A large lava flow forms Burroughs Mountain on the NE flank of Mount Rainier. The 3.4 km³ flow is up to 350 m thick and is 11 km in length. The flow erupted about 500,000 years ago at the onset of an initial growth period of modern Mount Rainier and overlies block-and-ash flow deposits. The flow is perched on a ridge top and has ice-contact features, indicative of its emplacement against the margins of a thick Pleistocene glacier.

Photo by Lee Siebert, 1982 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Rainier