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-Radius = 6000 km-Mass of the earth = 6x10^24 kg-Density of the earth = 5.52g/cc-Density of rock at the earth’s surface = 2.67g/cc-The study of earthquakes led to the understanding of the layers of the earth-When rocks in the subsurface break up and slip along a fault, they generate shock waves that travel outward to form an earthquakeLayers of Earth-Changes in depthoPressure increasesoTemperature increases
oGeothermal gradient: The rate at which T changes with depth. Geothermal gradient DECREASES with depth. The crust-The earth’s crust floats on a denser mantle-Continental crust is thicker, less dense-Oceanic crust is thinner, more denseThe mantle-Solid rock, 2885km thick, 82% of the Earth’s volume-Convecting-Moho: the line that splits the crust and the mantleThe core-Iron rick sphere with radius of 3400 km-Seismic waves segregate two radically different parts-The outer core is liquid, inner core is solid (greater pressures keep the inner core solid)Lithosphere-Asthenosphere-Lithosphere: the outermost 100-150 km of EarthoBehaves rigidly, as a non-flowing materialoComposed of crust and upper mantle oMaterial that makes up the tectonic plates-Asthenosphere: upper mantle that is below the lithosphereoShallow under oceanic lithosphere, deeper under continentaloFlows as a soft solidTwo types of lithosphere-Continental: 150 km thickoFelsic to intermediate crustal rocksoLighter, less denseoMore buoyant – floats more -Oceanic: 100 km thickoMafic crust: Basalt and gabbrooHeavier more denseoLess buoyant (sinks more)Lecture 4 – Layers of the Earth & Tectonic Plates-0 on a topographical map is sea-level-The temperature of the earth increases with increasing depth -Atmosphere increases then decreases and then increases again
-The velocity of a seismic wave changes at increasing depths, and at a certain depth the change is abrupt (moho)Plate tectonics-Earth’s lithosphere can be broken into 20 plates that interact (12 majorplates, many microplates)-Each plate is a piece of the lithosphere and can have both continent and ocean environments. Oceanic and Continental Lithosphere Systems-Broken into many pieces or “plates”-Character is different in continental and oceanic environments -A plate can contain both environmentsContinental drift-Continental drift was the precursor to the theory of plate tectonics-Tectonics: the study of large scale movements and deformation of the Earth’s lithosphere. Evidence-Glacial evidenceoEvidence of glaciers found on five separated continents 180 million years ago. -Paleoclimatic evidenceoPlacing Pangaea over the Late Paleozoic South poleoWegener predicted rocks defining Pangaea climate beltsTropical coalsTropical reefsSubtropical desertsSubtropical evaporates-Fossil evidenceoFossils of identical species found on widely separated land (nonswimming mammals)-Matching mountain beltsoDistinctive rock assemblages and mountain belts match across the AtlanticLecture 5 – Continental DriftCriticisms of Wegener’s Ideas-Wegener had multiple lines of strong evidence-He couldn’t explained how or why the continents moved