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| Mt. St. Helens, Or (3-26-1995) |
Today is the anniversary of Mount St Helen's blowing its top 5-18-1980. I remember this date like it is one of my babies. Its really easy to do for me. Its the day before my oldest sisters wedding anniversary, and it was the time I was planning on graduating with my masters. Unfortunately I changed topics and advisers and that date got delayed a year but it still sticks with me. Mainly because it was one of the most exciting things a geologist could live through. I couldn't get enough information about the eruption back then. Its all what my department talked about for days and days. Ever since then it has had a hold on me. I know last year was its big 30 anniversary and I would have written about it then but I didn't have a blog then so nothing was done. I'm just glad there were others out in the geoblogsphere to do it justice. Now I'm kind of glad I didn't because since then I've gotten to see the San Fransisco Mountains in Arizona and the two remind me so much of each other. I don't know if its the time of year I visited them or whatever. I decided to learn a little bit more about them....
When you go to the pacific northwest coast the first thing that catches your eye as you fly there is the mountains that are sticking out from the clouds.
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| Looking at the volcanic mountains in Washington State, from an airplane flying to Canada. ( 7-18-2010) |
If you investigate you find out that they are Stratovolcanoes or composite volcanoes or stratocone. Stratovolcanoes are typically thought of as conical in shape. They are formed by the combination of volcanic eruptions spewing forth pyroclastic materials and layers of lava. For years Mt St. Helen's was used as an example of a stratovolcano with its classic shape, and layering. Now we have to use Mt Rainer as an example because St Helen's lost her figure. (Oh well that's what happens as you get older - you loose your figure and they look to younger ones as examples).
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| Mount Rainer, Washington St. (3-27-1995) |
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| Mt. St. Helens, Oregon (3-26-1995), from Johnston Ridge Observatory. |
Ever since she blew her top I couldn't wait to go see her. I finally was able to on March 26,1995 (46 16'59.36"N & 122 12'59." W). Here are some of the pictures I took back then of Mt St. Helens. What surprised me most was I was expecting the area to be totally devastated. I did see some evidence of that, but I also saw a lot of regrowth. It amazed me how resilient mother nature is and what had come back in just a very short amount of geologic time of 15 years.
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| Driving up OR 504 to see the top of Mt St Helens, Or (3-26-1995) |
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| Seeing some of the destruction that was still present from the eruption of Mt St Helens, 15 years later (3-26-1995) |
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| Johnston Ridge Observatory, viewing the mountain top of Mt St Helens, Or. (3-26-1995) |
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| Mt. St. Helens 15 years after 5-18-1980, the trees are still left where they fell. |
I was glad I had gotten to see Mt St. Helens when I did. I never forgot it.
So this year when I went to Arizona and got to fly by the San Fransisco Mountains (35 19'52" N &
111 40'19"W)I was amazed at how they reminded me of St. Helen. I remember studying way back when that The San Fransisco Mountains were thought to be Stratovolcanoes because of its composition but it just wasn't shaped like a typical one. There was a lot of discussion as to why it looked so different but nothing was ever proposed to convince everyone. That was until St. Helens blew her top. Now it seems like a reasonable assumption that the San Fransisco mountains were probably formed in the same way.
While I was in Arizona I was able to pick up a very informative book by Wendell A. Duffield called 'Volcanoes of Northern Arizona' (2005) at the Grand Canyon. I really like the way he showed how the two volcanoes are similar in appearance and just the easy to read way in which volcanoes are formed. So here I am using my own pictures to go along with his stuff.
Here's some of my pictures of the San Fransisco Mountains as we were flying by it.
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| San Francisco Mountain (3-29-2011) |
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| San Francisco Mountain, AZ (3-29-2011) |
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| San Francisco Mountain, AZ (3-29-2011) |
Now to compare the two.
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| Mt St Helens. Or |
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| San Fransisco Mtn., AZ |
Don't you think the two look very similar and could have formed the same way with magma seeping into the volcano and the the flank expanded outward until it pasted the angle of repose fracturing the flank which then allowed gases to escape resulting in its top being blown off.
For more info on Mt. St. Helen here's Wikipedia
Mt._St._Helens.
And here's for
San_Francisco_Mountain. I hope this has been of some help.
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