What is obsidian and why is it important to the geologic history of the Jemez Mountains? How far away has obsidian from the Jemez Mountains been found?
Obsidian is a shiny, black volcanic glass that is found throughout the Valles Caldera and Jemez Mountains. It is formed by rapidly cooling lava with a high silica content. Broken edges of obsidian are extremely thin and sharp, providing tremendous benefit to humans as arrowheads, points, spears, knives, and scrapers. Such tools are as sharp as surgical steel. One of the primary uses of the Valles Caldera to humans for over 10,000 years has been collecting obsidian to construct tools such as mentioned above, and in trading such tools. When a piece of obsidian is fractured, it begins to absorb hydrogen from the air at a set rate. Under a high-powered microscope, one can examine the length of the hydration rind formed through this absorption of hydrogen on a piece of fractured obsidian and roughly determine from that when the obsidian was broken. From this evidence, we know that people have used the Caldera for 10,000 years. Each volcano around the world has its own chemical fingerprint.
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