Spill Over
by Marnie Patchett
Title
Spill Over
Artist
Marnie Patchett
Medium
Photograph - Photograph
Description
Little Glass Mountain Geologic Area offers a rare glimpse of a young volcanic glass flow. It covers over one square mile, mostly on Shasta�Trinity National Forest, with about 100 acres on Klamath National Forest.
Just over 1,000 years ago, Little Glass Mountain was formed as viscous lava oozed out of one of the vents along the southwest flank of Medicine Lake Volcano and moved slowly down slope, building up the spectacular high flow front of broken obsidian and pumice you see from the road today. Glass flows are an uncommon and intriguing phenomena. Because the eruption at Little Glass Mountain was so recent, we are afforded the unique view of an intact flow.
The black glass is called obsidian, and the frothy, airy rock is called pumice. Red hues are the result of weathering or oxidation during eruption.
The first eruptions from the vent were explosive and produced tephra, a deposit of small fragments of pumice, glass, ash, and broken rock fragments from the older, underlying lava flows. When lava began to ooze out of the vent, some of it contained large gas bubbles. Pumice formed at the top of the flow as the lava continued to release gas before it solidified. Solid obsidian also formed as it cooled. On the top and bottom of the flow, volcanic rocks were broken up as the flow advanced, forming breccias.
Obsidian within the Medicine Lake Highlands has been used for thousands of years by numerous American Indian tribes. With a cutting edge sharper than a surgical scalpel, obsidian was formed into a variety of everyday tools. Often these tools, and the flakes from their manufacture and maintenance, are the only traces left of past human activities on the landscape. Obsidian from the Medicine Lake Highlands was a principal trade item and has been found as far away as California's northwestern coast and central valley. Obsidian and obsidian source locations have spiritual as well as functional value for American Indians; as such these areas continue to be of special interest to today's American Indians.
Collection of obsidian from Little Glass Mountain Geologic Area is prohibited.
Uploaded
August 10th, 2016
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