29 min
Overview
The one-square-mile Big Obsidian Flow is one of the most memorable features in a landscape of outstanding volcanic features in the Newberry National Volcanic Monument. This lava flow, composed of black glass (obsidian) and pumice, is the youngest in Oregon and issued forth only 1,300 years ago. The lava erupted from a magma chamber two to four miles deep at a temperature of 1600 degrees Fahrenheit. At first, the eruption was gas-charged and explosive. Later, the lava emissions slowed to a 100-foot-high silica-infused creep that produced a thick dome over the vent. Three layers emerged: white pumice from the frothing of the lava's surface; glassy obsidian in the middle; and gray pumice charged with huge bubbles on the bottom. Lighter pumice attempted to rise, while heavier obsidian tried to sink and a general mixing and shattering of liquid and solid components resulted in the fractured landscape you see today. Native Americans took full advantage of the natural resource and fashioned obsidian fragments into tools and weapons, such as spear and arrow heads. Note that collecting obsidian is forbidden within the Newberry National Volcanic Monument.
Trail Stats
1.3 km
61 m
2012 m
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Photos
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