According to CNN, Japanese scientists expected this new island to last several years before eroding and slipping back into the ocean, but now its continued growth means it could remain above sea level a lot longer.
LiveScience reports the older island was formed when it last erupted in 1974. Now that it's conjoined with the new island, on which lava is still flowing, the island could continue to grow in size.
Niijima's volcano is reportedly the most powerful one in the area. Similar islands have formed in the past but have since eroded and disappeared.