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III. Layers of the Earth Inner core Outer core Inner core A. Crust 1. The thin topmost layer. a. 5 km – 40 km thick b. Coolest layer 2. Two types of crusts a. Continental b. oceanic c. Thickest in Mountainous regions and thinnest in oceanic regions. B. Mantle 1. It is about 2,900 km (1,800 miles) thick 2. Makes up nearly 80 % of the Earth's total volume and 68% of its mass. 3. The mantle rock is so hot that it is often partially molten. a. 1,600- 3,200oC C. Outer Core 1. 2. The outer core is so hot that the metal is always molten. Temperature range is 3,200 – 4,000oC D. Inner Core 1. 2. 3. 4. The hottest of all the layers. a. Temperature range is 4,000 –4,500oC The inner core is solid iron and nickel. Pressures are so great that it cannot melt, even though temperatures are so hot. The most dense layer E. Lithosphere Includes the crust and the upper mantle. 2. It is cool and rigid. 1. Lithosphere F. Asthenosphere Hot and semi-liquid 2. Consists of the portions below the lithosphere. 3. Convection of the molten rock occurs here. 1. IV. Plate Tectonics 1. Theory of Continental Drift – A theory developed by Alfred Wegener, a German Meteorologist, who theorized the world’s landmasses had once been joined in a giant super continent called PANGAEA A.PANGEA Permian Triassic Era 225 mya 220 mya Cretaceous period Jurasic Era 135 mya 65 mya Present 1. Fossil Evidence Supporting Continental Drift 2. Rock Evidence 3. Evidence from Glaciers Theory of Continental Drift 4. Plate Tectonic Theory A. B. A theory that says the entire Lithosphere of the earth is divided in pieces called plates. Plates are constantly moving on top the aesthenosphere. 1. Two types of plates a. Continental plates b. Oceanic plates B. How the theory came to be Continental drift was hotly debated off and on for decades following Wegener's death before it was largely dismissed. 1. Major breakthroughs helped create the plate tectonic theory. a. ruggedness and youth of the ocean floor b. seafloor-spreading hypothesis c. documentation that the world's earthquake and volcanic activity is concentrated along oceanic trenches and submarine mountain ranges. Evidence of Sea –floor spreading Evidence from Mapping Earthquakes and volcanoes Map of the tectonic plates C. Plate Types 1. Divergent Plates Boundaries a. Two plates moving apart. b. Magma moves up to the surface and solidifies making new crust c. In the oceans, most often. 2. Convergent Plates Boundaries a. Two plates collide. b. Oceanic plates are more dense then continental plates. c. Forms trenches and mountains Subduction Zone - the dense, leading edge of the oceanic plate actually pulls the rest of the plate into the asthenosphere 3. Transform Plate Boundaries a. Two plates grind past each other side by side. b. This type of boundary separates the North American plate from the Pacific plate long the San Andreas fault Boundary Features