A different kind of threat looms beneath Mount Shasta this fall

MOUNT SHASTA, CALIF. — Mount Shasta, California's fifth-tallest peak is classified as a potentially active volcano in Siskiyou County. While the last known major volcanic eruption occurred nearly 3,200 years ago and no eruption is imminent, a different kind of threat could come to nearby towns this fall.

The stratovolcano in Northern California is home to some of the largest and oldest glaciers in the state of California. When the mountain experiences extreme weather events even as high as 14,000 feet, impacts can be felt well downstream.

Lack of snow cover, drought, heat waves, and intense rainfall can have effects on the glaciers on Mount Shasta, causing rapid glacial melt and destabilization of rock leading to a combination of flash flooding, mudslides and even debris flows including trees, rocks and sometimes vehicles into it's glacially-fed channels like Whitney Creek, Mud Creek and Ashe Creek.

As warmer fall storms approach towards the end of the October bringing heavy rains to higher elevations of the mountain, flash flooding from rapid glacier melt could occur along Whitney Creek and Mud Creek impacting towns like Weed on the northern slope of Mount Shasta, and McCloud to the south.

These effects in the past have lead to highway closures and evacuations due to safety hazards like mass movements of boulders, mud, and trees, including a recent event this summer along Whitney Creek following intense thunderstorms in August.

Shasta-Trinity National Forest says to, "please respect these events they can happen at any time and largely without notice."

Mud Creek and Whitney Creek both have an especially long and active history of debris flows sourced from glaciers. Mud Creek was particularly active during a prolonged drought in the 1920s, with the largest event occurring in August 1924 after a winter with very little snow that was then followed by a hot summer, cutting off McCloud’s water supply and burying an area up to one mile wide, five-miles long, and over ten-feet deep with mud and debris.

After a relatively long period of quiet, punctuated by a few events—including multiple during a drought period in the late 1970s, an event on Whitney Creek in 1997, and another on Mud Creek in 2014—Forest officials say the mountains glacially-fed channels became active again in the summer of 2021.

Forest officials with Shasta-Trinity National said they are working closely with scientists at the U.S. Geological Survey’s California Volcano Observatory to improve monitoring and scientific understanding of debris and mudflows on Mount Shasta for both public safety and the protection of natural resources in the future.

As warmer fall storms approach with heavy rainfall this fall, now is the time to know your evacuation zones at community.zonehaven.com in preparation of flash flooding and debris flows in Siskiyou County.