* Astronomy

Scientists find possible trigger for volcanic super-eruptions

The "super-eruption" of a major volcanic system occurs about every 100,000 years and is considered one of the most catastrophic natural events on Earth, yet scientists have long been unsure about what triggers these violent explosions.
However, a new model presented this week by researchers at Oregon State University points to a combination of temperature influence and the geometrical configuration of the magma chamber as a potential cause for these super-eruptions.
Results of the research, which was funded by the National Science Foundation, were presented at the annual meeting of the Geological Society of America in Minneapolis, Minn.
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Title: A rapid mechanism to remobilise and homogenise highly crystalline magma bodies
Authors: Alain Burgisser, George W. Bergantz,

The largest products of magmatic activity on Earth, the great bodies of granite and their corresponding large eruptions, have a dual nature: homogeneity at the large scale and spatial and temporal heterogeneity at the small scale. This duality calls for a mechanism that selectively removes the large-scale heterogeneities associated with the incremental assembly of these magmatic systems and yet occurs rapidly despite crystal-rich, viscous conditions seemingly resistant to mixing. Here we show that a simple dynamic template can unify a wide range of apparently contradictory observations from both large plutonic bodies and volcanic systems by a mechanism of rapid remobilisation (unzipping) of highly viscous crystal-rich mushes. We demonstrate that this remobilisation can lead to rapid overturn and produce the observed juxtaposition of magmatic materials with very disparate ages and complex chemical zoning. What distinguishes our model is the recognition that the process has two stages. Initially, a stiff mushy magma is reheated from below, producing a reduction in crystallinity that leads to the growth of a subjacent buoyant mobile layer. When the thickening mobile layer becomes sufficiently buoyant, it penetrates the overlying viscous mushy magma. This second stage rapidly exports homogenized material from the lower mobile layer to the top of the system, and leads to partial overturn within the viscous mush itself as an additional mechanism of mixing. Model outputs illustrate that unzipping can rapidly produce large amounts of mobile magma available for eruption. The agreement between calculated and observed unzipping rates for historical eruptions at Pinatubo and at Montserrat demonstrates the general applicability of the model. This mechanism furthers our understanding of both the formation of periodically homogenised plutons (crust building) and of ignimbrites by large eruptions.

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Learning from Volcanic Eruptions 200 Million Years Ago

Morgan Schaller, Jim Wright and Dennis Kent report that the level of atmospheric CO2 went from about 2,000 parts per million to 4,000 parts per million and then shrank back to pre-eruption levels over the next 300,000 years. This implies that events of this scale have the potential to rapidly double the concentration of CO2 in earth's atmosphere. Their work, funded by a grant from the National Science Foundation, was based on measurements on cores taken from sites in northeastern New Jersey. Schaller is a PhD student, Wright an associate professor and Kent a professor of earth and planetary sciences in Rutgers School of Arts and Sciences.
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Insight into volcanic eruptions, courtesy of space

Scientists are crediting satellite imagery with helping to predict where volcanic eruptions could strike. It is well known that earthquakes can stress Earth's crust and trigger subsequent quakes, but there has been no proof of this for volcanoes until now.
In September 2005, a volcanic event in Ethiopia's Afar Desert forced magma up through rocks in a crack, known as a dyke, resulting in a 60-km-long tear in Earths crust. Over the next four years, 12 more dykes were created in the same region near the Red Sea.
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