Ring of Fire

Origin of Magma

Factors that influence the generation of magma from solid rock
Partial melting
Igneous rocks are mixtures of minerals
Melting occurs over a range of temperatures
Produces a magma with a higher silica content than the original rock

Plate Tectonics and Igneous Activity

Global distribution of igneous activity is not random
Most volcanoes are located on the margins of the ocean basins (intermediate, andesitic composition)
Second group is confined to the deep ocean basins (basaltic lavas)
Third group includes those found in the interiors of continents