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Oceans & Shorelines
Chapter 13
| Question | Answer |
|---|---|
| Continental Rifting | The birth of a new ocean basin; splits landmasses into 2 or moer smaller pieces |
| Why oceanic lithosphere subducts | Its overall density is greater than that of the mantle (results in 90 degree descent); younger lithopshere is more buoyant (buoyant subduction) |
| Supercontinent Cycle | Rifting and dispersal of supercontinent is followed by a long period as fragments are reassembled |
| Four Layers of the oceanic crust | Unconsolidated sediments, pillow lavas, interconected dikes, Gabbro |
| oceanic crust froms from | basaltic magma; partially melted mantle, periodite (olivine) |
| interaction between seawater and oceanic crust | water circulates downard through fractured crust; basaltic rock altered by hydrothermal metamorphism; hydrothermal fluids dissolve ions of various metals; precipitate ions on seafloor as particle-filled clouds (black smokers) |
| Wind-generated Waves | provides most energy qffecting shorelines |
| Crest | Top of wave |
| Trough | low area between waves |
| wave height | difference in height between trough and crest |
| wave length | horizontal distance between crest to crest, or trough to trough |
| wave period | time interval between passage of two successive troughs or crests |
| height, length, and period of a wave depend on... | wind speed, length of time wind has blown, and fetch |
| fetch | the distnace the wind has traveled across open water |
| Wave oscillation | wave energy moves forward, not the water; occur in the open sea in deep water. |
| Wave of translation | begins to form in shallower water when wave begins to "feel the bottom"; as speed and length diminish, wave grow highe; steep waves collapse on shoreline; advacnes up shore and forms surf |
| Wave erosion | Caused by wave impact and pressure, and abrasion by rock fragments |
| wave refraction | bending of a wave; causes wave to arrive nearly parrallel tothe shore |
| consequences of wave refraction | wave energy is concentrated against sides and ends of headlands; spreads out in bays and wave attack is weakened; straightens irregular shorelines over time. |
| beach drift | zigzag pattern casued by movign sediment when wave reaches the shoreline at an angle. |
| oblique waves | produce long-shore currents; flow parallel to the coast; easily move fine, suspended sand and rolls larger sand and gravel along bottom. |
| shoreline features vary depending on... | rocks along shore; curretns; weave intensity; and whether the shore is stable, sinking, or rising. |
| features caused by wave erosion | wave-cut cliffs; wave-cut platforms; sea arch; sea stack |
| spits | elongated ridges of sand extending from land into mouth of adjacent bay; often hooks landward in repsonse to currents; like a finger pointing in direction of long-shore current |
| baymouth bar | sand bar that completely crosses the bay |
| tombolo | ridge of sand that connects an island to the mainland or another island |
| Shoreline erosion is influenced by: | Proximity to sediment-laden rivers Degree of toctonic activity Topography and compositon of land Prevailing wind and weather patterns Shape of coastline |
| Three basic responses to shoreline erosion problem: | Building structure Beach Nourishment Abandonment and relocation of buildings away from the beach |
| Structures built to potect shoreline | Jetties (in pairs); Groins (Single); Breakwater Ussually not an effective means of protection |
| Beach Nourishment | the addition of large quantaties of sand to beach system |
| Atlantic and Gulf Coast | Broad, gently sloping coastal plains; tectonically quiet region, natural development occurs mainly on the barrier islands |
| Pacific Coast | relatively narrow beaches backed by steep cliffs and mountain ranges; significant narrowing of beaches is a major problem, shoreline erosion varies considerably from one year to the next largely due to sparodic occurences of storms |
| Millionaires Folly | Homes built near cliff edge, ocean erodes cliff face, weight casues ground to fall, home is now at cliff edge. |
| coriolis effect | an effect due to earth's rotation that casues a freely moving body to veer from a straight path |
| emergent coasts | develoep because of uplift of area or drop in sea level; featuers include wave-cut cliffs and wave-cut platforms |
| submergent coasts | caused by subsidence of land adjacenet to sea or rise in sea level; features include higly irregular shoreline and estuaries |
| estuaries | drowned river mouths |
| tides | daily changes in elevation of ocean surface; caused by gravitational forces of moon and sun |
| spring tides | occur during new moon and full moon; gravitational forces of moon and sun combine to crate especially low or hide tides |
| neap tides | daily tidal range is at its least; occur during first and thrid quarter of the moon; gravitational forces of moon and sun are offset |
| flood currents | tidal currents that advance into coastal region as tide rises |
| ebb currents | tidal currents that are seaward-moving as the tide falls |
| tidal flats | areas affected by tidal currents |
Created by:
rayannahunter
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