In the future, the hottest tourist destination in Hawaii may not be the beaches of Waikiki or the surf of Waimea Bay.
It could be an island called Loihi–an island no one has yet set foot on.
Loihi (pronounced lo-EE-hee) is an active volcano hidden 3,000 feet beneath the waves. In about 15,000 years, it will break the surface and become the newest land in the Hawaiian chain.
Someday Loihi will be home to palm trees and long sandy beaches. But right now, “Loihi is an island in the womb,” says Alexander Malahoff, who studies Loihi as director of the Hawaii Undersea Research Laboratory at the University of Hawaii at Manoa.
Scientists are taking advantage of Loihi’s infancy to study the volcano closely. Along the way, they’re learning about the processes that build islands and fuel volcanoes. Researchers reported on what they’ve learned about Loihi at a meeting in San Francisco of the American Geophysical Union.
In July and August, a violent swarm of earthquakes shook the underwater volcano. It was the most intense group of quakes ever known to strike the Hawaiian islands, and it’s teaching scientists about the tremendous geologic forces that have built the island chain.
In the course of those several weeks, Loihi’s summit dropped more than 100 feet as the earthquakes shook it.
“Loihi shows us the process of how volcanoes work,” said graduate student Joe Resing of the University of Hawaii. “They build themselves up, and then they fall down again.”
“Going to Loihi is a way to catch what’s going on.”
Oceanographers discovered Loihi in the early 1950s about 20 miles off the southeast coast of the Big Island of Hawaii. At first they thought Loihi was an old, inactive seamount, or underwater mountain. But in 1970, the seamount shook with an intense swarm of earthquakes. Scientists went to have a look at the supposedly dead peak and discovered instead that Loihi is an active volcano.
Loihi is fueled by the same jet of hot rock from Earth’s interior that supplies the volcanoes of Kilauea and Mauna Loa on the Big Island. The jet, or hot spot, is responsible for creating the entire chain of Hawaiian islands.
Geologists think that the hot spot has remained stationary over the last few million years as a piece of Earth’s crust moved across it. The hot spot continually burns volcanoes into the crust, creating a trail of peaks on the ocean floor.
Because the crustal plate is moving toward the northwest, the youngest volcanoes in the chain lie in the southeast. The Hawaiian islands grow progressively older to the northwest, trailing off into a series of even older, eroded mountains underwater that were formed in the same manner and extend all the way to Alaska.
Loihi has been growing as the newest Hawaiian island for a few hundred thousand years. It’s already nearly two miles high–taller than Washington’s Mount St. Helens was before its cataclysmic eruption in 1980.
But Loihi certainly doesn’t look anything like Mount St. Helens. Loihi is a rubbly pile of debris built into a long underwater ridge, roughly 16 miles by eight miles. In fact, the seamount was named for its shape–Loihi means “long one” in Hawaiian.
As the volcano erupts, fresh lava pours out onto its surface and hardens into rock, making Loihi a little taller. Over time, the seamount builds itself up through eruptions.
Sometimes, though, the volcano tumbles back down. The earthquakes that shook Loihi in July and August, for example, caused the highest point on the summit to crumble into a deep pit. In just a few days, the area known as Pele’s Vents–which once was the highest point on the summit–collapsed into the 1,000-foot-deep crater known as Pele’s Pit.
Life is pretty unsteady for volcanoes like Loihi.
“Loihi’s really just a loose pile of rubble with hot water pouring through the whole thing,” says Malahoff. “It’s a wreck.”
All the Hawaiian islands are built on such rubbly underpinnings, he adds.
Malahoff is quick to point out that the greatest danger from the quakes at Loihi isn’t the groundshaking or eruption itself. Rather, it’s the chance that the earthquakes could trigger a tsunami that would strike the nearby islands within a matter of minutes–far too short a time for adequate warning, he says.
Malahoff and other researchers are working to understand Loihi’s insides in order to help prevent such a disaster.
The earthquake swarm of last summer provided them with an opportunity to study Loihi’s activity firsthand.
In the first two weeks of the swarm, seismologists picked up more than 4,000 tremors. More than 100 of these quakes were greater than magnitude 4. Right away, researchers from the University of Hawaii wanted to figure out what was going on underwater.
The researchers scrambled for grant money and managed to get a ship for a scientific cruise in early August, just as the main group of earthquakes was dying off. The scientists actually felt a couple of the earthquakes; they felt like “a big wave jolting the ship,” according to one scientist on the cruise.
In late September and early October, two other previously scheduled research cruises also visited Loihi.
On these cruises, the researchers studied the chemicals that Loihi was spewing out from its hot-water vents. The scientists lowered vials over the side of the boat at various points directly above the volcano and farther away, and then took water samples.
The samples told the researchers that Loihi was undergoing some of its most violent eruptions ever witnessed.
“We could see clearly that something very catastrophic had happened early on,” says Francis Sansone, an oceanographer at the University of Hawaii and co-leader of two of the recent cruises.
As far as 30 miles away from the volcano, the water samples still showed strong chemical traces of a huge eruption. Whatever that early eruption was like, says Sansone, “it was a big one.”
The researchers also went down to the volcano itself to get a firsthand look at what had happened.
Oddly enough, they couldn’t see any fresh lava coating the summit of Loihi. Somehow, all the material that was erupted–an estimated 75 million cubic meters of it–collapsed back down the pipes from where it erupted.
“It’s a big mystery what happened to all that material,” says Malahoff.
Three thousand feet underwater, the scientists got a glimpse of the eerie world of a submarine volcano.
On the summit of Loihi live an odd assortment of creatures that thrive off the hot water spewing from the volcano. Biologists have found only one species of worm and one of shrimp living on Loihi, occasionally getting scorched during eruptions.
This is in stark contrast to the wide variety of such species that thrive at underwater vents along other ridges in the middle of the oceans.
