Kamaʻehuakanaloa Seamount (previously known as Lōʻihi) is an active submarine volcano about off the southeast coast of the island of Hawaii. Kamaʻehuakanaloa is the newest volcano in the Hawaiian–Emperor seamount chain, a string of volcanoes that stretches about northwest of Kamaʻehuakanaloa. Unlike most active volcanoes in the Pacific Ocean that make up the active plate margins on the Pacific Ring of Fire, Kamaʻehuakanaloa and the other volcanoes of the Hawaiian–Emperor seamount chain are hotspot volcanoes and formed well away from the nearest plate boundary. Volcanoes in the Hawaiian Islands arise from the Hawaii hotspot, and as the youngest volcano in the chain, Kamaʻehuakanaloa is the only Hawaiian volcano in the deep submarine preshield stage of development.
Kamaʻehuakanaloa began forming around 400,000 years ago and is expected to begin emerging above sea level about 10,000–100,000 years from now. At its summit, Kamaʻehuakanaloa Seamount stands more than above the seafloor, making it taller than Mount St. Helens was before its catastrophic 1980 eruption. A diverse microbial community resides around Kamaʻehuakanaloa's many hydrothermal vents.
In the summer of 1996, a swarm of 4,070 earthquakes was recorded at Kamaʻehuakanaloa. At the time this was the most energetic earthquake swarm in Hawaii recorded history. The swarm altered of the seamount's summit; one section, Pele's Vents, collapsed entirely upon itself and formed the renamed Pele's Pit. The volcano has remained relatively active since the 1996 swarm and is monitored by the United States Geological Survey (USGS). The Hawaii Undersea Geological Observatory (HUGO) provided real-time data on Kamaʻehuakanaloa between 1997 and 1998. Kamaʻehuakanaloa's last known eruption was in 1996, before the earthquake swarm of that summer.
Naming
The name Kamaʻehuakanaloa is a Hawaiian language word for "glowing child of Kanaloa", the god of the ocean. This name was found in two Hawaiian mele from the 19th and early twentieth centuries based on research at the Bishop Museum and was assigned by the Hawaiʻi Board on Geographic Names in 2021 and adopted by the U.S. Geological Survey. From 1955 to 2021 the seamount was called "Lōʻihi", the Hawaiian word for "long", describing its shape. The change to Kamaʻehuakanaloa was made in an effort to be more culturally appropriate given native Hawaiian traditions for naming.
Characteristics
Geology
Kamaʻehuakanaloa is a seamount, or underwater volcano, on the flank of Mauna Loa, the Earth's tallest shield volcano. It is the newest volcano produced by the Hawaiʻi hotspot in the extensive Hawaiian–Emperor seamount chain. The distance between the summit of the older Mauna Loa and the summit of Kamaʻehuakanaloa is about , which is, coincidentally, also the approximate diameter of the Hawaiʻi hotspot. Kamaʻehuakanaloa consists of a summit area with three pit craters, a long rift zone extending north from the summit, and a long rift zone extending south-southeast from the summit. The thick crater walls of Pele's Pit – averaging in width, unusually thick for Hawaiian volcanic craters – suggest its craters have filled with lava multiple times in the past.
Until 1970, Kamaʻehuakanaloa was thought to be an inactive volcano that had been transported to its current location by sea-floor spreading. The seafloor under Hawaii is 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. New oceanic crust moves away from the spreading center. Over a period of years, the sea floor under Hawaii moved from the East Pacific Rise to its present location 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.
thumb|right|Three-dimensional rendering of the seamount|alt=3D map of Kamaʻehuakanaloa
Kamaʻehuakanaloa is built on the seafloor with a slope of about five degrees. Its northern base on the flank of Mauna Loa is below sea level, but its southern base is a more substantial below the surface. Thus, the summit is above the seafloor as measured from the base of its north flank, but high when measured from the base of its southern flank. Continued volcanism is expected to eventually give birth to an island at Kamaʻehuakanaloa. It experiences frequent landslides; the growth of the volcano has destabilized its slopes, and extensive areas of debris inhabit the steep southeastern face. Similar deposits from other Hawaiian volcanoes indicate that landslide debris is an important product of the early development of Hawaiian volcanoes.
Activity
Kamaʻehuakanaloa is a young and fairly active volcano, although less active than nearby Kīlauea. In the past few decades, several earthquake swarms have been attributed to Kamaʻehuakanaloa, the largest of which are summarized in the table below. The volcano's activity is now known to predate scientific record keeping of its activity, which commenced in 1959. Most earthquake swarms at Kamaʻehuakanaloa have lasted less than two days; the two exceptions are the 1990-1991 earthquake, lasting several months, and the 1996 event, which was shorter but much more pronounced. The 1996 event was directly observed by an ocean bottom seismometer (OBS), allowing scientists to calculate the depth of the earthquakes as to below the summit, approximating to the position of Kamaʻehuakanaloa's extremely shallow magma chamber.
The low-level seismic activity documented on Kamaʻehuakanaloa since 1959 <!-- mismatch: 1959–1952. 1959 is the "correct" number --> has shown that between two and ten earthquakes per month are traceable to the summit. Eruption possible, but uncertain. Eruption uncertain.
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| An earthquake swarm on Kamaʻehuakanaloa in 1952 was the event that first brought attention to the volcano, previously thought extinct.
The final two weeks of the earthquake swarm were observed by a rapid response cruise launched in August 1996. 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. The scientists' assessment laid the groundwork for many of the expeditions that followed. Follow-up expeditions to Kamaʻehuakanaloa took place, including a series of crewed submersible dives in August and September. These were supplemented by a great deal of shore-based research.
Submersible dives in August were followed by NOAA-funded research in September and October 1996. 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 crater across and deep formed out of the rubble. The event involved the movement of cubic meters of volcanic material. A region of of the summit was altered and populated by bus-sized pillow lava blocks, precariously perched along the outer rim of the newly formed crater. "Pele's Vents", an area on the southern side, previously considered stable, collapsed completely into a giant pit, renamed "Pele's Pit". Strong currents make submersible diving hazardous in the region.
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|Early Sept. 1997
| Studies of hydrothermal vents (Batiza and McMurtry, Chief Scientists)
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| October 2006<br />October 2007<br />October 2008<br />October 2009
| FeMO (Fe-Oxidizing Microbial Observatory) cruises to investigate iron-oxidizing microbes at Kamaʻehuakanaloa.<br />
Much is learned about Kamaʻehuakanaloa's microbial community.
thumb|right|R/V (research vessel) Kaʻimikai-o-Kanaloa (KoK) launching [[Pisces V, a battery-powered submersible. The R/V KoK was the support ship for the Kamaʻehuakanaloa Undersea Research Laboratory (HURL).|alt=A submarine, hanging from the back of a ship via a crane, is lowered into the water.]]
Geologists suspected the seamount could be an active undersea volcano, but without evidence the idea remained speculative. The volcano was largely ignored after the 1952 event, and was often mislabeled as an "older volcanic feature" in subsequent charts. In 1978, an expedition studied intense, repeated seismic activity known as earthquake swarms in and around the Kamaʻehuakanaloa area. Rather than finding an old, extinct seamount, data collected revealed Kamaʻehuakanaloa to be a young, possibly active volcano. Observations showed the volcano to be encrusted with young and old lava flows. Fluids erupting from active hydrothermal vents were also found.
In 1978, a US Geological Survey research ship collected dredge samples and photographed Kamaʻehuakanaloa's summit with the goal of studying whether Kamaʻehuakanaloa is active. 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. An expedition from October 1980 to January 1981 collected further dredge samples and photographs, providing additional confirmation. Studies indicated that the eruptions came from the southern part of the rift crater. This area is closest to the Hawaiʻi hotspot, which supplies Kamaʻehuakanaloa with magma. Another autonomous observatory was positioned on Kamaʻehuakanaloa in 1991 to track earthquake swarms.
Repeated multibeam bathymetric mapping was used to measure the changes in the summit following the 1996 collapse. Hydrothermal plume surveys confirmed changes in the energy, and dissolved minerals emanating from Kamaʻehuakanaloa. Hawaiʻi Undersea Research Laboratory, HURL's submersible Pisces V allowed scientists to sample the vent waters, microorganisms and hydrothermal mineral deposits.
Ecology
Hydrothermal vent geochemistry
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! Vent
Microorganisms
The vents lie below the surface, and range in temperature from 10 to over . The vent fluids are characterized by a high concentration of (up to 17 mM) and Fe (Iron), but low in sulfide. Low oxygen and pH levels are important factors in supporting the high amounts of Fe (iron), one of the hallmark features of Kamaʻehuakanaloa. These characteristics make a perfect environment for iron-oxidizing bacteria, called FeOB, to thrive in. An example of these species is Mariprofundus ferrooxydans, a member of the class Zetaproteobacteria. The composition of the materials was similar to that of black smokers, that are a habitat of archaea extremophiles. Dissolution and oxidation of the mineral observed over the next two years suggests the sulfate is not easily preserved.
A diverse community of microbial mats surround the vents and virtually cover Pele's Pit.
The Hawaiʻi Undersea Research Laboratory (HURL), NOAA's Research Center for Hawaiʻi and the Western Pacific, monitors and researches the hydrothermal systems and studies the local community.
Macroorganisms
Marine life inhabiting the waters around Kamaʻehuakanaloa is not as diverse as life at other, less active seamounts. Fish found living near Kamaʻehuakanaloa include the Celebes monkfish (Sladenia remiger), and members of the cutthroat eel family, Synaphobranchidae. 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. Dives conducted after the 1996 earthquake swarms were unable to find either the shrimp or the worm, and it is not known if there are lasting effects on these species.
From 1982 to 1992, researchers in Hawaiʻi Undersea Research Laboratory submersibles photographed the fish of Kamaʻehuakanaloa Seamount, Johnston Atoll, and Cross Seamount at depths between . A small number of species identified at Kamaʻehuakanaloa were newly recorded sightings in Hawaiʻi, including the tasseled coffinfish (Chaunax fimbriatus), and the Celebes monkfish.