Lahar deposit from 100,000 year old debris avalanche off north side...

Geologist examining 100,000-year-old lahar deposit exposed along Underwood Hill Road, near the mouth of the White Salmon River in Washington. The lahar, derived from a large debris avalanche off the north side of Mount Hood, flowed down the Hood River, crossed the Columbia River, and traveled several miles up the White Salmon River before stopping. Here, the deposit is about 40 feet thick and about 300 feet above present river level.