Japan's Meteorological Agency says rocks that spewed from an undersea volcanic eruption has formed new land near Ioto Island, also known as Iwojima, in the Pacific Ocean.

The island of Ioto is part of the Ogasawara island chain and is located more than 1,200 kilometers south of the center of Tokyo.

The agency on Thursday reported on the volcanic activities in October.

The agency said it was informed by Maritime Self-Defense Forces, which has an air base on the island, of the eruption that occurred on October 21 off the southern coast of Ioto.

Water columns containing black dirt were reportedly spewing out of the sea at intervals of between less than a minute and a few minutes and reaching heights of up to 100 meters.

The agency analyzed satellite images and conducted an aerial survey by experts on October 30 to confirm the new land formed north of the eruption site.

The agency said that this is the first discovery of new land formation off the coast of Ioto.

The land has grown this month to about 300 meters in length from north to south.

Agency officials said the eruption has scaled down since Wednesday evening. They said the islet may not remain as land, as land made of rocks can easily be swept away by waves.

The agency also announced that the island of Kuchinoerabujima in Kagoshima Prefecture has seen a sharp increase in the number of volcanic quakes since early November. About 320 quakes were observed on Wednesday alone.

The meteorological agency is warning that the risk of an eruption that could affect a designated area is increasing.

The agency is urging people within 2 kilometers of two craters on the island to be on alert for large volcanic rocks and pyroclastic flows that could come from an eruption.