Extrusive rock Extrusive rock Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff.This is as opposed to intrusive rock formation, in which magma does not reach the surface. The main effect of extrusion is that the magma can cool much more quickly in the open air or under seawater, and there is little time for the growth of crystals. Sometimes, a residual portion of the matrix fails to crystallize at all,
Volcanism plate tectonic activity, but some earthquakes are generated as a result of volcanic activity (though that itself is ultimately driven by the same forces). These are formed where water interacts with volcanism. These include geysers, fumaroles, hotsprings and mudpots, they are often used as a source of geothermal energy. The amount of gas and ash emitted by volcanic eruptions has a significant effect on the Earth's climate. Large eruptions correlate well with some significant climate change events. When magma cools it solidifies and forms rocks. The type of rock formed depends on the chemical composition of the magma and how