The island of lava appeared Thursday, just offshore from the northern edge of the Big Island, the United States Geological Survey said.
Of the 13 injured passengers, four were taken by ambulance to Hilo Medical Center, according to the Hawaii County Fire Department. All other passengers who went to the hospital were treated for minor scrapes and burns.
Officials were interviewing injured passengers at a hospital. Visitor numbers spike each time Kilauea, which has erupted nearly continuously since 1983, sends a tongue of lava toward the ocean. Clearly, though, accidents can happen when things are more unpredictable.
The explosion left a gaping hole in the roof of the tour boat, which had been taking visitors out to view lava plunging into the sea.
USGS believes the island most likely formed from lava flow at fissure eight - one of 24 fissures spotted at the volcano. But from where lava is hitting the ocean to the harbor is about an hour's boat ride, depending on waves.
Although still engaging in some curious volcanological behavior, Kilauea's not making worldwide headlines anymore, partly because its eruption has somewhat settled into a consistent pattern.More news: China shocked by Trump’s upscaling of trade aggression
Lava is flowing into ocean on the southeast side of the island.
The interaction of lava with the ocean creates "laze", a corrosive seawater plume laden with hydrochloric acid and fine volcanic particles that drifts downwind and can irritate the skin, eyes and lungs.
Although you might not think that a tiny lava pile so close to the mainland would count as an island, the definition used is a piece of land surrounded by water, and so this little guy fits the bill.
He said that the crew didn't pick up on any warning signs before the explosion.
"Some of those were superficial injuries", she said. It prohibits vessels from getting closer than 984 feet (300 meters) from ocean-entry points.
The eruption has destroyed hundreds of homes since it began on May 3. But the only serious injury during the past two months was to a man who was hit by flying lava rock that broke his leg.