Panum Crater
Encyclopedia
Panum Crater is a volcanic cone that is part of the Mono-Inyo Craters
, a chain of recent volcanic cones south of Mono Lake
and east of the Sierra Nevada, in California
, USA. Panum Crater is between 600 and 700 years old, and it exhibits all of the characteristics of the textbook rhyolitic
lava dome
.
Rhyolitic volcanoes are characterized by having large amounts of silica (quartz) in their lava. The content of silica at Panum is about 76 percent. It makes the lava very viscous
, or thick, and very glass
y. Products of this rhyolitic eruption are pumice
and obsidian
, the volcanic glass that Native Americans used to make arrow points and scrapers.
Panum Crater formed in a sequence of events. The first event was caused by magma
rising from deep within the Earth's crust. When this extremely hot, liquid rock made contact with water just below the surface, the water expanded into steam and a large, violent eruption occurred. So much debris was blown out that a gaping crater was left behind.
Once this debris was blown out, a fountain of cinder
s shot up a great distance into the sky. As this huge amount of ash and pumice began to fall back towards the earth, it formed a pumice ring, or cinder cone, about the original vent. You can still see this cinder cone today.
Following the violent eruptions of the first two phases, the remainder of the thick magma slowly rose to the surface in a series of domes. Each dome began with an outpouring of the viscous, rhyolitic lava which hardened and formed a cap over the vent. As magma continued to push up, the cap (or dome) shattered and fell to the outside of the newly formed dome. This happened so many times that a new mountain was created out of these broken pieces, called crumble breccia. The mountain continued to build in this manner until the force within the volcano weakened and no more new domes formed. The final one still stands today.
As the final dome hardened, a period of spire building began. Thick lava pushed up through cracks of the hardening dome and formed castle-like spires. If you can imagine toothpaste squeezing through the opening of a tube and forming a small tower before it topples over, you can imagine how these spires form. Most of the spires at Panum fell over and broke because of their rapid cooling and because of many small explosions at their bases. Most of the rocky debris you see at the top of the dome is the remains of spires that have crumbled.
Mono-Inyo Craters
The Mono–Inyo Craters is a volcanic chain of craters, domes and lava flows in Eastern California that stretches from the northwest shore of Mono Lake to the south of Mammoth Mountain. The chain is located in Mono County in the U.S. state of California...
, a chain of recent volcanic cones south of Mono Lake
Mono Lake
Mono Lake is a large, shallow saline lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in a basin that has no outlet to the ocean...
and east of the Sierra Nevada, in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, USA. Panum Crater is between 600 and 700 years old, and it exhibits all of the characteristics of the textbook rhyolitic
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
lava dome
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
.
Rhyolitic volcanoes are characterized by having large amounts of silica (quartz) in their lava. The content of silica at Panum is about 76 percent. It makes the lava very viscous
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
, or thick, and very glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
y. Products of this rhyolitic eruption are pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
and obsidian
Obsidian
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
, the volcanic glass that Native Americans used to make arrow points and scrapers.
Panum Crater formed in a sequence of events. The first event was caused by magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
rising from deep within the Earth's crust. When this extremely hot, liquid rock made contact with water just below the surface, the water expanded into steam and a large, violent eruption occurred. So much debris was blown out that a gaping crater was left behind.
Once this debris was blown out, a fountain of cinder
Cinder
A cinder is a pyroclastic material. Cinders are extrusive igneous rocks. Cinders are similar to pumice, which has so many cavities and is such low-density that it can float on water...
s shot up a great distance into the sky. As this huge amount of ash and pumice began to fall back towards the earth, it formed a pumice ring, or cinder cone, about the original vent. You can still see this cinder cone today.
Following the violent eruptions of the first two phases, the remainder of the thick magma slowly rose to the surface in a series of domes. Each dome began with an outpouring of the viscous, rhyolitic lava which hardened and formed a cap over the vent. As magma continued to push up, the cap (or dome) shattered and fell to the outside of the newly formed dome. This happened so many times that a new mountain was created out of these broken pieces, called crumble breccia. The mountain continued to build in this manner until the force within the volcano weakened and no more new domes formed. The final one still stands today.
As the final dome hardened, a period of spire building began. Thick lava pushed up through cracks of the hardening dome and formed castle-like spires. If you can imagine toothpaste squeezing through the opening of a tube and forming a small tower before it topples over, you can imagine how these spires form. Most of the spires at Panum fell over and broke because of their rapid cooling and because of many small explosions at their bases. Most of the rocky debris you see at the top of the dome is the remains of spires that have crumbled.