Hawaii Volcanoes National Park

By Patrick Totty

Since the theme for this wintry month’s issue is warm places, we thought we’d seek out a national park that’s not only located in a sunny clime but makes its own heat.

Inevitably we settled on Hawaii Volcanoes National Park on the Big Island of Hawaii. With its virtually continuous volcanic activity, this 500-square-mile park offers its 1 million annual visitors an almost bird’s-eye look at one of earth’s great wonders: an island that grows before their very eyes, adding the equivalent a square mile to its area every 20 years.

(Between 1983 and 2000, Kilauea’s eruptions added 550 acres of new land to the island of Hawaii – an average of 32 acres per year. At that furious rate of new land formation, which is most likely an anomaly, Hawaii is growing by one square mile (640 acres) every 20 years. Come back in 10,000 years and the island will have added 500 square miles to its current area of just over 4,000 square miles.)

You may ask why with such a high rate of land formation Hawaii hasn’t already grown to the size of a Borneo or New Guinea. The answer is that the geological forces that created the island chain also conspire to destroy it.

The first of the Hawaiian Islands to pop into existence was distant Midway, almost 1,500 miles northwest of the Big Island. A “hot spot” under the ocean, created by a weakness in the crust, allowed magma to thrust above the ocean surface as volcanoes and begin the process of land building.

As long as Midway remained on top of that hot spot, it received new infusions of area-increasing lava. At one time, the island towered as impressively above the sea as Kauai.

But tectonic drift pushed Midway inexorably northwest, away from the hot spot. Once removed from its source of replenishment – volcanoes – the island began inevitably shrinking from wind and water erosion. Today, Midway barely rises above sea level. In a not too distant future, it will lie beneath the ocean.

This process was repeated several times over the years. The hot spot created Kauai, Lanai, Molokai, Oahu, Lihue, Maui and the Big Island. Although the process will take years, as the islands move away from the hot spot, erosion will reduce them to Midway’s condition.

Once you understand the process of island formation, it becomes all the more astonishing when you realize that the Big Island is estimated to be a mere 800,000 years old. There are rocks in Australia that are 4,000 times older than Hawaii. 

So, what sort of volcano is responsible for this prodigious construction? Geologists will tell you that there are two kinds of volcanoes: strato and shield. Strato volcanoes are the big Vesuvius and Mt. St. Helens-type bruisers that spew immense volumes of superheated ash, pumice and poisonous gases into the atmosphere. The poor townspeople of Pompeii who died en masse in 79 A.D. from Vesuvius’s big blow mostly expired from suffocation, not flesh-combusting burns.

Shield volcanoes, which are the park’s variety, can be just as high as stratos – Mauna Loa, the park’s high point at 13,677 feet, would tower over Etna or Stromboli – but are shaped less like steep cones and more like broad, gently sloping arcs. Their effluvia are dramatically different, too: red-hot rivers of molten rock, sometimes moving at the speed of a slow walk, pushing seaward in fiery channels. In comparison to their strato kin, these volcanoes can seem positively tame.

However, they’re not. Their lava may be slow moving, but it’s also inexorable. Heated to nearly 2,000 degrees F, this is hot stuff that no man-made material can long resist. The good news is that if you’re in its path, there’s usually enough time to scurry out of its way. But once it arrives at your house, car, garden, your pet gopher, whatever, the objects in question are toast, then vapor, and then a constituent part of the flaming slurry.

The most active volcano in the park is Kilauea, a low-rising, almost constantly active source of lava. It’s almost constantly in the news, either sending yet another new stream of lava into the ocean or, more ominously, in the direction of towns and villages. In any case, Kilauea may be the best and (relatively) safest place on earth where ordinary people, taking precautions, can get very close to a lava flow.

Two useful URLs: The first goes to the park’s home page; the second to a boffo site that explains Hawaii’s land-building plate tectonics.

http://www.nps.gov/havo/home.htm

http://www.biosbcc.net/ocean/marinesci/02ocean/hwgeo.htm