Floating volcanic rock raft appears in 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 made up of thousands of pieces of pumice stone which is very lightweight meaning it can float on water.

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

Sailors are being warned to avoid area, to stay clear of potential hazards.