Welcome to Poorna Pal's 'Earth Revealed' telecourse (Geology — 101: Physical Geology; section #7695) at the Glendale Community College

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Earth's Oceans

|Module 1 Home     05/05/15

Home | Quizzes  |  Module 1 | Module 2 | Module 3 | Module 4 | Module 5

Help available 'Online'

Help available at this site

• Practice Exercise/Quiz at Book's Website:

  • Internet Exercises

  • 'End-of-Chapter' Questions

  • "Multiple" Choice Quiz

  • "True/False" Quiz

  • "Matching" Quiz

• Chapter Links at the Book's Website:

  • Overview

  • Learning Objectives

  • Glossary

  • Web Links

  • Related Readings

  • "Virtual Vista"

  • Animations

  • Boxed Readings

• Quizzes etc:

  Information on Quiz-1, Test-1 and other Quizzes, Tests, Class Meetings, Final Examination

• Video Episodes:

  • Episode 104: The Sea Floor

  • ŠC—m’ê THE SEA FLOOR(’n‹…‚ð’T‚é EARTH REVEALED�@4)�@–{‘̉¿Ši18,000‰~

• Video Study Guide:

  • Mike Strickler's Study Guide for the Video Episode 104

  • Ruth Lebow's Study Guide for Earth Revealed

• Poorna's Outlines:

  • Earth's Oceans

You may need to download the Adobe Acrobat Reader to view this PDF file

• Textbook Chapter: 3 (The Sea Floor)

This chapter describes the morphology of the ocean floor which is significantly different from that of the land. Beneath the thin layer of sediments, the ocean floor rocks are basaltic. This points to their volcanic origin. Unlike the mountains on land, the axis of a mid-ocean ridge is typically a median valley. These ridges also have symmetric bathymetric and age profiles, with youngest rocks at the ridge axis and progressively older rocks farther from the axis. This leads to the model of sea floor spread, and the mapping of the ocean floor using marine magnetic anomalies. The most conspicuous feature of the ocean floor, however, is the young age of these rocks. Indeed, whereas rocks on land have ages ranging from the present to up to about 4.2 Ga (billion years), ocean floor rocks older than ~200 Ma (million years) do not exist. Clearly, about 72% of the earth's surface that is now covered by the oceans has been created within the past ~200 Ma. Since earth's total surface area has remained substantially unchanged over the geologic past, the most widely accepted explanation is that, as new surface area is created at the spreading submarine ridges, an equal surface area is lost in subduction zones. In the oceans, such zones exist in the form of deep sea trenches. Understanding the sea floor and its evolution is therefore crucial to the plate tectonics postulate discussed in the next module.

(based on the chapter introduction)

• Some Dictionaries and Glossaries ONLINE:

  • McGraw-Hill 'Access Science' Dictionary

  • Dictionary of Scientific Quotations

  • Harcourt Dictionary of Science and Technology

  • Interesting WWW sites about science

  • Enchanted Learning Science Dictionaries

  • Glossarist Earth Science Glossary

  • USGS Glossary

  • USGS Photo Glossary of Volcanic Terms

  • USGS Water Science Glossary of Terms

  • GeoMan's Glossary of Earth Science Terms

  • Glossary of Natural History Terms

  • Desert Environment and Geology

Click on the image below for the interactive high resolution image of global ocean bathymetry at NOAA (National Ocean & Atmospheric Administration) Laboratory for Satellite Altimetry.

Clicking on the image below will take you to the NGDC (National Geophysical Data Center) 2- minute latitude/longitude grid (1 minute of latitude = 1 nautical mile, or 1.852 km) color relief images of the earth's surface.

Clicking on the map alongside will enable you to view and download the original digital map of ocean floor ages from the NGDC (National Geophysical Data Center).

Sea-Floor Spreading and Subduction Model This USGS Open-File Report 99-132 (On-Line Edition) by John C. Lahr describes how to build a model of the outer 300 km (180 miles) of the Earth that can be used to develop a better understanding of the principal features of plate tectonics, including sea-floor spreading, the pattern of magnetic stripes frozen into the sea floor, transform faulting, thrust faulting, subduction, and volcanism.

North Cascades Geology: Sea-Floor Spreading This USGS page compares magnetic stripes on the sea floor to the magnetic reversals in basalt on the land as seen in a vertical cliff and explains how this supports the sea floor spread model.

Click on the title below to read David Sandwell's article 'EXPLORING THE EARTH FROM MARS'.