Hawaiian hot spots: viewing volcanoes on the Big Island

Geologists like to astound the rest of us by being prodigal with time. It strains our sense of history to be told -- as visitors to Mauna Loa are -- that this 700,000-year-old, 30,000-foot mass of lava is just a youngster. But many rooted attitudes get shaken up here. For this is a place of such intense scientific interest that even the most casual visitor catches on to the excitement.

The most interesting parts of Mauna Loa and its sidekick, Kilauea, lie within the Hawaii Volcanoes National Park on the ``Big Island'' of Hawaii. It's an odd place, with a look of barrenness and past disaster. The vegetation is mostly stumpy, starved-looking trees and grasses. The occasional craters are large steep-sided holes, like pit mines, their greatest peculiarity the wisps of smoke that rise here and there from the bottom.

The Park Service has marked points of interest, such as the names of various pits and craters, and dates of different lava flows. Strangest to me were holes that exude a steady stream of hot wet air, like the breath of a huge subterranean animal.

From the side, Mauna Loa is one of the least assertive mountains I've ever seen; so broad and sloping it looks lower than it is. The experience of being here is not one of jarring heights and jagged inclines, but of gentle rises and gradual mounds.

It's not most people's idea of a volcano. But the reason you can poke around in safety is the same reason the mountain is the shape it is: The lava is so fluid that it runs a very long way, instead of piling up around a central crater. Although some precautions are necessary around any erupting volcano, this is one that thousands of rubberneckers run toward rather than away from.

Hawaii Volcanoes National Park received 2.8 million visitors in 1983, most of whom stayed less than 3 hours. They come by bus, stop at the Volcano House to look at the Halemaumau crater (until 1924 the site of a spectacular sea of fire), and pop over to the ranger station for an explanatory movie.

But for those who have more time to spend on this fascinating corner of the world, there's Bill Ebersole's ``Hawaii Natural History Tours.''

Mr. Ebersole, who has degrees in geology and marine geology, has worked as a geophysicist and a teacher. He describes his five-day tours of the Big Island as ``just like a rolling road show. The whole idea of my operation is to get people to understand the processes they see.'' He offers a variety of tours for small groups, but he also works through Elderhostel, a nonprofit educational organization for people age 60 and over.

I joined ``the rolling road show'' and 12 delightful Elderhostelers in midtour late one day at the park center. We headed off in Ebersole's van to the Thurston Lava Tube, one of the largest lava tubes open to the public. Before we went into this dripping tunnel, now bare of stalactites thanks to souvenir hunters, Ebersole explained its curious origin.

The outer edges of very fluid pahoehoe lava tend to cool and solidify so that the hot lava starts to encapsulate itself, leaving a flowing, red-hot interior. (The daring can actually stand quite close to glowing pahoehoe, and not feel much heat.) When the eruption ceases, the lava continues to flow, leaving behind these lava tubes. ``All pahoehoe flows are shot through with [them],'' says Ebersole.

That evening we bedded down in a bunkhouse, with the firm promise from Ebersole to wake us if Kilauea erupted during the night. (It didn't; an eruption was imminent, but it happened a week or so later.)

After a night of, alas, uninterrupted sleep, we began the next morning with a lecture on volcanoes, both general information and specific facts about the one that lay almost beneath our feet. Ebersole explained the reason scientists give for volcanoes being here, far from the edges of the Pacific crustal plate, the so-called Rim of Fire.

``Very deep, thousands of kilometers, in the interior of the earth -- probably due to the radioactive decay of minerals -- there is a point source of heat, directly beneath this island,'' says Ebersole. ``[From that point] a column of heat rises through the interior of the earth, and where that column of heat intersects the plastic layer, partial melting of the rock begins -- not complete melting; if it were complete, then there would be erupting mantle rock here.''

The latitude and longitude of this ``hot spot'' are relatively constant over long periods of geologic time. Meanwhile, this plate of Pacific lithosphere is moving in a northwesterly direction at about 3 to 5 inches per year, he explains.

If you look at a map of the Pacific Basin, you'll see that the islands are arranged in archipelagoes along the same angle as the Hawaiian Islands. This alignment indicates that they were formed by the same process, which Ebersole describes as ``a fixed hot spot that leaves these trails of volcanoes behind like smoke blowing behind a fire.''

The Hawaiian Islands, from Kauai, the oldest, to Hawaii, the youngest, are a perfect illustration. What is especially interesting is that the ancient Hawaiians had a myth that the fire goddess Pele first made her home in Kauai, then moved from one island to another, ending up on the island of Hawaii. Her legendary path fits the present scientific knowledge.

After the lecture, we piled into the van and headed for the Chain of Craters Road. The road takes you past all the volcanic high spots, past the smoking craters, the smooth, shiny pahoehoe and prickly surfaced lava called a`a (pronounced ``ah, ah'') caked over the fields. Ebersole pointed out places where the lava, at 2000 degrees C., flowed around a tree, creating a perfect mold of its bark before the tree burst into flame.

He dropped our group at ``Devastation Trail,'' once 1,250 acres of ohia forest, now a mostly lifeless moonscape of gray pebbles after the 1959 eruption of Kilauea Iki. In one area there are a few straggly ohia trees; these ``played possum'' (went dormant) for 10 years, Ebersole says.

The ohia tree, legend had it, was Pele's tree. Not only does it grow all over, but it has a red shaving-brush-like flower, like a little fire. Sharp-eyed hikers on Devastation Trail may notice Pele's tears -- dark brown blobs of volcanic glass.

We made a stop at the observatory of the United States Geological Survey. According to Ebersole, a temple dedicated to Pele, called the Temple of Wailing or Weeping Priests, used to be on this same spot. The temple was occupied 24 hours a day by the priests of Pele, who chanted and presented offerings continually. ``The whole idea was to keep Pele happy and keep the lid on,'' he says.

These ancient priests watched Pele's every mood. Today 30 or 40 technicians and scientists from the US Geological Survey are doing the same thing, keeping their own 24-hour-a-day vigil over Pele, ``and I'm sure wailing a lot every time it erupts . . . with glee.'' Practical details

Mr. Ebersole offers a variety of day and overnight trips for small groups.

Custom trips can be arranged: cost varies between $40 and $50 a day. Write Mr. Ebersole at Star Route 8-1502, Keaau, Hawaii 96749.

Mr. Ebersole offers a five-day trip (which covers different sites of interest around the Big Island) through Elderhostel; if you qualify (age 60 or over) write for their catalog: Elderhostel, 100 Boylston Street, Boston, Mass. 02116. The cost is $200 per person.

The National Park Service Station offers some helpful booklets for those who come on their own. The best general guide is ``Volcano Watching,'' by Robert and Barbara Decker. Another good one is ``Hawaii Volcanoes, the Story Behind the Scenery,'' by Glen Kaye.

The park rangers offer nature walks in summer.

This part of the Big Island has freakish weather. Bring a sweater and rain gear and be prepared to put them on and take them off them frequently throughout the day.