Winnemucca Lake Beach Terraces
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The subject of this earthcache is beach terraces, but I would first like to describe the climatological and environmental conditions that led to their development in the first place. Secondly, I will describe the flora and fauna that existed in that wetter period.
The last great ice age, the Wisconsin, ended between 10.000 and 13,000 years ago and it occurred over the northern hemisphere around the world. (Heaton 1990). It is estimated that in this period the streams that entered the Great Basin Region carried between 5 to 10 times more water than they do today and precipitation was 1 ½ – 2times present values (Smith et al 1983). This combined with an estimated drop in temperature of 10 – 15 F and a significant decrease in evaporation, resulted in the development of large lakes in the Great Basin area and throughout the northern hemisphere as well (Heaton 1990.).
As you might expect the biota of the Great Basin was also quite different than we see today. Plant fossils from Wood Rat middens show enormous differences, both in species composition and biomass. Valley's of the central Great Basin that are now dominated by grasses, Sagebrush, Shadscale, and other small desert plants, were composed of subalpine conifers, Bristlecone Pine, Engelman Spruce and Juniper (Heaton 1990). Elevations above about 6,000 feet, which are common across the Great Basin, were dominated by continuous coniferous forests dominated by Bristlecone Pine.
The large mammals of today's Great Basin consist of Mule Deer, Pronghorn Antelope, Bighorn Sheep, Mountain Lions, and the introduced Horse. From the last ice age many of the large mammals have gone extinct, but were made up of Short-Faced Bear, Mammoth, Camels, Horse, Muskox, and Bison, the latter of which did not go extinct. The most abundant large mammals of the period were Horse, Camel, Llamas, and Bighorn Sheep (Heaton 1990).
Geological evidence is what first lead geologists to recognize the drastic changes that had taken place in earlier times (Russell 1885 and others). Numerous beach terraces in the Basin are evidence that former sizable lakes existed in the past. One of the largest of these lakes was Lake Lahontan when at it's greatest extent extended to Walker Lake to the south, Honey Lake to the west,, southern Oregon to the north and Winnemucca to the east. The lake had no outlet to the sea, similar to it's remnants Pyramid and Walker Lakes'. Playas left behind include Black Rock, Smoke Creek, parts of Honey Lake and Winnemucca Lake where this earthcache will be located. At it's maximum stage during the final high stand, called the “Sehoo” high stand by geologists, Lake Lahontan's elevation was approximately 4370 feet and occurred approximately 13,000 years ago (Adams and Wesnousky 1998). The surface area of the Lake was over 8500 square miles and had a maximum depth of near 900 feet near what is now Pyramid Lake (Wikipedia 2010). It would have been one of the largest lakes in North America.
If you have ever driven through the Great Basin in many areas the beach terraces are quite remarkably easy to see. A terrace is a geological term that describes a step-like landform that borders lakes and river floodplains and represents the former position of a floodplain or lake (Wikipedia 2010). Beach terraces are formed by the erosional action of the waves on the shoreline or accumulation of sediment in shallow water, or some combination of both. Large terraces are typically formed by a prolonged period at that elevation (Bowman 1971).
So why is it that geologists and other scientists are studying the geomorphology of beach terraces that occur in the modern Great Basin? The answer, in most instances, is to attempt to recreate a reliable and consistent chronology (age) of the rise and fall of the lakes in the Lahontan Basin (Bowman 1971) And from my cursory examination it appears they have done so.
Once researchers find a significant beach terrace they start looking for material that may show how old it is. Some of the material they start looking for are the following:
- Exposed carbonate materials such as tufa, oolites, and gastropods (snail shells)
- Woody material in sedimentation areas.
- Rock varnish that formed on rocks on the terraces.
- One unique find was camel bones that was preserved by being buried in the sediment behind a beach barrier, which is of course a source of carbon (Adams and Wesnousky 1998)
- Other measurements are also taken, but that is beyond the scope of this discussion
After finding this material many methods are available to establish their age.. These include.but may not be limited to the following:
-Tephrochronology is the use of volcanic ash from a past single eruption of a volcano that can be used to create a chronological framework.
- Palynology is the use of fossils such as pollen, spores, dinoflagellate cysts, chitinozoans, and organic material.
-Magnetostratigraphy is a technique where samples are analyzed to determine their magnetization, or the polarity of the material that that stratum was laid down in. It's kind of like working with tiny compasses
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-Radiocarbon dating is a method that uses the radioisotope carbon-14. In plant material for instance, the carbon is taken up from the atmosphere during photosynthesis. By knowing the decay of carbon-14, a well known exponential rate, the sample is compared to that of today's atmosphere and the estimate of age can be made.
The main goal of studying the geomorphology and sedimentology of these ancient lakes and their beach terraces is primarily to produce a record of valuable information regarding past environments, archaeological record, and paleoclimate.
-A Brief History of Winnemucca Lake-
If you have access to Google Earth you will notice the many different beach terraces that Winnemucca Lake has created. The lighter colored rings that circle the lake from the highest stand to the bottom playa are numerous. Winnemucca Lake rose and declined with that of the larger Lahontan Basin. When the levels were low the Lake only received water when Pyramid Lake overflowed in what is known as Mud Slough into the adjacent basin. Russell (1885) described significant water in the Lake, however I could not find any record keeping even into the early 1900's of lake level.. An interesting artifact of this rise and fall is a light color, probably carbonate, on the Pyramid island from which Pyramid Lake is named. The island has a light colored girdle about one-fifth up from current lake level. The girdle was formed when Pyramid Lake rose at or near the overflow point when the water flowed into the Winnemucca Lake Basin (Benson, U.S. Geological Survey undated paper). Dr. Ira LaRivers, a deceased biology professor from the University of Nevada, Reno, and a member of my thesis committee, described to me a period in the late 1930's when the last remaining species of fish in the lake (Lahontan Tui Chub) all died in a huge fish kill over just a few days. He attributed the fish kill to a lack of oxygen in the lake water. Dr. LaRivers describes the lakes and fisheries of the Lahontan Basin in his book “Fishes and Fisheries of Nevada” (1962). Following the late 1930's through the early 1950's the basin only supported a wetland at it's south end before it went completely dry. Human occupation of the Winnemucca Lake area began approximately 3000 to 4000 years following the last highstand of Lake Lahontan. Shelters and caves in the area have been excavated by archaeologists in the immediate vicinity on Falcon Hill near Waypoint #2 and others. Artifacts found in these excavations include evidence of the exploitation of the Lake's resources such as fish caches, fishing nets and weirs (Pedrick 1985).
-Winnemucca Lake Beach Terraces-
The coordinates given above for the earthcache will take you to a beach terrace formed by Winnemucca Lake in the past 100-200 years (rough estimate). Notice how it rises above the surrounding terrain, about 3-4 feet, and is composed of washed cobble on the surface and generally follows a consistent elevation as it runs in a general north-south direction. This beach terrace is at approximately 3860 feet in elevation. Parking can be found at Waypoint #1 and is located just off of HWY 447. It has a very solid surface and any two wheel drive vehicle is acceptable. The parking area is large enough to accommodate many vehicles and leads to a gate that can be lowered for access to the terraces, which are located roughly 100 yards to the east.
After visiting this beach terrace I have set up another point of interest thanks to Dr. Ken Adams at the Desert Research Institute, who has written numerous scientific articles on the geomorphology of beach terraces and the rise and fall of the ancient lakes of the Lahontan Basin. The location he suggested is at the approximate location of the “sehoo” highstand of about 13,000 years ago and parking is available at Waypoint #2 which is within approximately 20 feet of it's elevation. Although it is difficult to see the beach terrace in the landscape, it is interesting to view the Winnemucca lake Basin to the south and imagine an earlier time when water covered the area. At this highstand Winnemucca lake was almost 600 feet deep and provided a habitat for large Lahontan Cutthroat Trout, Cui-ui and other native fishes. Falcon Hill is also nearby, where a cave is located that archaeologists discovered evidence of prehistoric human occupation.
-To Log this Earthcache-
Answer the following questions and email them to the developer of the site and when you log the cache add a photo of your group at the site and include the number of people in the group.
-Question 1) How deep was the water in Winnemucca Lake, at it's deepest point, when the beach terrace was formed at the given coordinates for the earthcache?
-Question 2) The fetch of a lake is a term given to the length of water over which a given wind has blown (Wikipedia 2010). Fetch is a large factor in beach terrace development, the larger fetch, the more development. (all this time you thought fetch was something your dog did). Given that the predominant winds in this area are from the south, and the location of the Winnemucca Lake beach terrace, would you expect potential for terrace development to be low, medium, or high?.
-Basic Visitor Use and Public Safety Information for Public Lands in Nevada-
All visitors need to plan ahead and prepare for outings in Nevada's public lands by:
1).Knowing the regulations and special concerns for the area you are planning to visit. Such as obeying the laws that prohibit the collection or destruction of artifacts.
2).Carrying a map and GPS unit and/or compass. Maps are available for purchase at all BLM offices and from the Nevada Bureau of Mines and Geology (www.nbmg.unr.edu).
3).Being aware that cell phones DO NOT usually work in the rural areas away from major highways.
4).Staying on existing roads and trails.
5).Planning for extreme weather, hazards, and emergencies.
6).Carrying a full size spare tire, extra food, and warm clothes.
7).Leaving your travel plans with a responsible party, including the date and time of your return.
8).Linking to “Tread Lightly and Leave No Trace” websites (www.treadlightly.org or www.int.org)
9).Remember the geocaching motto of “Cache in Trash Out”.
-References-
Adams, K. D.. and S. G. Wesnousky. 1998. Shoreline processes and the age of the Lake Lahontan highstand in the Jessup embayment, Nevada. Geological Society of America. Bulletin. V.110 No.10 pp.1318-1332.
Benson, L. V., 1978. Fluctuations in the level of pluvial Lake Lahontan during the last 40,000 years.Quat. Res.V. 9, pp. 300-318.
Benson, L. V. Undated U.S. Geological Survey Report on the tufa of Pyramid Lake
Bowman, 1971. Geomorphology of the shore terraces of the late Pleistocene Lisan Lake (Israel). Paleogeogr., Paleoclimatol., Paleoecol.. V.9, 183-209.
Heaton, T. H., Quaternary mammals of the Great Basin: Extinct Giants, Pleisstocene Relicts, and Recent Immigrants: Chapter 15 in: Causes of Evolution: A Paleonological Perspective. Ross, R. M.
and W. D. Almon (eds.) University of Chicago Press, pp. 422-465..
Pedrick, K. E. 1985. The lake range quarry Washoe County, Nevada. Contributions to the study of cultural resources. Bureau of Land Management Technical Report No.14
Smith, G. W. and F. A. Street-Perrott. 1983. Pluvial lakes in the western United States. In: Late-Quaternary Environments of the United States: V.1, The late Pleistocene, Porter, S. C. (eds.)
University of Minnesota Press, pp. 259-293.
Russell, I. C. 1885. Geological History of Lake Lahontan: A Quaternary lake of Northwestern Nevada.U.S. Geological Survey.
Monograph 11. 288 pgs.
Congratulations to motoringwest for the FTF
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