Mauna Kea shield with parasitic cinder cones Composite or stratovolcanoes Mount Shasta and Shastina, California. Photo by Tom Casadevall, May 9, 1979. Colored regions received more than 2 cm of ash, with meter-scale deposits close to the vent areas. Debris-flow avalanche deposit from Mount St. Helens formed on 18 May 1980.
Hummocky surface is typical of avalanche deposits.
This photograph shows a large dacitic block from Mount St. Helens within a matrix of smaller sized and more mafic composition fragments. Erosion has carved into the debris avalanche to provide exposures of individual blocks. Although the blocks are coherent masses, they have been extensively fractured and can be excavated with a shovel. Mount Shasta and debris avalanche hummocks. The slopes of Smith Creek valley , east of Mount St. Helens, show trees blown down by the lateral blast.