Mowing the Lawn to Map the Ocean Floor, One Long, Slow Pass at a Time

A scuba diver explores an old, wooden shipwreck in Lake Michigan. The waters of the Great Lakes are so cold that they preserve the many wrecks on bottom.

Related underwater reading: Gene and Sandy Ralston use specialized sonar on their boat to locate bodies under water.

As Matthew Braga reports at The Verge, we’re flithy rich with land maps, ones that show us “how the planet has changed, and how we’ve changed the planet,” over time, but that’s not the case where land is covered by water. The treasure trove of information to be gleaned from mapping the world’s oceans could help scientists understand climate change. Enter BEN, an automated map-making boat Braga met while it plotted Lake Huron. According to Braga, “we’ve mapped just 9 percent of the world’s oceans to modern standards,” which is “why BEN and vehicles like it hold so much promise.” (Note, the fantastic illustrations in this piece were done by the incomparable Zoë van Dijk. Check out some of her illustrations for Longreads.)

It was just past midnight when the Ironton punched a 200-square-foot hole in the side of the Ohio. It was dark, the waters were rough, and the Ohio, a wooden bulk freighter loaded with flour and feed, was no match for the Ironton, a schooner heavy with coal. The Ohio sank within half an hour, and the Ironton soon followed, taking five of its crew down too.

Their ghostly hulls have sat largely undisturbed at the bottom of Lake Huron since colliding in late September 1894 — just two of the many wrecks that lie in a treacherous stretch of water called Thunder Bay off Michigan’s northeastern coast. Some are so well preserved by the lake’s frigid freshwater that their unbroken masts point definitely towards the surface, rigging still intact. Others have dishes in the cupboards, a century late for dinner. A few years ago, local media reported that divers found a 1927 Chevrolet Coupe amid the wreckage of a steamship, covered with algae and barnacles, but nonetheless pristine. You can thank the rocky shoals, frequent fog, and sudden gales of Thunder Bay for turning what was once the bustling marine interstate of America’s early industrial age into a modern-day museum of Great Lakes maritime history. Locals called it “Shipwreck Alley.”

Divers flock from all over the world to see the wrecks for themselves each year — and last spring, they were joined by an unusual interloper: an autonomous boat named BEN. BEN is a self-driving boat that’s been tasked with making maps, and it was brought to Thunder Bay to help lay bare the long-lost secrets of the lakebed.

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