Although the Kama‘ehuakanaloa Seamount has been a little restless recently, new information about the undersea volcano is still sparse.
The volcano, formerly called Lo‘ihi Seamount, is located about 22 miles off the Big Island’s southeastern coast and will one day become the youngest of the Hawaiian Islands when it finally grows tall enough to break the water’s surface.
The seamount’s most recent eruption was in 1996, and although the volcano displayed some activity last November and again in January, it’s unclear when it will erupt again.
Ashton Flinders, research geophysicist for Hawaiian Volcano Observatory, said the volcano’s most recent activity was on Jan. 21, when researchers detected a swarm of about 16 earthquakes. All of them were of very low magnitude — “basically magnitude zero” — and originated from deep below sea level, but the activity was notable for the volcano.
“Since then, we’ve detected only about seven more quakes,” Flinders said.
In November, there was a spate of more vigorous activity: about 70 earthquakes, about half of which exceeded magnitude 2.0, originating from a shallower point below sea level. Flinders said that swarm likely could have centered around the volcano’s magma chamber.
But that activity, too, still doesn’t indicate much about the seamount.
“We can only really ‘see’ these quakes from one direction,” Flinders said, explaining that there are no underwater instruments around Kama‘ehuakanaloa, and observations must be made from land. “It’s hard to get the full picture, we can’t triangulate anything.”
Flinders compared the volcano to seeing a picture of a person from behind: “If the angle is just right, you might be able to see part of his face.”
Consequently, it’s difficult to be certain about anything the seamount does. There was one incident in 2020 when the volcano was rocked by 100 minor quakes, to the point that it seemed more like one long quake, Flinders said. That sort of activity could indicate a possible eruption, he said, but it’s unclear whether it did.
“The accessibility of the volcano is just not good for us,” Flinders said. “We’ve got to wait five, 10 years between snapshots.”
The U.S. Geological Survey — which runs HVO — and other research organizations have placed instruments around Kama‘ehuakanaloa in the past and sent submersible expeditions. But those are expensive, and the instruments tend to be short-lived against the wear of the ocean.
Beginning in 1997, the University of Hawaii deployed the Hawaii Undersea Geostationary Observatory — or HUGO — which Flinders described as a collection of instruments connected directly to the Big Island by an enormous fiber-optic cable.
“That would be a great thing to pursue,” Flinders said, but added that the cable and instruments were cost-prohibitive to maintain against corrosion and wear. HUGO went offline in 1998 and was retrieved from the seabed in 2002.
But Flinders said the volcano remains a fascinating object of study, not least because of its remoteness.
“We focus on Mauna Loa and Kilauea — and Haleakala, which I think we sometimes overlook — because of their potential impacts to communities,” Flinders said. “Kama‘ehuakanaloa presents no risk to communities, but plenty of opportunities for studying volcanism.”
Flinders added that, with the volcano’s highest point still located about 990 meters (about 3,200 feet) below sea level, the vast amount of water between the seamount and the Big Island means that no seismic activity caused by Kama‘ehuakanaloa can feasibly impact Big Island residents, based on our current understanding of the volcano.
And when the volcano finally does become an island, Flinders said neither he nor anyone else currently alive will be around to see it — it’s expected to break the ocean surface in about 10,000 to 100,000 years.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.
