The Secrets of a Six Million-Year-Old Whale Graveyard

Hundreds of ancient marine mammal fossils point to four mass strandings in the same place.

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Feb 26 2014, 12:15pm
Image: Adam Metallo/Smithsonian Institution

This is a huge ancient whale graveyard that likely contains hundreds of marine mammal skeletons buried in Northern Chile’s Atacama Desert. Today, paleontologists from the Smithsonian Institute and a team of Chilean researchers published a paper exploring what exactly they’d found, and how these animals came to be mass stranded.

The fossil site was discovered in 2010 during work on the Pan-American Highway, and the Smithsonian Institute recalls that the scientists therefore had little time to investigate the finds before they were paved over. They wrote that they discovered, “over 40 skeletons of rorqual whales, sperm whales, seals, aquatic sloths, walrus-whales and predatory bony fish.”

If some of those don’t sound like the kind of thing you can see at Sea World, it’s because the fossils dated back six to nine million years ago. To put that in perspective, “anatomically modern” Homo sapiens have only been around for about 200,000 years.

Image: Smithsonian Institution

The site was particularly interesting because the researchers identified four distinct stranding events; something was repeatedly killing the marine animals en masse. Owing to the way the skeletons came to rest, they surmised that the animals had died at sea before being swept into the same spot for burial, which is known as Cerro Ballena (“Whale Hill”). The likely culprit: toxic algae. 

“In modern settings, HABs [harmful algal blooms] are the only known natural cause for such repeated, multispecies accumulations,” they wrote. It’s the same kind of thing that’s killing off marine creatures like Florida’s manatees today. In this case, they suggested that runoff from rivers in the iron-rich Andes would have caused the perfect conditions for toxic algae to form. The animals would die from poisoning, either from breathing the toxins in or eating contaminated prey, and get washed onto the tidal flats.

In the shallows, other large marine animals wouldn’t be able to get to them and disturb the bodies, and there weren’t any large land animals around in the area back then.

With the release of the paper, the Smithsonian has made some awesome 3D imaging resources related to the site public. Because the researchers were under such time pressure with the imminent construction of a road over the site, they turned to 3D scanning to preserve a record of the entire area before moving the fossils to museums. 

Video: Smithsonian's Digitization Program Office/Youtube

Nick Pyenson, the first author of the paper, explains in the above video that as the skeletons were unearthed right next to a major road, vibrations from vehicles going past could damage the remains, so they had to preserve as much scientifically relevant information as possible, as soon as they could. 3D imaging was the best way to cover the whole area, fast. “What we’re talking about is a site that’s about three football fields in size covered in skeletons and fossil remains,” he said.

If you fancy yourself as a digital Indiana Jones, you can play around with 3D models of the fossils and maps of the dig site at a dedicated online portal. 

Meanwhile, the University of Chile aims to set up a research base near Cerro Ballena to set about discovering the estimated hundreds of remaining fossils in the natural mass burial site.