Volcanic Activity

Volcanoes are a natural hazard that can have serious impacts on communities. In Thurston County, the two most significant threats are from Mount Rainier and Mount St. Helens. Mount Rainer is an active stratovolcano located about 50 miles southeast of the County. Mount St. Helens is another active stratovolcano about 100 miles northwest of the County. Mount St. Helens is perhaps best known for its catastrophic eruption on March 16, 1980, causing widespread damage and 57 fatalities.

While the chances of a major eruption from Mount Rainer or Mount St. Helens in the near future are low, it is important for communities to be aware of the potentially catastrophic hazards and to be prepared to the possibility of an eruption.

Lahars

Lahars are a type of volcanic mudflow that can be formed during volcanic activity. They are created when ash, rock, and debris from a volcano mix with water, creating a slurry-like substance that can flow downhill at high speeds. Lahars can occur when volcanic activity causes melting snow and ice on the mountain, or when heavy rainfall triggers landslides.

Lahars can pose a serious hazard to communities located downstream from a volcano in lower elevation valleys. They can cause damage to buildings, infrastructure, and natural habitats as they move, and can pose a serious danger to people in their path. Lahars can travel at high speeds and can be difficult to outrun, so it is important for residents to be aware of evacuation routes and follow evacuation orders if a lahar threat is imminent.

United States Geological Survey (USGS)

The USGS monitors and studies volcanic activity in the United States and around the world to better understand the underlying processes and to provide information that can help reduce the impacts of volcanic activity on communities. This includes monitoring volcanic eruptions and providing alerts to the public and other agencies when an eruption or lahar is imminent or underway. Learn more about volcanic hazards on the USGS’s website.