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Posts tagged "volcanology"

dynamicafrica:

#EarthDay: Mount Nyiragongo is a stratovolcano situated in the Virunga Mountains of the Albertine Rift inside Virunga National Park, in the Democratic Republic of the Congo. The volcano has an elevation of 3,470 m (11,385 ft).

The main crater is about two km wide and usually contains a lava lake (see photo) that has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably. Not much is known about how long the volcano has been erupting, but since 1882, it has erupted at least 34 times with the two most recent eruptions occurring in 1977 and 2002, both resulting in destruction of nearby human habitats and loss of lives, mostly due to asphyxiation by carbon dioxide.

Activity at Nyiragongo is ongoing, but currently confined to the crater.

Nyiragongo and nearby Nyamuragira are together responsible for 40% of Africa’s historical volcanic eruptions.

The Democratic Republic of Congo is home to a total of five different active and extinct volcanoes.



Crystals in Picabo’s rocks point to ‘recycled’ super-volcanic magma chambers
Oregon researchers: Evidence from Yellowstone hotspot track suggests a long haul before new eruption
(Above: university of Oregon geologist Ilya Bindeman, left, and graduate student Dana Drew, working in Bindeman’s stable isotope laboratory)
EUGENE, Ore. — (Oct. 11, 2013) — A thorough examination of tiny crystals of zircon, a mineral found in rhyolites, an igneous rock, from the Snake River Plain has solidified evidence for a new way of looking at the life cycle of super-volcanic eruptions in the long track of the Yellowstone hotspot, say University of Oregon scientists.
The pattern emerging from new and previous research completed in the last five years under a National Science Foundation career award, said UO geologist Ilya N. Bindeman, is that another super-eruption from the still-alive Yellowstone volcanic field is less likely for the next few million years than previously thought (see related story, “Not in a million years, says Oregon geologist about Yellowstone eruption”). The last eruption 640,000 years ago created the Yellowstone Caldera and the Lava Creek Tuff in what is now Yellowstone National Park.
The Yellowstone hotspot creates a conveyor belt style of volcanism because of the southwest migration of the North American plate at 2-4 centimeters (about .8 to 1.6 inches) annually over the last 16 million years of volcanism. Due to the movement of the North American plate, the plume interaction with the crust leaves footprints in the form of caldera clusters, in what is now the Snake River Plain, Bindeman said.
The Picabo volcanic field of southern Idaho, described in a new paper by a six-member team, was active between 10.4 and 6.6 million years ago and experienced at least three, and maybe as many as six, violent caldera-forming eruptions. The field has been difficult to assess, said lead author Dana Drew, a UO graduate student, because the calderas have been buried by as much as two kilometers of basalt since its eruption cycle died.
The work at Picabo is detailed in a paper online ahead of publication in the journal Earth and Planetary Science Letters.
The team theorized that basalt from the mantle plume, rocks from Earth’s crust and previously erupted volcanoes are melted together to form the rhyolites erupted in the Snake River Plain. Before each eruption, rhyolite magma is stored in dispersed pockets throughout the upper crust, which are later mixed together, according to geochemical evidence. “We think that this batch-assembly process is an important part of caldera-forming eruptions, and generating rhyolites in general,” Drew said.
In reaching their conclusions, Drew and colleagues analyzed radiogenic and stable isotopic data — specifically oxygen and hafnium — in zircons detected in rhyolites found at the margins of the Picabo field and from a deep borehole. That data, in combination with whole rock geochemistry and zircon uranium-lead geochronology helped provide a framework to understand the region’s ancient volcanic past.
Previous research on the related Heise volcanic field east of Picabo yielded similar results. “There is a growing database of the geochemistry of rhyolites in the Yellowstone hotspot track,” Drew said. “Adding Picabo provides a missing link in the database.
Drew and colleagues, through their oxygen isotope analyses, identified a wide diversity of oxygen ratios occurring in erupted zircons near the end of the Picabo volcanic cycle. Such oxygen ratios are referred to as delta-O-18 signatures based on oxygen 18 levels relative to seawater. (Oxygen 18 contains eight protons and 10 neutrons; Oxygen 16, with eight protons and eight neutrons, is the most commonly found form of oxygen in nature)
The approach provided a glimpse into the connection of surface and subsurface processes at a caldera cluster. The interaction of erupted rhyolite with groundwater and surface water causes hydrothermal alteration and the change in oxygen isotopes, thereby providing a fingerprinting tool for the level of hydrothermal alteration, Drew said.
"Through the eruptive sequence, we begin to generate lower delta-O-18 signatures of the magmas and, with that, we also see a more diverse signature," Drew said. "By the time of the final eruption there is up to five per mil diversity in the signature recorded in the zircons." The team attributes these signatures to the mixing of diverse magma batches dispersed in the upper crust, which were formed by melting variably hydrothermally altered rocks — thus diverse delta-O-18 — after repeated formation of calderas and regional extension or stretching of the crust.
When the pockets of melt are rapidly assembled, the process could be the trigger for caldera forming eruptions, Bindeman said. “That leads to a homogenized magma, but in a way that preserves these zircons of different signatures from the individual pockets of melt,” he said. This research, he added, highlights the importance of using new micro-analytical isotopic techniques to relate geochemistry at the crystal-scale to processes occurring at the crustal-wide scale in generating and predicting large-volume rhyolitic eruptions.
"This important research by Dr. Bindeman and his team demonstrates the enormous impact an NSF CAREER award can have," said Kimberly Andrews Espy, vice president for research and innovation and dean of the graduate school at the University of Oregon. "The five-year project is providing new insights into the eruption cycles of the Yellowstone hotspot and helping scientists to better predict future volcanic activity."
The four co-authors with Bindeman and Drew on the new paper were: Kathryn E. Watts, who earned a doctorate in geology from the UO in 2011 and now is the Mendenhall Postdoctoral Research Fellow at the U.S. Geological Survey, Menlo Park, Calif.; Axel K. Schmitt of the University of California, Los Angeles; Bin Fu of the Australian National University, Canberra; and Michael McCurry of Idaho State University.

Crystals in Picabo’s rocks point to ‘recycled’ super-volcanic magma chambers

Oregon researchers: Evidence from Yellowstone hotspot track suggests a long haul before new eruption

(Above: university of Oregon geologist Ilya Bindeman, left, and graduate student Dana Drew, working in Bindeman’s stable isotope laboratory)

EUGENE, Ore. — (Oct. 11, 2013) — A thorough examination of tiny crystals of zircon, a mineral found in rhyolites, an igneous rock, from the Snake River Plain has solidified evidence for a new way of looking at the life cycle of super-volcanic eruptions in the long track of the Yellowstone hotspot, say University of Oregon scientists.

The pattern emerging from new and previous research completed in the last five years under a National Science Foundation career award, said UO geologist Ilya N. Bindeman, is that another super-eruption from the still-alive Yellowstone volcanic field is less likely for the next few million years than previously thought (see related story, “Not in a million years, says Oregon geologist about Yellowstone eruption”). The last eruption 640,000 years ago created the Yellowstone Caldera and the Lava Creek Tuff in what is now Yellowstone National Park.

The Yellowstone hotspot creates a conveyor belt style of volcanism because of the southwest migration of the North American plate at 2-4 centimeters (about .8 to 1.6 inches) annually over the last 16 million years of volcanism. Due to the movement of the North American plate, the plume interaction with the crust leaves footprints in the form of caldera clusters, in what is now the Snake River Plain, Bindeman said.

The Picabo volcanic field of southern Idaho, described in a new paper by a six-member team, was active between 10.4 and 6.6 million years ago and experienced at least three, and maybe as many as six, violent caldera-forming eruptions. The field has been difficult to assess, said lead author Dana Drew, a UO graduate student, because the calderas have been buried by as much as two kilometers of basalt since its eruption cycle died.

The work at Picabo is detailed in a paper online ahead of publication in the journal Earth and Planetary Science Letters.

The team theorized that basalt from the mantle plume, rocks from Earth’s crust and previously erupted volcanoes are melted together to form the rhyolites erupted in the Snake River Plain. Before each eruption, rhyolite magma is stored in dispersed pockets throughout the upper crust, which are later mixed together, according to geochemical evidence. “We think that this batch-assembly process is an important part of caldera-forming eruptions, and generating rhyolites in general,” Drew said.

In reaching their conclusions, Drew and colleagues analyzed radiogenic and stable isotopic data — specifically oxygen and hafnium — in zircons detected in rhyolites found at the margins of the Picabo field and from a deep borehole. That data, in combination with whole rock geochemistry and zircon uranium-lead geochronology helped provide a framework to understand the region’s ancient volcanic past.

Previous research on the related Heise volcanic field east of Picabo yielded similar results. “There is a growing database of the geochemistry of rhyolites in the Yellowstone hotspot track,” Drew said. “Adding Picabo provides a missing link in the database.

Drew and colleagues, through their oxygen isotope analyses, identified a wide diversity of oxygen ratios occurring in erupted zircons near the end of the Picabo volcanic cycle. Such oxygen ratios are referred to as delta-O-18 signatures based on oxygen 18 levels relative to seawater. (Oxygen 18 contains eight protons and 10 neutrons; Oxygen 16, with eight protons and eight neutrons, is the most commonly found form of oxygen in nature)

The approach provided a glimpse into the connection of surface and subsurface processes at a caldera cluster. The interaction of erupted rhyolite with groundwater and surface water causes hydrothermal alteration and the change in oxygen isotopes, thereby providing a fingerprinting tool for the level of hydrothermal alteration, Drew said.

"Through the eruptive sequence, we begin to generate lower delta-O-18 signatures of the magmas and, with that, we also see a more diverse signature," Drew said. "By the time of the final eruption there is up to five per mil diversity in the signature recorded in the zircons." The team attributes these signatures to the mixing of diverse magma batches dispersed in the upper crust, which were formed by melting variably hydrothermally altered rocks — thus diverse delta-O-18 — after repeated formation of calderas and regional extension or stretching of the crust.

When the pockets of melt are rapidly assembled, the process could be the trigger for caldera forming eruptions, Bindeman said. “That leads to a homogenized magma, but in a way that preserves these zircons of different signatures from the individual pockets of melt,” he said. This research, he added, highlights the importance of using new micro-analytical isotopic techniques to relate geochemistry at the crystal-scale to processes occurring at the crustal-wide scale in generating and predicting large-volume rhyolitic eruptions.

"This important research by Dr. Bindeman and his team demonstrates the enormous impact an NSF CAREER award can have," said Kimberly Andrews Espy, vice president for research and innovation and dean of the graduate school at the University of Oregon. "The five-year project is providing new insights into the eruption cycles of the Yellowstone hotspot and helping scientists to better predict future volcanic activity."

The four co-authors with Bindeman and Drew on the new paper were: Kathryn E. Watts, who earned a doctorate in geology from the UO in 2011 and now is the Mendenhall Postdoctoral Research Fellow at the U.S. Geological Survey, Menlo Park, Calif.; Axel K. Schmitt of the University of California, Los Angeles; Bin Fu of the Australian National University, Canberra; and Michael McCurry of Idaho State University.

Mystery of Bizarre Icelandic Lava Pillars Solved

The mystery of a series of strange, knobby pillars of rock that formed in Iceland has been solved.

A creeping lava flow and a stream of water mixed to create hollow, rough pillars that dot the Skaelinger Valley in Iceland. The surprise is that these towers could form at all on land. Until now, researchers thought that whenever water and lava met on land, either explosive steam or pillow-shaped lava formed.

"These had never been observed or described before as features seen on land. They’ve been described at mid-ocean ridges 2 miles [3 km] under water," said study co-author Tracy Gregg, a geologist at the University at Buffalo in New York.

Troll wars?

Gregg was hiking in Iceland in 1998 when she came upon the strange pillars, which almost look like trees without branches. Some of the tallest are 8 feet (2.4 meters) high, and up to 3.3 feet (1 m) wide. 

Local lore had it that trolls had fought a war in the valley, tossing these rocks in the process.

Gregg was not convinced by the troll war theory. The rough spires looked eerily like features she had been studying deep in the ocean.

"I was so excited. As soon as I saw these things I knew what they were," Gregg told LiveScience.

At mid-ocean ridges, or points in the deep ocean where the continental plates are peeling apart, lava seeps out of the ocean floor. Hot water rises up through this pillow lava and cools the nearby lava into rock, and as lava levels rise, spires grow, and remain even after lava flows have ebbed.

But no one had ever documented such pillars on land.

Unfortunately, Gregg didn’t get a chance to study the pillars again until 2010, when her graduate student Kenneth Christie received a grant to study the structures in Iceland.

Pillar formation

Gregg and Christie concluded that Skaelinger’s odd formations formed just like underwater lava pillars, during the famed Laki Eruption of 1783, when a volcanic fissure in southern Iceland oozed lava for eight months. That eruption was so big that it killed at least 50 percent of the island’s livestock and a quarter of its population. Benjamin Franklin noted Europe’s hazy skies from the volcano’s ash in his journal at the time, and made some of the first speculations to link volcanoes and climate, Gregg said.

As slow-moving lava inched its way across the Skaelinger Valley, the lava created a temporary dam on the river that flows through the valley, probably forming a small pond, Gregg said. The meeting of slow-moving lava and water formed spires similar to those found deep in the ocean.

Once lava levels in the valley fell, the hardened, hollow pillars remained.  

The findings may force geologists to rethink how lava and water interact on land. Normally, when water and lava meet, water either drowns the lava, forming pillowlike structures, or the lava heats the water in a flash till it turns to steam that explodes, Gregg said.

Iceland and Mars

It’s also possible that lava pillars may occur elsewhere on Earth. These spires, born in past eruptions, can also provide insight into the historical climate, Gregg said.

"If we find them somewhere else on Earth, it tells us that when that lava was in place, that the area was wet," she said.

She’s also planning to look at high-resolution images from Mars for signs of lava pillars, which would be a telltale sign that the Red Planet once had water.

The lava pillars are described in a forthcoming issue of the Journal of Volcanology and Geothermal Research.

That’s no crater! First explosive supervolcanoes found on Mars

By Amina Khan
October 2, 20133:22 p.m.

This image shows digital elevation data overlaid on daytime thermal infrared images of Eden Patera, a depression on Mars now thought to be the remnant of an ancient supervolcano. Red colors are relatively high and purple-gray colors are low. (NASA/JPL/GSFC/Arizona State University October 2, 2013)

Hiding among the craters in a pockmarked Martian plain lie supervolcanoes that were so powerful that their explosions left deep scars in the ground, scientists say. The first supervolcanoes ever found on Mars, described online Wednesday in the journal Nature, could go a long way to explaining the Red Planet’s mysterious internal and atmospheric history.While cold and dead today, Mars was once a hotbed of volcanic activity – and yet, we know very little about this aspect of its early evolution, said lead author Joseph Michalski, a planetary geologist at the Planetary Science Institute in Tucson.

“Vulcanism is a thread which is woven through every aspect of Martian geology,” Michalski said. “So this is clearly important for understanding heat flow [and] origins of the atmosphere because the atmosphere is formed through outgassing of volcanoes.”

Volcanic remains also made their way into sedimentary rocks, Michalski said. Such layered rocks make up Mt. Sharp in the middle of Gale Crater, where NASA’s rover Curiosity is headed to search for signs of life-friendly environments.

But even though volcanoes clearly played a major role in Martian history, scientists simply don’t see enough dead volcanoes to explain all of the deposits built into the planet’s surface.

"In fact, 70% of the crust was resurfaced by basaltic volcanism, with a significant fraction emplaced from as yet unrecognized sources," the study authors wrote.

So where did it all come from?

Michalski said he may have chanced upon the answer. He was studying a densely cratered area in the north of Mars called Arabia Terra when he noticed a particular depression called Eden Patera that stood out from the rest.

Or rather, it stood in — at 1.1 miles deep, it was far deeper than a crater made by an asteroid slamming into the surface. An impact crater tends to erode over time, becoming shallower.

Eden also lacked the other defining features of such craters, including a ring of ejected debris, a high ridge surrounding the basin and a mound in the middle.

Michalski teamed up with vulcanologist Jacob Bleacher of NASA’s Goddard Space Flight Center to study Eden and two other suspect craters. They concluded that these were the remains of supervolcanoes that could have exploded and put billions of tons of volcanic ash into the air, transforming the environment.

Such a volcano, like one from the quiescent supervolcano in Yellowstone National Park, would be thousands of times more powerful than the dramatic 1980 eruption of Mt. St. Helens in Washington. And this is the kind they think is made by Eden, which is roughly 43 miles wide. 

These eruptions are so massive that once the magma chamber empties, the volcano collapses, leaving a crater-like depression called a caldera. This could explain why no one has found these supervolcanoes before: They don’t look like shield volcanoes such as Olympus Mons, Mars’ roughly 13-mile-high monster and the second tallest mountain in the solar system.

Shield volcanoes, the most common kind found on Mars, are created as lava pours out in layers over time, forming a flattened peak.

But in explosive volcanoes formed over a hot spot of magma, the gases trapped in rising magma create bubbles that explode to the surface, hurling volcanic ash into the air.

“It’s sort of like getting the bends,” Michalski said, referring to the sickness that divers can face when swimming back up to the surface too fast. “When you get the bends it’s because there’s gas dissolved in your blood and as you come up too quickly, the blood bubbles out of the gas, and that can kill you. So you’ve got to come up slowly. Magma does the same thing.”

The magma would have been basaltic, which usually isn’t as explosive, Michalski said. But because of Mars’ lower gravity, perhaps even basaltic magmas could have gone off with a bang.

These supervolcanoes probably erupted some time within the first billion years of Mars’ life, Michalski said.

It’s possible that the explosive supervolcanoes only existed early in Mars’ history when the magma was still full of gas and could bubble up ferociously. As that gas escaped into the atmosphere, the rest of the magma would have poured out sluggishly to create shield volcanoes, like soda that has lost its fizz. 

Either way, Arabia Terra might have been a good spot for supervolcanoes because the crust there is strangely thin, making it a good spot for magma to seep through, Michalski said.

Eden Patera was the clearest case of the three that the duo studied, he said, but the researchers are looking to find more calderas hiding in plain sight.

The findings provide a crucial link between what we see on Mars today and how it got there in the first place, Michalski added.

“It’s our hope that this discovery will help to open the Pandora’s box on that kind of evaluation of the early volcanic history,” he said.

inlovewithgeosciences:

“A tourist at a town in southern Chile watches the cloud of ash billowing from Puyehue volcano on June 5, 2011.”

Credit: Victor Rojas/XinHua/Corbis

Volcanoes and the Little Ice Age: Not the Smoking Gun?
By

There is the tendency in our fast-paced world for lots and lots of articles to get written about science before anyone beyond the researchers and the reviewers actually sees the science. This is mostly thanks to the fact that press releases come out before the actual study – and who has time to read a study when there is a handy press release with all the bits? Yesterday saw an example of just this – a whole lot of “news” without a lot of assessment of the study itself.

The paper itself is called “Abrupt Onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks” by Gifford Miller and a host of coauthors (mostly climatologists) in the Geophysical Research Letters. After seeing a post about it on Dot Earth, I knew that the media would eat this up and wouldn’t you know it, within hours there were dozens of articles mostly telling us what the initial press release already said … and not much else. It took a while for the PDF of the article to appear on the GRL website, but after it did, I sat down with it to see what the “smoking guns” were that they identified.

I’m not going to discuss the climate models or interpretation – more or less, they sampled moss and lake sediment in Canada and Iceland to constrain the dates of the onset of the Little Ice Age. Then, they used climate models and data about volcanic atmospheric sulfur (from Gao et al., 2008, more on this paper in a bit) to model how the atmosphere and oceans would respond and if it correlated with their ages. The long and short is they found that a large sulfur loading in the atmosphere could trigger increased sea ice that would prompt cooler global climate, thus the Little Ice Age.

Continue reading over at Wired.