A volcanic eruption in Tonga has created a new island - although scientists say it could soon disappear.

The volcano has been erupting for a month in the Pacific Ocean about 40 miles north west of the capital Nuku'alofa. Last week it disrupted international air travel to the Tongan archipelago for several days.

New Zealand volcanologist Nico Fournier said he had travelled by boat close to the new island to take a look. He says it is made mainly of scoria - dark volcanic rock - and it measures about 1.1 miles by 0.9 miles, and rises about 110 yards above sea level.

"It's quite an exciting site, you get to see the birth of an island," he said.

"Visually it was quite spectacular, but there was no big sound coming with it, no boom. It was a bit eerie."

He said that once the volcano stops erupting, it will probably take the ocean no more than a few months to erode the island entirely. He said it would need to be made of lava or something more durable to survive.

He added that the ocean around the island is probably fairly shallow, perhaps only about 300ft-650ft deep.

Mr Fournier, who works for New Zealand agency GNS Science, said the volcano was mainly belching steam into the atmosphere, and that the small amount of ash it was sending out was rising no more than 1.2 miles.

That will come as a relief to airlines as it is the ash that can be dangerous to planes.

He said there is no name yet for the new island, and he has been told that any naming rights will fall to Tonga's king, Tupou VI.