Global Volcanism Program | Image GVP-03234
This aerial photo shows the lobate morphology of the Glass Mountain obsidian flow, which erupted around 950 years ago from a series of vents near the buried east rim of Medicine Lake caldera. The eruption originated from a series of NW-SE-trending vents, seen here diagonally across the photo from the upper left. Three dacite flows to the east are overlain by rhyolite flows towards the west. The flow at lower left is the dacitic Hoffman flow, erupted only a few hundred years prior to the Glass Mountain flow.
Photo by U.S. Geological Survey (published in Green and Short, 1971).