Chp 4: Continental Margins and Ocean Basins

evolved from using lead lines to echo sounders, followed by multi-beam echo sounders, and then satellite altimetry (measures sea surface height to map seabed)

what are the major advances in mapping the bathymetry of the ocean floor over time?

1. oceanic ridges

2. trenches

3. abyssal plains

4. abyssal hills

5. seamounts

6. guyots

what are the primary features of deep ocean basins?
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6.

passive margin include the continental shelf, shelf break, continental slope, and continental rise
shelf break at 120-140 meters

what are the features of a passive continental margin, and at what depth is the shelf break?

active margins are on the leading edge of tectonic plates and have narrow shelves (ex: West coast)
passive margins are not on plate boundaries and have broad shelves (ex: east coast)
submarine canyons cut into shelf and slope (to transport sediments)

what is the difference between an active and passive margin, and what feature cuts into the shelf/slope to transport sediments?

turbidity current

an underwater sediment flow driven by gravity

the continental shelf is the shallow area less than 125 meters deep (often pink/red)
continental slope is the complex, steeper area ranging from 125 to 3,000 meters deep

how can you identify the continental shelf and slope in the northern Gulf of Mexico?

active margin is much narrower because of subduction

how does the structure of an active margin differ from a passive margin?

18,000 years ago

when did the last phase of global warming start?

milankovitch cycles

what has been the major cause for sea level changes over the last 250,000 years?

reveals the position of the last low sea level stand

how does the depth of the continental shelf break relate to sea level change?

at the edge of the current continental shelf (125 meters below present sea level)

where was the coastline located 18,000 years ago?

caused by evaporation as the gulf began to open and form roughly 200 million years ago

what caused the massive salt deposits in the Gulf of Mexico, and when did this happen?

sedimentary basins created where salt domes collapsed

what are the big holes found in the continental slope of the northern Gulf of Mexico?

deep ocean is primarily covered by pelagic sediment (fine grained fallout of biogenic and terrigenous particles)

what is the major source of sediment for the deep ocean that is different from continental margin