blackfoot-valley

to many thousands of feet thick spread from the polar regions to cover all of what is now Canada and large parts of the northern United States and Europe. It was towards the end of the last glacial period that the maximum extent of the ice sheets during the last ice ages is believed to have been reached. No- tice we say ice ages here, not “the ice age”, which has been, and still is, a term popularly used for the most recent one. Long after the realization that there was a past ice age which entered the scientific consciousness during the mid- 1800s and that geologists finally dated its last retreat to 10,000 plus years ago, it was thought that this was the Ice Age. But as the twentieth century ad- vanced it became increasingly clear that it was only the most recent episode of many ice “ages,” often lasting close to 100,000 years and separated by warmer periods called interglacials, typically lasting 10,000 years, during which the ice sheets retreated. We are presently living during one of these “interglacial” pe- riods. In our present region, it needs to be emphasized that what is now Mon- tana is located at the very southern edge of the great American icecap, 1. Glacial Lake Missoula 2. Clark Fork River Valley 3. Camas Prairie 4. Channeled Scablands 5. Dry Falls 6. Flood Debris 7. Eratics 8. Temporary Lakes 9. Columbia River Gorge 10. On to the Pacific 17