Part 1: Orientation: Franklin Lake Playa, north of Eagle Mountain
(Click here to go to the Bing map also shown below)
If you are only here for the guided picture tour, by all means go to the next page!
Go to second Franklin Lake Playa page: starting from south
If you would like to read why this is not your ordinary dry-lake bottom, keep reading on this page.
Franklin Lake Playa is not just another boring dry lake bed. It is a place with several interesting, almost living, features, in my opinion. Just for fun I looked at several scientific publications describing some features of the playa that are of interest to me. [Click on the titles to see the abstract and the larger publication that I am grossly oversimplifying here.]
1. The first paper was of interest because there was exploration for dissolved silver and gold in the briny waters beneath the playa. There are metals in that water, yes, but not silver or gold, at least not in quantities that are exploitable.
At the 2007 Geological Society of America (GSA) Denver Annual Meeting (28–31 October 2007), a paper was presented entitled TRACE-METAL ACCUMULATION IN BRINES AND SALTS OF FRANKLIN LAKE PLAYA AND THE ASH MEADOWS AREA OF NEVADA AND CALIFORNIA. It was authored by GOLDSTEIN, Harland L., BREIT, George N, YOUNT, James C., and REYNOLDS, Richard L., all of the United States Geological Survey, Denver Federal Center.
This paper caught my attention because it surprised me. Trace elements like arsenic, chromium, molybdenum, selenium, tungsten, uranium and vanadium are present in high concentrations in the briny water underneath Franklin Lake Playa, but --and this is what surprised me-- not in the salts that occur on its surface. These metals are in the water discharged, and partly evaporated, at Ash Meadows to the north. At Ash Meadows there is surface evaporation and so high concentrations of these metals occur in the remaining salty water and in the salts on the surface. Salty water leaving Ash Meadows underground along the Carson Slough drainage continually moves up to the surface and evaporate along the way, leaving a salty surface (as seen in a previous page on this website). Closer to the playa, when the briny water has to move through a deeper layer of sedimentary material toward the surface, in response to evaporation at the surface, its metals-load prefers to stay in the water moving laterally rather than upward, which includes water vapor moving up, as well as films of liquid water. I'll quote the authors here: “Saline water is 1-3 m below the ground surface beneath the playa rather than <0.5 m depth in salt-accumulation areas in Ash Meadows and along Carson Slough. The contrast in metal concentrations may be attributed to preferential retention of metals in the brine beneath Franklin lake playa because capillary transport is the primary mechanism of salt supply to the ground surface.” Why does anyone care? “The metal-rich salts are of particular concern as they are entrained in wind-blown dust that disperses the metals over a broad area.” In other words, these metals are poisonous in higher concentrations. Don't go tasting salts in the desert.
2. This second publication was of interest since it discusses the features and processes that make this place interesting.
John B. Czarnecki did his PhD work on Franklin Lake Playa. His results are published in a US Geological Survey Water-Supply Paper, number 2377, entitled Geohydrology and evapotranspiration at Franklin Lake playa, Inyo County, California. It was published in 31 Dec1997.
Czarnecki's report explains why there is running water in several boreholes, and why there are mounds with water near -or even at- the surface in the northern part of Franklin Lake Playa. By the time the water gets to the playa, it has entered under a confining layer (a layer of clay-rich sediment probably), and as the water moves south under that layer, new water coming from the north puts it under pressure. The confining layer lets little water through to the surface except in a very few localities. Where water comes up to the surface, mounds form when wind-blown dust and sand settle on the wetted surface. This is ideal for a plant community, and “phreatophytes” --plants that suck moisture from an upwelling water source-- thrive and support wildlife. Further south in the playa the water level drops but there is still continual upward movement along capillaries and by vapor flow to satisfy surface evaporation demand. It is a very hot place usually visited by dessicating (hot and dry) winds. So water continually evaporates and moves along films on the sediment particles, upward, keeping the playa moist and the surface clays expanded and soft. The spongy surface of the playa is like walking in snow: tiresome. At the eastern edge of the playa there is more evaporation, and so there is a saltier surface there. Saltgrass is especially abundant in the saltiest areas, and other, larger plant species are at least relatively salt tolerant.
The playa ends at Eagle Mountain. I find Eagle Mountain to be a fascinating chunk of rock. I was curious about its formation, and thus consulted three papers on the internet about Eagle Mountain. [Click on the titles to see the abstracts that I am again grossly oversimplifying here.]
These papers give an indication of the nature of the layers in the mountain, how they got tilted and folded as they are, and give some hint as to the time span over which this block of rock has moved about 60 miles from where it originated.
The first paper was presented at the 2009 Portland Geological Society of America (GSA) Annual Meeting (18-21 October 2009), titled: ECOLOGICALLY ZONED MICROBIAL REEF AT EAGLE MOUNTAIN, CALIFORNIA, by PETERSON, Christopher D. (Geosciences, California State University Chico)
The paper suggests that some of the alternating layers seen in this mountain represent flows of materials from shore, leading to shale layers, intermixed with quiet periods of limestone formation. There is a microbial reef evident in a specific zone within the mountain, it is rich in sea life fossils.
Another paper, this one presented at the 2002 Denver GSA Annual Meeting (October 27-30, 2002) is titled STRUCTURAL GEOLOGY OF EAGLE MOUNTAIN, AMARGOSA VALLEY, CA. It is by COOK, Benjamin and MILLER, Martin G. (Dept of Geological Sciences, Univ of Oregon, Eugene).
This paper suggests that five sequential events shaped this mountain, and describes these events. One of the events is a folding episode, with undetermined cause but likely related to deformation along the Furnace Creek fault zone. Eagle Mountain sits at the terminus of that fault zone.
A paper published in the GSA Bulletin; April 2001; v. 113; no. 4; p. 419-442 and titled Distribution and provenance of the middle Miocene Eagle Mountain Formation, and implications for regional kinematic analysis of the Basin and Range province. It was authored by four persons from the California Institute of Technology, Nathan A. Niemi, Brian P. Wernicke, Robert J. Brady, and Jason B. Saleeby, and one person from the California State University at Northridge, George C. Dunne.
The paper suggests that some rocks on Eagle Mountain are from 11 to 15 million years old and come from more than 60 miles away. These are rocks from the Cottonwood Mountains to the west-northwest. These rocks flowed down to the sea along an alluvial fan and became part of the layers of rock that make up Eagle Mountain. They were moved to their present location by extensional (Basin-and-Range-forming) and strike-slip faulting over the last 11 to 12 million years.
I knew it was an interesting rock!
So let's start our walks through the Franklin Lake Playa (probably has not been a lake since the last ice age about 10,000 years ago because a channel has been cut, perhaps during the last ice age, alongside Eagle Mountain, that drains the area into Death Valley. A similar thing happened at the Amargosa River Canyon near Tecopa, where there was also a lake that drained. To see water actually moving along this channel, click here and see my pages on the 2005 phenomenon of water moving from here all the way into the bottom of Death Valley.
Go to second Franklin Lake Playa page: from the south to the central and eastern part of the playa
Go to third Franklin Lake Playa page: water sources in the north to central part of the area
Go to fourth Franklin Lake Playa page: exploring the northern drainages
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