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Transcript
PLATE TECTONICS, EARTHQUAKES, AND THE STRUCTURE OF THE EARTH GOALS FOR THE LECTURE • Students will write and discuss various ideas related to the physical structure of the Earth (9C, 10A, 10B, 10C, 10E, 10F) • Students will write and discuss ideas related to plate tectonics, as well as follow its progression through history(10D) WHY DOES THE EARTH LOOK LIKE THIS? • Where did the tectonic plates come from? • They came from the ancient land masses the used to cover the Earth HISTORY • Has the Earth always looked like this? • What did the Earth look like in the past? HISTORY • What name do we give this place? • • When was this? • • Pangea 200 million years ago (mya) Before there was Pangea, the Earth looked even less like it does today HISTORY • About 160 mya, Pangea began to break apart. • Laurasia and Gondwanaland were the dominant land features. HISTORY • About 120 mya, Laurasia and Gondwanaland began to break apart. • Continents we might recognize were the result. HISTORY • 80 mya, Madagascar breaks off from India as India begins its race across the Indian Ocean. HISTORY • 40 mya, Inland seas in the North American Plate and Asian plates drained and India began to push up the Himalayan mountains. TODAY FOSSIL EVIDENCE • Organisms have left fossil evidence of their existence on continents across oceans. • Originally thought to be caused by organisms traveling across the ocean on “Rafts.” FOSSIL EVIDENCE • Other theories suggested organisms crossed over land bridges that were once exposed. FOSSIL EVIDENCE • A 3rd theory surfaced known as Island stepping stones. EVIDENCE THAT THIS IS WHAT REALLY HAPPENED… CONTINENTAL DRIFT • Alfred Wegener publishes The Origin of Continents and Oceans in 1915. • Proposes that the continents were once all part of a large landmass called Pangea, and then drifted apart. CONTINENTAL DRIFT • This idea matured into our current theories of Plate Tectonics • The surface of the earth is divided into about 20 plates. PLATE TECTONICS • All plates contain both continental and oceanic crust. • This is a major departure from continental drift. THE THEORY • Plates are rigid structures and will always move as a distinct unit. • The distance between two points on a tectonic plate will always be the same LITHOSPHERE • The layer of solid rock that surrounds the Earth and a thin layer of molten rock beneath it. ASTHENOSPHERE • The molten rock beneath the lithosphere. WHERE DO THINGS CHANGE? • At the boundaries between plates. • 3 categories • Divergent • Convergent • Transform DIVERGENT WAIT NO… DIVERGENT BOUNDARIES • Occur at oceanic spreading centers, typically called “Mid-Ocean Ridges” • 2 “Plates” are being pulled apart by magma from underneath that is pushing upwards • Process known as Seafloor Spreading CONVERGENT BOUNDARIES • 3 classifications of Convergent Boundaries • • • Oceanic-Continental Oceanic-Oceanic Continental-Continental CONVERGENT BOUNDARIES • Subduction Zone(vocabulary)- the place where one tectonic plate rides up over another and causes it to be pushed down and recycled (melted) CONVERGENT BOUNDARIES • Oceanic-Continental • Result in the formation of Volcanic Arcs along the boundary CONVERGENT BOUNDARIES • Oceanic-Oceanic • Result in the formation of Island Arcs • Chains of volcanic islands that form along oceanic plate boundaries CONVERGENT BOUNDARIES • Oceanic-Oceanic boundaries will also result in the formation of Trenches • These are places where the ocean is deeper than the surrounding area due to subduction. CONVERGENT BOUNDARIES • Continental-Continental • Result in the formation of mountain ranges made from deformed (squeezed) native rock CONVERGENT BOUNDARIES TRANSFORM BOUNDARIES • Plates move in opposing directions on either side of the boundary.