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Birth of New Hawaiian Island by William Broad  NY Times Science 10/8/1996

Rising from deep within the earth is a jet of molten rock that cuts large holes in the Pacific seabed, forming new volcanoes and eventually whole new islands as well, its brood including Maui and Oahu.  Each year, the jet, the Earth's most intense, spews enough lava to build a road that would circle the earth TWICE.  It has been thundering and exploding and erupting lava for tens of millions of years.

Now, scientists have descended in a submersible to probe an episode of explosive violence at the jet's leading edge accompanying the birth throes of a new Hawaiian island.  Their target, a half mile down, was the summit of Loihi, which has suddenly become one of the worlds most active volcanoes.

"It's nerve-racking" Dr Alexander Malahoff, the expedition's chief scientist, said of his dives into the dark, churning waters. "The top of the volcano is a physical wreck."

In July and August, the site was rocked by thousands of seaquakes, including the strongest ever  recorded around Hawaii.  Since the volcanic seamount is only 17 miles southeast of the big island of Hawaii, disaster officials feared that the deep violence might set off tidal waves at the surface that could devastate the big island as well as more distant shores of Oahu, including Honolulu and Waikiki Beach.

Land was in fact spared. But Dr. Malahoff and other scientists who dove to the craggy recesses of the undersea volcano discovered a riot of landslides, toppled rock formations and a bus-size volcanic boulders strewn over four or five miles.  But this was not the result of a major eruption.  The turmoil at the volcano's top had collapsed its summit, creating a murky crater more than a half-mile wide and 1000 feet deep.

This was a Mt. St. Helens sized volcanic event," Dr Malahoff said at a news conference on Friday at the National Press Club in Washington.  "Pete's Dome, an area on the southern rim of the volcano that previously had been considered very stable had simply vanished."

He made three dives into the volcanic depths in as many days late in Sept. 1996, and the dives continued through October 1996.  The team is diving in a Pisces submersible, which can carry three people down a little more than a mile and therefore is limited to exploring the volcano's summit.  The whole seamount rises almost three miles from the ocean floor.

Dr. Malahoff is a director at the Hawaii Undersea Research Lab at the University of Hawaii, and dives are financed by the National Oceanic and Atmospheric Administration. Diving into the new crater, Dr. Malahoff found vents spewing a mixture of superheated water, dissolved minerals and microbes that thrive in the seabed's rocky substratum.  Churning clouds of particles often limited visibility to about a yard or less.

And tricky currents posed dangers. Waters flowed into the newly formed pit,   percolated through the volcano's hot interior and rushed out over a lip on the volcano's western edge.  The scientists had to avoid getting sucked down by the inrush ton one side and pushed up by the out-rush of the other.  

They say the tumult is part of the volcano's halting upward growth.  Lava flows build it up, and avalanches and collapses and cataclysmic explosions knock it down ‘and widen it, creating a larger base for the next stage of building, Tens of thousands of years are expected to pass before the volcano's fiery summit rises above the waves. The fight is between construction and destruction.” Dr. Malahoff said at the news conference.

Avalanches are well known to have shaken the steep sides of Loihi, but no episode this violent has ever before been studied up close. Scientists say the event sheds important new light on the dynamics of island building as well as a whole range of environmental issues, like the extent to which explosive releases of volcanic gases like carbon dioxide may be contributing to the greenhouse warming of the earth. Such releases, they say, may augment human ones.

And it is aiding overall studies of the Hawaiian jet, the earth's most dynamic zone of volcanic upheaval.  Beneath the big island of Hawaii, it powers the fireworks of both the Kilauea and Mauna Loa volcanoes.

We think it is rather large, as much as 200 kilometers in diameter-or about 125 miles, Dr. James G. Moore, a geologist with the United States Geological Survey in Menlo Park. Calif., said an interview. "Loihi is the first manifestation of volcanic activity on that crust", added Dr. Moore, who has studied the Hawaiian volcanoes. "Its the leading edge.”

The great heat engine within the Earth stirs a sea of hot plastic rock that melts through the crust in places, with the vast majority of the surface action taking place in the hidden darkness of the deep sea.

In places, the interior heat gives birth to jets or plumes of hot material that are stationary in relation to the deep earth but continuously rise toward the surface. Over the eons, the Jets pierce plates that move slowly overhead, much as a blowtorch would melt holes in a steel plate moving by.

The gigantic plates that make up the earth's crust move over the jets at the rate of a few centimeters a year, or about as fast as fingernails grow.

As a result of this SLOW creep, a single jet aver the ages can leave a

Trail of extinct, progressively older volcanoes in the plate above.

Such a trail is seen the Pacific, where the Hawaiian hot spot has

formed not only the Loihi volcano but a chain of extinct ones that  run west-ward

across the Pacific plate from Hawaii and then turns northward to form the Emperor seamount chain., extending to the northwest corner of the ocean. In all, the chain covers thousands of miles and mirrors tens of millions of years of volcanic action.

The bend where the Hawaiian chain turns into the Emperor chain represents a change of plate motion that occurred about 40 million years ago. 

The volcanic islands are slowly pared down by landslides  and sink deeper into the sea, usually leaving only the newer ones at the head of the chain above water — or struggling to break through the waves.

Loihi,  which means “long one” in Hawaiian and is pronounced low-EE-hee,  and is an elongated monster 13 miles wide and 25 miles long.  The `Pacific sea bed on which it rests isl~3.4 miles down at its lowest point.  During eruptions and outbursts over tens of thousands of years. Loihi has grown until the volcano is now more than 2.8 miles tall.  Its stirrings are carefully monitored by several government agencies including the National Oceanic and Atmospheric Administration, an arm of the Commerce Department, and the United States Geological Survey, which maintains a network of seismometers on the big island. Seismometers measure faint vibrations in the ground that tell of distant earthquakes

ear~tLoihi has heaved with seaquakes before, most recently in 1991, but not like this summers torrent of violence. The quakes prompted Harry Kim, the Civil Defense director of Hawaii County. which encompasses the big island, to warn residents to head for higher ground immediately if they felt an earthquake, since there would be no time for sirens or emergency broadcasts before a tidal wave struck.

Island residents are used to coping with threats of tidal waves generated by distant earthquakes far across the ocean, but not local ones. 

To better understand what was happening and, in part, to help develop ways to predict and warn of future dangers, Dr. Malahoff and his team dove into the depths. 

 "Eventually something will happen," he said of disasters on land touched by the deep volcano, " but maybe not in our lifetimes.” 

In trying to unravel the mystery of the deep upheaval, the team early on monitored the violence with microphones suspended from buoys and detected cracklings that sounded like the flow of deep lava.  But submersible probings of the northern Summit in the area of the cracklings revealed no new flows, only old ones.

What the team did discover, based on a comparison with older observations, was that a huge part of the volcanoes summit had collapsed in the frenzy of destruction.  "Nobody,"“ Dr. Malahoff said. “has ever observed the formation of these pitcraters.”

 The collapse of the summit probably look two or three days, he said, and its slowness was a godsend.. A quick collapse would have generated. a huge tsunami, or tidal wave. A likely possibility, he said, is that he slow collapse was provoked when the hot lava from the volcano’s interior oozed out of its flanks at a depth somewhere below the region where the Pisces submersible could explore.

 ex’ 1 In the most dangerous moment of the series of dives, Dr. Malahoff and two  colleagues ventured down to bottom of the new crater past fractured walls of towering rocks that were threatening to fall.. Later, at the crater’s bottom 1,000 feet the summit, the anxious team in the submersible, heard the rumble of a distant landslide.

At the base of the huge cliff, the team found a big vent belching hot water and clouds of microbial snow in the area around the vent painted  with orange and red—and flapping lettucelike leaves of bacterial slime.