WLW: UC geologist explains giant floating rock in Pacific

Algeo, a professor of geology in UC's McMicken College of Art and Sciences, said the island was formed from a volcanic eruption deep underwater.

"The rock floats because it's full of air bubbles," Algeo told  show hosts Eddie Fingers and Rocky Boiman. "The air bubbles form in the lava. A pumice rock can consist of up to 90 percent air bubbles. That allows it to float. It's actually less dense than water."

News accounts suggested the pumice island could help the imperiled Great Barrier Reef. But Algeo said any benefits would be short lived.

"It might have a very positive short-term influence," he said. "A lot of marine organisms can latch onto these pumice fragments. You might repopulate some corals in the Great Barrier Reef from pumice floating in. But the main stresses on the Great Barrier Reef are much greater than that."

Algeo said half of the reef has died because of recent warming of ocean currents.

As for the pumice island? Algeo said once the gas escapes from the rock, the pumice eventually will sink to the ocean floor.