非常好的资料-板块漂移学说.ppt

板块漂移学说 I. Introduction (cont.) E. Forces shaping the Earth at the surface and from within 1. Surficial Processes Solar energy and gravity shaping the landscape 2. Internal Processes Internal energy and forces that buckle and break Earth’s crust If External Processes Only? Question: If 550 million tons of rock are broken down and transported to the sea from the United States each year, Why has our continent not been worn flat after the billions of years of its existence and Why haven’t the oceans been filled in? 1. Surficial ProcessesResults of the “External Heat Engine” Weathering Chemical and Mechanical Breakdown of ?solid rock into ?sediments Erosion Removal of rock and sediment from source by Gravity, wind, water, ice Surficial Processes (cont.)Results of the “External Heat Engine” Transport over large distances by water, wind and ice. Surficial Processes (cont.)Results of the “External Heat Engine” Deposition of large amounts of sediment in seas and oceans 2. Internal Earth Processes Results of the “Internal Heat Engine” Evidence of internal energy and forces working on our earth. Intricate landscapes Volcanoes Earthquakes Geothermal Gradients (deeper is hotter) 3. Formation of Earth Formation of the Planets The mass of the center of the solar system began nuclear fusion to ignite the sun The inner planets were hotter and gas was driven away leaving the terrestrial planets The outer planets were cooler and more massive so they collected and retained the gasses hence the “Gas Giants” Differentiation of the Planets The relatively uniform iron-rich proto planets began to separate into zones of different composition: 4.6mya Heat from impacts, pressure and radioactive elements cause iron (and other heavier elements) to melt and sink to the center of the terrestrial planets Further Differentiation of Earth Lighter elements such as Oxygen, Silicon, and Aluminum rose to form a crust The crust, which was originally thin and heavy (iron rich silicate) Like