EAR 110 Lecture Notes - Lecture 4: Plate Tectonics, Continental Crust, Continental Drift
6 Oct 2016
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Document Summary
Plate tectonics: the explanation of how the earth works. Earth"s outer shell is broken into rigid plates that move. Moving plates change the face of planet earth. The theory of plate tectonics evolved in the 1960s. By 1968, evidence for plate tectonics was overwhelming. Lithosphere is made of both crust and the upper mantle. The lithosphere is in motion over the asthenosphere. Described by archimedes more than 2200 years ago. Floating solids displace water equal to their mass. An iceberg sinks until the water it displaces is equal to the total mass of iceberg. This concept applies well to the lithospheric plates. Plates move continuously at a rate of 1-15 cm/yr. Slow on a human time scale; extremely rapid geologically. Margins far from the plate boundaries are passive . Rifting has progressed to a mid-ocean ridge formation. Forms a long, thin ocean basin with young oceanic crust.
