Tag Archives: plate tectonics

Stellar pollution shows exoplanets are more diverse than we thought — but few are like Earth

Artist’s impression of an exoplanet. Image credits: IAU/L. Calçada.

For Earth to be able to support life, a lot of things needed to be just right. The Sun had to be the right size and brightness, and just at the right distance from the Earth; the atmosphere that protects the planetary surface from harmful radiation; the chemistry needed for water and the seeds of life; and a crust and plate tectonics. We don’t often think about plate tectonics as a key ingredient for life, but it is. Without a crust, plate tectonics couldn’t exist, and without plate tectonics, life as we know it couldn’t exist.

The crust is where dry, hot rock from the deeper parts of the Earth interact with the water and air on the surface, producing new minerals and rocks. New crust is constantly being produced and destroyed, and if this didn’t happen, the seafloor could become rigid and much more unfriendly to life. New research is suggesting that plate tectonics is essential to life as we know it.

There are also two types of crust on Earth: basaltic and granitic. The basaltic crust is dark and heavy, and sometimes called oceanic crust. Meanwhile, granite crust is light and accumulates into continent-sized rafts that move in this “sea of basalt.” It’s sometimes called continental crust. When an oceanic crust moves against the continental crust, the heavier and denser oceanic one subducts (or goes under the other one).

But our planet’s crust may be a rarity, at least in our corner of the universe.

Image credits: USGS.

Keith Putirka from California State University, Fresno, and Siyi Xu of the Gemini Observatory analyzed the atmospheres of 23 nearby white dwarfs, looking for signs of so-called “pollution” — chemical traces that stars can pick up from nearby planets as they explode into red giants.

“White dwarfs start out like our Sun, and late in life expand to become a red giant, and then collapse to a very small size – about the size of Earth,” Putirka told ZME Science. “As the star collapses, planets orbiting the star (at least those not obliterated during the red giant phase) can orbit close enough to the star that they are destroyed by tidal forces. The debris that results can fall into the star’s atmosphere. This infalling debris is the “pollution” that is measured by astronomers, and records the composition of the formerly orbiting planetary objects.”

The researchers found that some contain high amounts of calcium (Ca), but all have very low silicon (Si) and high magnesium (Mg) and iron (Fe) amounts. This suggests a composition closer to the mantle of exoplanets, and not at all what you’d expect to see from a planetary crust.

Roughly speaking, the Earth consists of a crust, a mantle, and a core. Although the movement of plate tectonics is driven by movement from the mantle, it’s the crust that is fragmented into rigid plates (hence the “plate” tectonics). But there seems to be no sign of a granitic crust — or even other crust types. So plate tectonics may have not existed on these planets, or if it did, it was very different from what we see on Earth.

Magma circulation driving the movement of plate tectonics.

“It’s hard to say whether granitic crusts might exist on other planets, or not,” Putirka explained to ZME Science. “In our Solar System, granitic crust only exists in any great abundance on Earth, and its abundance is probably related to our abundant surface water and plate tectonics, which are also unique to Earth. The exoplanets that once orbited white dwarfs have silicate mantles (all the rocky material between the iron core and the crust) that are very different from Earth – so different that plate tectonics and crust formation might occur very differently.”

“Some exoplanets may have mantle compositions that might yield very thick granitic crusts and more abundant continental material than on Earth. Others have mantle compositions that might not produce any continental crust at all. Many of these planets may look totally unlike anything we see in our inner Solar System.”

More questions

The findings have important implications for potential life on other planets — but it’s hard to interpret just what this means. But what is clear is that we need to have a broader view when we consider exoplanet environments.

“I think it’s fair to say that the trajectory of biological evolution is dependent upon geologic history. For example, if a planet has abundant water, but no granitic crust, then nothing like the terrestrial life as we see on Earth could possibly evolve – because there would be no terra firma for such evolution to take place. But we don’t yet know how such odd exoplanets (in the white dwarf database) might evolve from a geologic standpoint because, up to now, we have focused our laboratory experiments (on how rocks melt or deform) based on questions about how Earth-like (or Mars-like or Moon-like) planets might evolve. But the compositions we see in the white dwarf data indicate planets that are mineralogically very different, and so require new experimental studies.”

Ultimately, this study still shows that there’s plenty we don’t know about the Earth — if we did, we’d have a better idea of what makes it so special (if anything). There are still plenty of questions we need to answer about our planet, and only once we do (and once we study our solar system neighborhood more closely) will we be able to understand planets outside of our solar system as well.

“My take on our findings is that it reflects back on what we still don’t know about Earth and our rocky planetary neighbors.,” Putirka concludes “Earth not only has abundant water and life, but two very distinct kinds of crust – one of which (granitic, continental crust) is effectively unique in our solar system, and is essential for human evolution. Earth is also the only planet that has a long history of plate tectonics.”

“How and why did these features appear on Earth, and what inhibited their development elsewhere in our own Solar System? Tectonics and crust formation are surely sensitive to planet size, orbital radius, and planet composition. To what extent can we change any of these parameters and still end up with a habitable planet – and/or something that, geologically, looks roughly like Earth? We’ll have better answers to these questions when we conduct new experiments, and when we start exploring Venus, and when we shift our focus from trying to find life on Mars to instead better understanding the geological conditions that limited evolution there in the first place.”

The study “Polluted white dwarfs reveal exotic mantle rock types on exoplanets in our solar neighborhood” was published in Nature Communications.

Earth’s history gets rewritten by a single drop of water

Using just the remaining of a single microscopic drop of ancient water, a group of researchers was able to rewrite the history of the Earth’s evolution and change the time when plate tectonics actually started on the planet.

Credit: Flickr

Plate tectonics is a continuous recycling process that directly or indirectly controls almost every function of the planet, such as atmospheric conditions, mountain building, natural hazards, the formation of mineral deposits and the maintenance of the oceans.

The large continental plates of the planet continuously move thanks to this process, while the top layers of the Earth are recycled into the mantle and replaced by new layers through processes such as volcanic activity.

The plate tectonics was initially thought to have started about 2.7 billion years, but that has now changed. A team of researchers used the microscopic leftovers of a drop of water that was transported into the Earth’s deep mantle to show this process actually started 600 million years before that.

“Plate tectonics constantly recycles the planet’s matter, and without it, the planet would look like Mars,” says Professor Allan Wilson, who was part of the research team. “Our research shows that plate tectonics started 3.3 billion years ago now coincides with the period that life started on Earth. It tells us where the planet came from and how it evolved.”

For their research, published in the journal Nature, the team analyzed a piece of rock melt, called komatiite – named after the Komati river near Barberton in Mpumalanga where it most commonly occurs – that are the leftovers from the hottest magma ever produced in the first quarter of Earth’s existence.

Despite most of the komatiites were obscured by later alteration and exposure to the atmosphere, small droplets of the molten rock were preserved in a mineral called olivine. This allowed the team to study a perfectly preserved piece of ancient lava as part of their research.

“We examined a piece of melt that was 0.01mm in diameter, and analyzed its chemical indicators such as H2O content, chlorine, and deuterium/hydrogen ratio, and found that Earth’s recycling process started about 600 million years earlier than originally thought,” said Wilson. “We found that seawater was transported deep into the mantle and then re-emerged through volcanic plumes from the core-mantle boundary.”

Earth is the only planet in our solar system that is shaped by plate tectonics and without it the planet would be uninhabitable. The research offers insight into the first stages of plate tectonics and the start of a stable continental crust.

“What is exciting is that this discovery comes at the 50th anniversary of the discovery of komatiites in the Barberton Mountain Land by Wits Professors, the brothers Morris and Richard Viljoen,” said Wilson.

Earth may have generated its own water – geologically

A new study may have finally found where Earth’s water came from. There are currently two competing theories, with one claiming that our planet generated its own water geologically, while the other suggests that water was brought by icy comets or asteroids from outside. A new study concluded that most of the water we see today likely comes from the Earth’s mantle.

Water beneath the surface

Image via Special Papers.

Until recently, the idea that water came to Earth from somewhere else in the solar system seemed to have more support, but studies conducted by the European Space Agency on the Rosetta missions showed that water almost certainly didn’t come from comets. Wendy Panero, associate professor of earth sciences at Ohio State, and doctoral student Jeff Pigott believe that when the Earth formed, it had huge bodies of water in its interior, and has been continuously supplying water to the surface via plate tectonics, circulating material upward from the mantle.

Researchers have long known that there is some water in the earth’s mantle, but nobody knows just how much. Because you can’t go 40 km deep and study the mantle, you have to rely on indirect information and computer simulations.

“When we look into the origins of water on Earth, what we’re really asking is, why are we so different than all the other planets?” Panero said. “In this solar system, Earth is unique because we have liquid water on the surface. We’re also the only planet with active plate tectonics. Maybe this water in the mantle is key to plate tectonics, and that’s part of what makes Earth habitable.”

The thing is, when we’re talking about water in the mantle, it’s not actually liquid water – what seems dry to the human eye may actually have significant quantities of water – in the form of hydrogen and oxygen waters. Hydrogen is typically stored in crystal voids and defects, while oxygen is usually plentiful in most minerals. Certain reactions can free up the hydrogen and oxygen, resulting in water; but could it be enough water to amount for the oceans we see today?

The key element here is ringwoodite.

High-Pressure Olivine

Olivine is a magnesium-iron silicate typically found in the mantle and igneous rocks. However, in the mantle, at very high pressures and temperatures, the olivine structure is no longer stable. Below depths of about 410 km (250 mi) olivine undergoes a transformation, transforming into ringwoodite or bridgmanite. Ringwoodite is notable for being able to contain hydroxide ions (oxygen and hydrogen atoms bound together) and previous research has already shown that the earth’s mantle holds huge quantities of water.

Now, this team has found that the mineral bridgmanite doesn’t contain enough water to play a significant role in this issue – so it’s all about the ringwoodite. But the question is – if ringwoodite is trapped in the mantle and the water is drained towards the surface in plate tectonics, how does our planet still have water reserves now, in the mantle?

But while they were creating some models and simulations of ringwoodite water behavior, another likely candidate emerged: garnet. Garnet could be a water carrier, transporting some of the water to the surface, while some of it still remains in the mantle.

“If all of the Earth’s water is on the surface, that gives us one interpretation of the water cycle, where we can think of water cycling from oceans into the atmosphere and into the groundwater over millions of years,” she said. “But if mantle circulation is also part of the water cycle, the total cycle time for our planet’s water has to be billions of years.”

 

 

Jupiter’s Moon Europa found to have Plate Tectonics

Europa, Jupiter’s icy moon is the only body in the Solar System found to have plate tectonics (besides Earth). A new study has found several defining features, including plate subduction, broken linear features and offset likely caused by strike slip faults.

Europa. Image via Wiki Commons.

An introduction to plate tectonics

Plate tectonics is one of the newest big theories in science. Developed in the 1960s, it claims that lithosphere, which is the rigid outermost shell of a planet (on Earth, the crust and upper mantle), is broken up into tectonic plates. These plates are not immobile – they move, especially because the Earth’s lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Here on Earth, that movement is at a few cm per year.

plate tectonics earth

Plate tectonics movement. Image via BBC.

The exact mechanism of movement is still a matter of debate (with underlying magma currents being a newer proposal). Other major factors play a role, the most notable being the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. It’s likely that all these forces (and probably others) work together to create the extremely complex movement we observe today.

So far, no other celestial body has been observed to have plate tectonics (other than Earth that is) – it’s the first time we can almost definitely say that we’ve found tectonic movement on an extraterrestrial body – and Jupiter’s moon was quite an unlikely candidate.

Europa’s plate tectonics

europa tectonics

Proposed structure of Europa. Image via NASA.

Up to 50 years ago, Europa held little interest for astronomers and geologists, but now, it is one of the most interesting bodies in the solar system. We regard it today as one of the places most likely to harbor life, and NASA is currently planning a mission to study it more carefully. So what changed?

Well, Europa is a moon of Jupiter primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. However, it is covered with extremely smooth ice – but that doesn’t mean it can’t host life; on the contrary!

Scientists believe that under the frozen surface, there lies a vast ocean of liquid water. Europa is under a constant state of tug and pull from its planet, and this gravitational war causes friction. The friction generates heat, which is why we believe that there is liquid water beneath the ice. To make things even more interesting, huge 200 km water plumes were observed spurting from Europa. On December 11, 2013, NASA reported the detection of “clay-like minerals” (specifically, phyllosilicates), often associated with organic materials, on the icy crust of Europa. For all its low temperatures and icy features – the moon is an extremely interesting place; and it just got more interesting!

Europa’s lineae, colorized. Image via NASA.

Dr. Simon Katterhorn, geologist and former professor at the University of Idaho and Louise Prockter, planetary scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland have discovered clear signs of plate tectonics on Europa. They studied lineae – dark streaks that cover the entire moon, caused by Jupiter’s gravitational attraction. They observed that some of these features appear to be moved – shifted, like in a strike slip fault. Other features appear to be abruptly ending, as if they were subducting under something else. The disappearance of material is entirely consistent with subduction, and when you also take into consideration the huge water plumes, it makes even more sense.

It’s pretty clear that we need a probe to better study this celestial body, and figure out its geological (and perhaps biological) secrets.

Journal Reference: Simon A. Kattenhorn& Louise M. Prockter. Evidence for subduction in the ice shell of EuropaNature Geoscience (2014) doi:10.1038/ngeo2245

Geophysicists find a layer of liquefied rock in the Earth’s mantle that acts as a lubricant for tectonic plates

Scientists at Scripps Institution of Oceanography at UC San Diego have found a layer of liquefied molten rock in Earth’s mantle that may be acting as a lubricant for the sliding motions of the planet’s tectonic plates. This discovery has very far reaching implications, which can solve some of the long standing geological puzzles, as well as lead to a better understanding of earthquakes and volcanism.

Electromagnetic measurements

plate tectonics1

They used a relatively common, but uniquely improved geophysical technique (magnetotellurics), which involved advanced seafloor electromagnetic imaging technology. They imaged a 25-kilometer- (15.5-mile-) thick layer of partially melted mantle rock below the edge of the Cocos plate where it moves underneath Central America. They basically deployed a vast array of seafloor sensors that monitor the natural electromagnetic signals to map features of the crust and mantle. Back in 2010, they started noticing something was weird – they were finding magma in unexpected places.

cocos plate 2

“This was completely unexpected,” said Key, an associate research geophysicist in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics at Scripps. “We went out looking to get an idea of how fluids are interacting with plate subduction, but we discovered a melt layer we weren’t expecting to find at all-it was pretty surprising.”

cocos plate

The marine electromagnetic technology employed in the study was originated by Charles “Chip” Cox, an emeritus professor of oceanography at Scripps, and further improved by Constable and Key. The method has been so successful, that since 2000, they have been working with big oil companies to map out offshore oil and gas reservoirs.

The planetary engine

Plate tectonics is, if you will, the backbone of modern geology and geophysics. It is not perfect, by any standards, but it is a good theory that describes the large-scale motions of Earth’s lithosphere; one thing that’s been puzzling is the exact forces and mechanisms that allow the planet’s tectonic plates to slide across the earth’s mantle; one theory was that as minerals go deeper in the mantle, the water they contain is ejected, and this results in a more ductile mantle that would facilitate tectonic plate motions. However, no clear data has been provided to confirm or infirm this theory.

“Our data tell us that water can’t accommodate the features we are seeing,” said Naif, a Scripps graduate student and lead author of the paper. “The information from the new images confirms the idea that there needs to be some amount of melt in the upper mantle and that’s really what’s creating this ductile behavior for plates to slide.”

Indeed, if there isn’t some major flaw with this study, then it could pretty much change the way we view this sliding mechanism.

tectonics lubricant

The orange area inside the dashed lines is the lubricant layer which facilitates the plate motion. The blue areas represents the Cocos plate subducting beneath the central American continent, and the black points are the earthquakes.

“This new image greatly enhances our understanding of the role that fluids, both seawater and deep subsurface melts, play in controlling tectonic and volcanic processes,” said Bil Haq, program director in the National Science Foundation’s Division of Ocean Sciences.

To get to the conclusion that there is a layer which acts as a lubricant, they studied the fluid content of the subducting plate offshore Nicaragua and Costa Rica. Magnetotellurics and controlled source electromagnetics imaged the porosity variations associated with lithospheric bending and cracking near the trench, as was suggested by a previous reflection seismic imaging. Analyzing the obtained parameters, they modeled this lubricant layer.

Their results, if valid, could help geologists better understand the genesis of some earthquakes, as well as some questions unanswered for decades.

“One of the longer-term implications of our results is that we are going to understand more about the plate boundary, which could lead to a better understanding of earthquakes,” said Key.

Now, the next step is to figure out how exactly is this layer formed and the source that supplies this magma.

Via Scripps Research Institute

Massive Indian Ocean quakes may signal tectonic break-up

The past few years have been marked by numerous seismic events, some of dramatic magnitude; aside from the huge 9.1 temblor in Japan, the world was also shocked by the pair of massive earthquakes that rocked the Indian Ocean on 11 April 2012. However, as geophysicists warn, this may only be the beginning – the birth of a new plate boundary.

A pair of massive earthquakes

Credits: Harvard University

The undersea earthquakes measured magnitudes of 8.6 and 8.2 and triggered tsunamis throughout the Indian Ocean. The damage was somewhat smaller than what you’d expect, but now, researchers claim their effects may be more far-reaching than first believed. Basically, the earthquakes were caused by accumulated geologic stress breaking the Indo-Australian plate apart; when they took place, they released energy across numerous faults and unleashed aftershocks for almost a week afterwards.

Ever since the 1980s, researchers believed the Indo-Australian plate is breaking apart, but until now, there hasn’t really been any conclusive evidence to support those claims. The April 11 earthquakes represents the most spectacular example of the process in action, as Matthias Delescluse, a geophysicist at the Ecole Normale Supérieure in Paris explains: “it’s the clearest example of newly formed plate boundaries,” he says.

Plate tectonics

According to generally accepted theories, the internal stressing and deformation of the Indo-Australian plate began some 10 million years ago; while the plate moved northwards, the Indian part was stopped by the Eurasian plate and dove under the Himalayas, rising them. However, the Australian part forged ahead, creating the tension which is breaking the plate apart today.

Gregory Beroza, a seismologist at Stanford University in Palo Alto, California, is also a believer in this model:

“The 2004 and 2005 earthquakes by themselves would not have caused this other earthquake. There had to be other stresses”, he says.

Earthquakes and strike-slips

Most earthquakes form at the boundary of tectonic plates, as you can see from the second picture above; one plate drifts beneath the other, creating massive earthquakes – this is called subduction. However, this is not the only form of contact between plates: plates or portions of plates can also slip by each other, horizontally, resulting in what is called as ‘strike-slip’ earthquakes. Typically, these earthquakes are smaller and less dangerous (though dangerous as well).

However, the first of the two earthquakes defied all expectations, being the largest strike slip earthquake on record, and one of the biggest to occur away from any plate boundaries.

Another study drew some pretty interesting, but worrying conclusion: the earthquake was created by accumulated stress throughout the plate, and the release of this stress created one of the most complex fault patterns in the world – something you really don’t want to hear if you live in that area. Typically, an earthquake like this shakes along a single fault, or maybe two if it’s a really big one; but this one shook no less than four faults, one of which slipped more than 20 meters. While this pattern has been described partially in previous work, nobody has analyzed slip amounts in so much detail: Beroza says that Lay and his team “do a splendid job of picking apart this very important earthquake” in their paper.

Aftershocks

So not only was this earthquake unique due to its high magnitude and slip, its aftershocks are also special. In yet another study, researchers found that for the six days following the temblor, aftershocks with magnitudes bigger than 5.5 occurred 5 times more often than normal.

“Aftershocks are usually restricted to the immediate vicinity of a main shock,” says lead author Fred Pollitz, a geophysicist at the US Geological Survey in Menlo Park, California.

However, this changes the general belief of how soon and how close aftershocks can occur after earthquakes, raising the importance of this particular earthquake even more.

“Every earthquake is important to study, but this earthquake is rather unique,” says Hiroo Kanamori, a seismologist at the California Institute of Technology in Pasadena.

Scientific sources: 1 2 3

Office workers gather on the sidewalk in downtown Washington, Tuesday, moments after a 5.9 magnitude tremor shook the nation's capitol. (c) J. Scott Applewhite/Associated Press

5.9 earthquake hits the US East Coast

A small, yet frightening earthquake, registered at 5.9 magnitude, sent shivers down people’s spines all the way from Ottawa, Canada to North Carolina as it hit the North American east coast.

Office workers gather on the sidewalk in downtown Washington, Tuesday, moments after a 5.9 magnitude tremor shook the nation's capitol. (c) J. Scott Applewhite/Associated Press

Office workers gather on the sidewalk in downtown Washington, Tuesday, moments after a 5.9 magnitude tremor shook the nation's capitol. (c) J. Scott Applewhite/Associated Press

The earthquake first caused ground shacking at 1:51 p.m. ET, when it measured 5.9 in magnitude and lasted only 45 seconds, according to the U.S. Geological Survey. Now, although the earthquake was fairly weak and, luckily, uneventful damage-wise it produced a lot of panic, mostly because of the more powerful shacking, despite the low magnitude. The epicenter was registered 4 miles southwest of Mineral, Va., near Richmond, Va., just about 80 miles south of Washington, D.C., however the depth of the quake was only 0.6 miles which explains the afformentioned shacking.

No injuries or damages have been reported thus far, despite this the east coast quake managed to unleash a mass hysteria. Verizon Wireless, AT&T and Sprint say their networks were congested as the quake sent people scrambling for the phones. Nevermind twitter, which was simply flooded with millions of quake reports in mere seconds as people quickly turned to their mobile phones. A lot of buildings throughout major metropolitan centers in the northeast were evacuated after the quake, in sight of a possible upcoming after-shock, and nuclear reactors at the North Anna Power Station in Louisa County, Virginia, were automatically taken off line by safety systems around the time of the earthquake.

US citizens are generally prepared for quakes, in the west coast that is. Earthquakes are so rare on the left side of the Atlantic that the whole event caught everybody off guard, which just goes to say how unpredictable quakes really are.

“It’s very unusual for an earthquake of this size on the East Coast,” said Thomas Hillman Jordan, director of the Southern California Earthquake Center at the University of Southern California in Los Angeles, in a telephone interview. “It’s a moderate size earthquake, and on the East Coast they tend to be felt over a much larger area.”

“This is a good reminder that even on the East Coast you want to be prepared,” he said.

People stand on the streets of Washington, Aug. 23, 2011, after evacuating from buildings following a 5.9 earthquake that hit northwest of Richmond, Va., shaking much of Washington, D.C., and felt as far north as Rhode Island and New York City. (c) Charles Dharapak/AP

People stand on the streets of Washington, Aug. 23, 2011, after evacuating from buildings following a 5.9 earthquake that hit northwest of Richmond, Va., shaking much of Washington, D.C., and felt as far north as Rhode Island and New York City. (c) Charles Dharapak/AP

The epicenter is located right in the middle of the North American continental crustal plat. The area around it, however, bears the scars left over from 200-300 million years ago when it used to be an active earthquake zone, at a time when the Atlantic Ocean rifted apart from Europe.

“Central Virginia does get its share of minor earthquakes, but an earthquake of this size on the East Coast is certainly very unusual,” says seismologist Karen Fischer of Brown University.

“We are just seeing pressure build up and release on those scars,” Fischer says. “There is a lot of debate on exactly what is going on down there and exactly how quakes this big happen in this kind of crustal zone.”

As important follow-up news of the event occur, this page will be updated to reflect them. Stay tuned for coverage.

The oldest known supercontinent was called "Rodinia" and formed some 1.1 billion years ago, when there also was only one superocean, which was called the "Panthalassic Ocean" (or "Panthalassa") and eventually became the present-day Pacific Ocean. (c) NASA

Texas was attached to Antarctica, 1.1 billion years ago

The oldest known supercontinent was called "Rodinia" and formed some 1.1 billion years ago, when there also was only one superocean, which was called the "Panthalassic Ocean" (or "Panthalassa") and eventually became the present-day Pacific Ocean. (c) NASA

The oldest known supercontinent was called "Rodinia" and formed some 1.1 billion years ago, when there also was only one superocean, which was called the "Panthalassic Ocean" (or "Panthalassa") and eventually became the present-day Pacific Ocean. (c) NASA

Despite an evident contrast, geologists claim that the region of modern day El Paso, Texas was once attached to the now icy continent of Antarctica, in an effort to piece together the giant pieces of a puzzle that formed a pre-Pangaea supercontinent.

“Most people are familiar with Pangaea,” said study co-author Staci Loewy, a geochemist at California State University, Bakersfield. “That was a supercontinent that formed 300 million years ago.”

About 1.1 billion years ago, most of the world’s landmass was contained within a supercontinent called Rodinia, Pangaea’s predecessor. Today’s continents came to be after a plate tectonics process, which continues to this day,  separated Pangaea into multiple  land masses about 250 million years ago.

If it might seem incredibly difficult to pinpoint where and when supercontinents formed or split, it’s because it is. Scientists have to trace ancient mountain belts or analyze a myriad of data filled with geological patterns to assert a sound geological statement.

In this particular case, the team of researchers, lead by Loewy, collected rocks from a region known as the North American Mid-continental Rift System – a volcanic zone stretching from Canada to the Franklin Mountains near El Paso. Another set of rocks was collected from the mountains in Coats Land in East Antarctica, on the coast of the Weddell Sea. The rock sampling in Antarctica was a bit more difficult, since most of the mountains were covered in ice, except “two tiny tips of mountain peaks,” Loewy said.

After a careful analysis of the samples from both regions, scientists concluded that the sites match in age and in lead isotope ratio, meaning that the volcanic rocks erupted in the same rift zone. Oddly enough, although hugely separated nowadays, scientists concluded in their study that the two landmasses were once connected.

“It’s such a neat thing,” she said, referring to the past ties between the West Texas desert and Antarctica’s glaciers. “It’s a quite spectacular contrast.”

While the study, published in the journal Geology, is extremely interesting, even more fascinating similar geological studies are been made, as scientists painstakingly try to trace down the origins of even older supercontinents.

“There are people who have put forth models of earlier supercontinents. One, called Columbia, [may have] existed from 1.8 to 1.5 billion years [ago],” Loewy said.

“And at 2.4 to 2.6 billion years ago, there seems to have been another major event,” she said. “There appear to have been multiple cycles throughout time.”

via

Quartz may be key to plate tectonics

Plate tectonics is one of the most important theories, from the point of view of its practical effects on society – just look at the earthquake in Japan, or the iminent one in California, for example. More than 40 years ago, a man named J. Tuzo Wilson published a paper in Nature, describing how ocean basins open and close, in what is taught today in every geology course as the Wilson cycle. Basically, some ocean basins will shrink and become seas, or even disappear, and some sea basins will become ocean basins.

His observations, known today as the “Wilson Tectonic Cycle” suggested that this process took place numerous times in Earth’s troubled history, most recently when the supercontinent Pangaea split into the continents we know today. Wilson’s ideas are extremely important for plate tectonics, as well as the processes which lie at the very core of earthquake formation and mountain genesis.

Since his paper was published in 1967, pretty much every study conducted on the topic supported this idea, but few managed to bring additional information. Now, new findings by Utah State University geophysicist Tony Lowry and colleague Marta Pérez-Gussinyé of Royal Holloway, University of London offered an interesting point of view on the whole subject.

“It all begins with quartz,” says Lowry, who published results of the team’s recent study in the March 17 issue of Nature.

The scientists used and described a new way of measuring the properties of the rocks located beneath the deep crust. This way reveals events that cause the Earth’s surface to crack, fold and stretch, and it displays the key role played by quartz.

“If you’ve ever traveled westward from the Midwest’s Great Plains toward the Rocky Mountains, you may have wondered why the flat plains suddenly rise into steep peaks at a particular spot,” Lowry says. “It turns out that the crust beneath the plains has almost no quartz in it, whereas the Rockies are very quartz-rich.”

He believes that it’s exactly those belts of quartz that set in motion the chain of events which leads to the mountain building rock cycle.

“Earthquakes, mountain-building and other expressions of continental tectonics depend on how rocks flow in response to stress,” says Lowry. “We know that tectonics is a response to the effects of gravity, but we know less about rock flow properties and how they change from one location to another.”

“Over the last few decades, we’ve learned that high temperatures, water and abundant quartz are all critical factors in making rocks flow more easily,” Lowry says. “Until now, we haven’t had the tools to measure these factors and answer long-standing questions.”

But now, thanks to EarthScope, that has all changed.

“This intriguing study provides new insights into the processes driving large-scale continental deformation and dynamics,” says Greg Anderson, NSF program director for EarthScope. “These are key to understanding the assembly and evolution of continents.”

“We’ve combined Earthscope data with other geophysical measurements of gravity and surface heat flow in an entirely new way, one that allows us to separate the effects of temperature, water and quartz in the crust,” Lowry says.

They found that even at a low seismic velocity ratio, even after separating the temperatures, quartz-rich crust appears in pretty much the same places as high lower-crustal temperatures modeled independently from surface heat flow.

“That was a surprise,” he says. “We think this indicates a feedback cycle, where quartz starts the ball rolling.”

However, if the temperature and water are the same, rock flow will tend to focus on the quartz because that is the weak link.

“Rock, when it warms up, is forced to release water that’s otherwise chemically bound in crystals,” he says

More info about the Earth Scope Project here

Quake moved Japan by at least 8 feet

The devastating seismic event that struck Japan is affecting the entire world, and even the entire planet. While smoke continues to rise from the catastrophic temblor, Japan seems to have moved 8 feet inland, or even more, according to the USGS.

“That’s a reasonable number,” USGS seismologist Paul Earle told AFP. “Eight feet, that’s certainly going to be in the ballpark.”

Friday’s terrible 8.9 tsunami unleashed a series of terrifying tsunamis that engulfed towns and cities on Japan’s coast, and caused the death of over ten thousand people.

The quake is the tectonic shift resulted from “thrust faulting”, along the boundary of the Pacific and North American plates. The Pacific plate “pushes” under the North American one at a rate of about 3.3 inches (83 millimeters) per year, but a major seismic event, such as this one, can give a significant push, with devastating consequences.

“With an earthquake this large, you can get these huge ground shifts,” Earle said. “On the actual fault you can get 20 meters (65 feet) of relative movement, on the two sides of the fault.”

This earthquake in Japan was just slightly less powerful than the one that killed 250.000 people in Sumatra, but almost 100 times more powerful than the one in Haiti.

“A magnitude 7.0 is much smaller than the earthquake that just happened in Japan,” he said. “We’ve had aftershocks (in Japan) larger than the Haiti earthquake.”