GEOL 1001 Chapter : Igneous Rocks
Document Summary
Igneous rocks form by solidification of magma or molten (liquid) rock. Most important type of rock earth"s crust is 95% igneous rock, while only. The earth is mostly solid; therefore magma forms within the earth through melting. Temperatures high enough to promote melting to produce magma occur in the mantle: general characteristics of magma. Rocks formed from lava are extrusive, or volcanic rocks. Rocks formed from magma at depth are intrusive, or plutonic rocks. Some magma reaches the surface and is extruded. Most magma ponds and solidifies within the mantle or crust and is intruded. Magma can be extruded (erupted) gently as lava or explosively as pyroclastic material. The lava cools and solidifies at earth"s surface. Most magma is emplaced at depth in the earth. An underground igneous body, once cooled and solidified, is called a pluton: types of intrusive igneous features. Dike a tabular, discordant pluton, contacts cross-cut layering in country rocks.
