There are two deep collapse pits, similar in size to Halema'uma'u at Kilauea's summit, located in the southern part of the summit region. Hot water escapes from vents near its summit and along its upper south rift zone. These observations, and the recovery of fresh, glassy lava fragments, indicate that Loihi is an active volcano destined to emerge as an island within the next 200,000 years, grow, and coalesce with Hawaii. Kilauea Volcano, in the explosive substage of the shield stage, and the most active volcano on Earth, has erupted 60 times since 1840. Its lava flows are interbedded with ash deposits produced by infrequent explosive eruptions, most recently in 1790.
Eruptions can occur anywhere at the summit or along the east or southwest rift zones.
The south flank of the volcano, bounded by the two rift zones, slips towards the ocean at rates of a few inches per year on a flat-lying fault about 6 miles deep. Mauna Loa Volcano, nearing the end of the shield stage, is declining in its eruption rate. Only three of its 36 eruptions since 1843 have occurred since 1950. In addition to the two prominent rift zones, repeated fissure eruptions have occurred randomly on the northern and northwestward flank of the volcano. In order to grow to its present estimated volume of roughly 10,000 cubic miles, Mauna Loa must have erupted, for much of its lifespan, at four or five times its historic rates.