Aerial footage captured by NHK shows that a new islet, formed from an undersea volcanic eruption near the Japanese Pacific island of Ioto, has been expanding.

The eruption occurred in late October in waters off the southern coast of Ioto.

An NHK camera on Monday captured volcanic activity from above. Eruptions were observed at an undersea crater at intervals of a few minutes, emitting black fumes reaching heights of about 100 meters.

The footage also shows the new land mass has changed shape. It looked round in October, but has turned into a J-shaped, long and narrow formation spanning more than 500 meters from north to south. The islet has moved closer to Ioto, and its tip is now just 200 meters away.

Associate Professor Maeno Fukashi of the University of Tokyo's Earthquake Research Institute accompanied the NHK crew.

He said the crater, which was barely beneath the sea surface a few weeks ago, has sunk slightly due to water erosion and is emitting volcanic gases and hot liquid.

He said the shape of the new islet has changed in a short time due to erosive actions off the islet and sedimentation of ejected rocks in the shallows near Ioto occurring simultaneously.

Maeno said that although there are no signs of a massive eruption at this stage, minor eruptions have continued, which may lead to the islet becoming connected to Ioto.