27.3% of the Ocean Floor Has Now Been Mapped

A map of the world showing where the seafloor has been mapped. New bathymetric data added in the past year is shown in red.
Seabed 2030

The Seabed 2030 project announced on Saturday that “27.3% of the world’s ocean floor has now been mapped to modern standards. The increase in data represents more than four million square kilometres of newly mapped seafloor—an area roughly equivalent to the entire Indian subcontinent.” The above map shows the progress to date, with new bathymetric data added over the past year indicated in red. Data compiled by this project is freely available via GEBCO’s global grid.

Previously: Mapping the Ocean Floor by 2030; ‘Cartographically Speaking, Water Sucks’.

Seafloor Features Mapped by Satellite

A map of the world showing the vertical gravity gradient on the ocean floor. The gradient is used to model seafloor topography. NASA Earth Observatory/SWOT.
NASA Earth Observatory (Michala Garrison/SWOT data)

“Mapping the seafloor isn’t the SWOT mission’s primary purpose,” says the JPL, and yet the Surface Water and Ocean Topography (SWOT) satellite is being used for more than measuring sea surface height: those ocean surface topography measurements can be used to infer features on the seafloor. NASA Earth Observatory:

Because geologic features like seamounts and abyssal hills have more mass than their surroundings, they exert a slightly stronger gravitational pull that creates small, measurable bumps in the sea surface above them. These subtle gravity signatures help researchers predict the kind of seafloor feature that produced them.

[…] Through repeated observations, the satellite is sensitive enough to pick up these minute differences, with centimeter-level accuracy, in sea surface height caused by the features below. David Sandwell, a geophysicist at Scripps Institution of Oceanography, and his colleagues used a year’s worth of SWOT data to focus on seamounts, abyssal hills, and underwater continental margins, where continental crust meets oceanic crust.

[…] Areas of decreased gravity (purple) are affiliated with depressions on the seafloor, while areas of increased gravity (green) indicate the locations of more massive, elevated features.

Only about a quarter of the seafloor has been mapped with traditional sonar methods, so you can see how a gap is being filled here. Next up is calculating the depth of the features being detected through this method.

‘Cartographically Speaking, Water Sucks’

Last October, on her Huge If True YouTube channel, Cleo Abram explored the state of deep ocean mapping, why it lags behind our mapping of, say, Mars, and what’s being done to chart the ocean floor at a higher resolution than currently exists (e.g. the Seabed 2030 project). All told this is a good and enthusiastic primer for the relatively uninitiated (though I do have to quibble with the statement that Marie Tharp’s maps have “largely been forgotten by history,” but then I’ve seen rather a lot about Marie Tharp’s maps and am a bit of an outlier).

Marie Tharp as Google Doodle

Google Doodle of Marie Tharp (screenshot)

Marie Tharp is the subject of today’s Google Doodle, with an interactive narration of her life story. That story—how Tharp’s pioneering work mapping the ocean floor helped prove the theory of continental drift—is familiar to long-time readers of this blog: this is the 12th post I’ve made about the legendary cartographer. But someone is going to be one of today’s lucky 10,000 because of this, and that’s not a bad thing.

Ortelius was a Google Doodle in May 2018.

More on Marie Tharp

A new article on the life and career of Marie Tharp, written by our friend Betsy Mason, was published by Science News earlier this month. Plenty has been written about Tharp, whose work mapping the ocean floor helped provide the evidence for continental drift: numerous articles, a 2012 biography, two books for children just last year. But that doesn’t mean that there aren’t still people who still haven’t heard of her, and should.

Marie Tharp at 100

July 30 marks the 100th anniversary of the birth of pioneering ocean cartographer Marie Tharp, whose seafloor maps provided evidence of continental drift. Columbia University’s Earth Institute is marking the event with blog posts, interviews, workshops and other social media and multimedia activity. See, for example, this overview of her legacy by Marie Denoia Aronsohn and a reprint of Tharp’s own piece, “Connect the Dots: Mapping the Seafloor and Discovering the Mid-ocean Ridge.”

The anniversary probably explains why two books about Tharp, aimed at children, are coming out this year:

Ocean Speaks: How Marie Tharp Revealed the Ocean’s Biggest Secret
by Jess Keating
Tundra Books, 30 Jun 2020
Amazon (Canada, UK) | Apple Books | Bookshop


Marie’s Ocean
by Josie James
Henry Holt, 22 Sep 2020
Amazon (Canada, UK) | Apple Books

Add those to Robert Burleigh’s Solving the Puzzle Under the Sea: Marie Tharp Maps the Ocean Floor (2016), also aimed at young readers, and Hali Felt’s 2012 biography of Tharp (for adults), Soundings, which I review here.

Older posts about Marie Tharp can be found here.

Update, July 30: Suzanne O’Connell at The Conversation: “As a geoscientist, I believe Tharp should be as famous as Jane Goodall or Neil Armstrong. Here’s why.”

Heinrich C. Berann

Henrich C. Berann, “Panorama of Denali,” 1994. U.S. National Park Service.

I can’t believe that, other than a brief mention in 2010, I’ve never written anything about the cartographic artist Heinrich C. Berann (1917-1992), whose work includes panoramic paintings for National Geographic and, in his later years, for the National Park Service. (To be honest, they remind me of Jim Niehues’s ski resort maps, but that surely should be the other way around.) He also worked with Marie Tharp and Bruce Heezen to turn their physiographic maps of the ocean floor into works of art.

Some links: Kottke looks at his panoramic paintings; so did All Over the Map last year. Also last year, The Map Designer has examples from Berann’s entire career. This site is maintained by one of Berann’s grandsons.

Soundings

I’ve been meaning to read Soundings, Hali Felt’s biography of Marie Tharp, since it came out in 2012. Since then I’ve seen a flurry of articles, interviews, videos and other tributes concerning Tharp, whose reputation, which grew during her lifetime, continues to grow in the 12 years since her death in 2006 at the age of 86.

The bare bones of Tharp’s story are therefore fairly well known: while mapping the floor of the Atlantic Ocean, she discovered the presence of the Mid-Atlantic Ridge—and, more specifically, its rift valley, providing tangible evidence of continental drift. Because continental drift was at that point considered to be a crackpot theory, it took some doing for Tharp’s discovery to be accepted; and when it was her contributions were to some extent minimized.

While Felt’s book is positioned as a biography, its strength is in the details of that pivotal discovery: how and where it was made, and by whom, and in what context. Tharp’s work was not done in a vacuum, and how and why she was where she was is important. Felt sets the stage for us: not only does she take us through Tharp’s early childhood and rather variegated education and her arrival in 1948 at the Lamont Observatory, she gives us a short history of that Observatory, of the theory of continental drift, of her colleagues—notably her lifelong collaborator (and possibly life partner) Bruce Heezen and Observatory director (and sometime antagonist) Maurice Ewing. More than anything else, Soundings provides context for Tharp’s discovery: by the time we’re done, we know how important it was, and why. We’ve been well briefed.

Physiographic Diagram: Atlantic Ocean

Felt is less successful in building a portrait of Tharp herself. Some areas of her non-work life—her childhood, family and college education, for example—are extremely well covered, but other areas have considerable gaps, particularly those involving her personal life. The nature of Tharp’s relationship with Heezen is only hinted at, as is an early, unsuccessful marriage to someone else. Her later life, supported by a motley gang of eccentrics called Tharpophiles, is also incompletely covered. The elisions, however unintended, are frustrating. I suspect the author was a prisoner of her source material, which in places she follows very closely; I would have liked it if more had been done to fill in the gaps.

Soundings was published in hardcover by Henry Holt in 2012. It’s available in paperback and ebook from Picador.

Amazon | iBooks

Mapping the Ocean Floor by 2030

Newsweek looks at efforts by a group of scientists and mariners to map most of the ocean floor by the year 2030. The objective was endorsed by a meeting of GEBCO, the General Bathymetric Chart of the Oceans, last June. The scale of the project is vast:

To date, more than 85 percent of the seafloor has not been mapped using modern methods. Since 70 percent of the Earth is covered in oceans, this means that we quite literally don’t know our own planet. “We know the surface of Mars better than we do the seafloor,” says Martin Jakobsson, a researcher at Stockholm University.

[Leventhal/MAPS-L]

Monterey Bay Area Seafloor Maps Released

New seafloor maps of the Monterey Bay area have been released as part of the California Seafloor Mapping Program. The maps “reveal the diverse and complex range of seafloor habitats along 130 kilometers (80 miles) of the central California coast from the Monterey Peninsula north to Pigeon Point.” [Leventhal Map Center]

Previously: Mapping the California Sea Floor.

Seafloor Gravity Map

seafloor
NASA Earth Observatory map by Joshua Stevens

The ocean floor is still very much terra incognita: only 5 to 15 percent of it has been mapped via bathymetry. But using military satellite measurements of the Earth’s shape and gravity field, a new map of the ocean floor has been created. “The result of their efforts is a global data set that tells where the ridges and valleys are by showing where the planet’s gravity field varies. […] Shades of orange and red represent areas where seafloor gravity is stronger (in milligals) than the global average, a phenomenon that mostly coincides with the location of underwater ridges, seamounts, and the edges of Earth’s tectonic plates. Shades of blue represent areas of lower gravity, corresponding largely with the deepest troughs in the ocean.”