Eruptions

Back from the field

I’m officially out of the mountains in the Mineral King area – the field work went great, we collected some fabulous Triassic-Jurassic rhyolites from a pendant in the Sierra Nevada Batholith (and also enjoyed blueberry-sized hail and an unfortunate hike through a thorny thicket). I’ll have more to say later, but now I’ll be diving headlong into working on papers during my few days here in Davis … but I’ll try to catch up on all your comments left while I was away!

i-972ff1f75405b891e0c1684a1b94bf1c-DSC_0032-thumb-400x266-53373.jpg
The Mineral King region of the Sierra Nevada in California. Click on the image to see a larger version. Image by Erik Klemetti, July 2010.

Comments

  1. #1 Dana Hunter
    July 20, 2010

    How lovely! Welcome back! Cannot wait for your report.

  2. #2 mike don
    July 20, 2010

    Great to ‘see’ you back Erik! Just two queries:

    What’s a ‘pendant’ in geological context?

    And more off-the-wall, was wondering where the name ‘Mineral King’ came from? I mean, all rock is minerals, obviously, but I feel that the namers of that area would probably have had more economically-interesting ones in mind than quartz and felspar

  3. #3 Chris
    July 20, 2010

    slightly off topic, but there seems to be a lot more very deep earthquakes around the world (100 – 700 km depth) range.

    Does anyone have an extensive database they can plot the depth of earthquakes vs. time? Could just be normal. Anyone?

  4. #4 stigger
    July 20, 2010

    2 Mike don: It is a downward extension of surrounding rock that protrudes into the upper surface of an igneous intrusive body.

  5. #5 Birger Johansson
    July 20, 2010

    Welcome back. I have two main questions: How do you and your co-workers cope with the heat and how do you cope with the insects? Just walking up those slopes must sap most of the energy…
    Another concern -when the Santa Ana winds start sending firestorms across the hills of California, is Sierra Nevada vegetation too moist to be affected?

  6. #6 Robert Hurst
    July 20, 2010

    About the recent earthquake activity, the Fox Islands, Aleutian Islands, Alaska earthquakes are at a depth of 10km so it would indicate that the Oceanic Crust is being affected. The New Britain region, Papua New Guinea quakes are at a depth of around 35km indicating that the continental crust is being affected, I don’t know if the two earthquake swarms are connected but it that both regions were having quakes at around the same time.

  7. #7 Onkel Bob
    July 20, 2010

    Birger, the winds known as the Santa Ana’s are a seasonal phenomenon that arrives usually in late September and extend through November. They are restricted to the San Bernardino mountains which are far to the south of the Sierra Nevada. The Sierra Nevada have fire events, usually lightning strikes in July – September, and those burns can be spectacular, the Foresta fire Yosemite in 1990, the Tehipite fire in SEKI in 2008 come to mind.

    As to walking – hiking through the Sierra Nevada, well, it’s not that hard. I hiked the John Muir Trail a couple of four times, usually averaged 15 – 20 miles a day, carrying anywhere from 50 – 70 lbs of gear. It’s not so much the heat (although it can be brutal) as it is the extremes (goes to 20 oF at night in August). The mozzies, well if one waits until mid August to start, then they are a minor nuisance because of the cold nights.

  8. #8 parclair NoCal USA
    July 20, 2010

    Ah, welcome back and welcome to Davis. Looks like you brought cooler weather with you.

    Birger. Onkel Bob, you’re right about the timing of the SantaAnas. But, we get them too in northern california, altho’ they’re called north winds. (One year the fires and winds were so bad, that here in the valley our smoke alarms had to be disabled because the smoke from the fires was so thick that they rang alot.)

    Surprisingly, the sierra doesn’t have that many pests. The worst are ticks, but wearing covering clothing, and/or lots of bug repellent, and it’s all okay.

  9. #9 Diane N CA
    July 20, 2010

    Birger, the fires that happen in the Sierras are due to one of three things, sometimes both: lightning strikes, people leaving campfires without getting them completely out or tossing cigs, and arson. Where I live, we had a fire that was terrible and some lost people started a fire to be found and it took off from that. The smoke was horrible. Northern CA that year had so many fires, mostly from lighting stikes, that smoke hung over the entire area for about six weeks. There was no wind at all, not even a slight breeze, to blow it out.

    The Cascades and Sierras do get a lot of lightning and what we don’t want to see is dry lightning: T-storms with no rain. There was one night here in N CA when we had over 1500 lightning strikes. Here, it started out like a normal T-storm, but all at once the sky lit up. Flash after flash after flash seconds apart. I had never seen anything like it and the weird part about it was there was almost no sound to it. Truly awesome. And a bit scarry.

  10. #10 Diane N CA
    July 20, 2010

    Parclair, we are talking about the same year! We did not have any wind at all for quite a while. The smoke here did not set off our alarms, but it was pretty bad. I think we had a Team 2 here so that tells you what kind of fire we were dealing with. It was called the Ralston Fire. Not good at all. And we have had a few arson fires started in the valley already. I am not looking forward to those idiots.

  11. #11 Diane N CA
    July 20, 2010

    Welcome back Erik. You are so close being in Davis. Wish there was time to meet you. Oh well…

  12. #12 EKoh
    July 20, 2010

    Erik,
    what, no chupacabra sightings?

  13. #13 Lurking
    July 20, 2010

    @Chris [3]

    I guess that’s a request.

    All Quakes worldwide Mag 6+ from 1973 to 2010 (current date) verses Depth.

    http://i26.tinypic.com/kd9378.png

    I cut the plot off below 200 km for clarity, but the moving average uses all of the data.

    The data is from a USGS Quake database query.

    @parclair NoCal USA & Diane N CA… a side comment:

    John Wilkes Booth was killed by Sergeant Boston Corbett of the Union Army. Corbett is believed to have eventually settled in a cabin near Hinckley, Minnesota, and is believed to have died in the Great Hinckley Fire of 1894. 420 square miles and six towns went up in four hours.

  14. #14 Renato Rio
    July 20, 2010

    Welcome back, Erik. Eager to know who won “doozy” volcano quest.

  15. #15 Holger, N California
    July 20, 2010

    Has anyone noticed the little earthquake swarm that occurred underneath Mýrdalsjökull?

    Most were at pretty shallow depth (~1 km). Not that it means much, but maybe it’s the beginning of bigger things for Katla?

  16. #16 Carl after Dinner
    July 20, 2010

    @Holger:

    Nope, it probably has nothing at all with a Katla eruption to do.
    First of all they are well scattered, they are weak, they are rather few, they are whey(protein) to shallow with only one deep under Godabunga.
    Instead they should be centered to reflect rising magma, strong (at least above 1.5, there should be many quakes (100s), and they should be deep in the beginning and then progressively work themselves upwards to about five kilometres.
    So this is only settlements in the ice covering Myrdalsjökull.

    On the other hand, as a wise man here said; “Katla goes after a beer!”

  17. #17 stephen tierney
    July 20, 2010

    Good to hear from you Eric

    http://hvo.wr.usgs.gov/kilauea/update/images.html

    The link is just a link to Kilauea lave flow pics currently burning their merry way over the access road and vegetation there. Quiet effective when yo zoom in might I add.

    Hats off to the scientist there…

  18. #18 Agent Goat
    July 20, 2010

    It’s about time I stopped lurking and made a comment, so I’ll add something slightly useful…

    People here are always attempting to dissect volcanic images for interesting info (like the ejya images a week or so ago), so I’d like to suggest that if you’re using firefox, the “image zoom” add-on is absolutely brilliant. Right-clicks give you zoom to several default sizes as well as a “custom” option, and holding right-click and clicking left gives you instant image fit without having to dig in menus. Great for teasing out details, to a point.

  19. #19 Jón Frímann
    July 20, 2010

    I want to point people out to this great picture of Eyjafjallajökull and the area after the eruption.

    omarragnarsson.blog.is/users/3b/omarragnarsson/img/p1012395.jpg

  20. #20 parclair, NoCal USA
    July 21, 2010

    @18 Jon Thanks for the link. I have a hard time wrapping my mind around the idea that I’m looking at a glacier. If I didn’t know better, I’d say I was looking at a mountain! Good to hear from you.

  21. #21 Renato Rio
    July 21, 2010

    #19 @Jón Fríman Good to hear from you!

  22. #22 Villard
    July 21, 2010

    I visited Iceland in april 2008 and took these photos at the base of Gigjökull glacier. Our tour guide mentioned the possiblity of an eruption up there even at that time. The small lake is gone as we see this part on the Thorolfsfelli webcam.

    http://www.flickr.com/photos/51115854@N06/4697346534/in/photostream/

    http://www.flickr.com/photos/51115854@N06/4696711651/in/photostream/

  23. #23 Chris
    July 21, 2010

    @Lurking Thanks, and appreciated but what I wanted to see was the Number of quakes(depth 100km to 700km) vs. Time.

  24. #24 bruce stout
    July 21, 2010

    @ Villard

    Thanks very much for sharing!

  25. #25 Lurking
    July 21, 2010

    @Chris

    The blue dots are the individual quakes.

    But if you want a binning run that gives a count like, x number per day, I can do that but it will have to be later. I have a bit of stuff to take care of today and it takes a little time to set up a binning sheet.

  26. #26 Holger, N California
    July 21, 2010

    @Carl after Dinner #16

    You may well be right. Nevertheless, the activity under Goðabunga continues today, although it’s still weak and relatively shallow. But all big things start small…

    Let’s hope this doesn’t develop into a more significant event, after all there are the predictions of Katla going after Eyjafjallajökull.

  27. #27 Kyle
    July 21, 2010

    These large swarms of shallow quakes always seem to happen when it is blowing a Gail up there, id say it was nothing more than the wind causing it.

  28. #28 Carl at Night
    July 21, 2010

    @26 & 27:

    Nah, no gale up there tonight.
    I also forgot to mention that the tremors and helicorders had an unusually low period and that the GPS measurements aren’t indicating anything to funny on the road.

    But, as said before… All it takes is Katla going for a beer with Askja and has a burp… Bom!
    Askja, Katla, and Hekla are extremly “short-tempered”, they normaly have about an hour of advance warning before going Ka-Blom on us so…

    So here’s my shitlist of volcanoes in Iceland. Bardarbunga, Askja, Lakagigar (Laki). Either one of those can if they go off badly really hurt us. Katla at maximum would probably not be anything near what they can do on a medium eruption. Remember that Bardarbunga and Laki are the two largest sources of Lava in historical times.

  29. #29 Chris
    July 21, 2010

    @Lurking. No probs. Binning yes, just an overall number per day or per week with depths between 100 to 700 when you have time. I’m guessing it’s going to be a low number (maybe) so grouping them per week rather than per day might be a better option. I’ll leave that up to you.

  30. #30 Lurking
    July 22, 2010

    @Chris

    Try this on for size. Depth 100 to 900 km, Mag 4.5 and greater, 1973 until now, 7 day and 30 day bin. Number of quakes per bin.

    http://i27.tinypic.com/10s4xti.png

  31. #31 chris
    July 22, 2010

    @Lurking. Perfect! Interesting, and thanks!

  32. #32 Lurking
    July 22, 2010

    Don’t forget that there is going to be “technology bias” in the plot as counted/reported efficiency goes up.

    I have no idea of how to correctly adjust for that.

  33. #33 chris
    July 22, 2010

    Okay but the bias shouldn’t account for the large increase between 2001 and 2008. Also between 1984 and 1994 it was relatively flat. Never-the-less I had never thought about taking a tech bias into account.

    I was just reading that digital recording of eq’s started in the 70′s and that in 1984 China allowed the USGS to install a number of new detection stations. I don’t think there would have been a dramatic increase in technology for the last 10 or even 20 years, but I’m not too sure.

  34. #34 Lurking
    July 23, 2010

    Localized increases (temporally speaking) are likely going to be the result of significant events where large chunks of the Earth are moving around. At the depths being plotted, you are ruling out most of the smaller faults. These deeper quakes are likely going to be associated with subducting plates and other going’s on down there.

    As for the technology bias, it only makes sense. It falls back to that tree in the forest thing. If no one was there to hear it, did it make a sound? Likewise, if no seismograph was there to record it, was there a quake? Odds are yes, but lacking any way of recording it we will never know.

    I think that the 7 day and 30 day bins worked pretty well.

    To round things out, here is the same dataset with the magnitudes converted to Joules, then summed in the 7 day bin.

    http://i25.tinypic.com/30kaa2h.png

  35. #35 chris
    July 23, 2010

    Nice, but I think it’s a nice way to indirectly observe something that we are mostly unaware of. Just out of curiosity are you using Matlab to build your plots?

  36. #36 Lurking
    July 23, 2010

    Dplot

    http://www.dplot.com/index.htm

    Can operate stand stand alone or integrated into Excel. Scriptable, can be invoked from Vbasic, C++ or any language that can throw a DDE call.

    I haven’t used MatLab, but I think the graphics are a bit easier to use than MathCad and Scientific Workbook.

  37. #37 Chris
    July 23, 2010

    Thanks!

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