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.

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