Mt. Rainier & Lahars
Did you know Mount Rainier is an active volcano? While we can't say how many times Rainier has erupted over the course of its existence, we do expect it to erupt again someday. The only questions is matter of when, and to what degree.
A Mount Rainier eruption will place the Puyallup valley at risk of catastrophe from a lahar, which is a volcanic mudflow that can reach 100 feet in height and travel 45 to 50 miles per hour. According to the United States Geological Survey (USGS), "Lahars look and behave like flowing concrete, and they destroy or bury most man-made structures in their paths".
Should Mount Rainier erupt, everyone in the valley will need to avoid the oncoming lahar by evacuating to higher ground. It's for this reason that the lahar warning siren system is tested on the first Monday of each month, and it's also why we provide a map showing recommended Volcano Evacuation Routes.
Learn more about Mount Rainier and lahars, courtesy of USGS.
Lahar Warning System
Pierce County Department of Emergency Management (PCDEM) expanded the number of outdoor warning sirens in 2020. PCDEM has 42 sirens in the Puyallup River Valley and the Nisqually River Valley. The recently upgraded sirens will have more capabilities to notify people of emergencies. They include voice warnings in English and Spanish, flashing lights to reach vulnerable populations, and verbal instructions based on the emergency. Testing happens the first Monday of each month. You can hear the tone and verbal instructions below.
In the Event of a Lahar
When a lahar has been detected, the system will use the "wail" siren to get people's attention. When you hear an emergency lahar siren, get to higher ground immediately!
Lahar Evacuation Routes
Lahar evacuation routes were developed to assist residents and visitors in finding higher ground in the event of a lahar. Click on the Evacuation Walk Time Map to see an estimated amount of time it would take to evacuate as a pedestrian. Click on the Evacuation Map to find the two closest lahar evacuation locations near you.
Bridge destroyed by lahar in North Fork Toutle River during eruption of Mount St. Helens, May 18, 1980.
(Credit: Waitt, Richard. Public domain.)
Open for Comment & Public Meetings
The US Geological Survey, Cascades Volcano Observatory (USGS) has requested a permit to expand the existing volcano monitoring system inside Mount Rainier National Park (MORA). Public involvement is a key part of the planning and decision-making process. To learn more about this process, visit the National Park Service (NPS) Planning, Environment, & Public Comment.
New Program Connects Girl Scouts to Volcanic Neighbors
Just in time for the 41st anniversary of the 1980 eruption of Mount St. Helens, Girl Scouts of Oregon and Southwest Washington (GSOSW) announced a brand new program, Our Volcano Neighbors, developed in partnership with the Mount St. Helens Institute (MSHI) and the United States Geological Survey (USGS). The program aims to teach girls about the cultural and geographical significance of Mount St. Helens and other volcanoes through hands-on STEM activities, career exploration and outdoor adventures.
What to Expect When You're Expecting a Volcanic Eruption
Learn about the five active volcanoes in the Washington Cascades, their hazards, and how you can be better prepared for an eruption. Hosted by the Washington State Emergency Management Division.
- Lahar Detection and Volcano Monitoring - National Park Service (NPS)
- Lahars on Mount Rainier - United States Geological Survey (USGS)
- Lahars - (USGS)
- River of Volcanic Mud and Debris (USGS)
- Mount Rainier Hazards - (USGS)
- Volcanoes and Lahars - Department of Natural Resources (DNR)
- Automated Lahar Detection Systems - (USGS)
- Are You Ready for An Eruption?
- How to be Safe if a Lahar Flows - Elementary School Edition
- Volcanic Hazards in Washington State
- Evacuation and Preparation
- Are You Volcano Ready?
- Pacific Northwest Seismic Network (PNSN)
- How Mount St, Helens Changed Our World
- Modeling the Dynamics of Lahars that Originate as Landslides on the West Side of Mount Rainier- USGS