The Divide Valley

We are in the center of Divide Valley, between the Pioneer Mountains on the west and the Highland Mountains on the east. Divide Creek flows below us from north to south. The valley, stream, and community to the south get their name from the Continental Divide, which is about 3 miles north of here. Stream erosion and fault movement shaped Divide Valley over the last 50 million years. It formed in two stages: 1. The first stage involved faulting along what is now the east side of the valley, and erosion from a south-flowing river. The river originated somewhere north of Butte in the headwaters of a system that drained into the Atlantic Ocean. The river carried fragments, or clasts, of volcanic and granitic rocks that filled the valley and hardened into sedimentary rocks. 2. Starting about 15 million years ago, east-to-west extension of the earth’s crust created the Basin and Range geologic province. Movement on both old and new faults widened and lowered the Divide Valley, creating a flat-bottomed, linear trough bordered by mountains. For over 1000 miles south along I-15, basins and ranges just like this dominate the landscape. Basin and Range extension continues to this day, generating earthquakes and rearranging stream drainages. It caused the Continental Divide to jump to where it is now – crossing the valley north of here at Feeley Hill. On this side of the Continental Divide, water flows into the Missouri River, which ultimately drains into the Gulf of Mexico. On the other side, all streams drain into the Columbia River and ultimately the Pacific Ocean.