EARTHSC 1G03 Lecture Notes - Lecture 5: Continental Crust, Plate Tectonics, Oceanic Crust

• School: McMaster University
• Department: Earth Sciences
• Course: EARTHSC 1G03
• Professor: Maureen Padden

Document Summary

Crust (0 to 40km thick) solid: the outermost zone of the earth (5-40km thick); apple skin, composed of: Continental crust (20-40km thick, granitic rocks, rich in si, al, na, and k. The lighter crust floats on the denser mantle, like wood or icebergs floating in water. Oceanic crust (2-10km thick, basaltic rocks, denser than continental crust and so sinks deeper, rich in fe & mg metals & heavy elements) Thinner than continental crust but sinks deeper: isostasy: The condition of balance or equilibrium in which the crust floats on the mantle. Outer core (~2240km thick) molten: abrupt changes in seismic velocities and density changes indicate that the outer core is molten, composed mostly of iron and silicon, responsible for earth"s magnetic field. Inner core (~1230km thick) solid: metallic, spherical core composed mainly out of iron and nickel, sharp reflection of seismic waves at 5140km deep boundary, solid, tons of pressure, heat from radioactive elements & gravitational collapse.