For an igneous rock to form, volcanism must be involved.
Igneous rocks are generally divided into two types: intrusive igneous rock and extrusive igneous rocks.
Intrusive igneous rock is where intrusive volcanism take place and the magma below surface cools down to form rock. One example is granite.
Extrusive igneous rock is formed where extrusive volcanism take place, the lava cools down to form rocks such as basalt and tuff.
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