Image copyright Japan coast guard Image caption The newer part of the island - Niijima - is now larger than the older portion, which last expanded in 1973-74 Image copyright Japan Coast Guard Image caption Niijima sprouted in November 2013, just 500m (1,640ft) from Nishino-shima, the older landmass Image copyright Japan Coast Guard Image caption The emerging island was monitored by Japan's coast guard as it grew in size Image copyright Japan Coast Guard Image caption By late December 2013, the new island was starting to merge with its older counterpart Image copyright Japan Coast Guard Image caption And by the beginning of this year, the islands were firmly linked Image copyright Japan Coast Guard Image caption The eruptions show no signs of abating so far previous slide next slide

A volcanic island in the Pacific Ocean has merged with its neighbour to form one landmass, the US space agency says.

The merged island lies some 1,000km (621mi) south of Tokyo, the result of eruptions on the seafloor that have spewed enough material to rise above the water line.

In November 2013, a new island sprouted near to Nishino-shima, another volcanic landmass that last expanded in the 70s.

Four months later, the new and old islands are one island.

The newer portion of the island - which was referred to as Niijima - is now larger than the original Nishino-shima landmass.

The merged island is slightly more than 1km (3,280ft) across.

According to Nasa, two cones have formed around the main volcanic vents and stand more than 60m above sea level.

Volcanic lava flows are reported to be most active now on the south end of the island.

The new landmass lies in the Ogasawara (Bonin) Island chain.