EPSC 201 Lecture Notes - Lecture 8: Shallow Focus, Subduction, Oceanic Trench
11 Mar 2013
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Document Summary
Continental drift (wegner, 1920s) is explained by plate tectonics (1960s). Key line of evidence for plate tec- tonics was the alternating magnet- ic pattern observed on the atlantic seafloor. It was anomalously posi- tive or negative, but in equal mag- nitude. This was unexpected because there is only one type of rock on the seafloor. Basalt lava that flows out onto the ocean floor. Halfway between canada and eu- rope, there is the mid-atlantic. It is a topographical high point in the sea floor. The pattern of anomalies is the same moving outwards from the ride. It is symmetric about the mid ocean ridge. The rocks get older away from the ridge, and at the ridge, the rocks are young. There is lava flowing out of the ridge forming basalt. Iceland is part of the mid-atlantic ridge that has come above the surface. They actually shut down air travel over the atlantic after volcanic erup- tions.
