Niijima Island broke through the ocean’s surface last Nov. 20 next to Nishinoshima, about 600 miles south of Tokyo.
While scientists at the time questioned how long the island would survive before being eroded by the sea, it defied expectations and grew to merge with its neighbor and form one landmass.
The newer portion is now larger than the original Nishinoshima, which last expanded during an eruption 40 years ago.
The combined islands now stretch about 3,300 feet across and have together reached about 200 feet in height above sea level.
NASA says that’s triple the height observed last December.
Many volcanic islets formed in the waters off Japan during the 1970s and 80s, but they have since been reclaimed by the pounding Pacific surf.
Photo: Japan Coast Guard