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From Wikipedia, the free encyclopedia

Panum Crater
Panum Crater at the foot of the Sierra Nevada
Highest point
Elevation7045+ ft (2147+ m) NAVD 88[1]
Prominence220 ft (67 m)[1]
ListingGreat Basin Peaks List[2]
Coordinates37°55′47″N 119°02′41″W / 37.9296487°N 119.0445904°W / 37.9296487; -119.0445904[3]
Geography
Panum Crater is located in California
Panum Crater
Panum Crater
Location in California
LocationMono County, California
Parent rangeMono–Inyo Craters
Topo mapUSGS Lee Vining
Geology
Mountain typeRhyolite lava dome
Volcanic fieldLong Valley Caldera Field[4]
Last eruption1325-1365 CE[5]

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, United States. 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 glassy. Products of this rhyolitic eruption are pumice and obsidian, the volcanic glass that Native Americans used to make arrow points and scrapers.[6]

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. The material that was thrown into the air by the steam, mainly old lake bottom sediments, was deposited around the new vent in little mounds.[4] So much debris was blown out that a gaping crater was left behind.[6]

Once this debris was blown out, a fountain of cinders 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. This cinder cone is still visible today.[6]

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.[6]

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. The formation of the spires was analogous to toothpaste squeezing through the opening of a tube and forming a small tower before it topples over. 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 at the top of the dome is the remains of spires that have crumbled.[6]

Flow banding in the obsidian dome

The central lava dome was erupted from degassed material and is made up of pumice and obsidian of the same composition. The difference between the two has to do with gas escaping as the magma cooled. The magma that created the dome had dissolved gas in it, like a bottle of seltzer water. As the magma rose towards the surface where there was less pressure on it than at depth, the gas expanded producing the holes or bubbles in the pumice. The magma that remained pressurized while it cooled quickly or that had already lost its gas, formed the obsidian.[4]

Flow banding containing both obsidian and pumice is common at Panum Crater. Another common texture, called breadcrust, can also be seen in the dome. Breadcrust textures form when the inside of a cooling rock is still hot with gas escaping from it while the outside surface has already cooled. As the gas expands from the inside, the outside surface cracks to allow the gas to escape.[4]

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  • Our Greatest Delusion
  • ITALY : AVERNO'S LAKE
  • Eastern Sierra trip ----- September 2012

Transcription

I'm not sure what I expected to find when I went to Chernobyl. I mean it's been so long since the nuclear reactor there melted down and spewed radioactive atoms across the land. So for almost thirty years this place has been virtually abandoned. These days workers are allowed into the zone but only for two weeks at a time. And that's not because the levels of radiation are too high, it's actually for psychological reasons. More than two weeks in a place like this will apparently make you think strange things. And I was only here for four days but I started to think about rocks. Yeah... rocks. Rocks appear to be permanent. I mean I know that they aren't. Mountains are constantly eroding and in places the crust is melting back into the mantle. Rock obviously isn't permanent but on the scale of a human life, it is and people recognized that fact - rocks are permanent - for thousands of years and I think that's what makes them important to us. I mean, "a diamond is forever" We build these monuments out of rock because they will outlast us and virtually every other material we can think of. Our modern structures of metal and glass are just rock refined by our ingenuity. Rocks are both practical and symbolic. We seek to indentify ourselves with rocks. We carve our heroes in stone because we want them to last forever and there's a way in which we want that kind of permanence for ourselves too. I think it's in the core of the desire to scratch our name into stone, put your initials in wet cement, really man-made rock, or fasten a padlock to a bridge. In this way we try to push our impermanence from our minds. The monuments, statues and bridges, they give us a sense of continuity, stability. That this is the way it is and the way it's always been. Like the way we first we concieved of stars: static, unchanging, eternal. And this way of viewing the world helps us maintain our greatest delusion: the thought that we are in any way eternal. We want to believe that some part of us, our consciousness or our soul will last forever. But what do you make of it then when you see stone is not even so permanent? Walking around Chernobyl I think it's understandable I started contemplating not only the permanence of rocks but also their decay, and by extension, our decay, death, what the world would look like without people. You know the closest I can come to imagining true nothingness is to picture the universe running really fast in reverse. All the galaxies squeezing closer together, stars expanding back into gas clouds and everything getting hotter and denser, compactifying until the whole observable universe could fit into a room and then sinking further into a tiny point and then... nothing. Not the nothingness of empty space but real nothingess which has no size and no time. To me that is probably what death looks like, a nothiness so complete you wouldn't even miss it. For that, you'd have to be there. But just as soon as I can form this thought, it evaporates like a void in nature. The world rushes in to fill it. And this make sense because the hardware I'm running has been developed over billions of years with the only requriement being that it frequently and accurately makes copies of itself and it would help not in the slightest in the goal of making copies if the hardware could accurately simulate its own non-existence. When we do acknowledge our impermanence, it is often through insipid catch phrases like "yolo" or it's in art projects like Damien Hirst's "The physical impossibility of death in the mind of someone living", which is just a huge shark in a tank of formaldehyde. A sense of our mortality should strike fear into us, like the sense I have when I'm swimming hundreds of meters off shore and the water below is deep and dark and I can picture the shark swimming beneath me. The same kind of fate stalks us daily but not in this visceral way, just in trivial ignorable way. Hence the delusion. You're permanent like stone, always were and always will be. So we are left hardwired for denial, a selected inability to imagine true nothingness, an ephemeral sack of particles that thinks itself eternal. This delusion is comforting and it makes living easier. It might drive you crazy to be confronted with the ultimate meaninglessness of everything all the time, what we call nihilism. But the same delusion I'd argue is also debilitating. It lulls you into a false sense of security, inaction, like a due date a long time in the future. There's always tomorrow so we procrastinate living the life we truly desire and we live in more fear. The sense that your soul is eternal makes you cowardly because failure would stick with you forever. For really ever. Shame, embarassment, disappointment, they would never leave you. A distant horizon encourages you to play it safe. Live to fight another day, for after all there is always another day. And this is why I find nihilism liberating and emboldening. If you can really picture the nothingess that awaits you then what is there to be afraid of? Errors and humiliations will be forgotten but great achiements may not. We may have no meaning in the cosmic context of the universe but we make our own meaning daily with each other and this is the thought that leads to action: your days are numbered, you don't know what that number is but it's finite, so get busy with what it is you want to do. Time is running out.

References

  1. ^ a b "Panum Crater, California". Peakbagger.com. Retrieved 2014-12-29.
  2. ^ "Great Basin Peaks List". Toiyabe Chapter, Sierra Club. Retrieved 2014-12-28.
  3. ^ "Panum Crater". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved 2014-12-29.
  4. ^ a b c d Public Domain This article incorporates public domain material from "Panum Crater". Long Valley Caldera Field Guide. United States Geological Survey. Retrieved 2015-04-27.
  5. ^ Sieh, Kerry; Bursik, Marcus (1986). "Most Recent Eruption of the Mono Craters, Eastern Central California" (PDF). Journal of Geophysical Research. 91 (B12): 12, 539–12, 571. Bibcode:1986JGR....9112539S. doi:10.1029/JB091iB12p12539.
  6. ^ a b c d e Public Domain This article incorporates public domain material from "Panum Crater". America's Volcanic Past. Cascades Volcano Observatory, USGS. Archived from the original on 2002-10-22. Retrieved 2007-01-23.
This page was last edited on 11 November 2022, at 23:24
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