Vocabulary – Volcanoes, Earthquakes, Plate Tectonics, and Fossils – Flashcards
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crust
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Earth's outermost layer, which varies in thickness from about 5km to 60km and is separated from the mantle by the Moho Discontinuity
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epicenter
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point of Earth's surface directely above an earthquake's focus
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focus
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in an earthquake, the point beneath Earth's surface where energy release occurs
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inner core
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very dense, solid center od the Earth that is made of mostly iron with smaller amounts of oxygen, silicon, sulfur, or nickel
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magnitude
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measure of the energy released by an earthquake
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mantle
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largest layer inside Earth, lying directly above the outer core and that is made mostly of silicon, oxygen, magnesium, and iron
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normal fault
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break in rock due to tension forces, where rock above the fault surface moves downward in relation to rock below the fault surface
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outer core
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liquid core that surrounds Earth's solid inner core, and that is made mostly of iron
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primary waves
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waves that travel outward from an Earthquake's focus and cause particles in rocks to move back and forth in the same direction the wave is moving
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reverse fault
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break in rock due to compression forces, where rocks above the fault surface move upward and over the rocks below the fault surface
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secondary waves
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waves that travel outward from an earthquke's focus and move through Earth by causing particles in rocks to vibrate at right angles to the direction of the wave
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seismic waves
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energy waves that are produced at and travel outward from the earthquake's focus
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seismograph
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device used by seimologists to record primary, secondary, suface waves from earthquakes
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seismologist
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scientist who studiesearthquakes and seismic waves
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strike-slip fault
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break in rock due to shearing forces, where rocks on either side of the fault suface move past each other with little upward or downward movement
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athenosphere
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plastic-like layer below the lithosphere
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continental drift
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hypothesis proposed by Alfred Wegener that the states that continents have moved slowly to their current locations on Earth
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convection current
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cycle of heating, rising, cooling, and sinking that is thought to be the force behind plate tectioncs
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lithosphere
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rigid, outermost layer of Earth that is about 100km thick, and is composed of the crust and part of the upper mantle
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pangaea
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single large landmass made up of all the continents connected together that broke apart 200 million years ago
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plate
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surface along which rocks break and move
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plate tectonics
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theory that Earth's crust and upper mantle are broken into sections that move around on a plastic-like layer of the mantle
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seafloor spreading
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theory that magma from below Earth's crust is forced upward toward the surface at a mid-ocean ridge, flows from the cracks as the seafloor spreads apart and bcomes solid as it cools, forming new seafloor
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surface waves
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waves of energy that reach Earth's surface during an earthquake, travel outward from the epicenter, and move rock particles up and down, and side to side
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tsunami
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powerful seismic sea wave that can travel thousands of kilometers in all directions and that begins over an earthquake focus
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batholith
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largest intrusive igneous rock bodies that form when magma cools underground before reaching Earth's surface
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caldera
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large opening formed when the top of a volcano collapes
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cinder cone volcano
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steep-sided volcano made of loosely packed tephra
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composite volcano
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a volacano formed by alternating layers of tephra and lava and that is found mostly where Earth's plates come together
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crater
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steep-walled depression around a volcano's vent
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dike
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intrusive igneous rock body formed when magma is squeezed into a vertical crack that cuts across rock layers and hardens
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hot spot
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location in the mantle that is hotter than any other areas and that melts rock, which is forced up toward the crust as magma
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shield volcano
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a broad volcano with gently sloping sides
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sill
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intrusive igneous rock body formed when magma is squeezed into a horizontal crack that cuts across rock layers and hardens
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volcanic neck
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solid, igneous core of a volcano left behind when a volacno stops erupting
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vent
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an opening on Earth's surface where magma is forced up and flows out as lava
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volcano
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opening in Earth's surface that often forms a mountain when layers of lava and volcanic ash erupt and build up
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earthquake
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vibrations caused by breaking rocks along faults
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fault
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surface along which rocks break and move
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tephra
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bits of rock or solified lava dropped from the air
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fossils
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remains or traces of a once living organism reserved by rock
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pertified remains
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fossils that form when some or all of the original materials that made up the organisms are replaced with minerals
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carbonaceous film
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fossil formed when the remains of a once living organism are subjected to heat and pressure, leaving only a thin film of carbon behind
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mold
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fossil formed when an organism is buried, decays, and leaves behind a hollow place in rock
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cast
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fossil formed when sediments fill in a mold and harden into rock
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index fossil
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fossil of a species that existed on Earth for only a short time, were abundant, and were widespread geographically
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principle of superposition
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states that for undisturbed layers of rock, older rocks lie underneath younger and younger rocks
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relative dating
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method to determine the order of events and relative age of rocks by examining the position of rocks in a sequence
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unconformity
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gaps in the rock layers due to erosion, nondeposition, or both
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absolute dating
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process that uses the properties of atoms in rocks and other objects to determine their exact ages, in years
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radioactive decay
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release of nuclear particles and energy from unstable atomic nuclei
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half-life
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time needed for one half-life the mass of a sample of a radioactive isotope to decay
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uniformitarianism
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states that Earth processes happening today are similar to those that happened in the past
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radioactive dating
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process to determine the absolute ages of rocks by measuring the amounts of parent and daughter materials in a rock
