Coastal Geomorphology

Coastal Geomorphology - Coastal: 1 Coastal Geomorphology 1...

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Coastal: 1 Coastal Geomorphology 1 Sea Level Changes Waves Sediment Transport Erosion Sandy Beaches Barrier Islands Coral Reefs Classification of Coasts Coasts are the interface between land and sea and are often highly dynamic in terms of their geomorphology- they often have beautiful and dramatic landforms. The primary erosional force involved in coastal geomorphology is the waves crashing into the shore, although aeolian and tectonic processes are also significant on some coastal areas. Waves interact with a relatively small area along shorelines, so the force is often highly concentrated. We will begin our discussion of coastal processes by looking at factors which control where waves hit the shore and then move on to a more detailed look at waves themselves and how they move sediment and create landforms. Where waves encounter the shoreline is determined mainly by the elevation of the water: sea level. Sea level changes daily with the tides and over long time spans as sea level changes. Tides Sea level rises and falls along beaches twice each day (actually every 24 hours, 50 minutes). The tides are caused primarily by the rotation of the earth, the moon and the sun. The water on the side of the earth closest to the moon is pulled toward the moon, which forms a bulge in the ocean. This bulge follows the moon and when it gets to a shoreline, sea level rises. As the earth spins, water is pushed out by centrifugal force , especially on the side away from the moon. This creates a bulge of water, especially on the side away from the moon (the center of gravity is on the moon side, so there is more centrifugal force on the opposite side. This creates another bulge of water on the side away from the moon. The earth makes one rotation each day, so these two bulges make two high tides each day, with one higher than the other. The sun is also involved- the highest tides occur every two weeks when the moon and sun align (gravity from both working together). This is called the spring tide . One week after each spring tide the moon and sun are at right angles and the lowest high tide occurs. This is the neap tide . The tidal range (difference in elevation between high and
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Coastal: 2 low tides) varies from place to place and, as we shall see, this affects the area on which waves act. (This is a highly simplified explanation of tides—a correct version is more complicated, but we don’t have time for it.) Long Term Sea Level Changes While tides affect sea level on a daily basis, there are also longer term changes which take place. There are two general ways in which the point where the land meets the sea changes: actual change in sea level and change in the elevation of the coast itself. Sea Level Changes
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Coastal Geomorphology - Coastal: 1 Coastal Geomorphology 1...

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