<Table> <Tr> <Td> Shield Platform Orogen Basin Large igneous province Extended crust </Td> <Td> Oceanic crust: 0--20 Ma 20--65 Ma> 65 Ma </Td> </Tr> </Table> <Tr> <Td> Shield Platform Orogen Basin Large igneous province Extended crust </Td> <Td> Oceanic crust: 0--20 Ma 20--65 Ma> 65 Ma </Td> </Tr> <P> Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic . Igneous rock is formed through the cooling and solidification of magma or lava . The magma can be derived from partial melts of 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 . Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks . Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses . </P>

Which of the following is the most common way in to increase the variety of igneous rock types