ENVS 2250 Chapter Notes -Hydrofluoric Acid, Phreatic Eruption, Volcanism
2 Feb 2013
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Document Summary
Estimated 1500 active volcanoes around the globe (550 on land and the rest underwater) Lava when molten rock spills out onto the earths surface. Magma when molten rock is underground. It eruptions are large the effects can be felt on a regional/global scale i. e. tsunami. The most important global risk is when volcanic debris reaches the stratosphere: causing climate change. Shallow magma storage is typically at 3-4 km depth but in areas of thick crust: sometimes as deep as 30 km. Magma is a mixture of liquid, solid crystals and dissolved gasses. Bowen determined that certain minerals form at specific temperatures during the cooling of basaltic lava. Olivine crystalizes at the highest temp and quartz crystalizes at the lowest temp. During cooling and crystallization becomes depleted in elements like magnesium and iron and becomes enriched in elements like silicon. Pressure is highest deep in the earth, so as magma moves upward through the crust, gas is released.
