Feb 7, 2025
Mount Rainier is not the only volcano in the park. There are also several satellite volcanoes surrounding it. A couple of these satellite volcanoes formed about 105,000 years ago when new vents opened on the lower northwest flank of Mount Rainier. Lava flows of basaltic andesite (hotter, more fluid magmas than typical for Mount Rainier) spread across the Spray Park and Mist Park areas from cinder cones preserved as Echo and Observation Rocks. The vents were probably fed from a great depth rather than laterally from the same system that fueled Mount Rainier’s eruptions. Have you noticed these two two volcanic features when hiking in the area?
NPS/S. Redman Photo of Observation and Echo Rocks.
