerals.
The rock was found in Russia’s Udachnaya diamond mine in northern Siberia. The diamond company of Russia, ALROSA, loaned it to Earth and Planetary Sciences Professor Larry Taylor and a team of researchers from the Russian Academy of Sciences so they could study the rock to uncover the diamonds’ genesis.
Scientists believe that diamonds form at some 100 miles deep in Earth’s mantle and are carried to the surface by special volcanic eruptions. However, most mantle rocks crumble during this journey. This rock is one of only a few hundred recovered in which the diamonds are still in their original setting from within the Earth.
“It is a wonder why this rock has more than 30,000 perfect teeny tiny octahedral diamonds — all 10 to 700 micron in size and none larger,” said Taylor. “Diamonds never nucleate so homogeneously as this. Normally, they do so in only a few selective places and grow larger. It’s like they didn’t have time to coalesce into larger crystals.”
Taylor and his colleagues examined the sparkly chunk using a giant X-ray machine to study the diamonds and their relationships with associated materials. They also beamed electrons at the materials inside the diamonds — called inclusions — to study the chemicals trapped inside.
This created two- and three-dimensional images which revealed a relationship between minerals. Analyses of nitrogen indicated the diamonds were formed at higher-than-normal temperatures over longer-than-normal times. The images also showed abnormal carbon isotopes for this type of rock, indicating it was originally formed as part of the crust of Earth, withdrawn by tectonic shifts and transformed into the shimmery rock we see today.
“These are all new and exciting results, demonstrating evidences for the birth mechanism of diamonds in this rock and diamonds in general,” said Taylor. The findings were presented at the American Geophysical Union’s annual conference in San Francisco in December and will be published in a special issue of Russian Geology and Geophysics this month.
Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia
A new study links the March 2014 earthquakes in Poland Township, Ohio to hydraulic fracturing that activated a previously unknown fault. The induced seismic sequence included a rare felt earthquake of magnitude 3.0, according to research published online by the Bulletin of the Seismological Society of America (BSSA).
In March 2014, a series of five recorded earthquakes, ranging from magnitude 2.1 to 3.0, occurred within one kilometer (0.6 miles) of a group of oil and gas wells operated by Hilcorp Energy, which was conducting active hydraulic fracturing operations at the time. Due to the proximity of a magnitude 3.0 event near a well, the Ohio Department of Natural Resources (ODNR) halted operations at the Hilcorp well on March 10, 2014.
Hydraulic fracturing, or fracking, is a method for extracting gas and oil from shale rock by injecting a high-pressure water mixture directed at the rock to release the oil and gas trapped inside. The process of fracturing the rocks normally results in micro-earthquakes much smaller than humans can feel.
It remains rare for hydraulic fracturing to cause larger earthquakes that are felt by humans. However, due to seismic monitoring advances and the increasing popularity of hydraulic fracturing to recover hydrocarbons, the number of earthquakes – felt and unfelt – associated with hydraulic fracturing has increased in the past decade.
“These earthquakes near Poland Township occurred in the Precambrian basement, a very old layer of rock where there are likely to be many pre-existing faults,” said Robert Skoumal who co-authored the study with Michael Brudzinski and Brian Currie at Miami University in Ohio. “This activity did not create a new fault, rather it activated one that we didn’t know about prior to the seismic activity.”
Using a technique called template matching, the researchers sifted through seismic data recorded by the Earthscope Transportable Array, a network of seismic stations, looking for repeating signals similar to the known Poland Township earthquakes, which were treated like seismic “fingerprints.” They identified 77 earthquakes with magnitudes from 1.0 and 3.0 that occurred between March 4 and 12 in the Poland Township area. The local community reported feeling only one earthquake, the magnitude 3.0, on March 10.
Skoumal and his colleagues compared the identified earthquakes to well stimulation reports, released in August 2014 by the ODNR, and found the earthquakes coincided temporally and spatially with hydraulic fracturing at specific stages of the stimulation. The seismic activity outlined a roughly vertical, east-west oriented fault within one kilometer of the well. Industry activities at other nearby wells produced no seismicity, suggesting to the authors that the fault is limited in extent.
“Because earthquakes were identified at only the northeastern extent of the operation, it appears that a relatively small portion of the operation is responsible for the events,” said Skoumal, who suggests the template matching technique offers a cost-effective and reliable means to monitor seismicity induced by hydraulic fracturing operations.
“We just don’t know where all the faults are located,” said Skoumal. “It makes sense to have close cooperation among government, industry and the scientific community as hydraulic fracturing operations expand in areas where there’s the potential for unknown pre-existing faults.”
The paper, “Earthquakes Induced by Hydraulic fracturing in Poland Township, Ohio,” will be published online Jan. 6, 2015 and in print in the February/March issue of BSSA.
Ten years ago, one of the deadliest natural disasters in history killed 227,898 people in 14 countries around the Indian Ocean—nearly 170,000 of them in Indonesia.It began on the morning of December 26, 2004, about 150 miles (240 kilometers) off the west coast of Sumatra, when a magnitude 9.1 earthquake—the third largest since 1900—ruptured the ocean floor. Within eight minutes the fracture spanned 700 miles (1,127 kilometers), releasing 23,000 times more energy than the atomic bomb that destroyed Nagasaki, Japan. Parts of the seabed shifted 30 feet (9 meters) to the west-southwest.
But that was not the worst of it. Some segments of the fault also surged upward by tens of feet, and they lifted the whole column of seawater above them. At the sea surface, that set in motion a wave—a tsunami that traveled around the Indian Ocean. When it hit Sumatra, it was 100 feet (30 meters) high along parts of the northwest coast.
It was the tsunami that did the killing.
When the next tsunami strikes the Indian Ocean—and scientists are certain that another large one is inevitable, probably within the next few decades—will the region fare any better?
Hardest hit on that terrible day ten years ago was the Indonesian city of Banda Aceh, on Sumatra’s northern tip. More than 60,000 of its 264,000 residents perished—about 35 percent of the total lost in Indonesia. (Read more about the Indonesian and Japanese tsunamis.)
Vivi Yanti, an English teacher in the city, remembers the water as being warm, black, oily, and filled with debris. In streets jammed with fleeing people, Yanti glimpsed a woman running, holding the hand of a little boy, banging on the windows of passing cars, begging for a ride. No one stopped. “I escaped by riding with my uncle on the back of his motorcycle,” says Yanti. “I remember looking back, and at first I didn’t know what I was seeing—the water was carrying a big ship down the street. I told my uncle, ‘Drive faster.'”
Ten years later Banda Aceh has been rebuilt, and its population has climbed back to 250,000, almost what it was before the disaster. With smooth new highways and vibrant late-night cafés, the city has been transformed. Aside from a number of immaculately groomed mass graves, and a few intentional reminders of the disaster—such as the presence of a large ship marooned in a city park—most signs of the tsunami’s damage have been erased.
Like other countries ravaged by the 2004 tsunami, Indonesia is now linked to a tsunami detection system in the Indian Ocean. Once an earthquake has occurred, that system of seafloor sensors and surface buoys relays signals via satellite to government warning centers around the world, alerting them that a tsunami might be on the way.
NG ART; BRYAN CHRISTY. SOURCE: OREGON STATE UNIVERSITY
A decade ago such detectors existed only in the Pacific. Had they been deployed in the Indian Ocean in 2004, some of the 51,000 people who died in Sri Lanka and India would have been spared: The tsunami took two hours to cross the Indian Ocean, and timely warnings—or any warning at all—would have saved thousands of lives.
But Indonesia—the fourth most populous country in the world—is in a less fortunate situation. It borders a number of dangerous seismic faults, especially a long, arcing one called the Sunda megathrust, which parallels the islands of Sumatra and Java. The 2004 tsunami that began on that fault struck the Sumatran coast within 30 minutes of the earthquake. Even with a near instantaneous tsunami alert, many residents wouldn’t have had enough time to reach high ground.
Faced with such an unforgiving margin between life and death, Indonesia has struggled to improve public awareness and preparedness. A handful of evacuation shelters—three- or four-story buildings, some of them with open ground floors to let the wave pass through—have been built in Banda Aceh and other threatened cities. There’s a network of sirens to warn residents that a tsunami is imminent.
But much remains to be done, as the response to a recent earthquake made painfully evident.
A Practice Run Goes Badly
On April 11, 2012, when a magnitude 8.6 earthquake struck Banda Aceh, Indonesia’s National Tsunami Warning Center issued a tsunami alert within five minutes of the first tremors. The nation’s early warning system worked perfectly, but the local response to the alert does not bode well for future disasters. Officials in Banda Aceh had failed to establish clear emergency guidelines for the city. Although the earthquake didn’t generate a tsunami—the plates along the fault in this case slipped horizontally, not violently upward—people with horrific firsthand experience expected one, and panicked.
“The conditions were totally chaotic,” says Syarifah Marlina Al Mazhir, a lifelong resident of Banda Aceh who worked for the Red Cross during the 2004 tsunami. “Instead of evacuating to safe areas, people were going home or picking up the kids at school, which created traffic jams.”
Even worse, she says, the staff responsible for operating the tsunami sirens fled, and the city’s three multi-story tsunami shelters were locked.
“In Banda Aceh everything became paralyzed very quickly,” says Tom Alcedo, the head of the American Red Cross in Indonesia. “Roads to high ground got choked. All those people in their cars would have been swept away. It was a wake-up call.”
Ardito Kodijat, the director of the Indian Ocean Tsunami Information Center in Jakarta, says Banda Aceh and other coastal cities in Indonesia need to establish well-marked evacuation routes and conduct regular tsunami drills. Many people in Banda Aceh, he says, didn’t know that evacuation centers had been built. Others, having witnessed the ferocity of the 2004 tsunami, thought the structures would be unsafe, and tried to escape inland instead. “The people could have been much better prepared if there had been clear and strong guidance from the local government,” says Kodijat.
Banda Aceh, though, is probably not the most threatened of Indonesia’s cities. “The shoe dropped there already,” says Brian Atwater, a geologist with the U.S. Geological Survey. “It’s not at all clear how often earthquakes repeat, and whether the fault that broke in 2004 spent everything it had on that earthquake, or whether there’s something left in the bank. In the meantime, you have plenty of other places with poorly understood hazards. Padang is a next-shoe-drop kind of place.”
Geological evidence of past tsunamis suggest that the segment of the Sunda megathrust that lies off Padang, a city of one million on Sumatra’s west coast, may be overdue for an earthquake. Government officials in Indonesia and Padang are aware of the risk. As in Banda Aceh, evacuation routes have been planned and emergency shelters built.
But in Indonesia and other countries along the rim of the Indian Ocean, such measures may be insufficient to protect the hundreds of millions of people who live along the coasts. Even with the best warning systems and evacuation plans, there are simply too many people in harm’s way. In Southeast Asia alone, more than ten million people live within a mile of the coast. Short of moving Banda Aceh, Padang, and every other threatened coastal city miles inland, there’s no fail-safe defense against future tsunamis.
Kerry Sieh, a geologist at Nanyang Technological University’s Earth Observatory in Singapore, has spent more than 20 years studying the faults around Sumatra. Geologists like Sieh can tell us when earthquakes have occurred in the past, and when and where they’re likely to occur in the future. While they can’t tell us exactly when to run, they can say with certainty that many of us are living in dangerous places.
Given the sheer numbers of lives at risk, Sieh says, there is only so much governments can do, especially in poor countries like Indonesia, to prevent catastrophic losses from the inevitable future tsunamis. “Is good work being done?” Sieh asks. “Yes. There are people trying to educate; there are people trying to build vertical evacuation structures. But will it solve even 10 percent of the problem? I have my doubts.”
Note : The above story is based on materials provided by National Geographic. The original article was written by Tim Folger.
M9.1 Sumatra-Andaman Islands Earthquake Tectonic Setting and Seismicity Map
In the early hours of Dec. 26, 2004, one of the world’s most powerful earthquakes triggered one of the largest tsunamis in 40 years.
Sometimes known as the Christmas or Boxing Day tsunami, the December 26, 2004 Indian Ocean Tsunami is far from a distant memory, a decade after resulting in more than 200,000 casualities.
“The tsunami struck after the magnitude 9.1 Sumatra-Andaman Earthquake occurred off the northwest coast of Sumatra, Indonesia, causing catastrophic levels of destruction to countries around the Indian Ocean basin.”
The magnitude 9.1 Sumatra-Andaman Earthquake occurred on the interface between the India and Burma tectonic plates.
According to USGS scientists, the sea floor near the earthquake was uplifted several meters. The displacement of water above the sea floor triggered the tsunami, which caused catastrophic levels of destruction in countries around the Indian Ocean basin, reaching as far as the east coast of Africa.
The tsunami arrived in northern Sumatra approximately 30 minutes after the earthquake, in Thailand approximately an hour and a half to two hours after the earthquake, and in Sri Lanka approximately two to three hours after the earthquake.
The tsunami was only recently rivaled by the 2011 tsunami in Japan.
“The foremost impact, of course, is the loss of life in both cases,” said Eric Geist, USGS research geophysicist. “For the 2004 tsunami, the loss of life far outweighed damage to infrastructure, whereas for the 2011 tsunami, there was significant damage to infrastructure in Japan.”
Countries hardest hit by the 2004 tsunami included Sri Lanka, India, Thailand, Somalia, Maldives, Malaysia, Myanmar, Tanzania, Bangladesh and Kenya
Tsunami Research
The 2004 tsunami was the deadliest and one of the most destructive in recorded history.
Tsunami runup heights of more than 30 meters were observed along the west coast of Sumatra.
In Aceh and Sumatera Utara Provinces, Indonesia, at least 108,100 people were killed, 127,700 are missing and presumed dead and 426,800 were displaced by the earthquake and tsunami.
Bruce Richmond, a coastal geologist with the USGS Pacific Coastal and Marine Science Center in Santa Cruz, Calif,, along with USGS scientists Bruce Jaffe and Guy Gelfenbaum joined international survey teams to documenttsunami impacts, collect water level information, and map erosion and deposition of sediments to characterize the sedimentary record. The tsunami effects were studied in an effort to develop techniques to improve the identification of paleotsunami deposits in the geologic record.
“Our studies were conducted in a variety of coastal environments impacted by the tsunami and went a long way in helping us to understand the variability of deposits from a single event in multiple coastal settings,” Richmond said.
Future Implications and Preparation
Before the Indian Ocean Tsunami occurred, USGS geologists had been assessing tsunami hazards in California, seeking evidence of past tsunami deposits along California’s shores. “Not long after we started our California work in 2004, the Indian Ocean earthquake and tsunami struck which changed the focus of our efforts for several years,” said Richmond. “At the time, that tsunami was the largest natural disaster in our lifetimes, both in terms of lives lost and widespread impact. Our observations on many different shorelines around the Indian Ocean went a long way in helping us to understand the variability of deposits from a single event in multiple coastal settings.”
Geist, too, said he and his USGS counterparts’ research since then has focused on taking the lessons learned from the 2004 and 2011 tsunamis and applying them to hazard issues that affect the U.S. Could it happen here?
“Initially, my research focus was evaluating the performance of hazard assessment models if they had been used prior to the tsunami,” Geist said. “Since then, our research has focused more on taking the lessons learned from both tsunamis and applying them to hazard issues that affect the U.S.”
Bruce Jaffe, research oceanographer, said that earthquakes and tsunamis like those in 2004 have brought awareness and the need to study and prepare for these often underestimated hazards
“The take-home message is that we still have a lot to learn about what the real hazard of tsunamis are,” he said. “We’re getting there but it’s taking time.”
International Chronostratigraphic Chart latest version (v 2014/10)
Click here (PDF or JPG) to download the latest version (v 2014/10) of the International Chronostratigraphic Chart.
Translations of the chart: Japanese (v2014-02: PDF or JPG), Chinese (v2013-01: PDF or JPG), Spanish (v2013-01), Portuguese (v2013-01: PDF or JPG), Norwegian (v2013-01: PDF or JPG), Basque (v2013-01: PDF or JPG), Catalan (v2013-01: PDF or JPG) and French (v2012).
The old versions can be download at the following links: 2008 (PDF or JPG), 2009 (PDF or JPG), 2010 (PDF or JPG), 2012 (PDF or JPG), 2013/01 (PDF or JPG), 2014/02 (PDF or JPG) and the ChangeLog for 2012, 2013 and 2014.
Stone tool approximately 1.2 million years old. Credit: Image courtesy of University of Royal Holloway London
Scientists have discovered the oldest recorded stone tool ever to be found in Turkey, revealing that humans passed through the gateway from Asia to Europe much earlier than previously thought, approximately 1.2 million years ago.
According to research published in the journal Quaternary Science Reviews, the chance find of a humanly-worked quartzite flake, in ancient deposits of the river Gediz, in western Turkey, provides a major new insight into when and how early humans dispersed out of Africa and Asia.
Researchers from Royal Holloway, University of London, together with an international team from the UK, Turkey and the Netherlands, used high-precision equipment to date the deposits of the ancient river meander, giving the first accurate timeframe for when humans occupied the area.
Professor Danielle Schreve, from the Department of Geography at Royal Holloway, said: “This discovery is critical for establishing the timing and route of early human dispersal into Europe. Our research suggests that the flake is the earliest securely-dated artefact from Turkey ever recorded and was dropped on the floodplain by an early hominin well over a million years ago.”
The researchers used high-precision radioisotopic dating and palaeomagnetic measurements from lava flows, which both pre-date and post-date the meander, to establish that early humans were present in the area between approximately 1.24 million and 1.17 million years ago. Previously, the oldest hominin fossils in western Turkey were recovered in 2007 at Koçabas, but the dating of these and other stone tool finds were uncertain.
“The flake was an incredibly exciting find,” Professor Schreve said. “I had been studying the sediments in the meander bend and my eye was drawn to a pinkish stone on the surface. When I turned it over for a better look, the features of a humanly-struck artefact were immediately apparent.
“By working together with geologists and dating specialists, we have been able to put a secure chronology to this find and shed new light on the behaviour of our most distant ancestors.”
Reference:
D. Maddy, D. Schreve, T. Demir, A. Veldkamp, J.R. Wijbrans, W. van Gorp, D.J.J. van Hinsbergen, M.J. Dekkers, R. Scaife, J.M. Schoorl, C. Stemerdink, T. van der Schriek. The earliest securely-dated hominin artefact in Anatolia? Quaternary Science Reviews, 2015; 109: 68 DOI: 10.1016/j.quascirev.2014.11.021
Fossilised Acanthodes bridgei with eye tissues intact. Credit: Tanaka et al., Nature Communications
A fish eye from a primitive time when Earth was but one single continent, has yielded evidence of color vision dating back at least 300 million years, researchers said Tuesday.
Analysing the fossilized remains of a fish from the “spiny shark” family that lived long before the dinosaurs, scientists discovered light-sensing “rod” and “cone” eye cells—the oldest ever found.
“This is the first discovery of vertebrate retinal fossils,” said Gengo Tanaka from Japan’s Kumamoto University, who co-authored the study in the journal Nature Communications.
It is rare for palaeontologists to find eye remains, as the soft tissue generally decays within 64 days, the authors of the study said.
However, the Hamilton Quarry in Kansas is a treasure trove of unusually well-preserved fossils—an entire ecosystem having been rapidly buried under sediment.
They included the extinct fish Acanthodes bridgei—among the oldest known vertebrates with jaws.
It had a long, streamlined body and fins with spines, is believed to have lived in shallow, brackish water, and died out at the end of the Permian period about 250 million years ago when nearly 90 percent of species disappeared in the largest extinction in Earth’s history.
An A. bridgei specimen found at the quarry retained elements of the original eye colour and shape, and a light-absorbing pigment in the retina.
The remains had been preserved under a thin coating of phosphate, Tanaka told AFP.
Analysis of the tissue “provides the first record of mineralized rods and cones in a fossil,” said the study.
These, combined with light-absorbing melanin pigments, suggested the fish was “probably” able to see in low light using highly-sensitive rod cells, and by day using cone cells.
In modern animals, cone cells respond individually to light at specific wavelengths, thus allowing observation of different colors.
“The presence of cones indicates that A. bridgei likely possessed color vision”, the study said—though conclusive evidence is needed.
Vision is thought to have existed for at least 520 million years, but this is the first direct evidence of color-sensitive receptors.
A study of tooth enamel in mammals living today in the equatorial forest of Gabon could ultimately shed light on the diet of long extinct animals, according to new research from the University of Bristol.
Reconstructing what extinct organisms fed on can be a real challenge. Scientists use a variety of methods including the structure of an animal’s bones, analysis of its stomach contents and the patterns of wear left on the surface of its teeth. Geochemical methods have also proved useful but can be limited by poor preservation of the animal’s remains.
Dr Jeremy Martin, formerly of Bristol’s School of Earth Sciences and now at the Laboratoire de Géologie de Lyon: terre, planètes et environnement, University of Lyon/ENS de Lyon, and colleagues found that magnesium isotopes are particularly well suited to deciphering the diet of living mammals and, when used in conjunction with other methods such as carbon isotopes, they could open up new perspectives on the study of fossilised animals.
Dr Martin said: “Most chemical elements exist in distinct forms called isotopes which are characterized by different masses. Therefore, all the isotopes of an element will behave differently during a chemical reaction preferentially sorting out heavier ones from lighter ones.”
As noted by Dr Balter, who took part in the study: “Biological processes such as digestion involve important isotopic fractionations of the various elements assimilated through food consumption so the stable isotope composition of an organism tends to reflect its diet — we are what we eat.”
Scientists know that the carbon and nitrogen isotopes preserved in bone collagen can give direct evidence about an animal’s food intake. However, because of the rapid decay of organic matter, these inferences are limited to the recent past.
Dr Martin and colleagues explored the isotopic variability of one of the major elements that compose tooth apatite, the hardest biological structure to retain its pristine signal throughout the fossil record.
Teeth from various mammals living today in the equatorial forest of Gabon were purified for magnesium isotopes. The results show that the isotope ratios of magnesium 26 mg/24 mg increase from herbivore to higher-level consumers (such as carnivores) and, when used in conjunction with other geochemical proxies, serve as a strong basis to infer the diet of mammals.
Dr Martin said: “Many fossil groups do not have living analogues and inferring their diet is far from clear. Applying a new perspective to palaeoecology by using non-traditional isotopes (such as magnesium or calcium in conjunction with traditional approaches) holds great promise for our understanding of how such ancient organisms interacted with each other.”
Reference:
Jeremy E. Martin, Derek Vance, Vincent Balter. Magnesium stable isotope ecology using mammal tooth enamel. Proceedings of the National Academy of Sciences, 2014; 201417792 DOI: 10.1073/pnas.1417792112
NASA has contracted with two private space firms to prepare and execute missions to land on and mine asteroids for valuable resources. Space mining could help provide deep space missions with vital resources such as water, silicate or minerals. VIDEOGRAPHICS
The same autopod-building genetic switches from gar are able to drive gene activity (purple) in the digits of transgenic mice; an activity that was absent in other fish groups studied. Credit: Andrew Gehrke, the University of Chicago
Paleontologists have documented the evolutionary adaptations necessary for ancient lobe-finned fish to transform pectoral fins used underwater into strong, bony structures, such as those of Tiktaalik roseae. This enabled these emerging tetrapods, animals with limbs, to crawl in shallow water or on land. But evolutionary biologists have wondered why the modern structure called the autopod–comprising wrists and fingers or ankles and toes–has no obvious morphological counterpart in the fins of living fishes.
In the Dec. 22, 2014, issue of the Proceedings of the National Academy of Sciences, researchers argue previous efforts to connect fin and fingers fell short because they focused on the wrong fish. Instead, they found the rudimentary genetic machinery for mammalian autopod assembly in a non-model fish, the spotted gar, whose genome was recently sequenced.
“Fossils show that the wrist and digits clearly have an aquatic origin,” said Neil Shubin, PhD, the Robert R. Bensley Professor of organismal biology and anatomy at the University of Chicago and a leader of the team that discovered Tiktaalik in 2004. “But fins and limbs have different purposes. They have evolved in different directions since they diverged. We wanted to explore, and better understand, their connections by adding genetic and molecular data to what we already know from the fossil record.”
Initial attempts to confirm the link based on shape comparisons of fin and limb bones were unsuccessful. The autopod differs from most fins. The wrist is composed of a series of small nodular bones, followed by longer thin bones that make up the digits. The bones of living fish fins look much different, with a set of longer bones ending in small circular bones called radials.
The primary genes that shape the bones, known as the HoxD and HoxA clusters, also differ. The researchers first tested the ability of genetic “switches” that control HoxD and HoxA genes from teleosts–bony, ray-finned fish–to shape the limbs of developing transgenic mice. The fish control switches, however, did not trigger any activity in the autopod.
Teleost fish–a vast group that includes almost all of the world’s important sport and commercial fish–are widely studied. But the researchers began to realize they were not the ideal comparison for studies of how ancient genes were regulated. When they searched for wrist and digit-building genetic switches, they found “a lack of sequence conservation” in teleost species.
They traced the problem to a radical change in the genetics of teleost fish. More than 300 million years ago, after the fish-like creatures that would become tetrapods split off from other bony fish, a common ancestor of the teleost lineage went through a whole-genome duplication (WGD)–a phenomenon that has occurred multiple times in evolution.
By doubling the entire genetic repertoire of teleost fish, this WGD provided them with enormous diversification potential. This may have helped teleosts to adapt, over time, to a variety of environments worldwide. In the process, “the genetic switches that control autopod-building genes were able to drift and shuffle, allowing them to change some of their function, as well as making them harder to identify in comparisons to other animals, such as mice,” said Andrew Gehrke, a graduate student in the Shubin lab and lead author of the study.
Not all bony fishes went through the whole genome duplication, however. The spotted gar, a primitive freshwater fish native to North America, split off from teleost fishes before the WGD.
When the research team compared Hox gene switches from the spotted gar with tetrapods, they found “an unprecedented and previously undescribed level of deep conservation of the vertebrate autopod regulatory apparatus.” This suggests, they note, a high degree of similarity between “distal radials of bony fish and the autopod of tetrapods.”
They tested this by inserting gar gene switches related to fin development into developing mice. This evoked patterns of activity that were “nearly indistinguishable,” the authors note, from those driven by the mouse genome.
“Overall,” the researchers conclude, “our results provide regulatory support for an ancient origin of the ‘late’ phase of Hox expression that is responsible for building the autopod.”
This study was supported by the Brinson Foundation; the National Science Foundation; the Brazilian National Council for Scientific and Technological Development grants; the National Institutes of Health; the Volkswagen Foundation, Germany; the Alexander von Humboldt-Foundation, the Spanish and Andalusian governments; and Proyecto de Excelencia.
Additional authors include Mayuri Chandran and Tetsuya Nakamura from the University of Chicago; Igor Schneider from the Instituto de Ciencias Biologicas, Universida de Federal do Para, Belem, Brazil; Elisa de la Calle-Mustienes, Juan J. Tena, Carlos Gomez-Marin and José Luis Gómez-Skarmeta from the Centro Andaluz de Biología del Desarrollo, Sevilla, Spain; and Ingo Braasch and John H. Postlethwait from the Institute of Neuroscience, University of Oregon.
Reference:
Andrew R. Gehrke, Igor Schneider, Elisa de la Calle-Mustienes, Juan J. Tena, Carlos Gomez-Marin, Mayuri Chandran, Tetsuya Nakamura, Ingo Braasch, John H. Postlethwait, José Luis Gómez-Skarmeta, and Neil H. Shubin. Deep conservation of wrist and digit enhancers in fish. PNAS, December 22, 2014 DOI: 10.1073/pnas.1420208112
The surface of Mars was once wet, but no water flows there now. UC San Diego chemists and others took a close look at meteorite that may have been blasted from this huge rift across the planet’s surface. The image is a composite of hundreds of photos taken by NASA’s Viking missions in the 1970s. Credit: USGS, NASA
A new analysis of a Martian rock that meteorite hunters plucked from an Antarctic ice field 30 years ago this month reveals a record of the planet’s climate billions of years ago, back when water likely washed across its surface and any life that ever formed there might have emerged.
Scientists from the University of California, San Diego, NASA and the Smithsonian Institution report detailed measurements of minerals within the meteorite in the early online edition of the Proceedings of the National Academy of Sciences this week.
“Minerals within the meteorite hold a snapshot of the planet’s ancient chemistry, of interactions between water and atmosphere,” said Robina Shaheen, a project scientist at UC San Diego and the lead author of the report.
The unlovely stone, which fell to Earth 13 thousand years ago, looked a lot like a potato and has quite a history. Designated ALH84001, it is the oldest meteorite we have from Mars, a chunk of solidified magma from a volcano that erupted four billion years ago. Since then something liquid, probably water, seeped through pores in the rock and deposited globules of carbonates and other minerals.
The carbonates vary subtly depending on the sources of their carbon and oxygen atoms. Both carbon and oxygen occur in heavier and lighter versions, or isotopes. The relative abundances of isotopes forms a chemical signature that careful analysis and sensitive measurements can uncover.
Mars’s atmosphere is mostly carbon dioxide but contains some ozone. The balance of oxygen isotopes within ozone are strikingly weird with enrichment of heavy isotopes through a physical chemical phenomenon first described by co-author Mark Thiemens, a professor of chemistry at UC San Diego, and colleagues 25 years ago.
“When ozone reacts with carbon dioxide in the atmosphere, it transfers its isotopic weirdness to the new molecule,” said Shaheen, who investigated this process of oxygen isotope exchange as a graduate student at the University of Heidelberg in Germany. When carbon dioxide reacts with water to make carbonates, the isotopic signature continues to be preserved.
The degree of isotopic weirdness in the carbonates reflects how much water and ozone was present when they formed. It’s a record of climate 3.9 billion years ago, locked in a stable mineral. The more water, the smaller the weird ozone signal.
This team measured a pronounced ozone signal in the carbonates within the meteorite, suggesting that although Mars had water back then, vast oceans were unlikely. Instead, the early Martian landscape probably held smaller seas.
“What’s also new is our simultaneous measurements of carbon isotopes on the same samples. The mix of carbon isotopes suggest that the different minerals within the meteorite had separate origins,” Shaheen said. “They tell us the story of the chemical and isotopic compositions of the atmospheric carbon dioxide.”
ALH84001 held tiny tubes of carbonate that some scientists saw as potential evidence of microbial life, though a biological origin for the structures has been discarded. On December 16, NASA announced another potential whiff of Martian life in the form of methane sniffed by the rover Curiosity.
Carbonates can be deposited by living things that scavenge the minerals to build their skeletons, but that is not the case for the minerals measured by this team. “The carbonate we see is not from living things,” Shaheen said. “It has anomalous oxygen isotopes that tell us this carbonate is abiotic.”
By measuring the isotopes in multiple ways, the chemists found carbonates depleted in carbon-13 and enriched in oxygen-18. That is, Mars’s atmosphere in this era, a period of great bombardment, had much less carbon-13 than it does today.
The change in relative abundances of carbon and oxygen isotopes may have occurred through extensive loss of Martian atmosphere. A thicker atmosphere would likely have been required for liquid water to flow on the planet’s chilly surface.
“We now have a much deeper and specific insight into the earliest oxygen-water system in the solar system,” Thiemens said. “The question that remains is when did planets, Earth and Mars, get water, and in the case of Mars, where did it go? We’ve made great progress, but still deep mysteries remain.”
Reference:
Robina Shaheen, Paul B. Niles, Kenneth Chong, Catherine M. Corrigan, and Mark H. Thiemens. Carbonate formation events in ALH 84001 trace the evolution of the Martian atmosphere. PNAS, December 22, 2014 DOI: 10.1073/pnas.1315615112
Before leaving port, an undergraduate student acquires important control data (on-shore gravimetrics) using a gravitometer. Credit: Aric Velbel, Jurassic Magnetism
Imagine one day you woke up, and the North Pole was suddenly the South Pole.
This geomagnetic reversal would cause your hiking compass to seem impossibly backwards. However, within our planet’s history, scientists know that this kind of thing actually has happened… not suddenly and not within human time scales, but the polarity of the planet has in fact reversed, which has caused scientists to wonder not only how it’s happened, but why.
This week, as the National Science Foundation (NSF) research vessel R/V Sikuliaq continues its journey towards its home port in University of Alaska Fairbanks’ Marine Center in Seward, Alaska, she detours for approximately 35 days as researchers take advantage of her close proximity to the western Pacific Ocean’s volcanic sea floors. With the help of three types of magnetometers, they will unlock more of our planet’s geomagnetic history that has been captured in our Earth’s crust there.
“The geomagnetic field is one of the major physical properties of planet Earth, and it is a very dynamic property that can change from milliseconds to millions of years. It is always, always changing,” said the expedition’s chief scientist, Masako Tominaga, an NSF-funded marine geophysicist from Michigan State University. “Earth’s geomagnetic field is a shield, for example. It protects us from magnetic storms—bursts from the sun—so very pervasive cosmic rays don’t harm us. Our research will provide data to understand how changes in the geomagnetic field have occurred over time and give us very important clues to understand the planet Earth as a whole.”
Reportedly, the last time, a geomagnetic reversal occurred was 780,000 years ago, known as the Brunhes-Matuyama reversal. Bernard Brunhes and Motonori Matuyama were the geophysicists who identified that reversal in 1906.
Researchers Tominaga, Maurice Tivey (from Woods Hole Oceanographic Institution) and William Sager (from University of Houston) have an interest that goes further back in history to the Jurassic period, 145-200 million years ago when a curious anomaly occurred. Scientists originally thought that during this time period, no geomagnetic reversals had happened at all. However, data—like the kind that Tominaga’s team will be collecting—revealed that in fact, the time period was full of reversals that occurred much more quickly.
“We came to the conclusion that it was actually ‘flipping flopping,’ but so fast that it did not regain the full strength of the geomagnetic field of Earth like today’s strength. That’s why it was super, super low,” Tominaga explained. “The Jurassic period is very distinctive. We think that understanding this part of the geomagnetic field’s behavior can provide important clues for computer simulation where researchers have been trying to characterize this flipping and flopping. Our data could help predict future times when we might see this flipping flopping again.”
Interestingly, historical records have shown points where the flipping seems likely to occur but then seems to change its mind, almost like a tease, where it returns to its original state. Those instances actually do occur on a shorter time scale than the full-fledged flipping and flopping. Again, scientists are looking for answers on why they occur as well.
Better tools equal better data
For approximately three decades, researchers like Tominaga have been probing this area of the western Pacific seafloor. With her cruise on R/V Sikuliaq, Tominaga and Tivey come with even more technology in hand.
Thirty years ago, researchers didn’t have access to autonomous underwater vehicles (AUV) that could go to deeper, harder-to-reach ocean areas. However, that is just one of three ways Tominaga’s team will deploy three magnetometers during its time at sea. One magnetometer will work from aboard R/V Sikuliaq. Another will trail behind the ship, and the third will be part of the AUV.
“The seafloor spreading at mid-ocean ridge occurred because of volcanic eruption over time. And when this molten lava formed the seafloor, it actually recorded ambient geomagnetic data. So when you go from the very young ocean seafloor right next to the mid-ocean ridge to very, very old seafloor away from the mid-ocean ridge, a magnetometer basically unveils changes in the geomagnetic field for us,” Tominaga said. “The closer we can get to the seafloor, the better the signal. That’s the rule of thumb for geophysics.”
With the help of R/V Sikuliaq’s ship’s crew, Tominaga and Tivey, a cruise archivist who is also a computer engineer/scientist, and seven students (three of whom are undergraduates), the team will run daily operations 24 hours a day/seven days a week, deploying the magnetometers, collecting data and then moving on to the next site.
Naturally, the weather can waylay even the best plans. “Our goal is always about the science, but the road likely will be winding,” Tominaga said. “The most enjoyable part of this work is to be able to work together with this extremely diverse group of people. The Sikuliaq crew, the folks at UAF and those connected to the ship from NSF have all been committed to seeing this research happen, which is incredibly gratifying…. When we make things happen together as a team, it is really rewarding.”
Focus on fundamentals
Not surprisingly, this kind of oceanographic research is among some of the most fundamental, serving as a foundation for other research where it might correlate or illuminate. Additionally, because the causes and impacts of these geomagnetic changes are unknown, connections to currents, weather patterns, and other geologic phenomenon can still be explored also.
“NSF, along with the entire science community, has waited years for this unique state-of-the-art Arctic vessel, and the timing couldn’t be more critical,” said Rose DuFour, NSF program director. “Our hope is to use R/V Sikuliaq to help carry out the abundant arctic-based seagoing science missions that go beyond NSF-funded science and extend to those from other federal agencies, like Office of Naval Research as well.”
Tominaga notes that another key part to the cruise’s mission is record keeping; it’s why an archivist is part of her team. He even will blog daily (with pictures). As foundational research, it’s important to “keep every single record intact,” and she believes this broadcasting daily narrative will assist in this effort. Additionally, the plan is to share the collected data as soon as possible with other researchers who can benefit from it as well. “Without going there, getting real data—providing ground truth—how do we know what is going on?” Tominaga said, explaining fieldwork’s importance.
Tominaga is quite clear on what prompts her to keep one of the busiest fieldwork schedules, even during a season usually reserved for family and friends, sipping eggnog or champagne. “I was raised as a scientist/marine geophysicist, and I don’t just mean academically,” she said. “I really looked up to my mentors and friends and how they handed down what they know-so unselfishly. And when I was finishing my Ph.D., I realized that there will be a time I will hand down these things to the next generation. Now, as a professor at Michigan State University, I’m the one who has to pass the torch, if you will—knowledge, experience, and skills at sea. That’s what drives me.”
The sea ice in July 2014 as it begins to retreat from the Alaskan coast. Credit: University of Washington
The rapidly thawing Arctic Ocean may be a new frontier but some of the latest news from there concerns a clam that is believed to date back more than a million years.
Some bivalves retrieved from the ocean depths during a 2010 mapping mission in the Beaufort Sea turn out to be members of a species previously unknown to science, according to a study published in the journal ZooKeys.
Scientists from the U.S. Geological Survey, who were exploring the area aboard a Coast Guard icebreaking cutter, found the clam shells in a core sample dug with a 4-inch-diameter pipe into the seafloor.
The shells were found in the seafloor in water nearly 1.5 miles deep.
Once the shells were extricated from the Arctic Ocean sediment, a process accomplished at the USGS lab in Menlo Park, Calif., scientists could see that they were different from all other known species.
“I certainly didn’t know what they were,” said Paul Valentich-Scott, curator of malacology at the Santa Barbara Museum of Natural History, a mollusk expert recruited by the USGS geologists to be the lead author of the newly published study. “I definitely knew it wasn’t anything I had seen before.”
The clams, though small, were far bigger than others found far out in the Beaufort Sea – a couple of centimeters across instead of a couple of millimeters, Valentich-Scott said. They had a far rounder shape than others found in the general region, and maintained a thick brown skin, known as a periostracum, that was unlike the much thinner skin found on other clams, he said.
About 20 shells or shell fragments were found in sediments ranging from less than an inch below the seafloor to about 15 feet below.
Geologists, not biologists, conducted the mapping mission that resulted in the clams’ discovery, but they could tell that the shells were unusual, Valentich-Scott said.
“The chief scientist (Brian Edwards) recognized that there were some special animals out there,” he said.
That realization got Valentich-Scott involved in the project to identify the clams, work that included a comparison with known species documented as far away as Japan, New Zealand and Britain.
It turns out that this Beaufort Sea clam is not only a new species, but also a new genus, or category of species.
The genus is now named Wallerconcha, in honor of Thomas Waller, a paleontologist at the Smithsonian Institution. The new species name is Wallerconcha sarae, in honor of co-author Charles Powell’s daughter Sara.
Just how long the newly discovered clams lived in the region is unclear.
The site was a conical underwater formation known as the Canning Seafloor Mound, which rises about 590 feet high and stretches nearly 4,000 feet across. It is more than 90 miles off the coast of the Arctic National Wildlife Refuge. The expedition that made the discovery was a joint U.S.-Canada Beaufort Sea mapping mission, with scientists aboard both the Healy and a Canadian Coast Guard icebreaker, the Louis S. St-Laurent.
The most deeply buried samples were in sediment that, based on fossils it contained, was 1.8 million years old, Valentich-Scott said. But other samples closer to the seafloor surface were in far newer sediment, indicating that the clam may not be extinct.
The 1.8 million-year figure is considered “the oldest possible age it could be,” said Powell, a USGS research geologist. “Most likely, it’s been there for over a million years,” he said.
Live versions of the clams might even be somewhere near the samples collected in 2010, possibly right on the same sea mound but missed during the core sampling, he said. Unlike near-shore areas of the Arctic that have been transformed as sea levels rose and fell over past millennia, the habitat of this clam has not changed much, he said.
“It’s been pretty steady,” he said. “It’s dark and cold.”
