watch a video on coastal sea caves
Coastal Areas
A coastal zone is the interface between the land and water. These zones are important because a majority of the world's population inhabit such zones. Coastal zones are continually changing because of the dynamic interaction between the oceans and the land. Waves and winds along the coast are both eroding rock and depositing sediment on a continuous basis, and rates of erosion and deposition vary considerably from day to day along such zones. The energy reaching the coast can become high during storms, and such high energies make coastal zones areas of high vulnerability to natural hazards. Thus, an understanding of the interactions of the oceans and the land is essential in understanding the hazards associated with coastal zones. Tides, currents, and waves bring energy to the coast, and thus we start with these three factors.
types of coasts
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The character and shape of coasts depends on such factors as tectonic activity, the ease of erosion of the rocks making up the coast, the input of sediments from rivers, the effects of eustatic changes in sea level, and the length of time these processes have been operating.
- Rocky Coasts - In general, coastlines that have experienced recent tectonic uplift as a result of either active tectonic processes (such as the west coast of the United States) or isostatic adjustment after melting of glacial ice (such as the northern part of the east coast of the United States) form rocky coasts with cliffs along the shoreline. Anywhere wave action has not had time to lower the coastline to sea level, a rocky coast may occur. .
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In areas where differential erosion takes place, the undercutting may initially produces sea caves. If sea caves from opposite sides of a rocky headland meet, then a sea arch may form. Eventual weakening of the sea arch may result in its collapse to form a sea stack.
- Because cliffed shorelines are continually attacked by the erosive and undercutting action of waves, they are susceptible to frequent mass-movement processes which make the tops of these cliffs unstable areas for construction as you noted in your homework on mass movement processes.
- Along coasts where streams entering the ocean have cut through the rocky cliffs, wave action is concentrated on the rocky headlands as a result of wave refraction, as discussed previously.
estuaries
Coastal river valleys flooded by sea water are called estuaries. They are characterized by mixing of fresh and salt water. Most modern estuaries are related to sea level rise since the last glaciation.
tidal flats
These are zones along the coast that are flooded during high tides and form in the inter-tidal zones lacking strong waves. They are common behind barrier islands or in estuaries.
Last updated 4/29/13