GEOL 1001 Lecture : GEOL Lecture 7
Document Summary
Igneous rocks form by solidification of magma or molten (liquid) rock. In the crust (5% sedimentary rock) (95% igneous rock: on the surface (75% sedimentary rock, 25% igneous rock) Earth is mostly solid. therefore, magma forms within the earth through melting. Temps high enough to promote melting to produce magma occur in the mantle. Magmas ascend bc silicate liquids are less dense than equivalent solid rocks. 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 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 the earth"s surface. Most magma is emplaced at depth in the earth. An underground igneous body, once cooled and solidified, is called a pluton. Batholith- contacts crosscut layering in horizontal strata.
