A basketball-size chunk of molten rock, known as a lava bomb, crashed into a tourist boat off Hawaii’s coast this week, injuring 23 people who were there to watch lava flow off the Big Island, officials said.
The Coast Guard has opened an investigation into whether the boat was in a restricted zone when the lava struck.
The boat was touring near a lava flow around 6 a.m. on Monday in Kapoho Bay, on the island’s east coast, when molten lava showered down on the vessel’s metal roof, leaving a gaping hole, according to a statement from Hawaii’s Department of Land and Natural Resources.
After the boat returned to shore, 13 people were transported to the hospital and 10 people with minor injuries were treated on site. One passenger, a 20-year-old woman, seriously injured a leg, the statement said.
The source of the lava was Kilauea, one of the world’s most active volcanoes, which has attracted tourists in recent months who are eager to see the piping hot rock for themselves.
After the episode, all vessels were restricted from traveling within 300 meters, or about 330 yards, of the lava flowing into the Pacific Ocean, the Coast Guard said in a statement on Monday. Previously, tourist boats with experienced professional captains could get permission to operate 50 meters or more away from the lava, but they will no longer be able to do so, said Matthew West, a Coast Guard spokesman.
The captain of the boat, Shane Turpin, said he was well outside the zone at the time of the explosion, Reuters reported on Tuesday. Mr. Turpin did not respond to a request for comment.
A video of an explosion that was captured from another lava tour boat around the time the boat was hit shows a huge plume of dark smoke and red lava on the water’s surface.
The Kilauea volcano erupted from its summit earlier this year after days of small earthquakes. The lava flow has destroyed dozens of homes and other buildings, and the Hawaii County Civil Defense Agency urged tourists to steer clear of the area in May.
The volcano was active as of Monday morning, according to the United States Geological Survey.
The company that operated the boat, Lava Ocean Tours, is based in Hilo, Hawaii, and advertises itself as an “exciting way to experience the molten hot lava entering the sea.” The “Hot Spot” vessel that was hit by the lava bomb can seat up to 49 passengers, and each three-hour tour costs $225 to $250, according to the company’s website.
The explosion can be explained by molten rock coming in contact with ocean water, which causes the water to boil quickly, sending off plumes of steam, said Einat Lev, a volcanology expert and assistant professor at Columbia University. As the gas expands, it sets off the blast.
This interaction causes a “corrosive seawater plume” laden with hydrochloric acid and volcanic particles, which can irritate the eyes, skin and lungs, according to the Geological Survey.
Dr. Lev said the Kilauea volcano has had an “ocean entry,” or a location where the lava comes in contact with water, since the 1980s, attracting tourists who are willing to accept some risk to see the spectacle.
“People have been trying to look at this ocean entry for many years,” she said. “This one is flowing a little faster, so they might have been a little too close.”
Hawaii’s Department of Land and Natural Resources is also investigating the episode.