* Astronomy

Members Login
Post Info TOPIC: Volcanoes


L

Posts: 130042
Date:
RE: Volcanoes
Permalink  
 


Volcanoes Played Pivotal Role In Ancient Ice Age, Mass Extinction
Researchers here have discovered the pivotal role that volcanoes played in a deadly ice age 450 million years ago. Perhaps ironically, these volcanoes first caused global warming -- by releasing massive amounts of carbon dioxide into the atmosphere. When they stopped erupting, Earth's climate was thrown off balance, and the ice age began.

Read more

Title:
A major drop in seawater 87Sr/86Sr during the Middle Ordovician (Darriwilian): Links to volcanism and climate?
Authors: Seth A. Young, Matthew R. Saltzman, Kenneth A. Foland, Jeff S. Linder and Lee R. Kump

A large drop in seawater 87Sr/86Sr during the Middle Ordovician was among the most rapid in the entire Phanerozoic. New 87Sr/86Sr measurements from Nevada indicate that the rapid shift began in the Pygodus serra conodont zone of the upper Darriwilian Stage. We use a numerical model to explore the hypothesis that volcanic weathering provided the flux of nonradiogenic Sr to the oceans. A close balance between volcanic outgassing and CO2 consumption from weathering produced steady pCO2 levels and climate through the middle Katian, consistent with recent Ordovician paleotemperature estimates. In the late Katian, outgassing was reduced while volcanic weathering continued, and resulted in a cooling episode leading into the well-known end-Ordovician glaciation.

Source

__________________


L

Posts: 130042
Date:
Permalink  
 

Scientists measure the rate of ascent of volcanic magma
Plinian volcanic eruptions are notoriously destructive. These very powerful eruptions often occur after long periods of quiescence and are preceded by relatively short periods of seismic restiveness. Volcanoes that tend to show this kind of behaviour include Mount Vesuvius in Italy, Mt. Pinatubo in the Philippines and Mt. St. Helens in the USA. Professor Donald Dingwell of Ludwig-Maximilians-Universität (LMU) in Munich, together with Professor Jonathan Castro of the University of Orléans in France, has now been able experimentally to measure the speed with which molten rock rises during a Plinian eruption. The two scientists studied rocks that erupted from the volcano Chaitén in Southern Chile in May 2008. Their experimental analyses revealed that the magma must have ascended from the interior of the volcano to the surface within a period of only four hours. These results raise the disturbing prospect that it may not be practically possible to give adequate warning and carry out orderly evacuation procedures prior to this type of eruption (Nature, 8 October 2009).

Read more

__________________


L

Posts: 130042
Date:
Permalink  
 

Cosmic rays reveal erupting volcano's guts
A team led by Hiroyuki Tanaka of the University of Tokyo, Japan, had already shown that muons can reveal the mass of material inside a volcano. Now the team reports observations of Japan's mount Asama during an eruption on 2 February that spewed ash up to 20 kilometres away. Measurements from before and after the eruption show that between 11,000 and 70,000 tonnes of material left the volcano, agreeing with estimates of the total ash fall at 50,000 tonnes.

Read more

__________________


L

Posts: 130042
Date:
Supervolcanoes
Permalink  
 


'Rosetta Stone' of supervolcanoes discovered in Italian Alps
Rare uplift reveals for the first time the deep plumbing of a supervolcano

Scientists have found the "Rosetta Stone" of supervolcanoes, those giant pockmarks in the Earth's surface produced by rare and massive explosive eruptions that rank among nature's most violent events. The eruptions produce devastation on a regional scale - and possibly trigger climatic and environmental effects at a global scale.
A fossil supervolcano has been discovered in the Italian Alps' Sesia Valley by a team led by James E. Quick, a geology professor at Southern Methodist University. The discovery will advance scientific understanding of active supervolcanoes, like Yellowstone, which is the second-largest supervolcano in the world and which last erupted 630,000 years ago.
A rare uplift of the Earth's crust in the Sesia Valley reveals for the first time the actual "plumbing" of a supervolcano from the surface to the source of the magma deep within the Earth, according to a new research article reporting the discovery. The uplift reveals to an unprecedented depth of 25 kilometers the tracks and trails of the magma as it moved through the Earth's crust.
Supervolcanoes, historically called calderas, are enormous craters tens of kilometres in diameter. Their eruptions are sparked by the explosive release of gas from molten rock or "magma" as it pushes its way to the Earth's surface.

Southern Methodist University

__________________


L

Posts: 130042
Date:
RE: Volcanoes
Permalink  
 


Six Russian volcanoes erupt
Volcanic activity increases around the Kamchatka peninsular as six volcanoes erupt simultaneously.

Read more

__________________


L

Posts: 130042
Date:
Permalink  
 

Six Kamchatka Volcanoes Exhibit Activity Simultaneously For the First Time in Sixty Years
For the first time in sixty years six Kamchatka volcanoes exhibit activity simultaneously. They are Koryaksky, Shiveluch, Bezimyanny, Gorely, Karymsky volcanoes and Klyuchevskaya Sopka Volcano. All of them spout steam and gas almost simultaneously.

Read more

__________________


L

Posts: 130042
Date:
Permalink  
 

For decades, geologists have been puzzled by the mechanisms that give rise to the kind of volcanoes that form the so-called "ring of fire" around the Pacific Ocean. These arc volcanoes, which account for about 10 to 25 percent of all volcanoes, are produced when one of the plates that make up Earth's crust plunges beneath another plate, a process called subduction.
What was unclear was what factors controlled when, how and at what depth fluids and molten rock from these subducting plates are released, giving rise to the molten magma in the Earth's mantle that would then come spewing to the surface in the form of a volcanic eruption. This process produces many of the world's major deposits of important metals, so understanding how it works could help in locating these sources.
The mystery has now been solved, thanks to fieldwork, experiments and computer modelling carried out by Professor of Geology Timothy Grove of the Department of Earth, Atmospheric and Planetary Sciences (EAPS), graduate student Christy Till, and three colleagues. The results were published in the June 4 issue of Nature.

Read more

__________________


L

Posts: 130042
Date:
Volcanic eruptions
Permalink  
 


New research on infrasound from volcanic eruptions shows an unexpected connection with jet engines. Researchers at Scripps Institution of Oceanography at UC San Diego speeded up the recorded sounds from two volcanoes and uncovered a noise very similar to typical jet engines.
These new research findings provide scientists with a more useful probe of the inner workings of volcanic eruptions. Infrasound is sound that is lower in frequency than 20 cycles per second, below the limit of human hearing.
The study led by Robin Matoza, a graduate student at Scripps Oceanography, will be published in an upcoming issue of the journal Geophysical Research Letters, a publication of the American Geophysical Union (AGU). Matoza measured infrasonic sound from Mount St. Helens in Washington State and Tungurahua volcano in Ecuador, both of which are highly active volcanoes close to large population centres.

Read more

__________________


L

Posts: 130042
Date:
Volcanic Mesocyclone
Permalink  
 


A 200-year-old report by a sea captain and a stunning photograph of the 2008 eruption of Mount Chaiten are helping scientists at the University of Illinois better understand strong volcanic plumes.
In a paper to appear in the March 26 issue of the journal Nature, the scientists show that the spontaneous formation of a "volcanic mesocyclone" - a cyclonically rotating columnar vortex - causes the volcanic plume to rotate about its axis. The rotation, in turn, triggers a sheath of lightning and creates waterspouts or dust devils. The origins of these volcanic phenomena were previously unexplained.

Read more

__________________


L

Posts: 130042
Date:
Magma plumes
Permalink  
 


Computer simulations, paleomagnetism and plate motion histories described in the journal Science reveal how hotspots, centers of erupting magma that sit atop columns of hot mantle that were once thought to remain firmly fixed in place, in fact move beneath Earth's crust.
Scientists believe mantle plumes are responsible for some of the Earth's most dramatic geological features, such as the Hawaiian islands and Yellowstone National Park. Some plumes may have shallow sources, but a few, such as the one beneath Hawaii, appear to be rooted in the deepest mantle, near Earth's core.
Such deep plumes have long been thought to be so immobile that the motions of continental and oceanic plates were measured against them, but University of Rochester geophysicist John Tarduno and his colleagues at Ludwig-Maximilians, Münster, and Stanford universities have combined magnetic evidence from the Pacific sea floor with computer modelling to show how the plume beneath Hawaii likely bent - its root barely moving while its top moved nearly 1,000 miles across the underside of the Pacific Ocean.

Read more

__________________
«First  <  1 2 3 4 5 6 7 8  >  Last»  | Page of 8  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard