Sun experiences seasonal changes, new research finds

A number of NASA instruments captured detailed images of this coronal mass ejection on August 31, 2012. Although CMEs can damage sensitive technological systems, this one just struck a glancing blow to Earth's atmosphere. New research has identified quasi-annual variations in solar activity, which may help experts better forecast CMEs and potentially damaging space weathers. (Image courtesy NASA Goddard Space Flight Center.)

The sun undergoes a type of seasonal variability with its activity, waxing and waning over the course of nearly two years, new research concludes. This behavior affects the peaks and valleys in the approximately 11-year solar cycle, sometimes amplifying and sometimes weakening the solar storms that can buffet Earth's atmosphere.Full Story

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Discovering missing body parts of ancient fossils

Certain specimens of Dickinsonia, a fossil of the Ediacaran biota, are incomplete because ancient currents lifted them from the sea floor, a team of researchers led by paleontologists at the University of California, Riverside, has found. Sand then got deposited beneath the lifted portion, the researchers report, strongly suggesting that Dickinsonia was mobile, easily separated from the sea floor and not attached to the substrate on which it lived.Full Story

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SCIENTISTS SEE DEEPER YELLOWSTONE MAGMA DATE: APRIL 23, 2015

A new University of Utah study in the journal Science provides the first complete view of the plumbing system that supplies hot and partly molten rock from the Yellowstone hotspot to the Yellowstone supervolcano. The study revealed a gigantic magma reservoir beneath the previously known magma chamber. This cross-section illustration cutting southwest-northeast under Yelowstone depicts the view revealed by seismic imaging. Seismologists say new techniques have provided a better view of Yellowstone's plumbing system, and that it hasn't grown larger or closer to erupting. They estimate the annual chance of a Yellowstone supervolcano eruption is 1 in 700,000.

Credit: Hsin-Hua Huang, University of Utah

University of Utah seismologists discovered and made images of a reservoir of hot, partly molten rock 12 to 28 miles beneath the Yellowstone supervolcano, and it is 4.4 times larger than the shallower, long-known magma chamber.

The hot rock in the newly discovered, deeper magma reservoir would fill the 1,000-cubic-mile Grand Canyon 11.2 times, while the previously known magma chamber would fill the Grand Canyon 2.5 times, says postdoctoral researcher Jamie Farrell, a co-author of the study published online today in the journal Science.

"For the first time, we have imaged the continuous volcanic plumbing system under Yellowstone," says first author Hsin-Hua Huang, also a postdoctoral researcher in geology and geophysics. "That includes the upper crustal magma chamber we have seen previously plus a lower crustal magma reservoir that has never been imaged before and that connects the upper chamber to the Yellowstone hotspot plume below."

Contrary to popular perception, the magma chamber and magma reservoir are not full of molten rock. Instead, the rock is hot, mostly solid and spongelike, with pockets of molten rock within it. Huang says the new study indicates the upper magma chamber averages about 9 percent molten rock -- consistent with earlier estimates of 5 percent to 15 percent melt -- and the lower magma reservoir is about 2 percent melt.

So there is about one-quarter of a Grand Canyon worth of molten rock within the much larger volumes of either the magma chamber or the magma reservoir, Farrell says.

No increase in the danger

The researchers emphasize that Yellowstone's plumbing system is no larger -- nor closer to erupting -- than before, only that they now have used advanced techniques to make a complete image of the system that carries hot and partly molten rock upward from the top of the Yellowstone hotspot plume -- about 40 miles beneath the surface -- to the magma reservoir and the magma chamber above it.

"The magma chamber and reservoir are not getting any bigger than they have been, it's just that we can see them better now using new techniques," Farrell says.

Study co-author Fan-Chi Lin, an assistant professor of geology and geophysics, says: "It gives us a better understanding the Yellowstone magmatic system. We can now use these new models to better estimate the potential seismic and volcanic hazards."

The researchers point out that the previously known upper magma chamber was the immediate source of three cataclysmic eruptions of the Yellowstone caldera 2 million, 1.2 million and 640,000 years ago, and that isn't changed by discovery of the underlying magma reservoir that supplies the magma chamber.

"The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system," says study co-author Robert B. Smith, a research and emeritus professor of geology and geophysics at the University of Utah.

The three supervolcano eruptions at Yellowstone -- on the Wyoming-Idaho-Montana border -- covered much of North America in volcanic ash. A supervolcano eruption today would be cataclysmic, but Smith says the annual chance is 1 in 700,000.

Before the new discovery, researchers had envisioned partly molten rock moving upward from the Yellowstone hotspot plume via a series of vertical and horizontal cracks, known as dikes and sills, or as blobs. They still believe such cracks move hot rock from the plume head to the magma reservoir and from there to the shallow magma chamber.

Anatomy of a supervolcano

The study in Science is titled, "The Yellowstone magmatic system from the mantle plume to the upper crust." Huang, Lin, Farrell and Smith conducted the research with Brandon Schmandt at the University of New Mexico and Victor Tsai at the California Institute of Technology. Funding came from the University of Utah, National Science Foundation, Brinson Foundation and William Carrico.

Yellowstone is among the world's largest supervolcanoes, with frequent earthquakes and Earth's most vigorous continental geothermal system.

The three ancient Yellowstone supervolcano eruptions were only the latest in a series of more than 140 as the North American plate of Earth's crust and upper mantle moved southwest over the Yellowstone hotspot, starting 17 million years ago at the Oregon-Idaho-Nevada border. The hotspot eruptions progressed northeast before reaching Yellowstone 2 million years ago.

Here is how the new study depicts the Yellowstone system, from bottom to top:

-- Previous research has shown the Yellowstone hotspot plume rises from a depth of at least 440 miles in Earth's mantle. Some researchers suspect it originates 1,800 miles deep at Earth's core. The plume rises from the depths northwest of Yellowstone. The plume conduit is roughly 50 miles wide as it rises through Earth's mantle and then spreads out like a pancake as it hits the uppermost mantle about 40 miles deep. Earlier Utah studies indicated the plume head was 300 miles wide. The new study suggests it may be smaller, but the data aren't good enough to know for sure.

-- Hot and partly molten rock rises in dikes from the top of the plume at 40 miles depth up to the bottom of the 11,200-cubic mile magma reservoir, about 28 miles deep. The top of this newly discovered blob-shaped magma reservoir is about 12 miles deep, Huang says. The reservoir measures 30 miles northwest to southeast and 44 miles southwest to northeast. "Having this lower magma body resolved the missing link of how the plume connects to the magma chamber in the upper crust," Lin says.

-- The 2,500-cubic mile upper magma chamber sits beneath Yellowstone's 40-by-25-mile caldera, or giant crater. Farrell says it is shaped like a gigantic frying pan about 3 to 9 miles beneath the surface, with a "handle" rising to the northeast. The chamber is about 19 miles from northwest to southeast and 55 miles southwest to northeast. The handle is the shallowest, long part of the chamber that extends 10 miles northeast of the caldera.

Scientists once thought the shallow magma chamber was 1,000 cubic miles. But at science meetings and in a published paper this past year, Farrell and Smith showed the chamber was 2.5 times bigger than once thought. That has not changed in the new study.

Discovery of the magma reservoir below the magma chamber solves a longstanding mystery: Why Yellowstone's soil and geothermal features emit more carbon dioxide than can be explained by gases from the magma chamber, Huang says. Farrell says a deeper magma reservoir had been hypothesized because of the excess carbon dioxide, which comes from molten and partly molten rock.

A better, deeper look at Yellowstone

As with past studies that made images of Yellowstone's volcanic plumbing, the new study used seismic imaging, which is somewhat like a medical CT scan but uses earthquake waves instead of X-rays to distinguish rock of various densities. Quake waves go faster through cold rock, and slower through hot and molten rock.

For the new study, Huang developed a technique to combine two kinds of seismic information: Data from local quakes detected in Utah, Idaho, the Teton Range and Yellowstone by the University of Utah Seismograph Stations and data from more distant quakes detected by the National Science Foundation-funded EarthScope array of seismometers, which was used to map the underground structure of the lower 48 states.

The Utah seismic network has closely spaced seismometers that are better at making images of the shallower crust beneath Yellowstone, while EarthScope's seismometers are better at making images of deeper structures.

"It's a technique combining local and distant earthquake data better to look at this lower crustal magma reservoir," Huang says.

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Story Source:

The above story is based on materials provided by University of Utah. Note: Materials may be edited for content and length.

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Journal Reference:

Hsin-Hua Huang, Fan-Chi Lin, Brandon Schmandt, Jamie Farrell, Robert B. Smith, Victor C. Tsai. The Yellowstone magmatic system from the mantle plume to the upper crust. Science, 2015





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Conservation works: Forests for water in eastern Amazonia

Image of Xingu watershed collected by the Envisat/MERIS satellite in May of 2006 by the European Space Agency (ESA).

A new study published in the Journal of Hydrology led by Woods Hole Research Center scientist Prajjwal Panday found that large protected areas in the Xingu River Basin have helped shield this Amazonian watershed from the effects observed in its less-protected neighbor, the Araguaia-Tocantins.Full Story

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Climate connections: Examining climate changes of the past

Rapid climate change influenced marine ecosystems off the coast of Venezuela tens of thousands of years ago and was accompanied by simultaneous changes globally.

In common parlance, the phrase "global climate change" is often used to describe how present-day climate is changing in response to human activities. But climate has also varied naturally and sometimes quite rapidly in the past, with implications for the ocean and its ecosystems.

This is what University of South Carolina paleoceanographer Kelly Gibson and colleagues illustrate in a recent paper, which demonstrates the influence of rapid climate change on marine ecosystems off the coast of Venezuela tens of thousands of years ago and shows how changes there were accompanied by simultaneous changes globally.
One natural expression of global climate change familiar to most people is the coming and going of what are commonly called "Ice Ages" over the past several hundred thousand years, some of which coincided with the development of modern humans. The most recent glacial period, for example, occurred from roughly 90,000 years ago until 15,000 years ago, and Homo sapiens who had mastered the widespread use of fire were around for the entire duration.
The beginning and end of a glacial period are clearly times of global climate change, but there are also periods of abrupt change in climate patterns within those periods. Gibson's recent paper, published in the journal Paleoceanography, contributes to a better understanding of just how the oceans reflect those rapid changes.
Using core samples from the ocean's floor in the Cariaco Basin, a body of water in the Caribbean Sea off the coast of Venezuela, she measured the change in the ratio of two isotopes of nitrogen from about 35,000 to 55,000 years ago, right in the middle of the last glacial period.
Nitrogen isotope ratios can be used to estimate the change in the amount of bioavailable nitrogen over time. The various compounds containing nitrogen (such as nitrate, nitrite or ammonia) are essential nutrients for ocean life, particularly for phytoplankton that serve as the foundation of the food web. Measuring the ratio, Gibson says, can help scientists understand changes in primary productivity; that is, how much food there is for more complex forms of sea life, like crustaceans or fish, to "graze" on. And understanding primary productivity is important for understanding the changes in another compound of particular interest right now and for the foreseeable future: carbon dioxide.
"The primary producers, the phytoplankton, take carbon dioxide out of the surface waters and 'fix' it into a form of carbon that can sink down to the deep where it is stored," Gibson says. "That's one reason we care -- the ocean is the biggest sink of carbon dioxide, and by looking at nitrogen isotopes we can indirectly look at what draws down carbon dioxide."
Gibson and the team, which included her postdoctoral adviser Bob Thunell, a professor in the Department of Earth and Ocean Sciences in Carolina's College of Arts and Sciences, then correlated the changes in the Cariaco Basin with changes in other markers of climate change at other sites all over the globe.
"That's one thing this kind of research is really helpful for -- showing the teleconnections in the climate system," Gibson says. "So you see something in this one 4,000-square-kilometer basin off the northeast coast of Venezuela, but you see similar changes in the Arabian Sea and in the tropical Pacific, and you can link it all back to changes seen in an ice sheet in Greenland.
"So if ice is melting in the Arctic -- you might think well, poor polar bears, but it doesn't matter, right? It matters because you're going to feel that effect everywhere. The global climate system is very interconnected."
And the changes can take place very quickly on a geological, and even human, time scale.
"The climate transitions that we studied took place on millenial time scales, less than a thousand years, with some occurring over just decades to centuries," Gibson says. "So over the course of a human lifetime, these would have been changes that an individual would experience.
"As remarkable as it is that climate can change that quickly naturally, what is even more remarkable is that some of the rates of change we're experiencing today -- increases in atmospheric carbon dioxide for example -- are faster than anything we've been able to find in the past several million years of geologic history. The climate system has the ability to respond to these rapid changes, but only to a point. The more we know about natural rapid climate change, the better we can help climate modelers forecast how climate might change in the future now that human activity is added to the mix."

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Story Source:
The above story is based on materials provided by University of South Carolina. The original article was written by Steven Powell. Note: Materials may be edited for content and length.

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1. SCIENTISTS DISCOVER ELUSIVE SECRET OF HOW CONTINENTS FORMED

Esteban Gazel, a geoscientist at Virginia Tech, collects samples of lava in a variety of locations, in this case Etna, Italy, to probe the chemical evolution of the planet.

An international research team, led by a Virginia Tech geoscientist, has revealed information about how continents were generated on Earth more than 2.5 billion years ago -- and how those processes have continued within the last 70 million years to profoundly affect the planet's life and climate.

Published online today in Nature Geoscience, the study details how relatively recent geologic events -- volcanic activity 10 million years ago in what is now Panama and Costa Rica -- hold the secrets of the extreme continent-building that took place billions of years earlier.

The discovery provides new understanding about the formation of the Earth's continental crust -- masses of buoyant rock rich with silica, a compound that combines silicon and oxygen.

"Without continental crust, the whole planet would be covered with water," said Esteban Gazel, an assistant professor of geology with Virginia Tech's College of Science. "Most terrestrial planets in the solar system have basaltic crusts similar to Earth's oceanic crust, but the continental masses -- areas of buoyant, thick silicic crust -- are a unique characteristic of Earth."

The continental mass of the planet formed in the Archaean Eon, about 2.5 billion years ago. The Earth was three times hotter, volcanic activity was considerably higher, and life was probably very limited.

Many scientists think that all of the planet's continental crust was generated during this time in Earth's history, and the material continually recycles through collisions of tectonic plates on the outermost shell of the planet.

But the new research shows "juvenile" continental crust has been produced throughout Earth's history.

"Whether the Earth has been recycling all of its continental crust has always been the big mystery," Gazel said. "We were able to use the formation of the Central America land bridge as a natural laboratory to understand how continents formed, and we discovered while the massive production of continental crust that took place during the Archaean is no longer the norm, there are exceptions that produce 'juvenile' continental crust."

The researchers used geochemical and geophysical data to reconstruct the evolution what is now Costa Rica and Panama, which was generated when two oceanic plates collided and melted iron- and magnesium-rich oceanic crust over the past 70 million years, Gazel said.

Melting of the oceanic crust originally produced what today are the Galapagos islands, reproducing Achaean-like conditions to provide the "missing ingredient" in the generation of continental crust.

The researchers discovered the geochemical signature of erupted lavas reached continental crust-like composition about 10 million years ago. They tested the material and observed seismic waves traveling through the crust at velocities closer to the ones observed in continental crust worldwide.

Additionally, the researchers provided a global survey of volcanoes from oceanic arcs, where two oceanic plates interact. The western Aleutian Islands and the Iwo-Jima segment of the Izu-Bonin islands of are some other examples of juvenile continental crust that has formed recently, the researchers said.

"This is an interesting paper that makes the case that andesitic melts inferred to derive ultimately by melting of subducted slabs in some modern arcs are a good match for the composition of the average continental crust," said Roberta L. Rudnick, a Distinguished University Professor and chair of the Department of Geology at the University of Maryland, who was not involved in conducting the research. "The authors focus primarily on Central America, but incorporate global data to strengthen their case that slab melting is important in unusual conditions of modern continent generation -- and probably in the past."

The study raises questions about the global impact newly generated continental crust has had over the ages, and the role it has played in the evolution of not just continents, but life itself.

For example, the formation of the Central American land bridge resulted in the closure of the seaway, which changed how the ocean circulated, separated marine species, and had a powerful impact on the climate on the planet.

"We've revealed a major unknown in the evolution of our planet," said Gazel, who was the senior and corresponding author of the study.

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Story Source:

The above story is based on materials provided by Virginia Tech. Note: Materials may be edited for content and length.

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Journal Reference:

1. Esteban Gazel, Jorden L. Hayes, Kaj Hoernle, Peter Kelemen, Erik Everson, W. Steven Holbrook, Folkmar Hauff, Paul van den Bogaard, Eric A. Vance, Shuyu Chu, Andrew J. Calvert, Michael J. Carr, Gene M. Yogodzinski. Continental crust generated in oceanic arcs. Nature Geoscience, 2015; 8 (4): 321 DOI: 10.1038/ngeo2392
   
   Note: This journal is an extract from Science Daily. Click Here to visit link 

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