Dacite boulder in volcanic mudflow of the Devastated Area mudflow, from
the 1915 eruption of Lassen Peak (Photo 5). The angular joint surface are evidence
that the boulder was emplaced very hot but cooled rapidly in place contracting
to form the angular joint surfaces. Hammer for scale. Photograph by R. Forrest
Hopson.
Images of Volcanoes
To VolcanoWorld