URI Scientists Look For Blast Clues At Salty Brine Beach

Jul 16, 2015

State and federal officials are turning to researchers at the University of Rhode Island to help them understand what happened at Salty Brine State Beach over the weekend when a mini explosion knocked a woman into a jetty, leaving her with two broken ribs. A team of scientists will convene at the beach at low tide later today to collect samples in their search for answers.

Earlier this week, the U.S. Coast Guard worked with state and other federal investigators to remove a disconnected cable under the beach that used to power a navigational light on the jetty.

Now a team of researchers at the University of Rhode Island specializing in geology, soil science, and geochemistry will take over the scene. They’re going to gather long tubes of beach sand near the site of the blast to see if there’s a chemical explanation. Oceanographer John King is one of the researchers.

“Unfortunately, they’ve sort of dug down four feet, removed the cable, and churned everything up,” said King. “So whatever chemical gradient might have been there isn’t really there. So we are going to try to take some cores adjacent to what they dug up and try to get an undisturbed profile.”

The explosion didn’t leave behind any telltale residues. So that tells scientists the source of the explosion could have been a clean burning gas. Gas alone would not cause an explosion; something would have to ignite it.

King and his colleagues plan to examine the geology of the beach to find where gases could have been held or trapped. They have competing hypotheses about how gases may have formed and what may have ignited them. 

One theory is that decaying marine plants or animals, buried under the beach in an environment with little oxygen, produced methane gas and hydrogen sulfide, both of which are explosive when combined with a source of ignition. 

King said seaweed often washes onto the beach and gets buried in the sand, where it decays over time.  

“That’s actually pretty common on Rhode Island beaches, although exploding beaches are not common,” said King.

But state and federal investigators didn’t find any evidence of decaying seaweed even after they dug down four feet. King said that weighs against the methane gas theory.

A second hypothesis involves the disconnected cable under the beach. Geochemist Art Spivack said there’s a small probability that seawater could have corroded the steel cable, with the corrosion producing hydrogen gas. 

“So the cable wasn’t the direct – in this hypothesis – the cable wasn’t the direct source of the explosion or the ignition, but it could have produced the hydrogen by its corrosion,” said Spivack.

Natural environments can behave like batteries, adds Brian Heikes. He explains that weak electrical currents produced by sediments in seawater could travel even through a dead cable. And those currents can also create hydrogen gas. 

“Then the speculation is that somehow this weak [electrical] current and the hydrogen that was formed might have been trapped, and so what you then need is some sort of ignition source,” said Heikes. Ignition sources may include a cigarette, cigarette butt or lighter, “or static electricity could have provided the spark or the ignition source… and so that might give rise to an explosion.”

The researchers collecting the beach sand plan to share samples with a Department of Homeland Security lab based at URI. That lab contains sophisticated equipment to detect signs of manmade explosives that could have been missed by the bomb squad.

The goal is to ensure beachgoers are safe from any future potential blasts. For now, all theories about what could have happened are speculation, until the results from the analyses come back. URI scientists think it’s highly unlikely that such a blast could happen again.

Do you have insight or expertise on this topic? Please email us, we'd like to hear from you: news@ripr.org