GEOS 170A1 Lecture Notes - Lecture 7: Igneous Rock, Continental Crust, Oceanic Crust
6 Aug 2018
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Recap: mid-ocean ridges are higher than the surrounding ocean floor because the rocks below are warmer and less dense. Plate tectonics: divergent: the two oldest spots: northern atlantic & north-western pacific. Iceland & africa (a new ocean is forming which will split africa hundreds of years later. Iceland - decompression volcanism: the oldest oceanic crust occurs along the continental margins (farthest from ridge) and the youngest occurs at mid-ocean ridges, cold - thick, hot - thin, mantle not liquid - decompression melting. Plate tectonics: convergent plate boundaries: when thinking of subduction: (3 things, huge earthquakes, certain volcanic activities, deep trench, plate boundaries = edges of a plate = where plates touch, convergent means come together. Subduction zone: lithosphere is destroyed, most dangerous volcanoes, biggest earthquakes, ocean trench is boundary between plates, overriding plate dragged down, making trench, deepest places on earth (marianas 11km)
