Geol104 lecture 4 big to smallest: global tectonics to minerals. Plate tectonics: the explanation of how earth works: earths outer shell is broken into rigid plates that move, moving plates change the face of the earth. Lithosphere: hard bit under the crust, under that is the asthenosphere, the mantle. When you load it up the lithosphere bends into the asthenosphere. Dented for a period of time then pops back up. All called isostosy, the crustal rebound after a weight has been taken off. Principal of buoyancy: think of iceberg. Displaced water: crust is the same, continental: granitic crust. Sinks lower: at the himalayas the mass is pushing down on the lithosphere. Otherwise mountains would be in the atmosphere. Age of sea floor: core samples give us the age of the sea floor, show increasing thickness of sediments farther away from ridge axis, if magma cools and hardens it will record. Direction of the north pole: magnetic sea floor.