There are different types of magma. One is called felsic magma. Felsic magma is thick and has silica minerals. It mostly makes light-coloured rocks. Another type is called mafic magma, which is runny and has less silica. It usually makes dark-coloured rocks. Magmas can be intermediate between both types.
Magma may become solid by cooling slowly below the surface. This makes "plutonic" rocks such as granite. When magma comes out from the ground in a volcano it is called lava. Lava cools quickly, and forms other kinds of rock such as basalt.
When they come up through the crust, magmas may feed a volcano and come out as lava. But they may solidify underground to form an intrusion (magma which cools and becomes solid). Intrusions eventually cool down and become igneous dikes or sills.
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