Giant volcanic pumice rock raft floating in Pacific ocean

A giant volcanic rock raft has been found floating in the ocean.

The rock raft is about the same size as 20,000 football fields and was first spotted by Australian sailors earlier this month.

Scientists think the rock raft came from an underwater volcano near Tonga, which erupted earlier this month.

The volcanic rock is called 'pumice stone' and is very lightweight, meaning it can float on water.

Pumice is made when magma from a volcano cools really quickly in water.

The rock raft is made up of trillions of tiny pieces of pumice stone, so it looks like a floating island when they're all together.

Associate Prof Scott Bryan is a geologist studying the pumice samples at Queensland University of Technology.

He said that these kind of big rock rafts happen about once every five years in the area.

"It can be as if the whole surface [of the ocean] has turned to land".

Experts think the pumice will be good for the environment, providing homes for ocean creatures, and even helping to restore the Great Barrier Reef in Australia.

Sailors are being warned to avoid the area, to steer clear of potential hazards from the rocks.