Deposits from an explosive eruption
This welded ashflow tuff is from one of the few explosively erupted pyroclastic flows at Medicine Lake volcano. The eruption occurred about 130,000 years ago, at a time when the volcano was surrounded by glaciers, and initiated extensive melting and flooding. The chocolate brown tuff is composed of andesitic ash, and the dark lumps peppered throughout are glassy fragments of dacite.
Topic: Earth Science
Keywords: Medicine Lake (Mont.), Volcanic ash, tuff, etc., Volcanic eruptions, Volcanism