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Layers of the Earth Crust: land layer made up of rock and soil that we walk on (thinnest layer) Lithosphere: bottom portion of the crust and the upper mantle Upper Mantle: layer of pliable rock just below the crust where earthquake movement occurs Deep Mantle: thickest layer just below the upper mantle Outer Core: made of molten rock and metals just above the inner core Inner Core: solid center made of heavy metals; hottest layer Hydrosphere: all the water on Earth Page 1 of 2 Convection currents: caused by very hot material at the deepest part of the mantle rising, then cooling and sinking again; repeats this cycle Asthenosphere: heat deep inside the Earth that drives the movement of the Earth’s plates nearer the surface, located in the middle mantle Page 2 of 2 Continental Drift Geologist: scientist who studies the Earth Continental Drift: theory presented by Wegener; stated that continents were once one big supercontinent that drifted apart over many years to their present-day locations Pangaea: name given to the super-continent Mid-Atlantic Ridge: ridge in the Atlantic Ocean through which molten rock flows Sea-Floor Spreading: process where new crustal material forms at the ridges causing the old sea floor to spread apart on both sides of the ridge Magma: molten rock underground (called lava when on the surface of the Earth) Plate Tectonics Plate Tectonics: theory that the Earth’s crust is broken into pieces or plates; each plate includes material from a layer below the crust (mantle); plates slide on the lower portion of the mantle Divergent Boundary: places where the plates move apart (Mid-Atlantic Ridge) Convergent Boundary: places where the plates collide (Himalayan Mountains) Transform Boundary: places where plates slide horizontally past each other Faults Fault: cracks in the Earth’s crust caused by the movement of plates Normal Fault: 2 sides pull apart and 1 side falls below the other Reverse Fault: 2 sides push together and 1 side rises up over the other Strike-slip Fault: 2 sides slide horizontally past each other New Madrid is the fault closest to us; combination of a strike-slip and reverse Parts of an Earthquake Focus: point below the Earth’s surface where the earthquake starts Epicenter: point on Earth’s surface directly above the focus Surface Waves: waves that travel across surface of Earth and tear apart structures; can move side to side or up and down (Most destructive) Seismic Waves: vibrations from the sudden movement that travels through the crust; 2 types of waves P Waves: primary waves; travel like an accordion S Waves: secondary waves; travel like a twanged fork (slower) Aftershock(s): tremors/shaking after the earthquake occurs Seismograph: instrument used to measure the strength of an earthquake Tsunami: huge ocean wave caused by an earthquake Measuring Strength of an Earthquake Magnitude: amount of energy released by an earthquake Richter Scale: scale from 1 to 10 that ranks earthquakes according to magnitude (uses seismograph); for every unit increase the energy released is increased by a factor of 30 Mercalli Scale: scale from 1 to 12 (in Roman Numerals) that describes earthquakes based upon the amount of damage Volcanoes Volcano: an opening in the Earth’s crust from which hot molten rock moves from deep inside the Earth Ring of Fire: edges of Pacific Plate where many earthquakes and volcanoes occur Most volcanoes occur along plate boundaries Volcanoes can o Create new land o Create fertile soil Types of Volcanoes Shield Volcano: wide, flat mound created because lava from volcano is not as thick (viscous) and doesn’t clog up Cinder-Cone Volcano: has steep-sided cone created from volcanic explosion of thick magma that bursts free Composite Cone: symmetrical shaped cone; eruption may explode then have flowing lava; explosion “takes turns” between shield and cinder-cone type explosions Formation of Volcanoes Subduction Volcano: formed when one plate falls below the other (Mt. St. Helens & Mt. Vesuvius) Rift Volcano: formed when two plates pull apart (African Rift Valley) Hot-Spot Volcano: formed when magma melts a hole through the middle of a plate (Hawaiian Islands) Parts of a Volcano Magma: hot, molten rock inside the Earth Lava: molten rock on the Earth’s surface Crater: major vent at the top of the volcano Conduit: path from magma chamber to crater Cone: the volcano, formed by volcanic material Magma Chamber: stores molten rock Dike: vertical crack that holds harden magma Sill: horizontal crack that holds harden magma Fissure: long, thin fracture out to the side of the conduit More on Volcanoes Dormant: French word for “sleep,” a dormant volcano has not been active for a long time, but erupted in recorded history Extinct: has not erupted in recorded history Side effects of volcanoesGeyser: an opening in the ground through which hot water and steam erupts periodically Hot Springs: an opening in the ground where hot water and gases escape continually, but not erupt Geothermal Energy: heat from below the Earth’s surface; produces steam to run power plants that provide electricity