The coordinates are at a small road cut. Be sure to park off the pavement. Luckily the road cut is at a relatively high point so oncoming cars should see you.
As with all locations in National Parks, everything is protected, so leave it as you found it.
Lake Manly was the last of a chain of five lakes that formed along the Eastern Sierra during the Pleistocene following the recent glacial episodes. As the glaciers melted following the Tioga glaciation, about 20,000 years ago, and the Tahoe glaciation, about 75,000 years ago, melt water flowed down to the lowest basin in the area. At its largest, Lake Manly was 100 miles long and 800 feet deep. But the level of the lake would generally fluctuate depending upon the inflow from the glacial melt and the evaporation and percolation from the lakes. This 153,000 year old gravel bar is a older than the two major glaciations mentioned above so it is from an older Lake Manly. During this incarnation of Lake Manly, it was likely about 370 feet deep.
So what distinguishes this ridge of gravel from the many other piles of rock throughout Death Valley? Almost all the rocks in the valley, no matter the size have sharp angular edges. Now take a close look at the shape of the rocks found in the road cut. These rocks are very rounded and smooth, very unlike the rocks found in the rest of the valley. Rounded rocks are found around the edges of lakes or in stream beds where waves constantly roll rocks around smoothing the edges. The longer the rock is rolled around, the rounder and smoother the rock becomes. This is the natural version of the rock grinder kids get to polish rocks.
Logging requirements:
Send me a note with :
- The text "GC2V37P Lake Manly Beach Gravel" on the first line
- The number (including non-cachers) and names of the geocachers in your group.
- What is the range of rock sizes in the gravel bar?
- What shape are these rocks compared to the majority of the rocks in the area?
- Does the shape give a clue about the type of environment in which the rocks were deposited?
- Make a guess as to why gravel of this size would be left on the shore of a lake and why it would stay in the same place over thousands of years?
- (Optional) Post a picture of you/your gps next to the rounded rocks of the bar.
The following sources were used to generate this cache:
- Spear, Steven G. Ph.D., 2009, Death Velley Geology, A Field Guide and Virtual Tour of the Geology of Death Velly National Park and Environs, California and Nevada, Last Updated: August 25, 2009 http://www.palomar.edu/geology/DVWeb.htm
- Snow, J. Kent, and Daniel R. Lux, Tectono-sequence stratigraphy of Tertiary rocks in the Cottonwood Mountains and north Death Valley area, California and Nevada, in Cenozoic Basins of the Death Valley Region, The Geological Society of America, Special Paper 333, Lauren A Wright and Bennie W. Troxel eds. 1999font>