Kamaʻehuakanaloa Seamount[6] (previously known as Lōʻihi) is an active submarine volcano about 22 mi (35 km) off the southeast coast of the island of Hawaii.

At its summit, Kamaʻehuakanaloa Seamount stands more than 10,000 ft (3,000 m) above the seafloor, making it taller than Mount St. Helens was before its catastrophic 1980 eruption.

[15] Kamaʻehuakanaloa's north–south trending rift zones form a distinctive elongated shape, from which the volcano's earlier Hawaiian name "Lōʻihi," meaning "long", derives.

Observations show that both the north and south rift zones lack sediment cover, indicating recent activity.

The seafloor under Hawaii is 80–100 million years old and was produced at the East Pacific Rise, an oceanic spreading center where new sea floor forms from magma that erupts from the mantle.

Over a period of 80–100 million years, the sea floor under Hawaii moved from the East Pacific Rise to its present location 3,700 mi (6,000 km) west, carrying ancient seamounts with it.

When scientists investigated a series of earthquakes off Hawaii in 1970, they discovered that Kamaʻehuakanaloa was an active member of the Hawaiian–Emperor seamount chain.

In the preshield stage, Hawaiian volcanoes have steeper sides and a lower level of activity, producing an alkali basalt lava.

It experiences frequent landslides; the growth of the volcano has destabilized its slopes, and extensive areas of debris inhabit the steep southeastern face.

[5] As Hawaiian volcanoes drift northwest at a rate of about 4 in (10 cm) a year, Kamaʻehuakanaloa was 25 mi (40 km) southeast of its current position at the time of its initial eruption.

[14] The low-level seismic activity documented on Kamaʻehuakanaloa since 1959 has shown that between two and ten earthquakes per month are traceable to the summit.

The National Science Foundation funded an expedition by University of Hawaiʻi scientists, led by Frederick Duennebier, that began investigating the swarm and its origin in August 1996.

[25] Follow-up expeditions to Kamaʻehuakanaloa took place, including a series of crewed submersible dives in August and September.

These more detailed studies showed the southern portion of Kamaʻehuakanaloa's summit had collapsed, a result of a swarm of earthquakes and the rapid withdrawal of magma from the volcano.

A region of 3.9 to 5.0 sq mi (10 to 13 km2) of the summit was altered and populated by bus-sized pillow lava blocks, precariously perched along the outer rim of the newly formed crater.

Dives on the less active northern rim indicated that the terrain was more stable there, and high lava columns were still standing upright.

Between December 7, 2005, and January 18, 2006, a swarm of around 100 earthquakes occurred, the largest measuring 4 on the Moment magnitude scale and 7 to 17 mi (12 to 28 km) deep.

Another earthquake measuring 4.7 was later recorded approximately midway between Kamaʻehuakanaloa and Pāhala (on the south coast of the island of Hawaii).

[5] Geologist Kenneth O. Emery is credited with naming the seamount in 1955, describing the long and narrow shape of the volcano as Kamaʻehuakanaloa.

Rather than finding an old, extinct seamount, data collected revealed Kamaʻehuakanaloa to be a young, possibly active volcano.

Analysis of the photos and testing of pillow lava rock samples appeared to show that the material was "fresh", yielding more evidence that Kamaʻehuakanaloa is still active.

[5] Following a 1986 seismic event, a network of five ocean bottom observatories (OBOs) were deployed on Kamaʻehuakanaloa for a month.

In a dive conducted almost immediately after seismic activity was reported, visibility was greatly reduced by high concentrations of displaced minerals and large floating mats of bacteria in the water.

Hawaiʻi Undersea Research Laboratory, HURL's 2,000 m (6,562 ft) submersible Pisces V allowed scientists to sample the vent waters, microorganisms and hydrothermal mineral deposits.

It was designed to give scientists real-time seismic, chemical and visual data about the state of Kamaʻehuakanaloa, which had by then become an international laboratory for the study of undersea volcanism.

[35] Kamaʻehuakanaloa's mid-Pacific location and its well-sustained hydrothermal system contribute to a rich oasis for a microbial ecosystem.

Low oxygen and pH levels are important factors in supporting the high amounts of Fe (iron), one of the hallmark features of Kamaʻehuakanaloa.

Fish found living near Kamaʻehuakanaloa include the Celebes monkfish (Sladenia remiger), and members of the cutthroat eel family, Synaphobranchidae.

[39] Invertebrates identified in the area include two species endemic to the hydrothermal vents, a bresiliid shrimp (Opaepele loihi) of the family Alvinocarididae (described in 1995), and a tube or pogonophoran worm.

[41][42] A small number of species identified at Kamaʻehuakanaloa were newly recorded sightings in Hawaiʻi, including the tasseled coffinfish (Chaunax fimbriatus), and the Celebes monkfish.