GSA Today Geologic Past Series

As managing editor for The Geological Society of America’s (GSA) science & information magazine, GSA Today, I develop and write “filler” articles to work in around the science and news as needed. Most (if not all) magazines are built in blocks of 8 or 16 pages. You can’t have an odd number of pages; therefore, there are times I need to quickly get another article or house ad into the issue at the last minute to round things out.

In 2005 (my first year as managing editor of GSA Today, after serving as editorial assistant since 2003), I developed the “Geologic Past” series, pulling content from past issues of GSA’s first journal, GSA Bulletin (begun in 1889). The early issues of GSA Bulletin were not online, and I found some real “gold nuggets” in the older articles that I wanted to share with a modern audience.

Since 2005, I have written 17 articles (two of which are “in press” [not published yet]). I have written the two in-press articles based on abstracts from GSA’s 1963 annual meeting, in keeping with GSA’s 125th anniversary celebration this year (which looks back at the past 50 years of GSA science).

In the process of writing these articles, I always learn new, and to me, fascinating things, mostly based on the language in the article or the people involved. This is very much the case in one of the pending Geologic Past articles, and I have decided I want to pre-publish that article here. I don’t get a byline on the Geologic Past articles — it’s more or less implied that text without an author listed is written by the editorial staff (just me, in this case), and for this article, I’d like to know folks know I wrote it. Not for credit or anything like that — more to know what I find interesting (or NEATO) and, in this case, want more people to know about than just those (about 25,000 people) who read GSA Today. This one’s going into the April/May 2013 issue, unless I run out of room and have to cut it at the last minute. Editor’s note: this never did get into GSA Today.

Speaking of cutting: I have taken out the first paragraph and title of the article because they don’t work in this context. Also, I have drawn heavily from the writing of others, and credit is given both in the text and a list of references cited at the end of the article.


Marie Tharp

Marie Tharp and her globe of the seafloor. Image courtesy Lamont-Doherty Earth Observatory.

    In the past 50 years, much has changed in geoscience, not the least being the change in attitude toward the idea of continental drift from “an outrageous hypothesis” (Wise, 1963, p. 357) to the widely accepted theory of plate tectonics.

    GSA met for its 75th Annual Meeting in New York on 17–20 November 1963. More than 90 papers were presented there. A scan of the abstracts with the view to advancements in geoscience brings up many highlights, but one that stands out the most is the presentation by Bruce C. Heezen and Marie Tharp: “Oceanic Ridges, Transcurrent Faults, and Continental Displacements,” which is reproduced below:

    The Mid-Oceanic Ridge, a tectonic belt nearly 40,000 miles long and 200–1500 miles wide that girdles the earth, has been offset in numerous places by transcurrent faults in the Atlantic, Indian, and Pacific oceans. Although the axis of the ridge, the site of a shallow-focus earthquake belt, is now being deformed, the fracture zones are aseismic except in the crest zone of the Mid-Oceanic Ridge. The flanks of the Mid-Oceanic Ridge are aseismic and presumably of considerable age.
Recent investigations in the Indian Ocean reveal several north-south aseismic ridges and east-west aseismic fracture zones which together with the forked Mid-Oceanic Ridge produce a tectonic pattern much more complex than that of the other oceans.

    The location and origin of the Mid-Oceanic Ridge, of oceanic rises, aseismic ridges, and transcurrent fault systems must be accounted for in any hypothesis of continental displacement despite unique or exotic assumptions as to strength, viscosity, or composition of the oceanic crust and mantle. (p. 78)

    The team of Heezen (1924–1977) and Tharp (1920–2006) worked together from the mid-1940s to 1977. According to Cathy Barton, who wrote a biography of Tharp in 2002, the two “began mapping the sea floor to improve understanding of ocean-basin geology and to connect the oceans to the continents theoretically” (p. 215). During this process, writes Barton, Tharp “made an important discovery: a rift on the Mid-Atlantic Ridge.” It was Tharp’s interpretation of Heezen’s sea-floor data, says Barton, that “contributed to the reintroduction of continental drift theory and the 1960s geological revolution” (p. 215).

    Tharp is celebrated in the 2012 book, Soundings: The Remarkable Woman Who Mapped the Ocean Floor, by Hali Felt, as well as numerous articles, including a 7 Oct. 2011 “History of Geology” blog post, “Marie Tharp: The map that changed the world,” by David Bressan. The 1977 World Ocean Floor Map created by Heezen and Tharp is highlighted in a 24 Dec. 2010 “Georneys” blog post, “A famous ocean floor map,” by Evelyn Mervine, who writes that “prior to the pioneering work of Heezen and Tharp, almost nothing was known about the topography of the seafloor.”

    That fact is acknowledged in a 2008 GSA Joint Meeting abstract by Gary North: “Marie Tharp: The lady who showed us the ocean floors.” North writes that “Bruce [Heezen] sailed the oceans collecting the data and oversaw the projects, but the person who turned the Precision Depth Recordings and other geoscience data into the two-dimensional views of the bottoms was Marie.” North, the curator of Tharp’s cartographic materials in the Library of Congress, continues,

    Marie’s discovery of the trench in the middle of the Mid-Atlantic Ridge and her linkage of the major crustal plates for 40,000 miles around the Earth, showed us, and thus confirmed, the concept of plate tectonics and crustal movement. For the “non-drifters” of the time, which included their boss Dr. Maurice Ewing, this was a somewhat revolutionary concept which eventually erupted in conflicts, suspensions, and academic rivalry.

    Later in life, however, Tharp received many honors, including Columbia University’s first Heritage Award, the National Geographic Society’s Hubbard Medal, and the Woods Hole Oceanographic Institute Women Pioneers in Oceanography Award (North, 2008). In 1977, according to a New York Times obituary, Tharp was “honored by the Library of Congress as part of the 100th anniversary of its geography and map division.” The Earth Institute at Columbia’s Lamont-Doherty Earth Observatory established the Marie Tharp Fellowships in the Earth, Environmental, and Ocean Sciences to encourage women to study geoscience there.

    In her autobiographical notes related to the acceptance of the Woods Hole award, Tharp writes,

Not too many people can say this about their lives: The whole world was spread out before me (or at least, the 70 percent of it covered by oceans). I had a blank canvas to fill with extraordinary possibilities, a fascinating jigsaw puzzle to piece together: mapping the world’s vast hidden seafloor. It was a once-in-a-lifetime—a once-in-the-history-of-the-world—opportunity for anyone, but especially for a woman in the 1940s. The nature of the times, the state of the science, and events large and small, logical and illogical, combined to make it all happen. (Tharp, 2006)

Barton, C., 2002, Marie Tharp, Oceanographic Cartographer, and Her Contributions to the Revolution in the Earth Sciences: London, Geological Society Special Publication 192, p. 215–228, doi: 10.1144/GSL.SP.2002.192.01.11.
Bressan, D., 2011, Marie Tharp: The map that changed the world: History of Geology blog, 7 Oct. 2011, (last accessed 24 Jan. 2013).
Felt, H., 2012, Soundings: The Remarkable Woman Who Mapped the Ocean Floor: New York, Henry Holt and Company, 240 p.
Fox, M., 2006, Marie Tharp, Oceanographic Cartographer, Dies at 86: New York Times, 26 Aug. 2006, (last accessed 24 Jan. 2013)/
Heezen, B.C., and Tharp, M., 1964, Oceanic Ridges, Transcurrent Faults, and Continental Displacements, in Abstracts for 1963: Abstracts of papers submitted for six meetings with which the Society was associated: New York, Geological Society of America, GSA Special Paper 76, 1964, 341 p.
Mervine, E., 2010, A famous ocean floor map: Georneys blog, 24 Dec. 2010, (last accessed 24 Jan. 2013).
North, G., 2008, Marie Tharp: The lady who showed us the ocean floors: 2008 Geological Society of America Joint Annual Meeting, Abstract 523-10, (last accessed 24 Jan. 2013).
Tharp, M., 2006, Marie Tharp bio: Woods Hole Oceanographic Institution, 12 Dec. 2006, (last accessed 24 Jan. 2013).
Wise, D.U., 1963, An Outrageous Hypothesis for the Tectonic Pattern of the North American Cordillera?: GSA Bulletin, v. 74, no. 3, p. 357–362, doi: 10.1130/0016-7606(1963)74[357:AOHFTT]2.0.CO;2.

Marie Tharp and Bruce Heezen

Marie and Bruce and their seafloor map. Image courtesy Lamont-Doherty Earth Observatory.

About Kea Giles

Writer, photographer, editor, wife, friend, sister, dog mother.
This entry was posted in educational, fascinating, science, Uncategorized and tagged , , , , , , . Bookmark the permalink.

1 Response to GSA Today Geologic Past Series

  1. joy says:

    They gave me a copy of that map and it’s been on the wall. What do I look for to find out what what appears to be a hole NE of Solomon Islands actually is? It’s very obvious on the earthquake maps.


Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s