Lahars at Mount Shasta
Eruptions at the Hotlum and Shastina vents, about 10,000 years ago, produced many lahars, about 20 percent of which reached more than 20 km from the summit of Mount Shasta, and spread out on fans around the base of the volcano. Even larger lahars and floods extended beyond the base of the volcano and entered the McCloud and Sacramento Rivers. If they occur in the future, lahars may cover valley floors and other low areas as much as several tens of kilometers (10 km = 6.2 mi) from the volcano. They will also impact the systems of rivers which flow from Mount Shasta. A primary concern in this category is the Sacramento River.