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| place where ocean meets land. lowest tide to highest storm waves.. <10 - 100s of meters |
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| refers to the larger zone affected by the processes that occur at this boundary. from the shore inland... 10-100s km |
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| dynamic, interactive. change with time. product of their environment. |
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| all shores experience both erosion and deposition. The Pacific coast is dominated by erosion, the Atlantic and Gulf coasts are dominated by deposition. |
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| the depositing of material |
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| low tide to the low-tide breakers |
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| the location of a coast depends primarily on: |
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| global tectonic activity and the volume of water in the ocean |
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| the shape of a coast is a prodcut of: |
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| uplift and subsidence, erosion, and deposition |
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| coasts can be rearranged by: |
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| waves and tides, gradual changes in sea level, biological processes, and tectonic activities (location and volume) |
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| Coasts are mainly shaped by the sea and the action of waves. Waves act in different ways, through the processes of erosion, transportation and deposition. |
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| changes in sea level greatly influences coastal processes |
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| sea level changes can be eustatic changes or local changes. |
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| variations in sea level that can be measured all over the world ocean |
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1. amount of water in the world ocean varies: warmer periods, volcanic periods
- more ocean, higher seas
2. volume of the ocean's container may vary
- high rates of seafloor spreading
- high rates of sedimentation
- increase sea level
3. water itself may occupy more or less volume as its T rises or falls - warming raises sea levels (expansion) |
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1. tectonic motions
2. wind and currents, seiches, storm surges, and El Nino/La Nina event can force water up or down |
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dominant processes remove material
Erosion > deposition
- straight shores, cliffs, caves, platforms
- 70% of the US coastline |
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dominant processes add material (steady or growing)
deposition > erosion
- beaches, deltas
- 30% of the US coastline |
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| land erosino and marine erosion both work to modify the nature of a rocky coast. water dissolves minerals in the rocks, contributing to the erosion. sandstones - weather easily. crystalline rocks like granite - slow. |
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| large storms, crashing waves, particles in the waves, water itself |
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| stream erosion, freezing-thawing of water in rock cracks, glacial activity, rainfall, dissolution of acids from soil |
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| usually most rapid on high-energy coasts, areas frequently battered by large waves (e.g. Maine). Low-energy coasts are only infrequently attached by large waves (e.g. Gulf of Mexico) |
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| Features of an erosional coast at low tide |
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| Wave erosion of a sea cliff produces a shelf-like wave-cut platform (submerged limit of marine erosion) visible at low tide. |
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| Shorelines can be straightened by selective erosion |
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| Wave energy converges on headlands and diverges in the adjoining bays. The accumulation of sediment derived from the headland in the tranquil bays eventually smoothes the contours of the shore. |
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| deep, narrow bays. They are often formed by tectonic forces and later modified by glaciers eroding valleys into deep, U-shaped troughs. |
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| composed of sediments rather than rock. can evolve from an erosional coast. wide, sandy beaches. few/no cliffs. straight coasts. Most common forms are beach and deltas. |
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zone of loose particles (sediment) on the shore constant state of change.
cobbles, pebbles, gravel, very fine silt, lava, shells and shell debris, fragments of coral, glass or plastics. |
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| a zone of loose particles that covers a shore |
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| water washing onto the beach |
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| returning water to the ocean |
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| lower energy deposits sand |
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| higher energy erodes sand |
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| the movement of sediment along the coast, driven by wave action. A longshore current moves sediment along the shoreline between the surf zone and the upper limit of wave action. |
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| sections of coast in which sand input and sand output are balanced. Sand is introduced by rivers, transported southward by the longshore drift, and trapped within the nearshore heads of submarine canyons. |
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| if sediment gains and losses are approximately equal, the nearshore system is in equilibrium. If losses exceed gains, the beaches within the cell will shrink and possibly disappear. |
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| forms where the longshore current slows as it clears a headland and appraoches a quiet bay |
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| forms when a sand spit closes off a bay by attaching to a headland adjacent to the bay |
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| Depositional coasts can also develop narrow, exposed sandbars that are parallel to but separated from land |
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