Since April 28th, the volcano Merapi has been rumbling and threatening roughly 60,000 residents of Java, Indonesia. Although eruptions can be energetic enough to reshape the very earth -- forget about transient features like forests and cities -- resourceful Icelanders have demonstrated that technology offers hope for those who live around fire-mountains.

In 1973 residents of Vestmannaeyjar on the Icelandic island Heimaey defended their town against lava flows advancing from Eldfell, a newly forming cinder cone. The story reads a bit like mythology. The Earth spewed voluminous lava over Heimaey along with an arrogant boulder called Flakkarinn which rode atop the flow and threatened to destroy the island's critical harbor. But professor Þorbjörn Sigurgeirsson ("Þ" is like "Th") of the University of Iceland devised an elegant defense: counter earth and fire with water.

The numeric quantities involved in an effort to counter a damn volcano are difficult to grasp intuitively. For example, the total volume of lava that flowed out of Eldfell was roughly one quarter of a cubic kilometer. That description is roughly useless without some comparisons: it was enough material to add about one square mile to the island. Larger but in the same ballpark, Lake Meade contains about 35 cubic kilometers of water.

There were two techniques for deploying water against lava. First, seawater, sprayed on the advancing lava front, heated up and evaporated thereby causing the lava to cool, harden, and pile up. The result was a dyke that constrained and redirected following lava. Second, distributed by plastic pipes over a wide field of cooling lava, evaporating water could create internal cold spots that caused lava to trip over itself and grow deeper rather than spread farther. The effect was something like causing a lot of traffic jams on an otherwise fluid-flowing highway.

Over three months of pumping, the volume of seawater deployed was vast: about 6 million cubic meters. By comparison, about 100 million cubic meters of water flooded New Orleans following the hurricanes of 2005, and about 3.7 million cubic meters of trash had been removed from that city by 2006.

Delivery of so much water, quickly enough to be effective, required big pumps. Thus the dredger Sandey labored to slow the progress of Flakkarinn towards the fishing harbor that made Vestmannaeyjar viable. Sandey delivered 400 liters per second, which is about as hard as 10,000 sports fans might labor, or roughly the cardiac flow rate of 1,500 Olympic sprinters. Eventually, the Sandey helped freeze Flakkarinn, and the surrounding flow, 100 meters short of crashing into the harbor. That's the length of one regulation football cliché.

Evaporating seawater leaves its salt behind. In this image of Heimaey, taken after lava cooling operations, large white salt deposits are visible between Eldfell and the island harbor.

(image taken from USGS , modified by Ben Heasly)

The U.S.Geological Survey and University of Iceland estimate that about 220 million kilograms of salt are left over from evaporated seawater. The Titanic had a quarter of that mass.

Since unbroken rock is a reasonably good insulator, Eldfell's fields of cooling lava would remain hot, underground, for years. Characteristically, Vestmannaeyjar residents have drawn from that resource to heat water and generate electricity -- up to 40 million watts of power. That energy output is about four times the output of Togo, and about 13 times the output of a diesel locomotive. Perhaps surprisingly, it's only 16 times the peak power output of a blue whale.

As with Eldefell, and almost by definition, natural processes and human technology are apt to collide. In some areas, humans chronically have made bad technological choices that interfere with nature. Consider global warming caused by industrial greenhouse gasses and the far more frightening sister process of global dimming.

But it's hard to argue that Vestmannaeyjar's people should have abandoned their homes and allowed Eldfell to form naturally. Their intervention with nature was acute and focused on a positive goal. Indeed, their extraction of geothermal power which was made accessible by Eldfell's formation represents a harmonious interaction with nature. If only the role of technology were always so clearly indicated.

« Previous Next »