08/21/2026
How many lava domes can you see at Mount St. Helens today? This 1977 photo shows hikers heading up towards Dogs Head, a famous waypoint, ski destination, and glissade route for mountaineers before the May 18, 1980, eruption.
While Dogs Head can still be found on the northeast flank of the volcano, other old lava domes such as Goat Rocks were destroyed. Dogs Head formed during the Castle Creek eruptive period, approximately 2,000 years ago, and is composed of dacite (a viscous, silica-rich lava) like the current lava dome complex in the crater.
: The Castle Creek period is marked by a distinct change in eruptive behavior and lava composition, shown by alternating sequences of andesite, dacite, and basalt. It culminated with the eruption of the Cave Basalt lava flow, which poured down the southern flank of the volcano, forming lava tubes like (you guessed it) Ape Cave!
Sources: Roadside Geology of Mount St. Helens National Volcanic Monument and Vicinity by Patrick T. Pringle; U.S. Geological Survey Fact Sheet 2005-3045, 2005, Pre-1980 Eruptive History of Mount St. Helens, Washington (pubs.usgs.gov/fs/2005/3045).
Photo: From David Bruer's Mount St. Helens collection; photographer unknown.
