Science: Inferno in Idaho

The southwest corner of Idaho is a rugged land pocked by ancient volcanic activity. Once a desolate region covered by sagebrush, it has been reclaimed by irrigation. The soil, largely volcanic ash, is fertile with minerals. The rock beneath is honeycombed with caverns and air pockets, the result of ancient, igneous intrusions.

A fissure in the earth split the farm of Harley Robertson, soon widened as its sides fell in, became a canyon 200 ft. deep, its bottom crawling, heaving, puffing. It swiftly swallowed 20 acres of Robertson’s farmland. Other fissures snaked across his property, threatened 80 acres more. Salmon Falls Creek ran yellow with volcanic dust and yellow puffs spurted from dry fields. Muffled thunder rose from underground, as though boulders were detaching themselves from the roof of a subterranean cavern and falling to the floor. The first canyon continued growing in the direction of the stream. If it reached there geologists expected to see the river disappear underground. They feared a sudden, widespread collapse which might engulf adjoining farms, cause a destructive local earthquake.

Professor John H. Sawyer of Boise High School, longtime Idaho geologist, advanced two possible explanations:

1) “Millions of years ago a huge lava flow crept across south central Idaho, moving south, filling in canyons, leveling off the countryside. When the flow ceased, the upper crust cooled and hardened, while the lower lava continued flowing. Along the buried canyons the sub-lava flood tore out everything it could carry along, leaving vacant spaces roofed over by the cold crust. As the material weathered it began to collapse. This is now taking place on Robertson’s farm.

2) “There may be also a laccolith: a formation where lava once pooled into a cone. The top crust cooled but the hot material beneath found egress, leaving a bubble formation with the top separated from the bottom by perhaps 1,500 ft. In this case sinking would continue until a box canyon was formed.”