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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
Rift Communities
OCEAN BOTTOM
Continental Margins
Submarine Canyons
Trenches
Life on the Ocean Floor
COMPOSITION OF THE SEAFLOOR
Hydrogenous sediments
Biogenous sediments
Terrigenous sediments
Latitude
Longitude
Divisions of Latitude and Longitude
Navigating the Ocean
Chapter Objectives
• 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.
24 Geology of the Ocean
Key Terms
world ocean
ocean basin
ocean
Southern or Antarctic
Ocean
mid-ocean ridge (ridge
system)
oceanic basaltic crust
rift valley
fracture zone
faults
transform fault
escarpment
rift zone
Gondwanaland
continental shelves
continental slope
shelf break
submarine canyons
turbidity currents
hydrogenous sediments
biogenous sediments
terrigenous sediments
cosmogenous sediments
ooze
Antarctic Circle
meridian
prime meridian
Greenwich meridian
international date line
Chapter Summary
1. The world ocean is believed to have formed approximately 4.2 billion years ago
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
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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
4. The seafloor is covered with a variety of sediments that can be classified according to
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
Chapter Outline
I. World Ocean
A. When the Earth was formed, its surface was too hot for water to exist outside vapor state.
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.
26 Geology of the Ocean
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.
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
C. Moving continents.
1. In the 17th century, Sir Francis Bacon suggested that the continents might have
been connected.
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).
III. Ocean Bottom
A. Bathygraphic features.
B. Continental margin.
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1. Continental shelf.
D. Continental rise.
E. Shaping the continental shelves.
F. Ocean basin.
1. Abyssal plain.
G. Life on the ocean floor.
1. No light on abyssal plain means no photosynthesis.
IV. Composition of the Seafloor
A. Hydrogenous 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.
B. Reference lines.
1. Latitude: equidistant lines parallel to the equator and perpendicular to the
Earth’s axis of rotation.
a. Tropic of Cancer.
2. Longitude.
a. Prime meridian.
b. International date line.
28 Geology of the Ocean
Suggestions for Presenting the Material
1. There are many computer animations of Pangea separating with the geological time
2. The Savage Earth series on PBS has several episodes focusing on seismic activity and
3. Have students plot their latitude and longitude, and check these calculations with a
Classroom Discussion Ideas
1. Explain how the formation of the world ocean is related to the beginnings of organic
life on the planet.
Videos, Animations, and Websites
Videos
Earth Revealed: Birth of a Theory and Plate Dynamics. (Annenberg Video on Demand)
Savage Earth. (PBS series)
This series covers the drama of plate tectonics and its impacts.
How the Earth Was Made. (The History Channel)
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Animations
Earthguide Global Plate Reconstructions.
An animation detailing the movement of the Earth’s plates over the last 650 million
years.
Websites
USGS: The Story of Plate Tectonics.
Geology: An Introduction.
A useful website from Professor Haakon Fossen, University of Bergen, on the basics of
geology.
Ocean’s Alive.
What Is Navigation?
Suggested Answers to End of Chapter Questions
Multiple Choice
1. d. 71%
2. d. 4
10. a. determine latitude
Matching
1. b.
6. b.
11. c.
16. e.
Short Answer
1. What was the Earth’s early atmosphere like and how did it influence the evolution of
cells?
The Earth’s early atmosphere was formed from gases that escaped from Earth’s
2. What evidence supports the theory of plate tectonics?
Evidence for plate tectonics includes the fact that continental margins seem to fit
3. What processes are responsible for the formation and sculpting of the continental
shelves?
Continental shelves are the shallow seaward extension of the continent. The
4. What is a seamount and how is it formed?
5. Explain how the oceans were originally formed.
6. Explain how time can be used to help determine a ship’s longitude.
In the 1500s, the Flemish astronomer Gemma Frisius proposed that longitude
could be determined by setting a clock to exactly noon when the sun was at its
7. Explain how biogenous sediments are formed.
Biogenous sediments are formed when marine organisms with calcareous shells
8. Describe how the continents are thought to move apart.
Continents pull apart because rising convection currents in the mantle form new
32 Geology of the Ocean
9. What is the global positioning system?
GPS utilizes a system of satellites that can be used to find an exact position
Thinking Critically
1. How would you expect continental drift to affect the distribution of bottom-dwelling
marine organisms?
The ocean bottom is not densely populated with living organisms, owing to
2. Would you expect to find more actively swimming fish species above the continental
shelves or in the large expanses of open sea? Explain.
Fish will be more common over continental shelves because of nutrient input from
3. While doing research along a coastal area, you discover that the bottom sediments are
predominantly calcareous ooze. What does this imply about the local conditions?
Calcareous deposits are formed at ocean depths not exceeding 4000 meters, below
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Suggested InfoTrac® Articles
“Blindsided by Ferocity Unleashed by a Fault.” Chang, K. The New York Times, (March
2011).