The tragic history of Bikini Atoll mapped: Scientists show huge craters in sea floor blasted by atom bomb tests

The new map provides evidence for these nuclear tests, say researches from University of Delaware

PUBLISHED DEC 11, 2019

The extent of damage caused by the US nuclear testing has now been mapped. These tests, that were conducted 73 years ago, have left behind craters deep in the sea floor, around the remote Bikini Atoll — a chain of coral reef islands in the central Pacific.

The map — which is the most detailed one to date — provides evidence for these nuclear tests, say researchers from University of Delaware in their abstract.

The team carried out the survey to also investigate whether the seafloor and craters have changed over the years. And when they combed the seafloor, looking for the remains of the explosion, one crater caught them by surprise — most of it remained the same even after so many years.

In the mid-1946, the US bombed the region to test what their nuclear weapons were capable of. To that end, they deliberately positioned warships, tanks and other vehicles to simulate a nuclear war. The blasts created a giant mushroom cloud, engulfed the Pacific, sinking everything from the ships to the fleet.

A 3D colored illustration of the craters from the western end of Bikini Atoll. (University of Delaware)

Called Operation Crossroads, the US performed the first test: Able, which detonated 520 feet above the target fleet of ships and caused less than the expected amount of ship damage. On the other hand, the second one, the Baker test detonated 90 feet underwater and produced a giant mushroom cloud — captured in iconic photographs.

The aftermaths of the blasts have been recorded before. The US Navy collected data in 1946-1947. And in 1989-1990, another team led by the US National Park Service, which worked with the Navy and the US Department of Energy, tried to relocate and map the wrecks.

“While our maps were good, and based on many long hours in the water, they were not enough,” James Delgado, an archaeologist who worked in the earlier mission, said in a statement. "We needed a more accurate map that could only be done when sonar and survey technology caught up with our needs as scientists," he added.

So, in June this year, Arthur C Trembanis and his team were tasked with locating and characterizing the ghost fleet sitting on the bottom of the Pacific.

Using sonar, the team scanned the sea floor and traced out ships and other marine debris. The team mapped an area about 1.5 times the size of Central Park in New York City and created digital models of these areas.

A team member inspects one of the deck guns of the USS Saratoga, which was sunk by the blast of an atomic test in 1946. (University of Delaware)

Through this, scientists could look deep into the sea. They found that the interiors of the craters were rough. Much of the crater left by Test Baker was still visible and not filled with sediments, showing that the site has not changed with time. This contradicted the team's expectations of finding sediment in the craters.

There are smaller targets that can be mapped as well. "When people think of that photo with the mushroom cloud, that’s where we were. You see how dwarfed these massive ships were by that blast,” says Trembanis. “In many ways, I was struck by it being this idyllic, beautiful Pacific island and I thought ‘This was the site of the most violent explosions on the planet'. It’s still very much a puzzle, and we’d love to be able to go back.”

The study was presented at the Fall Meeting of the American Geophysical Union in San Francisco.