Chapter 11

Chapter 11 - Ch. 11: The Coast Beaches and Shoreline...

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Ch. 11: The Coast – Beaches and Shoreline Processes
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People are drawn to the coasts - 80% of the US population lives within access of the oceanic coasts. Shore – between lowest low tide and highest high tide Coast – extends from shore to as far inland as ocean-related features can be found Coastline – boundary between shore and coast Backshore – above the highest high-tide, covered only by storm surge Foreshore – portion of shore exposed during low tide, covered during high tide Nearshore – extending seaward from the lowest low tide to the low tide breaker zone (never exposed, but affected by waves) Offshore – seaward of the low tide breakers (ocean floor below wavebase - not affected by waves)
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Beach – sedimentary deposit of the shore area Wave-cut bench – flat bedrock surface carved out from continental shelf upon which beach deposits are made Berm – dry, gently sloping region at the base of the cliffs or dunes Beach face – wet, more steeply sloping portion of the beach between the berm and the waterline Longshore bars – offshore sandbars that parallel the shore Longshore trough – separating the longshore bar from the beach Swash – the seawater that flows up the beach face after a wave breaks Backwash - the seawater that flows back down the beach face after a wave breaks
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Beaches composed of coarser particles will be more steeply sloping than beaches with finer particles. This is because coarse grain beaches will allow seawater to percolate through, dissipating energy and depositing grains on the shore face. Finer grains will make the beach less permeable, thus, water will wash back down the surface of the shore face, spreading out sediments on a more gently slope.
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Winter beaches v. Summer beaches In the summer, gentle waves result in strong swash and weak backwash, which causes net deposition of sand on the beach and allows it to build up a large berm with a steeper beach face.
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Winter beaches v. Summer beaches In the winter, stronger waves (from storms) result in weak swash and strong backwash, which causes net erosion of sand on the beach, causing the berm to shrink and the beach face to slope less steeply. Much of the eroded sand from the beach face and
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This note was uploaded on 03/22/2009 for the course GEOL 103 taught by Professor Dr.ries during the Fall '08 term at UNC.

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Chapter 11 - Ch. 11: The Coast Beaches and Shoreline...

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