Glacier Peak, Washington, USA

By ExploreNow Editor, on December 13th, 2011

Volcano Type:     Stratovolcano
Volcano Status:   Tephrochronology
Last Known Eruption:    1700 ± 100 years
Summit Elevation:    3213 m    10,541 feet
Latitude:    48.112°N    48°6’42″N
Longitude:    121.113°W    121°6’46″W

Glacier Peak, the most isolated of the Cascade volcanoes, rises to 3213 m above the rugged forested terrain of the Glacier Peak Wilderness Area in the North Cascades. Glacier Peak is a dacitic-andesitic stratovolcano with summit and flank lava domes; it resembles Mount St. Helens in its explosive vigor. More than a dozen glaciers descend its flanks, prompting its name. Although its summit towers 3000 m above surrounding valleys, the volcano was constructed above a high ridge and is itself less than 1000 m high. Repeated major explosive eruptions associated with lava dome growth during the late Pleistocene and Holocene deposited tephra over wide distances to the east. Voluminous pyroclastic flows and mudflows extended into the Puget Sound lowlands to the west and diverted several river courses into adjacent valleys. The latest eruption of Glacier Peak only a few hundred years ago was noted by indigenous Pacific Northwest Indians, and hot springs occur on its flanks.

Glacier Peak in the distance (Wayne Weber)

Glacier Peak is a small stratovolcano in the Cascade Range of Washington. There are over one dozen glaciers on the sides of this volcano. Most of the loose pyroclastic deposits have been eroded by these glaciers. The tops of the ridges to the northeast of the volcano are covered by lava flows. Small basaltic flows and cones can be found around the sides of Glacier Peak. Lava flows only extend a few km from the top of the volcano. Three hot springs flow from the ground around the volcano. Fresh looking dacite domes are positioned high on the north and south sides of the volcano. Warm ground and areas without snow surround these domes. Large fans of pyroclastic materials almost entirely fill the valleys on the east and west sides of the volcano.