Igneous rock is one of the three main rock types. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rocks can form with or without crystallization. Igneous rocks make up 90-95% of the top 16 km of the earth's crust by volume. The atoms and molecules of melted minerals are what make up magma this magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature. a decrease in pressure, or a change in composition. Over seven hundred types of igneous rocks have been found, but most of them under the Earth's crust. Examples of igneous rocks include basalt, granite, pumice, obsidian, tuff,
diorite, gabbro and andesite.
diorite, gabbro and andesite.