Columbia River

River Deposits

Water is the most destructive force on earth in the long term. Given enough time, water will tear down the most massive mountain range. But it can also create; the White Bluffs are the result of the ancestral Columbia River leaving deposits in its path, but eventually the river will tear them down, as well.

The ancestral Columbia River repeatedly changed its course over the past fifteen million years and left deposits of gravel, sand, silt and clay. The deposits were the result of the ancestral river’s growing restriction in the low areas of the Pasco Basin and lower Yakima Valley as the rising ridges of basalt grew. These processes changed the course of the Columbia River from a southerly direction (toward Yakima and Goldendale) to an easterly direction (toward Wallula Gap) and left behind the Ringold Formation. Later, regional uplift in the western United States caused the river to cut through its own earlier deposits (the Ringold Formation), exposing the Monument’s signature White Bluffs.

Today the Columbia River continues its erosion. The force that first exposed the White Bluffs is now wearing away its base. Groundwater, along with irrigation water seeping into the ground from northeast of the bluffs, makes them unstable. The result is the White Bluffs are sliding and sloughing into the Columbia River, giving back its ancestral deposits.