- What is a volcanic deposit?
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- A volcanic deposit is formed in a localized zone of the earth's crust. A volcano is basically a vent or fissure in the crust through which hot magma, gases or other fluids escape to the surface. These vents can be small or extremely large and depending upon the size can either change a localized area or a large region. In modern times we have not seen very many large events which have formed new mineral deposits. Many old calderas are testament to past events.
At the Maynard Topaz Mine volcanic activity was kind to the area since there was a naturally occurring bowl with a solid caprock which acted as a lid. Here the volcanic activity took place through vent pipes containing chemicals in a gaseous state which became trapped in the "pot". With nowehere to go the result was large crystals of topaz and other minerals. In the Bishop, California area and the Owens Valley in particular one can see cinder cones, ash deposits and geothermal activity. In fact the area near Mammoth, California is under observation for volcanic activity and has had a drastic increase in seismic activity (earthquakes). In the Mojave Desert there is also an area known as Cima Dome which is a pushed up region of the desert resulting from a near surface vent. Watch out on your drive to or from Las Vegas from Los Angeles.
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- Some interesting sites with pictures of minerals from volcanics......
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