GEO-100 (Cain) Coastal Zones and Processes Outline

GEO-100 (Cain) Coastal Zones and Processes Outline -...

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Chapter 7 : Coastal Zones and Processes Nature of the Coastline - One factor that influences the geometry of a coastline is plate tectonics. Continental margins can be described as active or passive in a tectonic sense, depending on whether there is or is not an active plate boundary at the continent’s edge. Active Margin – One at which there is an active plate boundary, with various sections of it involved in subduction or transformation faulting. (The Western margin of N. America) - Characterized by: Cliffs above the waterline A narrow continental shelf Relatively steep drop to oceanic depths offshore Passive Margin – Far removed from the active plate boundary at the Mid-Atlantic ridge. (The Eastern margin of N. America) - Characterized by: A broad continental shelf Extensively developed beaches and sandy offshore islands Beach – A gently sloping surface washed over by the waves and covered by sediment. Beach Face – That portion of the beach regularly washed by waves as tides rise and fall. Waves – Induced by the flow of winds across the surface of water, which sets up small undulations in that surface. Wave Base – The depth at which water motion is negligible. - As waves approach the shore and “feel bottom” (when the water shallows and to wave base), the orbits are disrupted, and eventually, the waves develop into breakers. Milling (or Abrasion) – The most efficient erosion of solid rock along the shore is through wave action – either the direct pounding by breakers or the grinding effect of sand, pebbles, and cobbles propelled by waves. Tides – The periodic regional rise and fall of water levels as a consequence of the effects of the gravitational pull of the sun and moon on the waterway envelope of oceans surrounding the earth. - The Earth’s rotation tends to cause a bulge in the water mass, greatest near the equator, where the velocity of the surface is most rapid and decreasing near the poles. - Superimposed on this effect of the earth’s rotation and acting at angles to it, are the effects of the gravitational pull of the Sun and especially the Moon. ( The closer the object, the stronger its gravitational attraction .) The moon therefore pulls most strongly on matter on the side of the earth facing it, least strongly on its opposite side. The combined effects of gravity and rotation cause bulges in the water envelope, two that are especially pronounced: Page  1  of  5
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Chapter 7 : Coastal Zones and Processes One facing the moon, where the moon’s gravitational pull on the water is greatest. Another on the opposite side of the earth, where the gravitational pull is weakest and rotational forces dominate. -
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This note was uploaded on 05/09/2008 for the course GEO 100 taught by Professor Thomasboving during the Fall '08 term at Rhode Island.

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GEO-100 (Cain) Coastal Zones and Processes Outline -...

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