Friday, January 29, 2016

Links: Pumice and Pumicite

In keeping with my recent posts about Glass Mountain, Siskiyou County, CA, I've put together a few links relating mostly to pumice:

Chesterman, C.W., 1956, Pumice, pumicite, and volcanic cinders in California and Technology of pumice, pumicite, and volcanic cinders [pdf; text]: CDMG Bulletin 174, 119 p.

Presley, G.C., 2006, Pumice, pumicite, and volcanic cinder, in Kogel, J.E., Trivedi, N.C., Barker, J.M., and Krukowski, S.T., eds., Industrial rocks and minerals (7th ed.): Littleton, CO, Society for Mining, Metallurgy, and Exploration, Inc., p. 743–754.

Pumice and Pumicite Statistics and Information - USGS links and reports.

What is the fate of the pumice rafts? (2012) - at Eruptions.

Pumice flows (down the page), a type of pyroclastic flow - at SDSU.

Pumice - at MEC.

Pumice - at Minerals Zone.

Pumice - at Sandatlas.

Pumice - at Volcano Discovery.

Tuesday, January 26, 2016

Hiking Down Glass Mountain

A few weeks ago, we were about to hike back down Glass Mountain after our short hike part way up the glassy rhyolite flow dome. We had taken some overview photos and had stopped at the old working in the foreground (above) to collect some scouring stones. (And then we went off on a float-testing tangent.)

I had vowed to myself, and to MOH, to keep my eye out for some reddish, oxidized glass on the way down...
...and indeed, I found some.
The pile of obsidian and pumice rubble is eroding from a part of the rhyolite flow that includes dense, black obsidian, white to tan-colored pumiceous rhyolite, and reddish brown to reddish orange oxidized rhyolite glass.
I've zoomed in a little here. The black glass looks a little bluish because it's reflecting the sky (what little of it was showing through the clouds).
The oxidized and probably partly devitrified (?) obsidian always seemed to be perched on the treacherously glassy scree slopes above the road we were hiking on. I didn't find any good examples of the orangey rock along the road, and I wasn't about to go climbing over the glassy talus, without sturdy boots and leather gloves.
This rock from in an earlier post shows thin, oxidized bands and streaks, and I'll have to let it stand for a closeup example, although the reddish orange color is not as intense as in some smaller pieces or in the outcrops above the road.
Looking out over the northern dacite flow, and beyond to Timber Mountain.
The photo really captures the blocky and jagged nature of the surface of the dacite flow. It wouldn't be easy to walk across that terrain; one should have very sturdy boots and equally sturdy leather or work gloves. And please don't even consider shorts!

The northern dacite flow is the darker flow area in the upper part of this Google Earth image. The rhyolite flow is the long, almost cylindrical-shaped area emanating from Glass Mountain itself, the small, grayish, round area west and a little south of center.
Read more about the geology in this post.
An old tree grew around a large obsidian boulder (and is therefore younger than the flow). Trees are fairly sparse. 
A geo-type walks down the trail.
Pine trees grow on the angle-of-repose slope, their trunks bent from downhill creep of the colluvium.
I've zoomed in here to take a closer look at a mass of oxidized, reddish brown obsidian near the base of a large, conchoidally fractured obsidian outcrop.
Finally! Down the trail just in time for lunch.
An unreadable metal sign in front of the dacite flow. Maybe it said "Keep Out," once upon a time.

Related Posts:
A Hike Up Glass Mountain
Views from Glass Mountain (and some geology)
Which of These Rocks, Mostly from Glass Mountain, CA, Will Float
The Conclusion of Our Float Test
Hiking Down Glass Mountain (this post)
Links: Pumice and Pumicite

Friday, January 22, 2016

Aerial Views of Two Northwest Volcanoes

My first view of Mt. Rainier out the window on New Year's Day was quite colorful, but the high-order rainbow effect of alternating pinks and greens was due to refraction, from shooting sideways through the Bombadier Q400's window toward the front of the plane.

I waited until Rainier moved fully into view for the next shot:
Photo looking almost due east.
The high peak on the left is Liberty Cap, at 14,112 feet (4301 m); the peak on the right is Point Success, at 14,158 feet (4315 m). The high point of the entire mountain, in the center and back behind the other two, is Columbia Crest, coming in at 14,411 feet (4392 m).

In the view above, we're looking at the head of the South Fork of the Mowich River just left of center in the foreground. The small ice field above and left of the river head is Edmunds Glacier. The shadowed icy mass to the left of Edmunds is the North Mowich Glacier, which is above the North Fork of the Mowich River (mostly out of view).

A radial dike runs from between the two closer and less elevated peaks to the lower right, into what is the headwaters of the North Puyallup River. The landform formed by the radial dike is known as Puyallup Cleaver.
Photo looking a little east of northeast.
Here we're looking almost straight up the andesitic dike that forms Puyallup Cleaver. This dike fed lavas that erupted between 280 and 190 ka (Pringle, 2008). The Puyallup Glacier is to the left (north) of the dike; the Tahoma Glacier is to the right (south). The steep headwall above Puyallup Glacier is called Sunset Ampitheater. Ice in Sunset Ampitheater spills (or flows) into both the Puyallup and the North Mowich Glaciers.

I was on the wrong side of the plane to see Mt. St. Helens, but had this great view of Mt. Adams as the sun went down and the light got pink. Notice the reddish irridescent lenticular cloud off to the side.
Mt. Adams looking almost due east.
Too bad I hadn't thought about my new camera on the Alaska-SeaTac leg of the flight! For some reason, I didn't think about it, and hence only got some not-so-great phone photos.

Tuesday, January 19, 2016

Finding a Thesis: On the Southern Route to the Top of Mineral Ridge

And so, we return once again to my seemingly never-ending thesis hunt. As you can see above, I've just arrived on eastern outskirts of Silver Peak, after crossing the Clayton Valley lithium brine fields.
Portion of the Goldfield 2° sheet, about centered on Mineral Ridge and what was then called "Silverpeak."
I took a close look at my maps, and noticed that not only did the Goldfield 2° sheet not show the Mary Mine that was on my list as a possible thesis area, but that there was only one route shown onto Mineral Ridge: a dashed light gray road north of town indicating a jeep trail I would presumably not be able to traverse in my '72 Opel.

I pulled out another map. No, make that two: The area was bifurcated by two 15' maps, Silver Peak and Lida Wash.
The Silver Peak and Lida Wash 15' quads, both from 1963, courtesy USGS.
Here I've joined the two maps together in a crude effort to create the effect of folding two maps together at the seam, as I probably did back in 1976.

On these combined maps, two routes to the Mary Mine became apparent to me: a southern and a northern route. The northern route took off from old Highway 47 (now S.R. 265), the paved road going north from Silver Peak, and headed westward along the northern side of Mineral Ridge. The southern route, Coyote Road, headed southwest out of Silver Peak and then turned westward along the southern side of Mineral Ridge toward and past Coyote Spring. Both routes are marked with double dashed lines. Another double dashed road heads nearly south for Oasis Divide, a pass over the Silver Peak Range into Fish Lake Valley.

Not knowing then what I know now—that my car would not have been able to make it up the mountain on either of these roads—I resolutely steered toward the southern route.
The end of pavement near the southwest end of Silver Peak, as seen in 2010. Coyote Road is the track going off into the center distance.
Coyote Road continues on as the bright track on the right. An unknown two-track on the left, not shown on any maps, including the 1987 7.5' quads, heads off toward some colorful volcanic hills.
Sign on Coyote Road just past the end of pavement.
Supposedly there was minimum maintenance on the Coyote Road when I drove it in 2010, although the road looked good to me. It looked as good as it did in 1985-87, when the county bladed it every time it got the slightest bit washboardy.
The Coyote Road is looking good as it descends back into Silver Peak from Coyote Springs, which is about 5 miles past the end of pavement.
I have no idea what the road looked like in 1976. I'm not even sure that I found the road.

From pavement in Silver Peak, I drove and drove down a wide, bladed but strongly corrugated dirt road for what seemed like miles and miles, surely at a slow speed, heading in a direction that didn’t seem quite right to me. I made it as far as some scrabbly-looking, knobby outcrops.

I drove back to Silver Peak. Was I on the right road?

Let's back up a bit on the Coyote Road―back into town, where it's still mostly paved―to it's present-day junction with the Nivloc Road.
Nivloc Road is on the left; Coyote Road is on the right.
The Nivloc Road goes to the defunct 16-to-1 mill, and the inactive 16-to-1 and Nivloc Mines (the junction on Google Street View).
What do our maps show? (See the maps, above.) The 1962 2° sheet shows two sub-parallel long-dashed gray roads going off to the Nivloc Mine, and no roads going up to Coyote Spring. One year later, the 1963 15' maps show double solid lines for the Nivloc Road and double dashed lines for the Coyote Road.

Which road did I take? That's a hard one to answer. My geographic memory (not always perfect but often fairly well oriented in north-south space) suggests to me that I was either on the often strongly washboarded Oasis Road or the often moderately washboarded Nivloc Road. Note: The washboard intensity of any given road means little as it will increase with time from its most recent grading (besides the other factors that affect intensity).

What about the outcrops I drove by? Had I been on the Oasis Road, it would have been more than 13 miles to the nearest outcrop, an unlikelihood given how long it would have taken in my Opel, and given that the maps said I didn't need to drive that far. On the Nivloc Road, it was about 4 miles to the first hills and a little farther, perhaps, to ones that might look "knobby." On the Coyote Road, it was about 3 miles to the first scrabbly hills, maybe a half mile or more to any exposures I might think of as knobby. Most likely I ended up on the middle road, the Nivloc. I'd have to guess that access to the top of Mineral Ridge was not much of a local or county priority in those days (as it would become by the mid-1980s), and that's why I didn’t find the possibly obscure turnoff I needed. But that is just a guess.

In any case, even if I had found the right road, in all likelihood I would not have been able to take my car much past Coyote Spring (maybe I could have made it about a mile and a half beyond the spring). I have seen some remarkable feats on that road, by people more experienced in off-road travel than I was back then, including a rather doubtful-looking but spunky Pinto driven to the top of Mineral Ridge by a driller's wife, who was delivering drill casings in the rear compartment of the hatchback, but I also know that Ford 150 4x4s of the era couldn't make the steep switchbacks on that hill in two-wheel drive, at least not without a lot of weight in the back.

At this point on my journey, it was noon or later, so I gave up on finding the southern route and drove into the town of Silver Peak.
Sign at the junction of the Silver Peak Road (road to Tonopah or Goldfield) and Main Street (S.R. 265).
To be continued...

Related Posts:
Thesis: Finding an Area
Finding a Thesis: Battle Mountain to Austin to Gabbs
Finding a Thesis: Pole Line Road
Finding a Thesis: Pole Line to Belmont
Finding a Thesis: Klondyke District
Finding a Thesis: A Joshua Tree Aside
Finding a Thesis: Into the Palmetto Mountains
Finding a Thesis: Farther into the Palmetto Mountains
Finding a Thesis: A Bit O' Geology in the Palmetto Mountains
Finding a Thesis: Future Stories from the Palmetto Mountains
Lida Summit Roadcut
Finding a Thesis: Next Stop, Silver Peak!
Finding a Thesis: Coming into Clayton Valley

Thursday, January 14, 2016

2015 Top Ten Posts at LFD...

...and—as for 20142013, and 2012—a few more. My rules, as modified from last year:
Because of the vagaries of stat reporting (in this case, by Google Analytics), I'm listing both the top ten posts for the year (in large font, with respective Top Ten number), and the top post for month's without a top-ten posting (non-Ten-rated posts are in a smaller font).
And so, here are the top 10 posts, plus 2 extra, along with a few pretty pictures:







July: No posts in July!






Tuesday, January 12, 2016

The Conclusion of Our Float Test

We're about to test the rocks I posted about last week.
We have six float candidates (description here).
I voted for rocks #2 and #3 (as counted from the left in the photo shown above), with a "might" for #1 and "probably not" for #5. I did have the distinct advantage of being able to hold the specimens, thereby testing the heft

In comments, I got votes for:
1) Howard: none of the above
2) Lockwood: #3, with maybe but "I'd guess not" for #1 and #2
3) Ivar the Old: #3 (after thinking about #2 and then throwing it out)
4) Mathias: #3 and #2 (a "maybe" on the latter)
Rock #1. The larger of our two scrubbing stone rejects.
I wasn't sure if this rock would float: It has a lightweight heft for it's size, but I'm more used to feeling the heft of hand sized rocks, testing to see if a rock is limestone/dolomite v. barite, or limestone/dolomite v. fine-grained diopside skarn. I placed it carefully into the water, with one flat side down rather than end on into the water.
It's floating!
It's bubbling like crazy, and so I suspect the smallish vesicles will fill up with water, and when it gets completely waterlogged, it will likely sink (not a part of this test).
Rock #2: The smaller of our scrubbing stone rejects (remember, you can read more about these scrubbing stone rejects and see more detailed pics here).
I voted that this rock would float, although truth be told, the vesicle size is very similar to that of Rock #1 (so why didn't I vote for both of them?).
It's floating!
Possibly a higher percentage of the upper surface, compared to the upper surface of Rock #1, is sticking up above the water, but it's hard to judge the relative percentage of the entire rock in comparison with #1. And once again, I think it would probably become waterlogged eventually, and then it would sink.

I was sure that Rock #3 would float. It's a large piece of classic pumice.
Yep, there it is, floating. Most of the rock is sticking out above the water, almost the reverse of the previous two examples.
The pumice has small to very large vesicles.
Close-up of the largest of the air pockets or vesicles.
Overall, the pumice is quite frothy looking.
Rock #4, a piece of banded rhyolite glass.
I knew this rock would sink but included it in the test because it's composed of glass of about the same chemical composition as the glass in the previous three rocks.
It's on the bottom, no surprise.
Rock #5, vesicular rhyolite, also from Glass Mountain.
This is a large rock, lightweight for it's size, but it felt denser to me than the scrubbing stone rejects (Rocks #1 and #2) and doesn't look as vesicular. Consequently, I expected it to sink.
I placed it into the water with one of the flat sides down, and let go of it slowly.
It's definitely on the bottom.
Rock #6, a flattish piece of slaty phyllite.
I knew this rock (which is not a single large piece of mica) would sink, but I included it in order to a test of a rock with a different makeup than the other five. I also chose it for it's flat shape, to test whether the shape might make it float.
Nope. It's gone.
Three of five rhyolite samples from Glass Mountain floated and could therefore be called pumice. Their vesicularity, in order from most vesicular to least vesicular, is as follows: Rock #3, Rock #2, Rock #1, followed by Rock #5, which didn't float, and followed a long ways by Rock #4, which also didn't float. The difference between Rock #5, an example of vesicular rhyolite flow rock, and Rocks #1 and #2, pumiceous rhyolite flow rocks (the scrubbing stone rejects) is not great and might not be apparent when doing field work. Rock #4, which consists of dense, glassy banded rhyolite, is not vesicular at all. Rock #6, not a volcanic rock and not from Glass Mountain, also didn't float. It probably has a density similar to or slightly lower than the density of the dense rhyolite glass of Rock #4.

And that concludes our float test.