Alaska's Hot Springs

For a land that has a reputation for being all ice and snow. Alaska has a goodly share of hot springs and flows of warm water. More than a hundred hot springs locations dot the Alaska mainland and another 24 reportedly gush forth from the Aleutian Islands.

A new publication "Geothermal Energy Resources of Alaska" contains a map and information on Alaskan hot springs and other geothermal resources. Prepared by Dr. Donald Turner and coworkers at the Geophysical Institute, this publication is the first to combine in one place the available information on Alaskan hot springs.

Two features of the Alaskan hot springs map stand out. One is that the springs are scattered all over the state. The other is that the springs group together in more-or-less linear arrays, the reason being that the springs are associated with linear geologic structures such as linear fracture zones or volcanic belts.

Virtually all of the hot water emerging in hot springs starts out as precipitation. From the ground surface it penetrates through faults or water-permeable layers deep enough in the ground to become heated before returning to the surface under hydrostatic pressure. In other words, the water must emerge from the ground at a lower place than it went into the ground.

In the Aleutian Islands and near the volcanic Wrangell Mountains, water can be heated at quite shallow depths by magma (molten rock) not far below the ground surface. The water that emerges from the band of hot springs stretching east-west across northcentral Alaska probably seeps more deeply into the earth where it is heated by still-warm rock solidified long ago.