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GEOLOGY OF THE OCEAN
Chapter Outline
WORLD OCEAN
Primitive Earth and Formation of the
Ocean
Ocean and the Origin of Life
The Ocean Today
THE CHANGING SEAFLOOR
Layers of the Earth
The Theory of Plate Tectonics
Moving Continents
Evidence of Seafloor Movement
Rift Communities
OCEAN BOTTOM
Continental Margins
Submarine Canyons
Continental Rise
Shaping the Continental Shelves
Ocean Basin
Abyssal Plains and Hills
Seamounts
Ridges and Rises
Trenches
Life on the Ocean Floor
COMPOSITION OF THE SEAFLOOR
Hydrogenous sediments
Biogenous sediments
Terrigenous sediments
Cosmogenous sediments
FINDING YOUR WAY AROUND THE SEA
Maps and Charts
Reference Lines
Latitude
Longitude
Divisions of Latitude and Longitude
Navigating the Ocean
Principles of Navigation
Global Positioning System
KEY CONCEPTS
ARE YOU STILL WONDERING?
QUESTIONS FOR REVIEW
SUGGESTIONS FOR FURTHER READING
Chapter Objectives
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Describe the formation of the early ocean and its role in the beginning of life on
Earth.
Identify the important features of the Earth today.
Diagram the layers of the Earth and describe their composition.
Summarize the theory of plate tectonics and the various zones between plates.
Compare and contrast convergent and divergent plate boundaries.
Explain the evidence for seafloor spreading and recognize that the historical
locations of the continents are very different than their current positions.
Identify the various geological features on the ocean bottom.
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Compare and contrast the various ocean sediments and their origins.
Describe the ways mariners navigated the oceans historically.
Explain the process of GPS.
Key Terms
world ocean
ocean basin
ocean
Southern or Antarctic
Ocean
sea
gulf
mantle
crust
lithosphere
asthenosphere
magma
mid-ocean ridge (ridge
system)
oceanic basaltic crust
rift valley
fracture zone
subduction zone
seafloor spreading
theory of plate tectonics
divergent plate boundaries
convergent plate
boundaries
faults
transform fault
escarpment
rift zone
Gondwanaland
Pangea
Laurasia
continental drift
rift communities (deep-sea
vent communities)
bathygraphic features
continental margin
continental shelves
continental slope
shelf break
submarine canyons
turbidity currents
continental rise
abyssal plain
abyssal hills
seamount
island arcs
guyot
hydrogenous sediments
biogenous sediments
terrigenous sediments
cosmogenous sediments
ooze
maps and charts
reference lines
equator
parallel
Tropic of Cancer
Tropic of Capricorn
Arctic Circle
Antarctic Circle
meridian
prime meridian
Greenwich meridian
international date line
chronometer
global positioning system
(GPS)
Chapter Summary
1. The world ocean is believed to have formed approximately 4.2 billion years ago
when water vapor escaping from minerals in the Earth cooled and condensed on the
Earth’s surface. Today, the four major oceans are the Atlantic, Pacific, Indian, and
Arctic Oceans.
2. The continental masses are not locked into position but are constantly moving at a
very slow rate. Continents move when the plates on which they rest move. The
crustal plates move horizontally when molten magma from the Earth’s core moves
to the crust and breaks through, pushing the plates apart and forming new crust.
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Geology of the Ocean
Old crust is removed in the deep trenches and other subduction zones of the ocean,
preventing the Earth from getting larger.
3. The seafloor can be divided into the continental margins, composed of the
continental shelf and the continental slope, and ocean basins. Sloping away from the
edge of the continental masses are the continental shelves. The transition between
the continental shelf and the deep seafloor is the continental slope. At the bottom of
the continental slope is the ocean basin. Some features of the ocean basin are the
abyssal plain, mountain ranges, ridges, valleys, trenches, and seamounts.
4. The seafloor is covered with a variety of sediments that can be classified according to
size or on the basis of their origin. Sediment particles can be formed by the action of
physical processes on rocks, from the shells of organisms, from the seawater, itself,
and from space.
5.
Navigators use charts and maps with lines of latitude and longitude to locate their
position while at sea. Lines of latitude run perpendicular to the long axis of the
Earth, which extends from pole to pole. Lines of longitude run perpendicular to the
lines of latitude. Modern navigational techniques use sophisticated electronic
equipment and satellites to help marine biologists find their location accurately
anytime, anywhere, and in any weather.
Chapter Outline
I.
World Ocean
A. When the Earth was formed, its surface was too hot for water to exist outside vapor state.
B. Oceans began to form 4.2 billion years ago and continued to evolve for the next 200
million years.
C. 70.8% of the Earth’s surface is currently covered by water.
D. Primitive Earth and the formation of the ocean.
1.
Primitive Earth was hot enough to melt iron and nickel in the planet’s core.
2.
Melting heavier elements moved toward the center of the planet, with lighter
elements moving toward the outside and cooling to form the Earth’s crust.
E. Oceans and the origin of life: first life forms evolved in the ancient ocean.
1.
20th century scientists believed that lightening, heat, and radiation may have
provided the energy necessary to synthesize the first organic molecules.
2.
Urey and Miller demonstrated that organic molecules could be synthesized from hot
gases in the primitive atmosphere.
F.
The ocean today.
1.
Ocean basins.
II. The Changing Seafloor
A. Layers of the Earth.
1.
Inner core.
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2.
Outer core.
3.
Lower mantle.
4.
Outer mantle.
5.
Crust—lithosphere, asthenosphere.
B. Theory of plate tectonics.
1.
In the early 1960s, H. H. Hess proposed that magma (molten rock) moved in
vertical convection currents in the asthenosphere.
2.
In areas where the convection cells cause the ocean floor to move in opposite
directions, magma comes to the surface and forms a volcanic ridge (mid-ocean
ridge).
3.
New oceanic crust is formed in these ridge systems (mountain ranges where
magma oozes out of the crust opening); oceanic crust is made of an igneous rock
called basalt.
4.
In some ridge systems, a valley (rift valley) runs parallel to the mountain range
in the center of the range; rift valleys are areas of volcanic activity.
5.
Subduction zone.
6.
Earthquakes and volcanoes coincide with the location of spreading centers and
subduction zones worldwide.
7.
Seafloor spreading.
8.
Divergent plate boundaries.
9.
Convergent plate boundaries.
C. Moving continents.
1.
In the 17th century, Sir Francis Bacon suggested that the continents might have
been connected.
2.
In the late 1800s, Eduard Suess suggested that the southern continents were
connected earlier in Earth’s geologic history; named this formation
Gondwanaland.
3.
In 1915, Alfred Wegener proposed a single supercontinent, termed Pangea.
4.
Wegener proposed that forces within the Earth broke Pangea apart into two
continents.
a. Northern continent, Laurasia (composed of North America, Europe, and
Asia).
b. Southern continent, Gondwanaland (composed of South America, Africa,
India, Australia, and Antarctica).
5.
Evidence for seafloor movement.
a. Glomar Challenger.
b. Magnetic field reversals.
6.
III.
Rift communities.
Ocean Bottom
A. Bathygraphic features.
B. Continental margin.
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Geology of the Ocean
1.
Continental shelf.
2.
Continental slope.
3.
Shelf break.
C. Submarine canyons.
1.
Turbidity currents.
D. Continental rise.
E. Shaping the continental shelves.
F.
Ocean basin.
1.
Abyssal plain.
2.
Abyssal hills.
3.
Seamount.
4.
Ridges and rises.
5.
Trenches.
G. Life on the ocean floor.
1.
No light on abyssal plain means no photosynthesis.
2.
Food web is dependent on organic matter from photic zone, above.
3.
Chemosynthesis, base of the food chain in hydrothermal vent communities.
IV. Composition of the Seafloor
A. Hydrogenous sediments.
B. Biogenous sediments.
C. Terrigenous sediments.
D. Cosmogenous sediments.
V.
Finding Your Way Around the Sea
A. Maps and charts: two-dimensional representations of the Earth’s surface, maps
represent terrestrial features while charts represent bathymetric features.
1.
Bathymetric charts.
2.
Physiographic charts.
B. Reference lines.
1.
Latitude: equidistant lines parallel to the equator and perpendicular to the
Earth’s axis of rotation.
a.
Tropic of Cancer.
b.
Tropic of Capricorn.
c.
Arctic Circle.
d. Antarctic Circle.
2.
Longitude.
a.
Prime meridian.
b.
International date line.
3.
Navigating the ocean.
4.
Sextet.
5.
Chronometer.
6.
Global Positioning System (GPS).
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