The Ocean Floor and Sea Floor Spreading

The Floor of the Earth's Ocean Basins

The class notes for this chapter are the same as for the previous chapter. You may view the Oceans power point presentation shown in class.

Chapter Objectives

After reading Chapter Eighteen, you should be able to:
1. Portray a continental margin, showing the shelf, slope, and rise.
2. Describe the development of turbidity currents in submarine canyons.
3. Illustrate the features of deep-ocean basins.
4. Describe the features of coral reefs, atolls, and seafloor sediments.
5. Review the concept of seafloor spreading.
6. Relate the development and breakup of Pangaea to the concepts of hotspots and seafloor spreading.

Introduction

When I was a freshman taking my first course in Physical Geology (1959) a commonly held point of view was that the ocean basins were permanent features. There was a great deal of interest in being able to sample sediment and rocks that were assumed to represent a "nearly complete" history of the Earth. Today we know that the Earth's ocean basins are relatively young; the oldest oceanic crust is Jurassic in age. We know that ocean basins form, evolve, collect sediment, and are eventually "destroyed".

Class Notes



Internet Resources

1. Dr. Robert Ballard, "discoverer" of the Titanic is in charge of the Jason Project. Read about their expedition to the Mediterranean Sea and hydrothermal vents

2. Peter Bentchly (Mr. Jaws) has a good essay that you should read: JAWS

3. The Theory of Continental Drift

   "The drifting of tectonic plates is an on-going process that has changed the configuration of the continents since their formation in Archean time."

Virtual Field Trip

"Located on the southeast margin of the large Enchanted Rock Batholith, the granite exposed is one of the Town Mountain Granite suite and is of Precambrian age -- approximately 1 billion years old."

Geologists use field trips much like a person in business uses case histories. The field trip to Enchanted Rock illustrates how detailed field studies can help elucidate the structure of the Earth.

Self-Quiz

Learning about geology from a computer screen is only half as fun as enjoying it in the field!
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Copyright by John C. Butler, July 29, 1995