Don't Poke Into Underground Volcano Chambers

Volcanoes have been much in the news this past year. The Mt. St. Augustine eruptions in Cook Inlet during the spring of 1986 is one example, but there were also other eruptions of Aleutian volcanoes which were not as well documented. The mysterious gas clouds emitted from an extinct water-filled crater in Cameroon during August killed at least 1,700 people, and the ooring lava flows on Hawaii destroyed the homes and fortunes of many people on the "Big Island" at the end of the year.

Scientists and laymen alike have often wondered what it would be like if it were possible actually to bore down to a magma chamber. (Magma is the molten rock that seethes beneath the surface before it finally emerges as lava.) Well, it has been done, although it was unexpected and unintentional.

Back in 1968, drillers in Iceland sank a borehole to a depth of over 3,700 feet to tap a hot-water aquifer for geothermal power near Namafjall. For nearly the next ten years, the hole produced the steam that was expected of it.

Then, on September 8, 1977, the whistling steam was suddenly replaced by a gusher which shot a column of lava about 100 feet into the air. The red-hot jet of molten rock gave off copious quantities of quantities of sparks and cinders, and was accompanied by a steady roar. The display lasted only a few minutes, after which the man-made "volcano" died down and then seemed to "clear its throat" by coughing up a few shots of glowing scoria (rough, bubbly pieces of lava). The borehole then placidly resumed its intended purpose of producing steam again. In all, about five tons of lava and scoria had been deposited at the surface.

Gudrun Larsen, Karl Gronvold and Sigurdur Thorarinsson of the University of Iceland describe the incident in Nature magazine, and speculate that it may have resulted from a minor fault shift that took place during the day.

The workers point out that the geothermal field is located only about five miles from a major volcanic crater (the Krafla caldera) and the magma is continuously siphoned off along "feeders" from the caldera. What appears to have happened is that the fault shift took place at about the same time that an injection of magma was occurring in the same location. So borehole, magma, and fault offset all were present at the same time and in the same place. Poof!