Download Geological and Physical Factors of the Marine

Geological and Physical Factors of the Marine Environment
1. The Sea Floor
a. The oceans cover most of the globe (71%) and play a crucial
role in regulating our climate and atmosphere
b. Average depth of the oceans is 4 km (3800 m). Pacific is the
deepest, Arctic is the shallowest.
2. Geography of the Ocean Basins
a. Oceans are divided into 4 large basins: Atlantic, Pacific,
Indian & Arctic
3. Topography of the ocean Floor
a. Continental Margins
i. Continental Shelf
 The part connected to the continent
 8% of the ocean floor
 Most productive portion of the ocean. Has most
life (more Fishing)
 Atlantic side of N. America is wide, Pacific side is
narrow
 Drops off at approximately100-200 meters
ii. Continental Slope
 Steeper gradient to the ocean floor
 Edge of the continent
iii. Continental Rise
 The boundary between the continental slope and
the ocean floor
b. Ocean Basin
i. Abyssal Plains – flattest part of the Earth
ii. Abyssal Hills – small hills on the abyssal plains
iii. Seamount – underwater volcanoes
iv. Trenches – deepest part of the ocean
v. Guyots – flat topped seamounts
vi. Ridges – mountain ranges within the ocean
vii. Rifts – cracks that are found generally by the ridges
c. Mid Ocean Ridges – formed when material rising from below
the mantle pushes up on the oceanic crust
i. Central Rift Valley – a great gap or depression caused
by the plates pulling apart at the center of the ridge
ii. Hydrothermal Vents – water seeps down through the
rifts, gets heated and forces its way back up thorough the
crust
4. Plate Tectonics – the mid-ocean ridge system is a continuous chain
of submarine volcanoes that run through the ocean basins.
Earthquakes and volcanoes are associated with the mid-ocean ridge.
The Earth’s surface is broken up into a number of plates that are
separated by the earthquake belts, which are trenches, ridges and
faults.
a. There are 7 major plates:
i. North American
ii. African
iii. Indian Australian
iv. South American
v. Eurasian
vi. Pacific
vii. Antarctic
b. Plate Boundaries
i. Convergence – 2 plates coming together
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The site of mountains
ex. Himalayas
ii. Divergence – 2 plates separating
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The site of sea floor spreading
New sea floor is formed
ex. Mid Atlantic Ridge
iii. Subduction – 1 plate goes under the other
The site of trenches
Where old sea floor is destroyed
ex. Hawaii, Marianas Trench
iv. Transform Fault – 2 plates going in opposite directions
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Site of earthquakes
Fault is a crack in the Earth’s crust
ex. San Andreas Fault