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CAUSES OF CHANGE: GEOLOGICAL EVOLUTION Objective: Understanding causes and effects of Geological Evolution Geological Evolution • First theory to describe Earth’s mountain ranges was better known as “dried Apple theory”- stated that as the Earth’s surface cooled it did so at unequal rates causes parts to collapse and created mountains. • Commonly believed until Alfred Wegner challenged it with his idea of Continental Drift (1911) Geological Evolution • Alfred Wegner noticed that rock and fossil formations on S. America and Africa were very similar. Theorized they were once connected under his idea of Continental Drift • Reaction to his idea was skeptical; He could not explain what caused continents to move Geological Evolution • WW II – changes this. The development of Sonar to find enemy submarines discovers that the ocean floor has many features unseen by humans. • Largest mountain chain in world • Deepest gaps in Earths Surface • Brings about theory of Plate Tectonics which restates Wegner’s original ideas *CAUSES OF CHANGE: GEOLOGICAL EVOLUTION* • What causes Geological Evolution/Plate tectonics? • Heat from the Earth’s core is the primary reason for the Geological Evolution of the Earth’s Surface. • Heat causes convection cells in mantle which cause UNEVEN movement of the Crust Continental Crust Lithosphere Asthenosphere Oceanic Crust Upper Mantle Outer Core Lower MANTLE Inner Core *Convection Cells* *CAUSES OF CHANGE: GEOLOGICAL EVOLUTION* • 3 Main Forces of Geological Evolution • COMPRESSION is the name of the force which causes Tectonic plates to move toward each other. • TENSION is the name of the force which causes the Tectonic plates to move away from each other. • SHEARING is the name of the force which causes the plates to move side to side. CAUSES OF CHANGE: GEOLOGICAL EVOLUTION • Common Terms of Geological Evolution: • Continental Drift is the theory that the Earth’s land surface drifted over time • Plate Tectonics is the theory that says the Earth’s surface is made up of giant plates which move. • Fault is the term used to describe a “crack” in the Earth’s surface. *CAUSES OF CHANGE: * GEOLOGICAL EVOLUTION • 3 Types of Plate Boundaries • Convergent Boundary is formed when two plates are moving toward each other. If crust is the same type it causes COMPRESSION which causes mountains to form. • If crust is different causes SUBDUCTION which causes both mountains and volcanoes to form. These areas are prone to the most violent Earthquakes and Volcanic Eruptions COMPRESSION *Subduction* CAUSES OF CHANGE: *GEOLOGICAL EVOLUTION * • Divergent Boundary is formed when 2 plates move away from each other. As a result a Rift Valley forms. These area contain volcanoes and earthquakes but generally are less violent then areas of Convergent Boundaries. *Rift Valley* Rift Valley CAUSES OF CHANGE: *GEOLOGICAL EVOLUTION* • Transform Fault Boundary is formed when the 2 plates rub against each other. Area is prone to earthquakes but not volcanoes. • The San Andres Fault is a great example of this type of boundary. San Andres Fault *CAUSES OF CHANGE:* GEOLOGICAL EVOLUTION • Hot Spot Volcanoes are volcanoes which appear in areas where crust is very thin and allows magma to burn through. Creates a chain of island as plate moves hot area. Hawaii is an example. Hot Spot Volcanoes