How Far Did Mt St Helens Lahar Travel?
Past lahars at Mount St. Helens have traveled from 50 to 100 km (30 to 60 mi) from source, often reaching the Columbia River via the Toutle-Cowlitz, Kalama, or Lewis Rivers. They are a greater threat to life and property in valley communities than any other volcanic phenomenon. How far did Mt St Helens pyroclastic …