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71 Cards in this Set
- Front
- Back
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how did early "scientists" view the ocean floor?
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completely flat, no relief, with the deepest parts in the middle
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the earliest attempt to measure ocean depth was done by _____ in ____
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Posidonius....85 BC
Posidonius used a rope with a weight attached to the bottom - used nearly 2 km of rope |
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what has provided most of our knowledge of the sea floor?
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echo soundings (they were very inaccurate)in the 1900s
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what did the German ship METEOR discover?
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a mountain range (the mid ocean ridge) stretching along the length of the south Atlantic
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describe the Precision Depth Recorder
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it was developed in the 1950s; it uses high frequency sound signlas to measure depth of the ocean floor with a resolution of 1 m
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what was the first multi-beam echo sounder
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SeaBeam
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give some examples of multi-beam echo sounders
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Sea Marc, GLORIA
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True or False: Hypsographic curves were used to determine if plate tectonics was operating on other planets
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True
(Thurman didn't actually answer the question whether or not plate tectonics was operating on other planets) |
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how accurately can sattelites measure ocean floor depth
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with in 3-4 cm
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who were the first people to produce modern maps of the sea floor?
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Walter Smith of NOAA and David Sandwell of Scrips Institution of Oceanography
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True or False: only 12% of the ocean floor has been mapped as extensively as the surface of the moon
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false.... it's 5%
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describe seismic reflection profiles
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provide information on the layring of sediment and rock layers on the sea floor because different sound frequencies bounce off different rock and sediment layers
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what (useful) information do hypsographic curves tell us?
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the relationship between ocean floor depth and land elevation
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what are the three major ocean provinces?
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continental marigns, deep ocean basins, and mid ocean ridge
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differentiate passive margins from active margins
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passive margins: no volcanic activity, away from plate boundaries, associated with rifting and sea floor spreading
active margins: next to lithospheric boundaries, tectonic activity (such as the Nazca plate subducting beneath S. American plate) |
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True or False: active margins have a broader continental shelf than passive margins
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false.... it's the other way around
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which margins are more common: convergent active margins or transform active margins?
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convergent active margins
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faults parallel to plate boundaries create _____, _____, and ______
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linear islands, banks, and deep basins
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what is the average continental shelf width?
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70km, but varies from 10km to 1500km
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what tipe of a margin is the california continental borderland?
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transform active margin
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true or false: transform margins have significant relief along coastlines
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true
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turbidity currents are analagous to what phenomena on land?
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flash floods
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what is the distance from the top of the Andes mtns to the bottom of the Peru Chile trench?
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15 km
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what is the average continental slope gradient?
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4 degrees (varies from 1 to 25 degrees)
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what is the slope of the continental slope on the US atlantic coast? pacific coast?
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atlantic: 2 degrees
pacific: 5 degrees |
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the Monterey Canyon near California is comparable in size and shape to what other feature on land?
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the Grand Canyon
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how far do submarine canyons extend?
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some start at the continental shelf, but most extend through the end of the cont. slope, about 3.5 km
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describe the continental rise along active margins
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it's not well developed, 'cuz the trench acts as a gutter that eats up sediment
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true or false: submarine canyons were eroded by rivers, similar to how the Grand Canyon was formed
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false (there is no evidence that sea level was lower than the continental slope)
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describe a graded bedding
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a stratification in which each layer of sediment shows a decrease in grain size from bottom to top, because the larger sediment particles settle quicker than smaller ones
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what is the continental rise made up of?
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turbidite deposits
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duck : lame as underwater avalanches : ________
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turbidity currents
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what is the largest submarine fan in the world?
describe it |
the Indus fan; lies 1800 km south of pakistan; the Indus river carries large amounts of sediment from Himalayas and deposits it in the fan;
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the Indus fan buries what famous geologican feature?
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the Carlsburg ridge, an active portion of the mid ocean ridge
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True or False: the Atlantic coast is dominated by submarine canyons from Hudson Canyon to Baltimore Canyon
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true
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how do the slopes of canyons that extend into the self vary with the slopes that extend into the continental slope?
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those that are confined to the continental slope have a steeper slope
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what are the 3 general shapes of turbidite deposits?
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fan, lobate, and apron-shaped
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why is the indus fan so large?
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i dunno, but one reason could be that the submarine canyons devide into several distributary channels, each of which distribute sediment to the fan
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how many volcanic peaks (approx.) are there in the pacific ocean?
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20K
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how deep are abyssal plains?
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4.5-6 km
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what is the name of the process by which fine particles and marine dust accumulate on the seafloor and cover up irregularities?
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suspension settling
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what is the height of most abyssal hills?
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200m
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how large (or small) must an abyssal hill be to qualify as an abyssal hill?
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less than 1 km
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how large (or small) must a seamount be to qualify as a seamount?
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taller than 1 km
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true or false: the pacific ocean has very few flat abyssal plains
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true...trenches act like black holes and suck up the sediment => sediment cannot cover up the irregularities of ocean floor
also pacific oc. is very big, so most sediment settles before it reaches the middle of the ocean |
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the Andes mtns and Japan are examples of what geological feature?
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volcanic arcs
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the Andes mountains are what specific type of volcanic arc?
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continental arc
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Japan is what specific type of volcanic arc?
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island arc
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how was the speed of turbidity currents first determined?
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a turbidity current broke the trans-atlantic cable during different time intervals south of Newfoundland; the distance between breaks in cables was known, and v = d/t
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how fast was the speed of the turbidity current that broke the trans-atlantic cable south of Newfoundland?
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80 km/hr on the cont slope
24 km/hr on the cont rise |
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how are large igneous provinces formed?
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by marine volcanic activity
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what are continental flood basalts?
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large igneous provinces on land
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give examples of continental flood basalts
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Snake river, Colombia river
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continental flood basalts produce how much lava in 1-2 million years?
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2 million km^3
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what is a back-arc spreading center?
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a divergent plate boundary that forms on the overriding plate at a trench; the overriding plate gets pulled inward, forming the back-arc spreading center
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what are serpentine seamounts associated with?
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a subduction zone's fore-arc region, which lies seaward of volcanic arc
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the mid ocean ridge covers how much of the earth's surface?
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23%
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what are fissures?
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cracks in the mid ocean ridge that are commonly observed
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what are pillow basalt and pillow lavas?
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smoot, rounded lobes of rock formed when hot magma comes into contacft with cold seafloor water
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name and describe the 3 main types of hydrotherman vents
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1. warm water vents (30 deg celcius) - water is clear
2. White smokers (30-350 deg celcius) - white water due to presense of Barium Sulfide 3. Black smokers (350 deg celcius) - emit black water due to presence of metal (Fe, Pb, Ni, Cu, Zn, Cr) sulfides |
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why does the water emitted at hydrothermal vents not steam even though its temperature is 300 deg celcius?
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there's a lot of pressure, which raises the boiling point of water
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what is the relationship between the volume of the ocean water and hydrothermal vents?
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the entire volume of ocean water is recycled through the hydrothermal vent system every 3 million years
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why aren't people mining for Au, Ag, and other metal sulfides near hydrothermal vents?
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it's too expensive
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where are metal deposits on land believed to have originated?
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deep sea hydrothermal vents near mid ocean ridges
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how are hydrothermal vent communities supported despite the lack of photosynthesis?
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bacteria and archaeons oxidize metal sulfides and act as primary producers the community
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what is the difference between oceanic rises and ridges?
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oceanic ridge = steeper slope, rugged, slow spreading rate
oceanic rise = less steep, and less rugged, fast spreading rate |
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how are transform faults and fracture zones oriented in relation to the mid ocean ridge?
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perpendicular to it
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describe transform faults
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they offset mid ocean ridge spreading; accomodate spreading on a spherical earth;
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wat's the difference between transform faults and fracture zones?
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transform faults: adjacent to transform plate boundary; plates move in opposite directions; many earthquakes; occur between offset mid ocean ridge segments
fracture zones: an intraplate feature, plates move in same direction, few earthequakes, occur beyond offset mid ocean ridge segments |
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give examples of transform faults
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San Andreas Fault, Alpine Fault, Dead Sea Fault
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give examples of fracture zones
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Mendocino Fracture Zone, Molokai Fracture Zone
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