The Ocean

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The Ocean

• EARTH The only planet w/ Oceans (or liquid
  water)
• Covers 71 of earths surface
• Divided into 4 large basins
• Pacific (largest, deepest)
• Atlantic
• Indian
• Arctic (smallest, shallowest)
• A fifth? The Antarctic

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Ocean basins
South pole view
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Ocean Basin Depths
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Interior of Earth
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The Difference Between an Ocean and a
ContinentROCKS!

• Continent very thick, very old, less dense and
  made up of Granite
• Ocean (floor) younger, more dense, not as thick
  and made up of Basalt
• Thus, the Ocean Floor sinks below the
  continent(s) and provides the habitats of marine
  organisms

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Continental Drift

• If we know the Continental Crust and Oceanic
  Crust have different densitieshow did they
  separate to become 7 continents and 4 oceans?
• We start (Pangea) 210 mya!

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PANGEA (the super continent)

• 180 million yrs. ago all continents were
  attached together and have slowly moved apart
  over time
• Discovered (S. F. Bacon, 1600s) Coasts of
  continents fit together like a puzzle.
• Lead to theory of continental drift and plate
  techtonics.

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Pangea (reptile fossils)
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• SoWHERE DID WE START AND WHERE ARE WE NOW?

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Figure 2.14a
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Figure 2.14e
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PLATE TECTONICS

• Continental drift leads to the theory of Plate
  tectonics
• Although Bacon discussed it in the 1600s, it was
  not understood until the 1960s.

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The Ocean Floor (P. Tectonics)

• Mid-Ocean Ridges
• Underwater mountain ranges
• Fault Crack in earths crust
• Rift Ocean crust separates creates cracks
• Earthquakes are common
• Trenches
• Deep depressions in the seafloor
• Mostly in Pacific, Volcanoes common

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Major features of Sea Floor
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CO 2
Mid-Atlantic Ridge (above sea
surface in Iceland)
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Sea-Floor Spreading (plate tectonics)

• New sea-floor forms at mid-ocean ridges (where
  the edge of these plates meet)
• Continental Drift If the plate (as it spreads
  away from the ridge) contains continental crust
  (on top) the continents drift (move) apart.

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How? Convection and Density!
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Figure 2.08
Sea Floor Spreading X-section of sea floor _at_
Mid ocean ridge
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Figure 2.07
Paleomagnetism Normal magnetism _at_ ridge crests
(but Reversed in other locations)
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We get

• Plate boundaries
• With geologic activity, such as earthquakes, that
  (may) correspond w/ these plate boundaries

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Earthquake and Volcano distribution
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Lithospheric plate boundaries
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How does everything move? Plate Tectonics!

• The earths upper layer, the lithosphere, is
  divided into plates
• Plates may contain sea-floor, continents, or both
• Plates are moving (few cm per year), floating on
  top of the earths molten mantle

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Subduction (plate techtonics)

• sea-floor is destroyed by plunging back into the
  earths interior at trenches
• When 2 plates collide, 1 dips below the other (in
  to the mantle) and 1 is destroyed (causing,
  sometimes, earthquakes)
• Ocean vs. Cont. plate ocean plate destroyed, can
  get coastal mountain ranges
• Ocean vs. Ocean plate 1 dips volcano or
  earthquake
• Cont. vs. cont none destroyed, mnt. Ranges fold
• 2 plates, no collision, lock/shear/earthquake (S.
  Andreas F)

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Figure 2.10
Continental Oceanic plate collision trench,
earthquake
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Figure 2.11
2 oceanic plates collide trench/earthquake
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Figure 2.13
San Andreas Fault (CA)
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Sea Floor Regions

• All of this plate movement and geologic
  activity that occurs under the water yields
  different sea floor regions
• Each dependent upon depth, width, slope etc.

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Regions of the sea-floor

• Continental Margins contain continental shelf,
  slope and rise
• Cont. shelf shallow, most rich (diverse)
• Deep Ocean Floor, Abyssal Plain
• The Ocean floor (on average) is 2-3.5 miles
  BELOW the oceans (water) surface!

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Figure 2.17
Continental margin
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Active vs. Passive Margins
An active margin is a geologically very
active area whereas a Passive margin is a
geologically in-active area.
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Figure 2.18
(Passive Margin) Continental Shelf (19 mi. off
of Atlantic City, NJ)
Toms Canyon
Shelf break
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The California Coast
Monterey Canyon
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Active Coast (CA)
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Margins

• We know what it looks like at the top of the
  (Continental) margin but what does it look like
  AT the margin (at the ridge line, deep under the
  oceans surface)?

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Figure 2.24
Black Smoker Hydro- thermal Vent (at
a Mid Ocean Ridge)
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Black Smoker, cross section
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Who are we?

• Iceland, Azores fault (mountain)
• Andes (mts.) subduction trench (o-c)
• Aleutian/Mariana (Is.) sub. trench (o-o)
• Himalayas (mts.) sub. Trench (c-c)
• Hydrothermal vents Deep Ocean
• See Fig. 2.5 for locations and other
  interesting places to visit.

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Major features of Sea Floor