Loihi

Lō‘ihi Seamount is an active volcano built on the seafloor south of Kīlauea about 30 km (19 mi) from shore. The seamount rises to 975 m (3,189 ft) below sea level and generates frequent earthquake swarms, the most intense of which occurred between July 16-August 9, 1996 (more than 4,000 events). An eruption at Lō‘ihi has yet to be observed, but research indicates that eruptions are both explosive and effusive. Lō‘ihi's volume is 1,700 km3 (407 mi3), and it is considered to be between pre-shield and shield stage.

The summit of Lō‘ihi is marked by a caldera-like depression 2.8 km (1.7 mi) wide and 3.7 km (2.3 mi) long. Three collapse pits or craters occupy the southern part of the caldera; the most recent pit formed during the 1996 earthquake swarm. Named Pele's Pit, the new crater is about 600 m (1,970 ft) in diameter and its bottom is 300 m (985 ft) below the previous surface! Like the volcanoes on the Island of Hawai‘i, Lō‘ihi has grown from eruptions along its 31-km-long (19-mi-long) rift zone that extends northwest and southeast of the caldera.

It's not known when Lō‘ihi will breach sea level. We can speculate that with a growth rate of 5 m (16.4 ft) per 1000 years it will take as much as 200,000 years to reach the ocean surface. It all depends upon the eruption rate.

The name Lō‘ihi means "long" in Hawaiian and was introduced in 1955 to describe the elongate shape of the seamount. More recently, Hawaiian scholars have found that stories of "Kama‘ehu," the red island child of Haumea (earth) and Kanaloa (sea) that rises from the deep in the ocean floor may also be a reference to this submarine volcano.

USGS