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339 Cards in this Set
- Front
- Back
aa flow
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a lava flow that develops a partially solidified surface as it moves forward, which breaks the surface into a rough, rubbly mass.
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ablation
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the loss of ice and snow from a glacier, generally through melting or evaporation.
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abrasion
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of a stream, the process by which a stream's rocky bed is eroded away by the constant friction and impact of tumbling rock fragments, gravel, and sediment.
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abyssal fan
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a fan-shaped accumulation of sediment that forms at the mouth of submarine canyons.
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abyssal plain
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a very flat expanse of horizontally deposited sediment that accumulates on the ocean floor at the base of a continental rise.
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accreted terrane
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a terrane that appears to have formed in place along a continent's margin through accumulation and orogeny.
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accretionary wedge
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an accumulation of marine sediment, derived from the subducting plate, that builds up at the edge of a subdiction zone.
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acid rain
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an environmentally harmful acidic rain that results from rain mixing with chemical pollutants in the atmosphere.
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active continental margin
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marked by a landward continental shelf, a continental slope that forms a sidewall of an oceanic trench and is much steeper than that of a passive continental margin, and an area of earthquake and volcano activity.
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advancing glacier
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a glacier that exhibits outward or downslope movement
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aftershock
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one of the small earthquakes that may follow the main earthquake
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A horizon
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the uppermost soil horizon; characterized by the downward movement of water
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alkali soil
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a pedocal type of soil toxic to plant growth because of its high salt content
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alluvial fan
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a feature similar to a delta; a large, fanlike accumulaton of sediment dropped where a stream emerges from rugged terrain, such as the edge between a mountain canyon and a flat plain
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alpine
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referring to high mountain regions
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alpine glaciation
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glaciation usually restricted to deep balleys in high mountainous terrain.
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angle of repose
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the steepest angle at which loose material will remain in place
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angular unconformity
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the contact that separates a younger, gently dipping rock unit from older underlying rocks that are tilted or deformed layered rock
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anticline
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a fold that is arched upward to form a ridge
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aphanitic
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fine grained
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aquiclude
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an impermeably layer such as clay that slows the flow of groundwater
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aquifer
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a porous, permeable, saturated formation of rock or soil through which groundwater flows easily
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aquitard
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a formation such as shale, clay or unfractured igneous rocks that slows water flow
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arc-continental convergence
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the result when intervening ocean is destroyed by subduction, welding an island arc to the continental edge
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arete
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a sharp ridge that commonly extends downward from a horn to separate two adjacent glacial valleys
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arroyo
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a narrow gorge with steep walls and a gravel bottom; produced over time by flash floods
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artesian well
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a well that taps water from a confined aquifer
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aseismic ridge
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a chain of seamounts and guyots (not associated with earthquakes)
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assimilation
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the process by which pieces of the country rock melt and mix within a body of magma
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asthenosphere
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an area composed of the flexible mantle beneath the lithosphere (lower mantle)
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atoll
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a circular reef in deep water that shelters a lagoon; the result of reef development around the flank of a volcano that has since subsided but to which the corals are still anchored
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axial plane
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of a fold, the plane that separates rocks on one side of a fold from those that dip in the opposite direction on the other side
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backarc basin
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the area on the continental side of an island arc or magmatic arc
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backarc thrust belt
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the belt of rocks that has been thrust toward the continental interior from the magmatic arc area along low-angle faults
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backswamp
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a poorly drained and marshy area behind a natural levee
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backwash
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the water that flows back down the beach into the surf zone
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bajada
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the joining of alluvial fans at the front of a mountain range in a rolling surface of sediment and gravel
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balanced budget
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of a glacier, a situation in thich there is neither advancement nor recession
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bar
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an elongate sedimentary accumulation of sand or gravel deposited by current action in a stream or other body of water
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barchan dune
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a solitary, crescent-shaped dune that forms in areas of sparse sand
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barchanoid dune
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a variety of dune intermediate between barchan and transverse dunes; barchanoid dunes form scalloped rows of sand perpendicular to the wind
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barrier island
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a large, elongate mass of sand that parallels a coast and forms an island
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barrier reef
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an elongate reef that develops offshore parallel to a coastline and is separated from the coastline by a deep lagoon
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basal sliding
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the movement of a glacier generated by its sliding on a thin film of water resulting from the pressure of the glacier's weight
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Basin and Range topography
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a series of steep mountain ranges separated by broad valley floors
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batholith
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a pluton larger that 100 km at the earth's surface; usually granitic and made up of diapirs
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beach
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the strip of sand or gravel (more rarely silt) that covers a shoreline from the low-water edge to a well-defined point of higher elevation
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beach drift
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the zig-zag pattern by which sediment is moved across a beach face by breaking waves
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beach face
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the side of a beach facing the ocean
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bedding
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the pattern (usually horizontal) of layering in which sediments are deposited
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bedding planes
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demarcations of different layers of sediment
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bed load
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of a stream, the heavier, coarser-grained earth material that travels on or near the bed of a stream; of wind, the heavier grains (usually sand) that hop and skip along the ground by saltation
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Benioff zone
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a zone that slopes downward from an oceanic trench and underneath the overlying crustal plate at 30 to 60 degrees; an area of earthquake origination
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bergshcrund
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a crevasse, commonly filled with rock fall debris, that forms where a glacier separates from a cirque wall
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berm
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the landward edge of a beach
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B horizon
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the middle soil horizon into which the leached materials from the A horizon often precipitate
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bituminous coal
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a common form of coal that is soft and black
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black smoker
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a submarine hot spring that results from high heat flows and convection currents at divergent plate boundaries and that deposits solid masses of metallic minerals
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blowout
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a bowl-like depression caused by deflation
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bottomset bed
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the finest silt and clay particles that are carried out from a delta into deeper water or slide down a delta front into deeper water
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Bowen's reaction series
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a description of the progression of mineral formation as magmas cool and crystallize
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braided stream
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a stream in which the water has lost its main channel and flows in an interconnectin network of rivulets around numerous bars
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breaker
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a high wave in which the crest falls forward in front of the main body of the wave
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breakwater
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a wall built parallel to the shoreline to provide quiet water
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breccia
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rock composed of coarse-grained, angular fragments of broken rocks that have been cemented together and lithified
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brittle strain
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strain that occurs when a stess is great enough to break or fracture a rock
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budget
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of a glacier, the ratio between ice gained and ice lost
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butte
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a landform resulting from the erosion of a mesa
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caldera
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a depression larger than a crater, at least 1 km in diameter, that forms at the top of a volcano when the summit is destroyed during an eruption or when the crater floor collapses into the magma chamber below
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caliche
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a hardpan formed by the precipitation of salt by evaporation
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calving
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the breaking off of large blocks of ice from a glacier
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capillary action
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the process by which surface tension causes water to rise up into unfilled pore spaces
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capillary fringe
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the lower part of the unsaturated zone that draws water upward from the saturated zone
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cast
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a fossil formed when the organic remains dissolved, leaving an opening (mold) shaped like the oraganism and later filled with calcite or silica
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cementation
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the step in lithification in which minerals fill some or all of the pore space and adhere to the sediment fragments, thus producing a sedimentary rock
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chemical sedimentary rock
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a sedimentary rock resulting from biological or chemical prcesses, generally underwater, that crystallizes minerals that accumulate on the sea floor
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chemical weathering
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the process by which rain, water, and atmospheric gases decompose minerals, destroy chemical and mineralogical bonds, and form new minerals
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chill zone
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the fine-grained edge of a rock intrusion
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C horizon
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the lowest soil horizon, which lies directly above the bedrock; composed partly of soil and partly of decomposing bedrock fragments
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cinder cone
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a feature composed of pyroclastic material (not lavas) ejected from a volcanic vent
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circum-Pacific belt
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an earthquake belt that folors the rim of the Pacific Ocean; the Ring of Fire
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cirque
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a steep-sided, cirular hollow carved in the top of a mountain from an alpine glacier
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clastic sedimentary rock
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a sedimentary rock formed from the consolidation of material such as gravel, sand, or clay (sediment) derived from the weathering and breakdown or preexisting rocks
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cleavage
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the ability of a mineral to break along preferred directions, usually along the faces of layered crystals
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coal
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a dark-colored sedimentary rock that contains a high percentage of organic plant material
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coast
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the strip of land near the ocean that includes the beach and the immediate inland area beside it
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coastal straightening
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the process of the headlands being cut back and the flanking beaches being widened
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collision boundary
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a convergent boundary that separates two continental plates that are pusshes into contact
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columnar structures
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cooled and contracted flood basalt in vertical, parallel, generally 6-sided structures (columnal jointing)
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compaction
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the step in lithification in which the grains of sediment are packed more tightly together
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composite volcano
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a volcano that consists of alternating layers of lava and pyroclastic debris; built up over millions of years, such volcanos are characterized by long periods of dormancy
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compressive stress
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stess applied to a rock from opposite directions, compressing and flattening the rock mass
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cone of depression
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the area and shape of a drawdown around a well
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confined aquifer
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an aquifer overlain by a less permeable bed that keeps the water in the aquifer under pressure
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connate water
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water trapped in the original sediments during depositino and lithification
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contact
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the plane of separation between any two different kinds of rock
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contact metamorphic deposit
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a hydrothermal deposit that results from hot solutions that leave a cooling intrusion and deposit minerals in cracks in country rock
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contact metamorphism
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the process by which country rock surrounding a hot magma intrusion is metamorphosed by the high heat flow coming from the intrusion
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contamination plume
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the elongate area of contaminated groundwater that is downgradient from the point source of leakage
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continental divide
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the topographic ridgeline that separates the streams that flow in opposite directions and empty into different oceans
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continental drift
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the theory that the continents were once joined together and somehow then split and moved apart
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continental glaciation
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glaciation that affects a broader, flatter part of a continental land mass than does alpine glaciation
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continental rise
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a very low-angle ridge of sediment that forms between the lower part of the continental slope and the abyssal plain
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continental shelf
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a shallow, very gently sloping platform that extends seaward from the edge of a continent
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continental slope
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an area that extends from the seaward edge of a continental shelf into the deep ocean at an average angle of 4 to 5 degrees
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continent-continent convergence
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the result when two continents collide
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continuous branch
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the type of magmatic differentiation in which minerals form continuously during cooling
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contour current
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a current that flows parallel to the edge of a continental slope
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convection currents
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currents within a material that are driven mostly by changing temperature gradients
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convergent boundary
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a fault boundary marked by plates that come together
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core
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the zone of the earth that includes the inner and outer core
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country rock
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the surrounding rock that invades in the formation of intrusive rocks
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crater
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the circular depression at the top of a volcano
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craton
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a continental interior that has been structurally inactive for a prolonged time, usually hundreds of millions of years or longer
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creep
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a mass-wasting event slow enough that it cannot be detected as it is occuring
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crevasse
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a deep crack of fissure in a glacier
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cross-bedding
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a sedimentary structure in which the bedding planes of a particular unit are inclined compared to the bedding of the enclosing rocks
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crude oil
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a liquid containing hydrocrabons that forms in organic-rich or fossil-rich seiments and rocks
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crust
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the outermost zone of the earth, its exterior layer
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crustal rebound
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the process by which crustal rocks that were downwarped by a glacier's wieght slowly return to normal elevation after the glacier's retreat
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daughter products
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products created as an element undergoes radio-active decay
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debris avanlanche
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a rapidly churning mass of rock debris, soil, water, and air that reaces down very sttep slopes
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debris flow
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a mass-wasting event in which movements and turbulence occur throughout the mass
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debris slide
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the rapid movement of a mass of debris as a single unit
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deflation
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the removal of sediment from a land surface by wind
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delta
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a thick, roughly wedge-shaped accumulation of sediment deposited at the mouth of a stream
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dendritic drainage pattern
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a veinlike drainage pattern that develops in a rock type that erodes uniformly, such as granite
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depositional coast
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a gently sloped coast that has been built up by sediments deposeted from longshore drift
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depth of focus
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of an earthquake, the distance between the epicenter and the focus
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desert
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an area that receives less that 25 cm (10 inches) of precipitation annually
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desert pavement
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a large surface of the desert floor that is covered by pebbles and stones that resemble rounded paving stones; caused by deflation or temperature changes
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desiccation crack
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a crack the develops when a muddy sediment is exposed to air and begins to dry out; these cracks combine to form a polygonal pattern
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detachment fault
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a low-angle fault above which is often a series of thrust faults and below which is undeformed bedrock
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dewatering
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the step in lithificatino in which increasing pressure squeezes out some of the water between sediment particles
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diapir
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a small magma blob resulting from localized melting of the crust; a component of batholiths
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differential stress
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stress usually caused by tectonic forces applied to a body of rock from different, but not opposite, directions, stretching the rock mass into an elongate shape
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differential weathering
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the result of the resistance of some rocks more than other rocks to weathering, creating uneven rates of erosion and sometimes spectacular formations
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differentiation
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the process by which a magma forms different minerals according to changes in temperature and pressure
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dike
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an intrusive rock that generally occupies a discordant, or cross-cutting, crack or fracture that crosses the trend of layering in the country rock
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dip angle
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the angle between the horizontal plane and a tilted bedding plane
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dip-slip fault
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a fault in which movement is parallel to the dip of the fault plane in an up or down direction between two blocks
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disconformity
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an erosional contact usually parallel to the bedding planes of the upper and lower rock units
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discontinuous branch
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the type of magmatic differentiation in which minerals form at discrete temperatures and not continuously during cooling
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disseminated deposit
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a hydrothermal deposit in which teh metal ore is evenly distributed in generally low concentrations throughout large masses of rock
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dissolved load
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earth material in a stream that has been dissolved into ions and carried in solution
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distributary
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a small, shifting channel that spreads out across a delta from the main river channel and disperses the sediment load
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divergent boundary
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a fault boundary marked by plates that move away from one another
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downcutting
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the erosion directly downward by a stream channel
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drainage basin
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the area drained by a stream and its tributaries
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drainage divide
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a ridge that separates one drainage basin from another
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drawdown
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a local lowering of the water table around a well
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drumlin
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a long, narrow, rounded ridge of till whose long axes parallel the direction a glacier traveled
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ductile
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of a rock, flowing plastically in response to stress
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dust storm
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a windstorm that carries large amounts of sand or sediment through the air
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earthflow
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the movement of earth material down a hillside as a viscous fluid; earthflows typically occur on steep slopes with thick soil cover that becomes saturated by heavy rains
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earthquake
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the ground shaking caused by rock that suddenly move or jolt in response to tectonic stress
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ebb currents
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tidal currents preceding low tide
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elastic rebound theory
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the theory that suggests that in some cases energy is stored in rock that is being bent (deformed) by tectonic forces until the energy in the rock exceeds the rock's chemical bonds and it breaks, realeasing energy and causing motion
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elastic strain
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strain after which the body of a rock returns to its previous shape when stress has been removed
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end moraine
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an extensive and typically crascent shaped pile of till built up at the front ot a glacier
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ephermal stream
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a stream the flows intermittently as a result of periods of sudden rainfall
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epicenter
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the point on the surface directly above the focus of an earthquake
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erosion
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the picking up of sediment and soil particles by an agent such as wind or water
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erratic
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a boulder that has been deposited by a glacier and is not derived from the local bedrock
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esker
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a long, winding ridge or outwash deposited in streams flowing through ice caves and tunnels at the base of a glacier
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estuary
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a drowned river mouth from an older coastline; appears as a long arm of ocean water extending inland from the coast
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evaporitic rock
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a rock formed from minerals that chemically precipitated from water
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exfoliation
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the process by which curved sheets of rock loosen and fall from a weathered rock surface
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exfoliation dome
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a large rounded landform (usually composed of intrusive rocks) that results from exfoliation
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exotic terrane
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a terrane that did not form naturally through accretion and has likely collided with the continental margin
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extrusive igneous rock
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igneous rock that crystallized from liquid magmas that reache the surface and were generally vented as volcanic lavas
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failed rift
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rifting that ceases before the crustal mass has been separated into parts
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fall
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a mass-wasting movement in which earth material free-falls from a steep face or cliff and generally collects at the base as talus
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fault
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an area in which rock has been displaced along a fracture, such as having one side that is moved up or down
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fault block mountain
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a mountain that is bordered on both sides by steeply dipping faults, such as a horst
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fault gouge
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the broken material within a fault
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fault plane
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a plane of fracture in a rock along which movement has occured
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felsic rock
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a rock the is rich in silica, potassium, sodium, and aluminum and that contains only small amounts of iron, magnesium, and calcium
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fetch
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the distance that wind travels over a surface of water
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fiord
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a steep-walled, fingerlike coastal inlet that was carved by glacial action and later flooded by the rising sea (fjord)
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firn
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rounded granules formed by the compaction of snow by pressure from overlying snow and cemented by ice
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first-motion studies
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studeis that indicate whether the first rock motion in an earthquake was a push (the rock moved toward the seismograph station) or a pull (away from seismograph station)
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fissile
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splitting naturally along layers
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flash flood
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flood resulting from very heavy rainfall over short periods
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flood currents
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tidal currents preceding high tide
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floodplain
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the area created on both sides of a stream when periodic flooding deposits mud and silt over extensive, low-lying areas
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flow
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a mass-wasting movement in which the mass moves downslope like a viscous fluid
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flowing artesian well
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a well that taps an aquifer under confining pressure that is sufficient to force the water to rise naturally to the surface through the well
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focus
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the point of origin of an earthquake
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fold
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a bend in a layered rock
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fold and thrust belt
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a mountain-building event in which rocks are folded during tectonic stress and detached as thin layers along thrust zones, which vertically stack the layers; typically occurs on the continental side of a magmatic arc
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folded mountain
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a mountain created by intense compressional forces that fold, fault, and metamorphose the rocks, a process that resulted in many of the world's biggest mountain belts
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foliation
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the alignment of parallel layers or bands of mineral grains in a rock subjectes to prolonged defferential stress and/or shearing
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footwall
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the block that underlies an inclined dip-slip fault
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forearc basin
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the relativily undistubed expanse of ocean floor between an accretionary wedge and an island arc
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foreland basin
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a shallow continental basin behind a magmatic arc, a result of subsidence.
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foreset bed
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a sandy bed that composes the main body of a delta
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foreshock
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one of the small earthquakes that may precede the main earthquake
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fossil
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the trace of a plant of animal in a sedimentary rock
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fossil assemblage
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a group of different kinds of fossils that coexisted; more useful than single types of fossils in determining the age of a formation
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fossil fuel
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coal, oil, or gas derived from organic-rich rocks
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fracture
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a crack in a rock along which no motion has taken place
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fringing reef
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a flat expanse of reef that is attached directly to shore
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frost heaving
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the process by which rock and soil are lifted berically by the formation of ice and repeated freezing and thawing
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frost wedging
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the widening and deepening of cracks by ice, breaking off pieces, and slabs of rock
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fumerole
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a vent in or near a volcano from which steam and other gases escape from molten rock below
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gaining stream
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a stream into which groundwater flows from the saturated zone
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geologic cross section
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a vertical "slice" across a map area; depicts the spatial relationships of rock units and structures beneath the surface
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geophysics
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a field concerning the application of the laws of physics to the study of earth
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geostatic pressure
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pressure that is equally applied to all sides of a deeply bured mass of rock
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geothermal energy
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the energy produced when exceptionally hot water underground is tapped by wells and used to generate electricity
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geothermal gradient
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the rate at which temperature increases with depth
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geyser
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an explosive hot spring that periodically erupts scalding water and steam; water temperatures in a geyser are generally near boiling
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geyserite
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a build-up of ledgelike layers, generally of calcite or silica, around a geyser
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glaciation
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the movement of an ice mass over a land surface
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glacier
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a large mass of ice that forms on land during cooler climatic periods
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Gondwanaland
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a paleocontinent that consisted of what is now Africa, India, S. America, Australia, and Antarctica
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gossan
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a rusty, iron-bearing cap; a remnant of a weathered metallic ore deposit at teh surface
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graben
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a feature formed when a block that is bounded by normal faults slips downward, usually because of a tensional force, creating a valleylike depression
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graded bed
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a bed in which the base consists of coarser material and subsequent upward through sand and silt to the finest clay sizes at the top
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graded stream
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a stream that has smoothed out its longitudinal profile to resemble a smooth, concave-upward curve
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gravity meter
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a device that measures the force of gravity between a mass inside the instrument and the earth
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groin
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one of a series of walls built perpendicular to the coast to widen beaches that are losing sand to longshore drift
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ground moraine
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a thin, widespread layer of till deposited across the surface as an ice sheet melts
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groudwater
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water derived from rain and melting snow that percolates downward from the surface and collects in the open pore spaces between soil particles or in cracks and fissures in bedrock
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guyot
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a submerged, flat-topped seamount that was once above sea level and was eroded flat by continual wave action
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half-life
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the time it takes for half of a known quantity of radioactive material to convert to daughter products
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halo
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the zone of metamorphism surrounding an intrusion in contact metamorphism
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hanging valley
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a valley that forms a cliff face witht the main valley it enters because its lower part has been eroded away by flacial action
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hanging wall
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the block that overlies the inclined fault plane in a dip-slip fault
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hardness
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a quality of minerals determined by teh Mohs hardness scale
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hardpan
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a layer of soil, usually the Bhorizon, that is so hard (usually cemented by CaCO3 or SiO2) that even a backhoe cannot break through it
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headland
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a rocky arm of a coastline that juts into the sea
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headward erosion
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erosion that results when a valley is extended upward above its original source by gullying, mass wasting, and sheet erosion
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headwaters
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the origination of a stream; usually in higher elevations of mountainous terrain
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heat flow
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of the earth in general, the amount of heat from the earth's interior that is lost at the surface
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heavy crude oil
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a dense, viscous petroleum that flows so slowly it is usually left behind in an oil field
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herringbone cross-bedding
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a distinctive pattern of alternating cross-bedding directions that is reflective of a rhythmic, high-energy environment, such as a tidal zone
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hinge line
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the center axis of a fold
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horn
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a sharply defined peak that has formed from erosional processes along the rim of a cirque
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horst
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a feature that results when a block that is bounded by normal faults experiences a compressive force that forces the block upward, forming mountainous terrain
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hot spring
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a spring with water 6 to 9 degrees centigrade (11 to 16 degrees F) warmer than the mean annual air temperature for the locality where it occurs
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hot springs deposit
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a disseminated metal deposit formed in response to hot spring activity at the surface of the earth
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hydraulic action
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the ability of flowing water to dislodge, pick up, and transport rock particles or sediment
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hydrogenous sediments
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sediments on the ocean floor that have chemically precipitated from seawater
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hydrologic cycle
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the continuous exchange of water between the atmosphere, oceans, continents, plants, and animals
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hydrothermal deposit
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of metallic ore, the result of the formation of rich deposits from hydrothermal solutions that circulate through fractured country rock
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hydrothermal rocks
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those rocks whose minerals crystallized from hot water or whose minerals have been altered by hot water passing through them
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hydrothermal vein
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minerals that are deposited from hydrothermal processes and fill a crack in the country rock
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iceberg
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a floating mass of ice that results from calving from a glacial face into the water of a lake or ocean
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ice cap
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a glacial ice mass that is centered on a highland area and migrates outward in all directions
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ice fall
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a blocky, piled-up ice surface that results when rapid ice movements rupture glacial crevasses
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ice sheet
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a glacier that covers a broad expanse of land and is not restricted by a channel
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igneous rock
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rock that at one time was molten and party of magmas or lavas and that then cooled
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incised meander
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a steep-walled canyon that results from the down-cutting of a meandering stream
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inclinometer
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a device on a compass used to measure dip angle
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inclusion
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a rock fragment enclosed within an intrusive rock unit
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index fossil
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a fossil of those species that lived only during a restricted period and that identifies the narrow time range during which the host rock could have formed
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inner core
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the spherical, solid, innermost part of the earth
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inselberg
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an isolated bedrock remnant of a former mountain front; may project through the pediment cover
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interior drainage pattern
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a drainage pattern in which streams empty into landlocked basins
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intermediate rock
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a general term for rock between mafic and felsic classifications
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intrusive igneous rock
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igneous rock taht formed from magmas that moved upward into craks and voids deep in the crust and that never reached the surface
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island arc
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a curved chain of islands that develops between an oceanic trench and a continental mass
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isoclinal fold
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a fold that has undegone stress great enough to compress its limbs together
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isostasy
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th equilibrium, or balance, between adjacent blocks of crust overlying the mantly
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isotope
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an atom of an element that contains a different number of neutrons in its nuclei than does another atom of the same element
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jetty
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a wall that is built on both sides of a harbor and that extende into the ocean to protect the harbor from sedimentation and destructive waves
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joint
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an opening in a rock along which the rock exhibits no displacement; generally an equilibrium response to cooling or unloading
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joint set
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a series of roughly parallel joints that occur in one direction
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jovian planets
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those outer planets that have densities less than 2g/cm3 (Saturn, Jupiter, Uranus, Neptune)
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kame
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a steep-sided mound of stratified till that was deposited by meltwater in depressions or openings in the ice or as short-lived deltas or fans at the mouths of meltwater streams
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karst topography
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an irregular land surgace dotted with numerous sinkholes and depressions related to underlying cave systems
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kettle
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a depression in glacial till that results when a buried block of glacial ice melts
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kettle lake
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a body of water occupying a kettle
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komatiite
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a typical ultramafic extrusive rock that is mostly olivine and pyroxene, with lesser feldspar
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laccolith
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an intrusive feature similar to a sill but formed from a more viscous magma that creates a lens-shaped mass between sedimentary layers, arching the overlying strata upward
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lahar
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a mudflow originating on a volcanic slope
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landslide
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a destructive, rapid mass-wasting event
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lateral erosion
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erosion that occurs when a stream meanders or braids back and forth across its valley floor or channel, undercutting and eroding its banks
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lateral moraine
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a moraine sonsisting of rock debris and sediment that have worked loose from the walls beside a velley glacier and have accumulated in ridges alog the sides of the glacier
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laterite
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a typically bright red, highly leached, residual soil that forms in tropic regions
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lateritic weathering
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weathering that results in residual deposits that become enriched through the chemical breakdown and removal of more reactive elements of a rock
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Laurasia
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the paleocontinent that once included the present-day landmasses of N. America and Eurasia
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lava
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magma that is extruded at the earth's surface, as from a volcano
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lava flood
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nonvolcanic lava that vents from deep cracks in the continental crust
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law of faunal succession
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a law that states that fossil species succeed one another in undisturbed rocks in a definite and recognizable order around the world
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law of original horizontality
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a law that states that most sedimentary rocks formed as nearly horizontal layers
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law of superpositition
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a law that states that in an undisturbed sequence of sedimentary rocks or lava flows, the overlying rock is younger than the underlying rock
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left-lateral strike-slip fault
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a strike-slip fault in which teh block across the fault appears to have moved to the left
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lignite
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a soft, brown coal produced by increasing temperature and pressure on peat
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limb
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one side of a fold
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liquefaction
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of a landslide, an occurence in which water-saturated soil moves downslope like a liquid
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lithification
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the hardening of sediment into a rock
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lithosphere
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an area composed of the crust and the uppermost part of the mantle
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loam
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soil that contains about equal amounts of sand, silt, and clay, as well as abundant organic matter
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loess
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silt and clay deposited by wind and weakly cemented by calcite
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longitudinal dune
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a large, symmetrical ridge of sand that parallels the wind direction; it can be over 100m high and over 100km long
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longshore current
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a strong current resulting from water bing pushed parallel to the shore by repeated wave action; primary transporter of sand in the shoreline environment
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longshore drift
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the movement of sediment parallel to the shore by wave action
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losing stream
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a stream whose channel lies above the water table and loses water into the unsaturated zone through which it is flowing
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luster
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the appearance or quality of light reflected from a mineral's surface
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mafic rock
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an igneous rock containing approximately 50& silica and relatively high percentages of iron, magnesium, and calcium
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magma
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molten rock that forms below the surface of the earth, usually at depths of 100km or greater
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magmatic arc
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a general term for belts of andesitic island arcs or inland andesitic mountain ranges (volcanic arcs) that develop along continental edges
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magmatic deposit
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of metallic ore, the result when the minerals settle to the bottom of an intrusive body and form thin, high-grade layers
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magmatic water
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water derived from magmas
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magnetic anomaly
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an area of magnetism that is either higher or lower than the average magnetic field for that region
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magnetic field
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of a planet, a magnetic force that surrounds the planet and probably originates from its metallic core
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magnetic pole
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a locality at which magnetc lines of force converge to create the strongest point in the magnetic field
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magnetometer
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a device for measuring the intensity of the magnetic field at the earth's surface
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mantle
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the middle zone o fthe earth, between the core and the crust
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mantle plume
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a "hot spot" in the crust where hot mantly material has ascended along deep penetrating cracks in the crust
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marine terrace
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a broad, gently sloping platfor offshore from a beach face
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marker beds
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those distinctive layers in a sedimentary sequence that allow exposures in defferent areas to be definitely correlated, or linked
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mass wasting
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the process of erosion whereby rock, soil, and other earth materials move down a slope because of gravetational forces
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meander
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a hairpinlike feature of a stream caused by erosion on the outside of a curve and deposition on the inside
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mechanical weathering
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the process by which rocks are physically broken down into smaller pieces by external contitions, such as the freezing and thawing of water in cracks in the rock
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medial moraine
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a long ridge of till that results when lateral maraines join as two tributary glaciers merge to form a single glacier
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Mediterranean-Himalayan belt
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a zone that runs through the Mediterranean region eastward through Asia and to the East Indies marked by frequent earthquake and volcanic activity
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member
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a distinctive rock layer that is part of a larger rock formation
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mesa
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a remnant flat-topped tower or column resulting from the weathering and erosion of a platueau's slopes
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metamorphic grades
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the different groups of minerals that crystallize and are stable at the different pressure and temperature ranges during regional metamorphism
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metamorphic rock
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a rock created by solid-state transformation of a rock mass into a rock of generally the same chemistry but with different textures and minerals
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metasomatism
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the process by which hot-water solutions carrying ions from an outside source move through a rock mass via fractures or pore space
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meteoric water
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water that is derived from the atmosphere as rain or snow and that moves down i8nto the bedrock from the earth's surface
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microseism
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a very small seismic tremor
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midoceanic ridge
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a deep crustal fault on the ocean floor that separates crustal plates and generates new ocean crust
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mineral
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a combination of elements that forms an inorganic, naturally occurring crystalline solid of a definite chemical composition
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Missippi Valley-type deposit
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a concentration of lead and zinc thought to be deposited in porous limestones and sandstones by low-temperature water that was driven out of deeper sediments by compaction
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modified Mercalli scale
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a ranking for the intensity of an earthquake, ranking it from 1 to 12 depending on the amount of resulting damage
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Mohorovicic discontinuity
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(the Moho) the first major boundary of the earth's interior; separates the crust from the underlying mantle
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Mohs hardness scale
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a scale from 1 to 10 on which the relative hardness of minerals is measured; named after its originator, Friedrich Mohs, a German mineralogist
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moraine
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an accumulation of till either lefter behind when a glacier recedes or carried on top of alpine glaciers
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mountain belt
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long chains of mountain ranges; typically thousands of km long
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mountain range
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a group of mountain peaks or ridges that form a discrete topographic area
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mountain root
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a bulge of continental crust downward into the mantle beneath a mountain
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mouth
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the terminus of a stream
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mudpot
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a kind of hot spring that produces boiling mud and realeases sulfurous gas
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