UW ESS 230 - Lecture Notes (28 pages)

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Lecture Notes



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Lecture Notes

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Pages:
28
School:
University of Washington
Course:
Ess 230 - Rivers and Beaches
Rivers and Beaches Documents

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Reading Material See class website Sediments from Oceanography M G Gross Prentice Hall Distribution of Marine Sediments Lithogenic sediment dominates near continents shelf slope rise because source from land glacial at high latitudes fluvial at all latitudes Biogenic sediment dominates away from lithogenic sediments usually away from continents exception calcareous sediment can dominate shallow low latitude areas calcareous sediment foraminifera found on flanks of mid ocean ridges because it dissolves in water 4000 m deep siliceous sediment found where nutrient supply is great nutrients stimulate marine productivity diatoms radiolarians Authigenic sediment and red clay dominates away from continents in water depths 4000 m not high prod because they are overwhelmed everywhere else by lithogenic and biogenic Deep sea sediments Sea Level Change Time scales of 10 000 years Sea level fluctuates due to climate change Cold periods more precipitation as snow not rain more snow remains for multiple years ice sheets form miles thick evaporation continues from oceans but return as runoff reduced cold temperatures cause sea water to contract sea level drops Warm periods less precipitation as snow glaciers melt warm temperatures cause sea water to expand sea level rises Sea Level Change Past 40 000 y Holocene past 20 000 y when sea level was rising Transgression transfer of shoreline landward Sea Level Rise Past 10 000 y Recent Sea Level Rise Example of step wise sea level rise Flooded river valley on the continental shelf in the Gulf of Papua between Australia and New Guinea 35 m deep This is a bathymetric chart cool colors are deep warm colors are shallow This valley might have been flooded quickly by step wise sea level rise 65 m deep Holocene Rise in Sea Level Cold period ice age ends 20 000 years ago Sea level stood 130 m below present sea level at edge of continental shelf shelf break Global sea level rose quickly 10 mm y until 7000 years ago Rate of global rise has been



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