A Brief Guide to the Parapet View, Sinnott Memorial, Crater Lake National Park by John Campbell Merriam, 1938
View 3: Lava Outpourings Through Splitting of Crater Rim
Devil’s Backbone, seen through the finder at this box, is an illustration of alava dike.In addition to spilling out as broad flows of melted rock, it is common for the tremendous mass of molten lava in a volcano to break through the mountain side. The lava filling of such a crack or fissure is known as a dike. After it cools the material filling these fissures is often harder than the surrounding rock. Subsequent wash of water may cut away the softer bordering material, leaving the hard filling of the fissure as a sharp ridge.
A diagram of the mountain in this box points out other radiating fissures or dikes. Specimens of these lavas are also shown.