coastalzones - Coastal Zones EENS 204 Tulane University...

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This document last updated on 30-Mar-2004 EENS 204 Natural Disasters Tulane University Prof. Stephen A. Nelson Coastal Zones Oceans and Coastal Zones The oceans play a major role in weather and climate because over 70% of the Earth's surface is covered by oceans. The atmosphere picks up most of its moisture and heat from the oceans and thus weather patterns and climate are controlled by the oceans. The oceans vary considerably in their depth. The deepest part of the ocean is called the abyssal plain. As the seafloor starts to rise toward continental margins it is called the continental rise . The continental slope is the steep slope rising toward continual margins. The gently sloping area along the margin of a continent is called the continental shelf . In addition, deep trenches that occur along zones where oceanic lithosphere descends back into the mantle are called oceanic trenches . And, ridges in the deep oceans that rise above the abyssal plains and where new oceanic lithosphere is created are called oceanic ridges . These features all effect the circulation of the oceans and the ecosystems that inhabit the oceans. Coastal Zones 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 Coastal Zones 3/30/2004 Page 1 of 13
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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 the energy to the coast, and thus we start with these three factors. Tides Tides are due to the gravitational attraction of Moon and to a lesser extent, the Sun on the Earth. Because the Moon is closer to the Earth than the Sun, it has a larger effect and causes the Earth to bulge toward the moon. At the same time, a bulge occurs on the opposite side of the Earth due to inertial forces (this is not explained well in the book, but the explanation is beyond the scope of this course). These bulges remain stationary while Earth rotates. z The tidal bulges result in a rhythmic rise and fall of ocean surface, which is not noticeable to someone on a boat at sea, but is magnified along the coasts. Usually there are two high tides and two low tides each day, and thus a variation in sea level as the tidal bulge passes through each point on the Earth's surface. z
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This note was uploaded on 11/20/2010 for the course LIR 30 taught by Professor Thornley,k during the Spring '08 term at Santa Rosa.

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coastalzones - Coastal Zones EENS 204 Tulane University...

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