TEST 4 STUDY GUIDE Passive margin no relative movement btw continent and ocean Active margin 2 continents coming together separated by deep ocean trench Trench convergent boundaries where lithospheric plates subduct into the mantle long relatively narrow deepest parts of ocean most 8km 11km most are in Pacific Continental shelf extension of adjacent continent narrower on active margin Broad flat from shoreline to continental slope 05 degree slope 200 meters deep may extend 100 km offshore underlain by continental crust NJ avg shelf 135 km Coastal plain area that is drowned when sea level rises 1 1000 gradient 1 meter sea level fall 1 km under water Epicontinental sea ocean that covers continent 90 million years ago western interior seaway displaced water on continent Graded shelf theory currents become less instense further off shore less turbulent sand then silt then clay graded bed courser at bottom finer on top deposited at waning current reality sand covers edge of continental shelf b c sea level changes Continental shelf break characterized by markedly increased slope gradients to ward the deep ocean bottom shelf break may be as shallow as 20 metres 65 ft and as deep as 550 me tres sediment flows Continental slope don t have a lot of sediment Submarine canyons a steep sided valley cut into the sea floor of the continental slope sometimes extending well onto the continental shelf Turbidity currents form of underwater landslide underwater density and gravity driven Turbidites the rock sediment produced by turbidity current essentially a graded bed Continental rise Abyssal plain flattest places on Earth 4 km water depth forms largest part of ocean contains submerged volcanoes called seamonts away from tectonic processes waves and tides at sea surface turbidites com ing off the shelf Lithogenic type of deep sea sediment terrigenous turdbidites derived from continents land pelagic clay red clay barren regions below the CCD with eolian volcanic and cosmic sources for mud Hydrogenic type of deep sea sediment manganese nodules very slow growth few cm per million years Biogenic type of deep sea sediment derived from organisms like those below o foraminifers made of calcite o coccolithophorids chalk calcite photosynthetic o diatoms silica siliceous photosynthetic o radiolarians silica carbonate ooze organisms more than 30 of sediment is an ooze o more than 48 of the ocean floor accumulates above CCD siliceous ooze sediments are concentrated in regions of upwelling ocean cur rents Manganese nodules found in many places of the seabed Distribution of sediments dilution destruction productivity Biological production reproduction of organisms Dilution by other particles Destruction by chemical calcium carbonate dissolves ccd carbonate compensa tion processes Carbonate compensation depth below CCD water holds more CO2 resulting in Hydrologic Cycle powered by sun atmosphere provides the link water from oceans more carbonic acid dissolving CO2 faster depths red clays too deep for carbonate carried onto land on earths surface o run off o evaporation transpiration infiltration water that soaks into ground source of ground water Water reservoirs any environment where water is stored oceans 96 glaciers 3 groundwater 1 surface water rivers and lakes 1 Groundwater abundant 70 times more fresh water below ground than above it constant available during dry periods widespread can flow from humid environments to where it is needed in dry regions tends to move slowly as seepage through pores of rock soil unconsolidated material Porosity the percent of the total volume of a rock that consists of pore spaces grains do not completely fill space sizes and shapes of particles compactness and arrangement determine poros ity igneous and metamorphic rocks have low porosity Permeability the capacity for transmitting fluids sands have high permeability small holes connectors do not allow water to pass through clay shall little to no porosity low porosity usually low permeability BUT high porosity does not mean high permeability in gravel openings are large but stuff is of many sizes pores get clogged fractured shale has secondary permeability because of its fractures Infiltration water that soaks into the ground source of ground water Water table top of saturated zone Zone of aeration open spaces are normally filled with air in soil Zone of saturation spaces are filled with water Aquifer sediment rock through which water flows easily Ex sand gravel limestone Confining bed sediment rock that restricts flow of water ex clay Perched water bodies Karst topography landscape which caves and sinkholes are so numerous they form a specific topography many small closed basins disrupted drainage pattern streams disappearing into the ground streams reappearing as large springs Stalactites icicle like cone Stalagmites upward pointing cone D Arcy s law depends on 2 things slope of the water table steeper faster permeability higher faster Springs location where the water table intersects the ground surface Artesian well a well in which water rises about the aquifer Sometimes pressure can lift the water above the ground and water will flow well water pumped into holding tank gravity maintains pressure from there to faucet Subsidence over pumping can cause grains to settle fissures and depressions Salt water intrusion pulling salt water into fresh water aquifers Stream a small narrow river a continuous flow of liquid air or gas Sheetwash a film of water a few millimeters thick that covers a ground surface Longitudinal profile stream features change from steeper at headwaters to flatter at the mouth Drainage basin or watershed a region drained by a single river or river system Divide a ridge that separates two adjacent drainage basins Base level lowest elevation a streambed can reach at a given locality streams erode their channel down to base level ultimate base level is sea level waterfall is an example of a local base level Discharge where groundwater flows from the surface discharge velocity x cross sectional area width x depth when area decreases and discharge stays the same velocity increases Capacity the ability of a given stream to carry sediment measured as the maximum quantity it can transport past a given point on the channel bank in a given amount of time Competence the degree of resistance of rocks to either erosion or deformation in terms of relative mechanical strength Braided streams multiple channel A channel