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The Ocean. EARTH: The only planet w/ Oceans (or liquid water) Covers 71% of earth’s surface “Divided” into 4 large basins Pacific (largest, deepest) Atlantic Indian Arctic (smallest, shallowest) A fifth? The Antarctic…. Ocean basins. South pole view. Ocean Basin Depths.

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The Ocean

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The ocean

The Ocean

  • EARTH: The only planet w/ Oceans (or liquid water)

  • Covers 71% of earth’s surface

  • “Divided” into 4 large basins

    • Pacific (largest, deepest)

    • Atlantic

    • Indian

    • Arctic (smallest, shallowest)

    • A fifth? The Antarctic…

The ocean

Ocean basins

South pole view

Ocean basin depths

Ocean Basin Depths

Interior of earth

Interior of Earth

The difference between an ocean and a continent rocks

The Difference Between an Ocean and a Continent…ROCKS!

  • 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

Continental drift

Continental Drift

  • If we know the Continental Crust and Oceanic Crust have different densities…how did they “separate” to become 7 continents and 4 oceans?

  • We start (Pangea) 210 mya!

Pangea the super continent

PANGEA (the super continent)

  • 180 million yrs. ago – all continents were attached together and have slowly moved apart over time

  • Discovered (S. F. Bacon, 1600’s) “Coasts of continents fit together like a puzzle.”

  • Lead to theory of continental drift and plate techtonics.

Pangea reptile fossils

Pangea (reptile fossils)

The ocean


Figure 2 14a

Figure 2.14a

Figure 2 14e

Figure 2.14e

Plate tectonics


  • Continental drift leads to the theory of Plate tectonics

  • Although Bacon discussed it in the 1600’s, it was not understood until the 1960’s.

The ocean floor p tectonics

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

The ocean

Major features of Sea Floor

The ocean

CO 2

Mid-Atlantic Ridge (above sea surface in Iceland)

Sea floor spreading plate tectonics

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.

How convection and density

How? Convection and Density!

Figure 2 08

Figure 2.08

Sea Floor Spreading:

X-section of sea floor @

Mid ocean ridge

Figure 2 07

Figure 2.07


Normal magnetism

@ ridge crests (but

Reversed in other


We get

We get:

  • Plate boundaries

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

The ocean

Earthquake and Volcano distribution

The ocean

Lithospheric plate boundaries

How does everything move plate tectonics

How does everything move? Plate Tectonics!

  • The earth’s 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 earth’s molten mantle

Subduction plate techtonics

Subduction (plate techtonics)

  • sea-floor is destroyed by plunging back into the earth’s 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)

Figure 2 10

Figure 2.10

Continental + Oceanic plate collision = trench, earthquake

Figure 2 11

Figure 2.11

2 oceanic plates collide = trench/earthquake

Figure 2 13





Figure 2.13

Sea floor regions

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.

Regions of the sea floor

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!

Figure 2 17

Figure 2.17

Continental margin

Active vs passive margins

Active vs. Passive Margins

An active margin

is a geologically

very “active” area;

whereas a

Passive margin is a




Figure 2 18

(Passive Margin) Continental Shelf (19 mi. off of Atlantic City, NJ)

Figure 2.18

Tom’s Canyon

Shelf break

The california coast

The California Coast



Active coast ca

Active Coast (CA)



  • 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)?

Figure 2 24






(at a




Figure 2.24

Black smoker cross section

Black Smoker, cross section

Who are we

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.

The ocean

Major features of Sea Floor

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