Thursday, July 31, 2008

Pink Playa Phenomenon

westOn Highway 50 looking west, with the Huck Salt Road turnoff just behind that little hill sticking south into the playa.

While driving through Four Mile Flat on Highway 50, between the turnoff to Sand Mountain on the east end and the dirt road to the Huck Salt Mine in the middle of the flat, MOH and I recently came across a somewhat common playa phenomena, wherein bacteria growing in the salty brine and partly dried-out salt crust left behind after the water evaporates (Google Maps).

Fortunately, there is a regulation road sign for Huck Salt Road on the west side of Fourmile Flat, so you won't get lost...
Huck Salt Road
Sand Mountain turnoff ...and a sign at the turnoff to Sand Mountain on the east side of Fourmile Flat.

east
Pinkish salt flats as seen from Highway 50 looking east toward the turnoff to Sand Mountain.

red
pink
southThe three photos above show closer views of the pink to red to orange salt on the south side of Highway 50.


water
more And two more views, above, one showing some actual water. In my experience, the pinkish salt does not occur year-round. It appears to need the right combination of water and evaporation, and possibly the right temperature.

The color is caused by salt-loving bacteria which are known as halophilic bacteria, part of the ancient archaebacteria kingdom or Domain Archae. Wayne's Word has this - and a lot more - to say about halophilic bacteria:

The bacteria produce a red carotenoid pigment which is similar to that found in tomatoes, red peppers, pink flamingos, and in many colorful flowers and autumn leaves. [Flamingos actually get their carotenoid pigments from their diet of shrimp and other crustaceans.] Carotenoid pigments are also the source of Beta-carotene, an important antioxidant and the precursor of vitamin A.
References:
Armstrong, W. P., 1981, The Pink Playas of Owens Valley, Fremontia 9: pages 3-10.

Armstrong, W. P., 1981, Why Owens Lake is Red, Desert Magazine, May 1981, pages 22-26.

The Halohandbook.


View Larger Map

Trilobite for Sale

ReBecca at Dinochick Blogs has already pointed this one out, but being a consummate trilobite lover, I just had to pass this on to anyone who might have missed her excellent post.

Besides being able to purchase a neat, colorful trilobite - for play, for teaching, or for decorating one's house or improving upon one's otherwise dull-looking collection of rocks and minerals - you can get a collection that includes replicas of 500 million-year-old animals of the Burgess Shale from the Royal Ontario Museum online. (The trilobite comes with the collection - see ReBecca's photos replete with scale bars, like this one, or go to the ROM webpage directly for your purchase.)

Trilobite for sale or rent
Olenoides makes a nice present.
Burgess Shale toys all around,
That's as much as I will propound...

Wednesday, July 30, 2008

Hazy Days Again

Due to the fire near Yosemite, it was quite hazy in Reno during our recent visit there, as you can see from this barely discernible view of Peavine Peak(above). The photo was taken from about six miles east of the peak.

More haze north of town, as seen from Highway 395 near Hallelujah Junction.

It was also hazy at the lake, but the water was enjoyable!

Tuesday, July 29, 2008

Flash Flood on Highway 50

brown bushes As MOH and I were driving over Mt. Airy Summit west of Austin the other day, our first clue that thunderstorms had caused a little flash flooding was the brown, muddy, knocked over bushes on the side of the road.

mud Our second clue was - lo and behold, some actual mud and wet ground - in Nevada!

disturbed Our third clue was that someone had recently been pushing some dirt around, as though the water and sediment had actually flowed across the road.

equipment Ah, and who's been moving the dirt? Yes, there was a little construction activity in progress as we drove slowly through!

summit1 Mt. Airy Summit is a broad, almost unnoticeable summit about 15 miles west of Austin, and all the flooding activity had seemingly taken place on the east side of the summit. It didn't look like there was a whole lot of drainage area upstream from the flash-flooded dry washes - some washes on the north side of the highway and some small drainages right along the road.

Mt. Airy Mesa, the hill shown in the photo above, is formed of columnar-jointed ash-flow tuff sitting on some white to light greenish-yellow poorly welded tuff or lake deposits, the latter of which are strongly clayey.

mapThese rocks units are denoted as Tt2 and Ts2 on the Geologic Map of the North-Central Nevada, which are designated as being in the 34 to 17 Ma range. The large square in the map above is a township, about six miles on each side. [Note: this map shows Highway 50 going through Railroad Pass to the south on the road now known as Nevada S.R. 722, formerly known as Route 2, and before that known as Highway 50.]

summit2 The drainage area for the flooding seemed small to me, and possibly the clay in the Ts2 unit contributed to runoff. The thunderstorm must have dumped a lot of water really fast in the highlands at least on the north side of the highway, and possibly on the south side. [Note: "dumped", "a lot", and "really fast" are technical terms - well, I mean, I wasn't there when it was raining, and can't find a single thing written about this little flash flood that must have taken place on July 24th.]

deposits If you're working in an area, you can examine flash-flood cuts and deposits like this one when they are fresh. In a year, come back and look again: the dry wash will look much the same, but the bushes will be in better condition. If you come back year after year, you can gradually get an idea of what a dry wash looks like after a certain time has passed, and you will be able to estimate the date of the last flash flood by looking at any dry wash anywhere.

The fact that a particular dry wash flooded within the last year, or hasn't flooded for ten years - using the above estimating method - doesn't really say anything about whether the dry wash is ripe to flood again anytime soon, so don't use that estimate as a guide to whether you are safe from being caught in a flash flood. Some drainages seem a little more prone to flash flooding, and some types of drainage areas are more dangerous to be in during a rainstorm.

It would have been fairly easy to get above the flash-flood at Mt. Airy Summit because very few of the dry washes overflowed their regular stream banks; when they did, the water wasn't very deep - judging from the muddy watermark on the sagebrush maybe a foot or two at most. However, there would have been no way of knowing at the time how long the rain would fall or what size the flash flood would be. So it's a good idea to get to high ground when rain is pouring all around you or when it's falling upstream. Flash floods can run for miles and can carry large boulders or even pickup trucks with them.

sand springsWe saw only minimal evidence for other flash flooding between Austin and Fallon, Nevada - above, a little flash flooding had been going on on the west side of Sand Springs Pass, about 25 miles east of Fallon. Location of the photo is near Bench Mark 4372 in the lower left (southwest) part of the linked-to MSRMaps map.

I've only been near one stream when it was in flash-flood mode. Water was roaring down the little stream on the west side of the Virginia Range south of Reno, Nevada. It never rose high enough to overflow the banks, but the sound of boulders smashing against one another was impressive.

Reference:
Stewart, J. H. and Carlson, J. E., 1976, Geologic map of north-central Nevada: Nevada Bur. Mines and Geol. Map 50, 1:250,000.

UPDATE 11Jul2010: A good place to view the results of the flash flood, some of which can still be seen east of Mt. Airy Summit, is to park south of Highway 50 on the dirt road shown below, and to cross to the north side where the wash is about the go under the road.


View Larger Map

Friday, July 25, 2008

Friday Field Photos: Wheeler Peak

All photos below are from the rock glacier on Wheeler Peak.

#1Photo #1

#2 Photo #2

Above, a couple pictures of cross bedding in the Prospect Mountain Quartzite - once a sandstone, now metamorphosed to a quartzite. Cross bedding can tell a geologist which way was up (if the rocks are in place in an outcrop instead of lying every which way on some rock glacier!). Which way is up in photos #1 and #2? Or are the boulders too small to determine the orientation?


#3 Photo #3


#4

Photo #4


#5

Photo #5

Photo #3 shows some faint, criss-crossing striations or grooves in a thin black shale bed remaining on one side of a quartzite boulder. Photo #4 shows similar but deeper striations or grooves on one quartzite boulder, enlarged in Photo #5. What does this mish-mash of orientations, seemingly quite random, tell us?

As usual, click to enlarge photos.

Wheeler Peak is inside Great Basin National Park

Thursday, July 24, 2008

Accretionary Wedge #11: Field Camp

This post is a submission to the July Accretionary Wedge, being hosted by Ron Schott at his Geology Home Companion Blog.

Field camp for me was a long time ago and far, far away (well, it was far away at the time, a lot closer now). The year was 1973. I was in a slump due to various personal events, and was taking two quarters off from what was supposed to be my junior year in undergrad school. It being my junior year, I was scheduled to take field camp that summer, somewhere amongst the roadcuts, stream beds, and kudzu of southern Virginia. Having never much liked the east coast (well, sometimes, but I was getting impatient to get back into the west by this late date in my young life), I really wasn't looking forward to the experience.

My dad had a great idea: go to field camp somewhere in the west. So that's what I ended up doing, with field camp becoming my first step to moving back to the west that I loved. He flew out with me, after giving me his Brunton, and we spent a couple days going here and there around Tucson, including the Desert Museum and the Kitt Peak Observatory. We found what to this day remains my favorite Mexican restaurant, La Fuente, although I haven't eaten there now in more than 15 years.

During field camp, we traversed the entire state of Arizona, from the north at Flagstaff and the Grand Canyon, to the east somewhere near Window Rock and possibly Kayenta, to some tiny place in central Arizona somewhere south of Winslow - ah, that was Young, Arizona - with a brief stop at San Manuel or Baghdad, a recoup day in Tucson, then down to southeastern Arizona, where we spent some time around Tombstone and Bisbee, and then spent most of our latter days mapping in the Chiricahua Mountains.

Lots of memories from field camp, but no photos. The first days we spent around the Grand Canyon, including an excruciating hike (for sea-level acclimated people like me) down to the Redwall Limestone - and back up. That was the tough part. Then, we did some stratigraphy and mapping at Wupatki, and a bit of mapping near Sunset Crater, and rode the lift to the top of San Francisco Mountain.

At field camp, I drank more Coors beer than I ever have since, finding out later that it was only favored by people from the east coast who couldn't buy it at the time, and was looked down on by most of the locals; I got stuck in the sand for the first time, and although I wasn't driving the Carryall, it wouldn't have helped at all if I had been; I learned how to pee exceptionally fast so no one would come over a cliff or around an outcrop and see me (we had 40 students, 10 of them women, and 10 professors, although not all the professors were there all at the same time, thankfully); I watched as poor Toya got a name for sitting on a cholla one hot afternoon somewhere in northern Arizona; I saw my first and last cock fight in that tiny place known as Young; and I helped fight a fire on our final mapping project in the Chiricahua Mountains - the cholla burned, but didn't disappear, and many outcrops were red from then on and difficult to distinguish from one another. We got fed by local ranchers that evening, and on the last day of mapping, G. Davis brought in a few cases of beer by helicopter. Later, we had an award night, with most awards being silly to hilarious (including the cholla incident), and all T.A.'s got thrown into the the local pond.

And I learned to sing: the Redwall's connected to the Supai, the Supai's connected to the Hermit, the Hermit's connected to the Coconino, the Coconino's connected to the Toroweap, the Toroweap's connected to the Kaibab, the Kaibab's connected to the Moenkopi, the Moenkopi's connected to the Shinarump, the Shinarump's connected to the Chinle, the Chinle's connected to the Moenave, the Moenave's connected to the Kayenta, the Kayenta's connected to the Navajo... it was at about this juncture that we gave up, having not spent too much time in anything above the Navajo Sandstone.

UPDATE: This Wedge was not published.

Wednesday, July 23, 2008

Crandall Canyon

The MSHA is set to release its findings tomorrow about the August 6, 2007 Crandall Canyon Mine collapse. It will be interesting to see what they say. A May, 2008 report entitled, Chairman Miller Statement on Findings of Investigation into Crandall Canyon Mine Disaster, by U.S. Representative George Miller (D-Calif), states that MSHA approved a faulty plan for retreat mining.

Retreat mining is a practice used in many coal mines; it involves the pulling of rock pillars as the miners retreat from an open room-and-pillar underground mine area. The pillars are ore; that's why they are pulled. The use of the room-and-pillar underground method, at least in coal mines, leaves more than 50% of the coal in the pillars. That's a lot of ore (coal in this case) to leave behind.

It doesn't matter whether the pillars in an underground mine are in gold ore or in a coal seam: they are there to hold up the mine. Pulling them involves an engineered or planned collapse of the mine section or room from which the pillars are pulled. It is not a mining method to be undertaken lightly or to be undertaken at all by anyone more concerned about profit than for miners' safety.

NIOSH has several links to information about safe use of retreat mining. According to their studies, reasons for failure of the practice wherein so-called "bumps" occur, as were reported at Crandall Canyon [these are actually rock bursts] usually have to do with "relatively thick overburden and extremely rigid strata occurring immediately above and below the mine coalbed" - but also have to do with certain mining practices that they recommend avoiding.

Volcanoes Accused of Evil Intent

Talk about anthropomorphism, volcanoes have now been labeled as evil by a certain non-geo blogger. Twice!

Bloggers of the geoblogosphere - Maria, The Volcanism Blog, and Chris Rowan - have come to the defense of the otherwise defenseless volcanoes of the world. After all, someone's gotta do it. Who's ever heard of a volcano hiring a lawyer? No need for that, though: we've got the geoblogosphere to the rescue!

It's all a question of balance, though. Without volcanoes, we would have no life. Without life we would have no extinctions. Without life, we would have no humans to bitch about volcanoes and extinctions. On and on, yada yada yada...

All I can say is:
Volcanoes of the World Unite! Don't put up with all this maligning of your no doubt pure intent!

Line and Azimuth

Every now and then, I go out to the drill site and "line out" a drill hole or two, which means that I mark lines on the ground to show the drillers which way to orient their rig when they are drilling an angle hole. Large, oil-type rigs don't require this sort of thing; I think they have built in directional devices.

There are several ways to line up a drill rig up on an azimuth. (Ya have to know which way to aim the rig unless you're just a random sort of geologist.) One way is to be there, Brunton in hand, sighting on some part of the rig as they line up in the general orientation of your chosen azimuth, which you perhaps mark simply by standing where you want them to point. Then you wave: a little to the right, a little to the left - it's a slow and clumsy way of doing things, IMO. Be sure to stand as far away from the rig as possible so your compass won't get pulled by that vast amount of metal known as the drill rig.

Another way involves biodegradable marking paint - often a fluorescent orange color - which will spray a line on the ground while you hold it upside down.

Humboldt Range
Humboldt Range with the south Florida Canyon area on the far left, looking northeast from I-80

The first time I was introduced to this kind of spray paint was several years ago while working outside the Florida Canyon Mine area in western Nevada [the ownership of Florida Canyon Mine is sometimes in flux, so some of these links may not remain current].

Standard

Area of drilling interest south of Florida Canyon, as seen looking east from I-80.

Instead of just using flagging tied to trees or bushes to mark the way to the next drill site, it can be convenient to spray paint LARGE arrows on the ground for the drillers to follow. It still can be a good idea to either show them the site first or to check up on them during their rig-up phase to make sure they are drilling the right site, but if signals are worked out in advance, that can become unnecessary.

arrow
As far as lining a drill rig up on an azimuth to drill an angle hole, another way is to draw a nice and tidy line on the ground with the above-mentioned spray paint. Because the paint is biodegradable, you can't do this too far in advance of moving the drill rig to the chosen site, especially if the monsoon is in town or if you happen to be expecting a snow storm or ground blizzard. Either one of these circumstances might require a modification of the spray paint method by the addition of using stakes along the laid-out line.

Stand at the location of the drill collar - where you expect them to drill - or just a little to the right or left of that. Mark the ground (with paint) where you are standing or put a painted stake in the ground. Move down azimuth in the opposite direction. That is, if the azimuth is 180 and you expect them to angle due south, move to the north. They will have to line the rig up in front of the drill collar, and so your line will have to run from the drill collar to the north. After making sure you aren't too close to large metallic objects such as pickup trucks, water trucks, drill pipe, or drill rigs, take a bearing on the stake or spot on the ground until you have lined up at the perfect azimuth. Then mark that spot on the ground or with another stake. Two or three spots farther and farther away from the original one are ideal for making the perfect bearing line, but two can do if you have a tolerance of a degree or so. Then, somehow, make a perfect line between your points using the spray paint.

One way to make a perfect line is to take some rope or string and tie it between the two end points, pull it taught, and paint the rope or string, along with the ground at the same time. Topofil string is ideal for this because it was designed for surveying purposes - it's lightweight, stretches so you can pull it tight even in a wind, and its also biodegradable. Wrap it around the stake at both ends of the line, around the stake and a rock you place on the ground, or around two rocks placed at both ends of the proposed line. Then, carefully paint the string, forming a line similar to the one seen below.

lineAfter that, have the drill rig move on to the site and let them line up with their tires on your painted line, or with their tires at some equal distance from the line. If you want, you can be present while they do this. If they are good at lining up, you might not need to be there.

Tuesday, July 22, 2008

Rock Glacier: View from Above!

rock glacierThis photo is courtesy of MOH, who climbed to the top of Wheeler Peak. Click to enlarge.


There it is, the rock glacier as seen from the top of Wheeler Peak. You can see how snow surrounds the entire rock glacier, and you can see the small, bluish green lake that sits in the lower part of the rock glacier. Also, note the difference between the smoother, rounded lobe of the upper portion of the rock glacier and the lumpy, more irregular lower portion of the rock glacier.

For another view, check out this MSRMaps image. The USGS image is dated 9/14/1999, and the lake is nowhere to be seen.

Wheeler Peak is inside Great Basin National Park

Monday, July 21, 2008

Rock Glacier: Near the Top

It may seem like this ongoing saga of rock glacier climbing is taking forever - but by the time MOH and I reached this level, that's what it seemed like to me, too - forever: take one step, pause, look around, breathe. Did the view change? Should I take another picture? (You may be thinking, "no," by this time!) Take another step, pause, breathe, look around. How much higher will we go?

Well, we got as far, as high, as the picture above. More rock glacier ahead! Still can't see if the snow, ice, or whatever is stuff of glaciers or not! And maybe the rocks, overall, are larger this high on the rock glacier - but I wasn't measuring, I was dragging myself around them!

Closer, closer...

The area in the above photo, right below the outcrop that splits the ice/snow chute in two, was where Osborn and Bevis (2001) saw and photographed a bergschrund. It's not visible above - could it be covered by snow still left in early July? Or could there be one lower down, below the highest ridge of the rock glacier?

Above, a photo taken just to the right of the previous one, showing the steep, cirque headwall made of layered Prospect Mountain Quartzite, with Wheeler Peak right at the top of it all.

Below, two photos with a closer view of the distorted bedding in the quartzite. Judging from some striated to slickensided surfaces on thin, dark shaly faces of quartzite blocks in the rock glacier, I suspect some bedding-parallel slip of some sort.

1) The photo above shows the lower, light-colored, quartzite near the base of the cirque headwall with some distortion along a contact with part of an overlying section of darker quartzite.

2) Above, higher still in the cliff, the darker layers show more distorted bedding and some folding.

References: see previous posts.
And also this additional one from John Van Hoesen at Geological Musings in the Taconic Mountains:

Van Hoesen, John G., 2003. Late Quaternary Glacial and Periglacial Environments, Snake Range, Nevada. [PhD Dissertation]: University of Nevada, Las Vegas. 225p.

And check this out from his website!

Wheeler Peak is inside Great Basin National Park.

Sunday, July 20, 2008

Rock Glacier: History and Links

As part of this ongoing rock glacier series, I thought I'd get into the history of the rock glacier a little bit, as it cannot be found anywhere online in any detail. Most of this information comes from Osborne and Bevis, 2001 (OB2001). I'll have some more photos later, including an aerial view from the peak!

According to OB2001, it was W. Eimbeck who first wrote about the glacier in 1883, with his writing then being reported on by I. C. Russell (1885). Osborn and Bevis go on to assert that W. F. Heald then rediscovered the glacier in 1955 (reported on by Heald, 1956), although Heald said that he didn't rediscover it, he discovered it. His discovery or re-discovery, depending on which account is accurate, was described in Desert Magazine in August, 1956, page 4, as follows:

Interest in [the Wheeler Peak] area as a potential national park developed in recent months after Weldon Heald of Tucson and Albert Marshall of Three Rivers, California, made the ascent of 13,061-foot [13,063] Wheeler Peak and ascertained that a glacier on the east slope of the mountain, first reported by the U. S.Geological Survey in 1883, was still active.... Following his ascent of Wheeler Peak, Weldon Heald wrote: "We arrived at the summit at noon. The view from the wedge-shaped crest of the Peak is utterly magnificent. From our perch on the topmost rocks, 13,061 feet above sea level, we looked out over a 360-degree panorama embracing thousands of square miles of deserts, valleys, hills and mountains in eastern Nevada and western Utah. Then we worked our way down the east slope to the edge of a 2000-foot sheer cliff. There in the depths of a cirque below we saw the ice field described by the Geological Survey in 1888. The surface was broken by what appeared to be a bergshrund, a secondary bergshrund [sic], and below these five parallel crevasses one above another. Every sign indicated that the ice was in motion and this was probably a true glacier."
And this is what Weldon F. Heald had to say about that, in the October issue of Desert Magazine, pages 31-32:

Received my August Desert today and feel you did a mighty fine job of presenting the subject of the proposed park or monument in the Wheeler Peak area—and Norton Allen made a fine map from my rough one. I think this will help the cause along greatly. There's one thing though that seems to be misunderstood. The glacier was not "re-discovered" in 1955, it was discovered. Although Eimbeck saw ice at the head of the cirque in 1883, he neither reported it as an active glacier nor suspected it was one. The reason is rather easy to explain. He did not see into the bottom of the cirque, where the glacier lies, and it is probable he would not have realized that the ice was active because it was covered with too much snow.

The ice Eimbeck saw and reported, and pictured in his engraving, is the neve tongue on the cliffs above the glacier. Many must have seen this upper ice but no one suspected that an active glacier lay in the hidden cirque beneath. We wouldn't have either except that I especially chose September of one of the driest years on record, when all the usual snow had melted away and left the naked ice beneath.

Old-timers tell me that a glacier has been supposed to exist on Wheeler Peak for years. However, it apparently was not this one but an ice field in Wheeler Peak's south cirque. We saw this too, but it is now greatly shrunken and definitely not active. So, inasmuch as no one knew or suspected that a glacier existed in Wheeler Peak's north cirque until 1955, I feel that it was definitely discovered then, and that we discovered it, not Eimbeck. However, it was his tip that made me scout for the ice — but I never had any idea I'd find an active glacier.
Others who wrote about the glacier after 1956 - as cited by OB2001 - include Lawrence (1958), Kramer (1962), Currey (1969), Waite (1974), and Osborn (1990). Some confusion apparently existed as to what to call the glacier and the rock glacier, with the glacier being referred to as follows (again from OB2001):
  • 'body of ice...that approaches the condition of a glacier'
  • 'glacieret'
  • 'ice mass'
  • 'active glacier'
  • 'ice field'
The rock glacier has been called by the following epithets, according to them:
  • 'moraine tongue'
  • 'mound of unstable moraine'
  • 'rock deposit'
  • 'rock glacier'

Various claims have been tossed around as to the active v. inactive status of both the glacier and the rock glacier, with the rock glacier sometimes being referred to as active and the glacier being called inactive to non-existent (the latter notably in an argument against the establishment of a National Monument or Park at Wheeler Peak - as per information from OB2001). It's the glacier that is (or has very recently been) active; it's the rock glacier that's inactive.

That most definitive paper I could find (OB2001) states that the glacier was active at the time of study, and that the rock glacier was not active (the study took place during the 1990's). They state that the "glacier grades into an ice-cored rock glacier downstream" - that would be down hill or down the ice gradient (or water gradient, if the thing is melting). And for various reasons - including topography, shape, vegetation, and presence or lack of certain tephra layers including ash from Mono Craters and Mt. Mazama - they determined that the upper portion of the rock glacier had an origin in the Little Ice Age (sometime from A.D. 1300 to A.D. 1850), and that the lower, lumpy part of the rock glacier had an origin sometime prior to A.D. 1200. Osborn and Bevis (2001) say "...shards of Mono Craters origin incorporated into the matrix of the lower rock glacier indicates a pre-1200 AD origin of that segment." This seems a bit confusing to me, because elsewhere in the paper, when refering to tephra from Mono Craters, they refer to the Mono Craters tephra that is dated at 1200 B.P. (not one from 1200 A.D.). So, I'm not sure what this means exactly, or maybe it has something to do with whether or not the C-14 dates are calibrated. There are numerous tephra layers from Mono Craters, with ages of 560 ± 20, 1200 ± 40, 2060 ± 75, 3730 ± 60, 7270 ± 70, 8235 ± 105, and 9710 ± 80 B.P. (dates from this site; calibrated or not?).

Because the Mazama ash doesn't occur anywhere in the southern Snake Range, according to Osborn and Bevis (2001), I presume that its absence in or on the rock glacier can't be used to determine whether the rock glacier is older or younger than the 6845 ± 50 B.P. carbon-14 date on the Mazama ash, or about 7,700 calendar years ago (Bacon, 1983). According to a map showing the distribution of the Mazama ash, by Sarna-Wojcicki, Champion, and Davis (1983) [per OB2001], the southern Snake Range may be right near the edge of the fallout lobe of the Mazama ash. I found two maps online; one is from Sarna-Wojckicki and Davis (1991), [published posthumously by J. O. Davis]; the other one has an undefined origin, but might be from S-W, C, and D (1983). The latter map is more detailed.

The bottom line is: active glacier (unless it has become inactive during the last decade) and inactive, ice-cored rock glacier.

Rock Glacier Definitions:
USGS Glossary of Glacier Terminology
USGS Rock Glaciers
J. Geophysical Research

References:
Bacon, C. R., 1983, Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.: Journal of Volcanology and Geothermal Research, v.18, p.57-115.

Currey, D.R., 1969. Neoglaciation in the mountains of the southwestern United States. Unpublished Ph.D. Thesis, University of Kansas.

Heald, W. F., 1956, An Active Glacier in Nevada: American Alpine Journal, 10 (1), 164-167.

Kramer, F.L., 1962. Rivers of stone. Pacific Discovery 15 (5), 11-15.

Krimmel, R.M., 2002, Glaciers of the western United States, with a section on Glacier retreat in Glacier National Park, Montana by Key, C.H., Fagre, D.B., and Menicke, R.K., Glaciers of the conterminous United States (J-2) in in Williams, R.S., Jr., and Ferrigno, J.G., eds., Satellite image atlas of glaciers of the world: U.S. Geological Survey Professional Paper 1386-J (Glaciers of North America), 405 p., ISBN 0-067-98290-X.

Lawrence, E., 1958. The Wheeler Glacieret of the Wheeler Peak area, White Pine County, Nevada. Unpublished manuscript, Nevada Bureau of Mines, Reno.

Meier, M.F., 1961, Distribution and variations of glaciers in the United States exclusive of Alaska, in General Assembly of Helsinki, 1960: International Association of Scientific Hydrology Publication No. 54, p. 420–429.

Osborn, G., 1990. The Wheeler Peak cirque and glacier/rock glacier. Unpublished report prepared for the Great Basin Natural History Association. University of Calgary Dept. of Geology and Geophysics.

Osborn, G. and Bevis, K., 2001, Glaciation in the Great Basin of the Western United States: : Quaternary Science Reviews 20, 1377-1410.

Russell, I.C., 1885. Geological history of Lake Lahontan, a Quaternary lake of northwestern Nevada. U. S. Geological Survey Monograph 11, 288.

Sarna-Wojcicki, A. M., and Davis, J. O., 1991, Quaternary tephrocrhonology, in Morrison, R. B. (ed.) Quaternary Non-Glacial Geology: Conterminous United States. Geological Society of America, Decade of North American Geology, Vol. K-2, Boulder, Colorado, 93-116.

Sarna-Wojcicki, A. M., Champion, D. E, and Davis, J. O., 1983. Holocene volcanism in the conterminous United States and the role of silicic volcanic ash layers in correlation of latest-Pleistocene and Holocene deposits. In: Wright Jr., H. (Ed.), Late Quaternary Environments of the United States 2. University of Minnesota Press, Mineapolis, pp. 52-77.

Waite, R., 1974. The proposed Great Basin National Park: A geographical interpretation of the southern Snake Range, Nevada. Unpublished Ph.D. Thesis, University of California at Los Angeles Geography Dept.

Friday, July 18, 2008

Monsoonish Weather While Mapping

field Nice view of The Field, with rain just about to happen.

raindrops Rain happens, and messes with my windshield.

rainRain. Around here it's called the monsoon. It comes up from the south, from Arizona way, moves into eastern Nevada and western Utah, hangs around for a while - or even all summer long.

Mosquitoes. Forgot to mention them in my Rules of the Desert. Take precautions if necessary. Drink some gin and tonics (at night, I'd say), to help keep the malaria away and to prevent any incipient onset of scurvy that might arise (well, for that, you've got to stick a lime in it!). Gin, made from juniper berries, is supposed to be good for all kinds of things (well, the berries are), but in a gin & tonic, it's supposed to be the best drink for counteracting the effects of heat, as Rod Smith of the Los Angeles Times has said:
"No other drink counters oppressive heat better than a gin and tonic. The Gatorade of British colonial days, it was what allowed Englishmen to join mad dogs out in the noonday sun."
.Outback Lemming, take note!

Tuesday, July 15, 2008

Rock Glacier: Higher and Higher

hiker So, we kept on hiking up the rock glacier because, after all, that's what hiking trails are for. There's MOH, hiking on the trail. Do you recognize the trail? It's the slight indentation in the generally rocky field of the rock glacier. We're still on its lower part (trust me on this one!).

The lighting was dramatic at times, due to some puffy cumulus clouds that developed in the afternoon. I took a few pictures as the lighting changed, first some shadows here, then there, shadows moving all around. In the photo above, you can see the rock piles of the lower part of the rock glacier in the foreground, with the cirque headwall of Wheeler Peak (that's the peak!) in the background.

Here's a close-up view of the snow/ice chutes feeding the small glacier hidden behind the upper part of the rock glacier. The bergschrund seen by Osborne and Bevis (2001) was just below the kind of triangular rock exposure in the center of the lower part of the ice/snow chute. The bergschrund, if present, can't be seen from this angle. So we'll have to climb higher! I hope you're not becoming affected by the altitude: we're at about 11,320 feet or about 3450 meters, depending on exactly where we are located.

upper ice chutesAbove, more of the interesting lighting, showing the ice/snow chutes above the glacier.

lake Oh hey, we came upon this neat little glacial lake (or pond), just before starting the climb to the upper part of the rock glacier. The water and melting ice or snow fills some small, irregular depressions in the lumpy rock glacier.

glacial turquoise I don't really know if this qualifies as a glacial lake, since the water is on a rock glacier and not on a glacier, but the color of the water is the milky turquoise blue typical of water containing rock flour created by glaciers. Of course, there should be plenty of rock flour in this glacial valley. The color, therefore, doesn't necessarily indicate that the water is coming from melting glacial ice. The presence of this tiny lake or pond could, however, be an indication of stagnation, either from the melting of ice within or beneath the rock glacier, or from the melting of the small glacier at the base of the cirque headwall. I don't really know how to test these ideas out without some kind of drilling (not likely), but I'm on my way upward to the upper part of the rock glacier so can't stay and ponder these questions for very long.


Reference:

Osborn, G. and Bevis, K., 2001, Glaciation in the Great Basin of the Western United States: Quaternary Science Reviews 20, 1377-1410.


Wheeler Peak is inside Great Basin National Park

Sunday, July 13, 2008

My First Geology Tool

I'm finally getting back to the first Brunton I ever used, an old K+E given to my dad by my mom when he graduated from college with his geology degree.

brunton closedBrunton on eastward-dipping Cambrian-Precambrian Prospect Mountain Quartzite (or possibly it's part of the Precambrian McCoy Creek Group).

brunton case Case for said Brunton sitting on the same outcrop. Coconino, what do you think - Prospect Mountain Quartzite? Anyone else have an opinion?

brunton on lineationsThe same Brunton resting parallel to lineations in mylonitic quartzite within 100 feet of the previous outcrop.

brunton on quartzite A more photogenic picture of the same Brunton sitting on a nearby quartzite outcrop.

outcrop with mountainLocation of the last two outcrop photos, on the whitish eastward-dipping quartzite seen in the foreground, with Wheeler Peak in the background.