[Rockhounds] Something going on in Yellowstone
Dora Smith
tiggernut24 at yahoo.com
Thu Jan 1 06:29:11 PST 2009
That's a flood basalt eruption. Yellowstone is a caldera volcano - they rather give new meaning to pyroclastic flow. It a very different critter, and it also doesn't resemble one of those cone volcanoes.
Yours,
Dora Smith
Austin, TX
tiggernut24 at yahoo.com
----- Original Message -----
From: J Bryan Kramer
To: Dora Smith ; Rockhounds at drizzle.com: A mailing list for rock and gem collectors
Sent: Wednesday, December 31, 2008 8:33 PM
Subject: Re: [Rockhounds] Something going on in Yellowstone
I guess I can answer my own question. From the Craters of the Moon site:
"A typical eruption along the Great Rift and similar basaltic rift systems in starts with a curtain of very fluid lava shooting up to 1,000 feet (300 m) high along a segment of the rift up to 1 mile (1.6 km) long.[25] As the eruption continues pressure and heat decrease and the chemistry of the lava becomes slightly more silica rich. The curtain of lava responds by breaking apart into separate vents. Various types of volcanos may form at these vents; gas-rich pulverized lava creates cinder cones (such as Inferno Cone – stop 4) and pasty lava blobs form spatter cones (such as Spatter Cones – stop 5).[7] Later stages of an eruption push lava streams out through the side or bottom of cinder cones, which usually ends the life of the cinder cone (North Crater, Watchmen, and Sheep Trail Butte are notable exceptions). This will sometimes breach part of the cone and carry it away as large and craggy blocks of cinder (as seen at North Crater Flow – stop 2 – and Devils Orchard – stop 3). Solid crust forms over lava streams and lava tubes (a type of cave) are created when lava vacates its course (examples can be seen at the Cave Area – stop 7)."
"http://en.wikipedia.org/wiki/Craters_of_the_Moon_National_Monument_and_Preserve"
Actually that site says that Craters has erupted 8 times with 500-3000 year periods between eruptions. The last one was 2000 years ago so they are expecting one within a 100 years. Seems like a long way from the Yellowstone hotspot tho. Unless the magma mass extends that far to the west. I'd guess over a 100 miles.
I actually had a personal learning experience at Craters. My room mate and I were in the Navy and got transferred from the Frisco Bay area to Arco/Idaho Falls. The day after we got there we ran out to Craters, it was July the 3rd. We were rockclimbers and wanted to explore some of the lava tubes so we carried our climbing gear into the park. Without encountering a ranger. The temp was about 80 degrees when we got to a lava tube window and roped up. We rappelled down, explored for an hour or so and came out to find it was now about 25 degrees and snowing heavily. Strange pellet like snow too.
But we were 40 feet down and the only way back up was up the rope. I used a prussic knot which lets you slide the knot up the rope (when you take your weight off the loop the knot is attached to) but holds firm when you put weight on the loop. That lets you climb up a rope by alternating feet (separate loop and knot for each foot). All was well on the 35 feet of free rope but when the rope got to the last 6 or 8 feet of lip, the rope was forced into the rock by my weight on the rope. My feet were still hanging free and my weight forced my feet out at and angle on the rope. That meant I had to pull the rope off the rock, take weight off one foot and try to slide that loop up the rope while holding it away from the rock face. All this dangling 35 feet up, in the snow (or maybe it was sleet) and freezing too since we just had light clothing on.
Things were looking grim, I was going up about an inch at a time (or so it seemed). My climbing buddy was shouting imprecations from below. I was getting very tired and cold. All of a sudden this detached hand grabs me by the collar and pulls me up to the top. It was a ranger and I was rather happy to see him...heh. We got my friend up and were happy to accept the tongue lashing lecture. It was darned stupid. But that was my intro to western mountain weather. I got another lesson on the road thru the park about black ice, later that year in the winter.
Oh I bought some Jumars right after that for those of you who have done some climbing.
BK
On Wed, Dec 31, 2008 at 20:11, J Bryan Kramer <codeburner at gmail.com> wrote:
Were the Yellowstone flows of the flood basalt type or did it build up an actual large dome and erupt from there? I had the impression that these were fissure type eruptions.
BK
On Wed, Dec 31, 2008 at 19:06, Dora Smith <tiggernut24 at yahoo.com> wrote:
OK, my site is fixed. http://www.tiggernut24.com/catastrophes.html
I bet there are people here who might have an idea what to make of this.
I incorporated some maps on my web site. The bulge and the earthquakes are occuring in and immediately around the northern part of the lake. Well, the bulge may be bigger, but taht seems to be where it's gotten attention.
One of the maps shows the location of previous lava flows, as indicated by two types of volcanic rock.
The danger of a caldera volcano, and the reason why pressure builds up to massive proportions, is typically the layer of hard volcanic rock over teh caldera.
Now, I don't know if there is in fact no volcanic rock wehre the lake is. The entire area where teh bulge and the quakes are is within the caldera. Which suggests that it should be covered with volcanic rock. However, if you notice, they are not where the rhyolite is.
None of it is where the basalt is; it's as if the most recent and largest eruption didn't do basalt.
Comments, anyone?
I added some new links to newer technical papers about the caldera and its behavior to my site. (I also added a link to the Wikipedia article and fixed three links to one web site that moved.)
Yours,
Dora Smith
Austin, TX
tiggernut24 at yahoo.com
----- Original Message ----- From: "J Bryan Kramer" <codeburner at gmail.com>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors" <rockhounds at lists.drizzle.com>
Sent: Wednesday, December 31, 2008 12:35 PM
Subject: [Rockhounds] Something going on in Yellowstone
About 60 km down:
<http://www.seis.utah.edu/req2webdir/recenteqs/Maps/Yellowstone_full.html>
I've seen some over-heated articles about the supervolcano erupting but it's
a bit early to worry about that.
BK
--
""It often seems to me that the night is much more alive and richly colored
than the day."
Vincent van Gogh
J Bryan Krämer
North Florida, USA
photos at:
http://pbase.com/photoburner
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""It often seems to me that the night is much more alive and richly colored than the day."
Vincent van Gogh
J Bryan Krämer
North Florida, USA
photos at:
http://pbase.com/photoburner
--
""It often seems to me that the night is much more alive and richly colored than the day."
Vincent van Gogh
J Bryan Krämer
North Florida, USA
photos at:
http://pbase.com/photoburner
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