Exploring the Global Mid-Ocean Ridge: A Quarter-Century of Discovery

By Macdonald, Ken C. | Oceanus, Spring-Summer 1998 | Go to article overview

Exploring the Global Mid-Ocean Ridge: A Quarter-Century of Discovery


Macdonald, Ken C., Oceanus


Professor of Marine Geophysics, University of California, Santa Barbara

There is a natural tendency in scientific investigations for increased specialization. Most important advances are made by narrowing focus and building on the broad foundation of earlier, more general research. This was certainly the case for the French-American Mid-Ocean Undersea Study submersible expedition launched 25 years ago. The mid-ocean target was the rift valley of the Mid-Atlantic Ridge spreading center. In the 1950s, Bruce Heezen of Columbia University's Lamont Geological Observatory collected wide-beam echo sounder cross sections of the rift valley and correctly surmised that it is part of a global rift system that wraps around the earth like the seam of a baseball. British and Canadian marine geologists took the next step and mounted a series of ambitious expeditions to study the Mid-Atlantic Ridge near 45 [degrees] N using every geophysical and geological tool available at the time. An American group focused its attention on the rift valley near 22 [degrees] N. However, the floor of the rift valley itself, where new oceanic crust intrudes and erupts, remained as obscure and enigmatic as ever. The hundreds of active volcanoes that occupy the floor of the rift valley were hidden from depth recorders by booming side-echoes of sound reverberating from the steep, 1,000 meter high cliffs of the valley.

Then, in 1972, three years after Neil Armstrong left the first human footprint on the moon, an international group of marine geologists initiated a bold advance: to explore the rift valley with the only vehicles that could take them there - submersibles. Despite a decade or so of deep-sea submersible experience, there was still considerable skepticism about their usefulness as scientific tools. However, those who believed prevailed, the French made the bathyscaphe Archimede and the submersible Cyana available, and the US offered the reliable underwater workhorse Alvin. The French-American Mid-Ocean Undersea Study (Project FAMOUS) was underway.

Precise base maps for the dive expedition were assembled using a US Navy classified multi-beam echo sounder, a French narrow beam echo-sounding system, and a deeply towed instrument package from the Marine Physical Laboratory at Scripps Institution of Oceanography (University of California, San Diego). I recall the hushed amazement aboard the research vessel Knorr when we first saw high-resolution, deep-tow depth profiles slowly burned into the paper of our malodorous precision depth recorders. The rift's center shape finally was revealed clearly as a deep trough nested within a wider rift valley, which contained many hills that appeared to be volcanic cones. These sonar records were the base maps for the dive expedition, and a team of geologists was assembled to be the first mid-ocean ridge divers using Archimede in the summer of 1973.

Alvin and the other submersibles certainly proved their worth as scientific tools during FAMOUS, and they have been heavily used ever since. Indeed, the French and also the Japanese have replaced their original subs with vehicles that can dive twice as deep, to depths exceeding 6,000 meters. The FAMOUS geological work showed that the rift valley is created by large faults that break through the newly formed oceanic crust and that active volcanoes are abundant along the rift valley floor. The youngest volcanoes form a narrow zone of oceanic crustal creation only 1 to 2 kilometers Wide, remarkable when compared to the dimensions of the plates, which are thousands of kilometers across. FAMOUS magnetic, geochemical, gravitational, and seismic studies resulted in the most detailed and comprehensive investigation of a spreading center up to that time. So much was learned that in 1977 two entire issues of the Bulletin of the Geological Society of America were dedicated to the results of this unprecedented expedition.

But the age of discovery on mid-ocean ridges was only beginning. …

The rest of this article is only available to active members of Questia

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

Exploring the Global Mid-Ocean Ridge: A Quarter-Century of Discovery
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Author Advanced search

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.