GEOG1710 1nd Edition Lecture 9 Outline of Last Lecture I Variation in Climate II Climate Change Outline of Current Lecture I Earth s Formation II Earth Structure III Perspectives on Earth IV Modern Theory Plate Tectonics Current Lecture Earth s Formation About 4 6 billion years ago Earth condensed from cloud of dust and gas Dominate matter was silica and iron Earth s temperature was so high that silica and iron were in a molten state Earth s Structure Cooled and solidified Heavy elements settled out and light elements rose to surface Lithosphere o Crust and upper mantle cool and rigid o Two types Continental Oceanic o Crust rocks minerals combination of elements Asthenosphere o Below lithosphere hot fluid like o Matter moves horizontally or vertically in this layer o Driven by convection in the mantle below These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Perspective on Earth Catastrophism catastrophic events shaped Earth s landscapes reject theory o Ex Grand Canyon split open in one day and stayed like that Uniformitarianism accepted theory all natural processes that affect the Earth s crust operate with the same intensity and under the same set of physical constraints now as in the geologic past Continental Drift proposed by Wegener in 1912 continents and landmasses have moved through Earth s history and continue to move today Wegner s evidence on Pangaea circumstantial o Coastal morphology o Rock types and mountain belts o Fossils o Records of past climates similar climates The great debate Wegener had no way to explain how the continents moved he incorrectly suggested continents plowed through ocean crust Modern Theory Plate Tectonics Lithosphere broken into segments called plates Evidence and mechanism mapping of mid oceanic ridges magnetic properties of sea floor rocks rocks on ocean floor are young and oldest rocks are close to the continents Movements of continents driven by convection and occurs via sea floor spread and subduction Divergent Boundaries tensile stress caused by pushing forces o Oceanic Oceanic old dense ocean crust gets subducted under young ocean crust volcanoes mountains and earthquakes o Ocean Continent dense ocean crust subducted under light continent crust volcanoes mountain building earthquakes o Continent Continent Collision of India and Asia Himalayas earthquakes and mountain building Transformation Fault Boundaries shear stress plates slide past one another without destroying of creating new lithosphere earthquakes and little volcanism San Andres Fault
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