Presentation on theme: "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."— Presentation transcript:
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
Interior of Earth
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 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) 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)
So…WHERE DID WE START AND WHERE ARE WE NOW?
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) 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
Major features of Sea Floor
CO 2 Mid-Atlantic Ridge (above sea surface in Iceland)
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.
Figure 2.07 Paleomagnetism: Normal ridge crests (but Reversed in other locations)
We get: Plate boundaries With geologic activity, such as earthquakes, that (may) correspond w/ these plate boundaries
Earthquake and Volcano distribution
Lithospheric plate boundaries
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) 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)
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 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 miles BELOW the oceans (water) surface!
Figure 2.17 Continental margin
Active vs. Passive Margins An active margin is a geologically very “active” area; whereas a Passive margin is a geologically in-active area.
Figure 2.18 (Passive Margin) Continental Shelf (19 mi. off of Atlantic City, NJ) Shelf break Tom’s Canyon
The California Coast Monterey Canyon
Active Coast (CA)
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)?
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.