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Oct 14 16:09 2009
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).
Oct 1 17:27 2009
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
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.
Sep 21 19:36 2009
'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
Sep 16 22:08 2009
Six Russian volcanoes erupt
Volcanic activity increases around the Kamchatka peninsular as six volcanoes erupt simultaneously.
Sep 13 09:41 2009
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
Volcano. All of them spout steam and gas almost simultaneously.
Jun 6 15:05 2009
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.
Apr 9 17:08 2009
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.
Apr 6 16:32 2009
A 200-year-old report by a sea captain and a stunning photograph of the 2008 eruption of
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.
Apr 6 11:58 2009
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.
Jan 6 00:31 2009
Climate researchers have shown that big volcanic eruptions over the past 450 years have temporarily cooled weather in the tropics - but suggest that such effects may have been masked in the 20th century by rising global temperatures. Their paper, which shows that higher latitudes can be even more sensitive to volcanism, appears in the current issue of
Scientists already agree that large eruptions have lowered temperatures at higher latitudes in recent centuries, because volcanic particles reflect sunlight back into space. For instance, 1816, the year following the massive
in Indonesia, became known as "
The Year Without a Summer
," after low temperatures caused crop failures in northern Europe and eastern North America. More extensive evidence comes in part from tree rings, which tend to grow thinner in years when temperatures go down.
This is one of the first such studies to show how the tropics have responded, said lead author Rosanne D'Arrigo, a scientist at the Tree Ring Lab at Columbia University's Lamont-Doherty Earth Observatory
The Earth Institute at Columbia University
The impact of volcanic forcing on tropical temperatures during the past four centuries
Rosanne D'Arrigo, Rob Wilson & Alexander Tudhope
Palaeoclimate records have demonstrated links between high-latitude climate changes and tropical as well as high-latitude volcanic activity. However, little is known about the impact of high-or low-latitude volcanic eruptions on tropical climate, particularly for the period preceding the instrumental record. Here we use annually resolved temperature-related records from corals, tree rings and ice cores to investigate the relationship between volcanism and low-latitude climate. Over the past 450 years, we find an association between low-latitude volcanic events and lower sea surface temperatures in the tropical oceans. The longest sustained cold period in recent centuries occurred in the early nineteenth century, following the eruption of Tambora and a second, unidentified but presumably tropical, volcano. We therefore conclude that the tropical ocean-atmosphere system has been sensitive to changes in radiative forcing caused by tropical volcanism over the past several centuries.
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