Chapter 12 Coasts Classification difficult task tectonics active

Chapter 12: Coasts

Classification (difficult task) © tectonics ©active ©passive © sea-level change ©may vary widely ©causes ©global (eustatic) © from +6 m to -125 m in the last 2 MY © volume of water available (can be tied up in ice) © capacity of ocean basins (can be reduced by faster seafloor spreading) © volume changes due to temp changes ©local © tectonics © isostacy

Primary Coasts ©characterisitics ©young ©usually shaped by terrestrial processes ©sea level change exposes new areas to erosion ©heavy deposition extends the land into the sea

Primary coasts © cut by land erosion, then flooded by sea-level rise ©drowned river valleys ©fjords © cut by wave erosion, then sea-level falls ©wave-cut terraces © built out by land processes ©river deltas - fig p 294 © moraines © volcanic © earth movement ©upward ©downward

Secondary Coasts ©old ©shaped by waves

Secondary Coasts: Wave Erosion © methods ©abrasion ©hydraulic pressure ©dissolution © effects ©sea cliffs ©sea caves ©sea stacks and arches ©wave-cut platform ©shore straightening ©caused by wave refraction ©waves focus on headlands

Secondary Coasts: Beaches © deposits that accumulate in low energy areas © sand is always being moved © profile fig p 300 © backshore - cliffs, dunes, seawall © berm crest © foreshore - intertidal zone © off shore - longshore trough and bar © rip currents © on-shore and off-shore © seasonal © big waves - sand moves off-shore © small waves - sand moves back on-shore © effect of sea walls

Secondary Coasts: Transportation & Deposition © longshore drift ©transportation ©wave motion pushes in at an angle ©gravity pulls straight out ©sand moves along the shore ©effects ©sand moves in the direction of the predominant waves ©barrier islands ©spits, baymouth bars, & tombolos ©effects of groins, piers, jetties, breakwaters

Secondary Coasts: Transportation & Deposition ©coastal cells ©sand moves ©entry point - cliffs, river, etc ©longshore drift ©exit point - submarine canyon ©human structures (dams, groins, jetties, piers, breakwaters) can block flow of sand

Other Types of Coasts ©reefs ©mangrove swamps ©estuaries

Estuaries © types © characterisitics ©salt-wedge ©partially mixed ©well mixed ©fjord ©reverse ©drowned river mouths ©fjords ©bar-built (barrier © value island lagoons) ©productive ©tectonic (grabens) ©sheltered ©brackish ©nurseries for the ocean ©lagoons & wetlands