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71 Cards in this Set

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