GEOL 104 Lecture : GEOL 104 Lect2

• School: Queen's University
• Department: Geological Sciences and Geological Engineering
• Course: GEOL 104
• Professor: Michael T.Mc Bride

Document Summary

With the exception of earth"s core, the remainder of the planet is basically a huge mass of igneous rock that is partially covered by a thin layer of sedimentary and metamorphic rocks. Igneous rock forms as molten rock cools & solidifies. Parent material for igneous rock = magma. Magma is formed by a process called partial melting. Magma rises to the earth"s surface because of buoyancy. It is less dense than the surrounding rocks. Magma that reaches the earth"s surface is called lava. Extrusive/volcanic - igneous rocks that form when magma solidifies at the surface. Intrusive/plutonic - igneous rocks that form when magma crystallises at depth (before reaching the surface) The greatest amount of igneous activity occurs at divergent plate boundaries. Substantial amounts of magma are also produced at subduction zones. Earth"s crust and mantle are composed primarily of solid (not molten) rock. Geothermal gradient - the rate at which temperature increases as the depth increases.