Magma rises 25% faster than previously thought
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ScienceDaily (Jan. 4, 2010) — Scientists have successfully determined the permeability of the asthenosphere in the Earth's upper mantle and thus the rate at which melt rises to the Earth's surface: it flows up to 25 times faster than previously assumed. Thermo-mechanical and geochemical models on melt flows in volcanoes now have to be reconsidered.
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With such models, the flow behavior of magma melt in the basic tectonic areas of the Earth, such as on mid-ocean ridges upon which new oceanic crust forms, or on volcanically active tectonic plate margins -- so-called subduction zones. For Schmidt, it is therefore clear that the existing models need to be revised in light of the constants now established. The melt that forms at a depth of about 120 kilometers does not need tens to hundreds of thousands of years to reach the Earth's surface as was previously presumed; it only takes a few thousand years. "If a volcano erupts today, its magma did not form during the last ice age, but during the reign of the Pharaohs and around the birth of Christ," states Schmidt
This casts magmatism in a whole new light. Due to the rapid ascent, the melt interacts much less with the rock it penetrates. This means that the geochemical signals that bring the magma to the surface come from far greater depths: "We are looking deeper than previously assumed," says the mineralogist. For the scientist, the rapid ascent also fits better with the fact that volcanoes are only active for a few thousand years and the observation that geochemical signals in the magma suggested a much faster rise until now
Cool. Or at least hot.
