Did decaying seaweed cause mysterious explosion on Rhode Island beach?

[USA] It’s been several days since a mysterious explosion propelled a beachgoer 10 feet into the air at Salty Brine Beach in Narragansett, Rhode Island, and authorities still have no idea why.

While speculation as to the cause of Saturday’s incident includes a methane explosion caused by decayed seaweed or other organic matter under the sand, Stephen Porder, associate professor of ecology and evolutionary biology at Brown University, told the Associated Press, “Everything at this point is entirely speculation.”

The beachgoer, Kathleen Danise, was thrown from her beach chair by the mysterious explosion, sustaining a concussion and a pair of fractured ribs when she was slammed into the rocks.

Witnesses have said that they heard a rumbling and a loud bang that sounded like a firecracker, a grenade or a gas explosion, then noticed a sulfur or butane smell. The blast left behind a “rift” in the sand — but little else.

Porder offered that methane might have built up from organic matter trapped underground when the jetty was constructed.

“You can definitely get an explosion. How you would have that sequence of events on that particular beach on that particular day, I don’t know,” Porder said. He also pointed out that it is typically places like swamps or areas in the arctic that produce high levels of methane.

“I’ve never heard of a methane explosion on the beach,” he added.

State Police Col. Steven G. O’Donnell said there was no physical evidence of an explosion, such as charring or debris. Dogs and chemical swipes detected no explosive residue, either. Officials also determined there was no natural gas line running underneath.

In addition, a “malicious attack” was ruled out.

As to the suggestion of a gas leak, authorities noted the nearest line was at least 100 feet from where the explosion took place. And late Monday, investigators with the Department of Environmental Management (DEM) noted that there were no records of a seismic event in Rhode Island, canceling out one of the propose theories.

Also on Monday, a cable used by the U.S. Coast Guard to power the navigational light at the end of the jetty, was dug up from the sand. A DEM spokeswoman said the cable was no longer live and there were no indications it was related to the blast. All the same, Coast Guard officials revisited the cable Tuesday, digging parts of it out of the beach to inspect it.

Rob Thieler, a marine and coastal geologist with the U.S. Geological Survey, had another theory about a possible source of methane: estuary sediments, which sometimes cause explosions when they decay. He said scientists have seen evidence of this phenomenon off the coast of Maine.

“The sea-floor surface looks like a golf ball, and these are presumably places where underlying methane produced by estuary sediment has violently escaped,” Thieler said.

This type of explosion could happen spontaneously, he said, though having it happen on a sandy beach is rare.

Despite the explosion, visitors to the beach weren’t scared away.


View original article at: Did decaying seaweed cause mysterious explosion on Rhode Island beach?




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