ERTH 2415 Lecture Notes - Lecture 4: 1700 Cascadia Earthquake, Himalayas, Juan De Fuca Plate
27 Mar 2018
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Document Summary
Tectonic environments: theory of plate tectonics is central to understanding natural disasters related to the. Nomenclature to describe hypocenter depth: shallow: 0 - 100km, deep 300 - 700 km. Intermediate 100 - 300km: no earthquake below 700 km since material in plastic mesosphere not rigid enough to break abruptly. Divergent zone: dominant deformation force: tension, stress is released in frequent, strong and shallow earthquakes. Formation of new oceanic lithosphere: centering: lithosphere centers over a hot region at depth, doming: increase in heat causes the earth"s lithosphere to bulge into a dome, rifting: area is pulled apart by tension. Rift: valley created in pulled-apart area: spreading: new oceanic lithosphere is formed in pulled-apart area. Example of young divergent zone east african rift system. Failed rifts: some divergent zones do not become fully developed spreading centers with oceanic floors, stops at stage 3 rifting , create zones of weakness in the crust.
