Location: Snohomish County, WA
Elevation: 3,213 m (10,541 ft)
Nearby towns: Darrington
Sitting relatively low on the skyline, Glacier Peak is mostly hidden from Puget Lowland residents, yet it is one of the more dangerous of the Cascade volcanoes. The volcano frequently and explosively produces dacite lava flows, tephra (ash) and far-reaching lahars (volcanic mudflows).
Geologic mapping has documented the extent of previous lahar runout in the Skagit and Stillaguamish river valleys. While Glacier Peak has shown no sign of eruption in the last few decades, lahar deposits in river valleys from past eruptions are reminders of the hazards Glacier Peak poses to nearby communities.
Lahar hazards are determined in part by figuring out where lahars traveled in the past. Evidence of massive lahars is abundant in many of the valleys that drain Glacier Peak. The above map shows the distribution of lava flows and lahars mapped at the surface. Volcanic hazard areas are shaded gray. Much of the past volcanic deposits have been either eroded or buried by rivers, glaciers or human development.
ERUPTION AND LAHAR HISTORY
Glacier Peak erupts frequently. The eruptions are typically explosive and occasionally voluminous. Most eruptions involve tephra, but many were accompanied by far-reaching lahars and dome-building.
Glacier Peak has erupted multiple times in the last 15,000 years. About 13,000 years ago, a series of large tephra eruptions occurred, accompanied by numerous lahars—one eruption was many times the size of the Mount St. Helens 1980 eruption. Within the last 5,000 years, the volcano produced frequent lava dome eruptions and subsequent dome collapse and lahars. The most recent eruption was only about 300 years ago.
Are You Volcano Ready?
- Get to know your local volcano’s hazards
- Register for notifications about the volcano’s activity
- Make a plan to prepare your entire family for an emergency
Visit the USGS website for more information on how to be volcano ready, view interpretive signs, and find lahar evacuation routes.
Click on the image (left) for a link to the poster.
Dragovich, Joe D.; McKay, Donald T., Jr.; Dethier, David P.; Beget, James E., 2000, Holocene Glacier Peak lahar deposits in the lower Skagit River Valley, Washington: Washington Geology, v. 28, no. 1/2, p. 19-21, 59.