Answer: Extrusive igneous rocks are formed when magma is cooled above the ground it forms on the earth's surface.
Explanation: Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.