The Origin Of Magma

some of the variation in the different types of volcanic eruptions can be understood by examining what causes magmas to have such a wide range in composition. Magmas come from deep within the Earth, but what conditions lead to the generation of melts in the interior of the Earth? The geothermal gradient reflects the relationship between increased temperature and increased depth in the Earth, and it provides information about the depths at which melting occurs and the depths at which magmas form. The differences in the composition of the oceanic and continental crusts lead to differing abilities to conduct the heat from the interior of the Earth, and thus different geothermal gradients. The geo-thermal gradients show that temperatures within the Earth quickly exceed 1,832°F (1,000°C) with increasing depth, so why are these rocks not molten? The answer is that pressures are very high, and pressure influences the ability of a rock to melt. As the pressure rises, the temperature at which the rock melts also rises. The presence of water significantly modifies this effect of pressure on melting, because wet minerals melt at lower temperatures than dry minerals. As the pressure rises, the amount of water that can be dissolved in a melt increases. Increasing the pressure on a wet mineral has the opposite effect

NAMES OF IGNEOUS ROCKS BASED ON SILICA CONTENT AND TEXTURE

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The Basic Survival Guide

The Basic Survival Guide

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