Evidence of glaciers can be found throughout the Easter Sierras. Lee Vining Canyon is no exception. This EarthCache examines the series of end moraines that can be found across the valley.
End moraines are piles of material deposited at the end of a glacier usually forming a ridge across the front of the glacier. This material comes from the material that becomes embedded in the ice as the glacier erodes material from the canyon walls and floor as it slowly moves down the canyon. Anything from huge boulders to dust becomes embedded in the glacial ice.
At the end of the glacier, the ice melts and the material that was embedded in the ice falls to the ground. If the climate remains stable for a long period of time, the end of the glacier remains at about the same place and the material can build up into a ridge of unsorted (containing a wide range of grain sizes) material called an end moraine.
End moraines can only be created as a glacier retreats. If the glacier grows, it will actually overrun the old end moraines destroying them. As a glacier retreats, it sometimes pauses for a time at the same spot or advances forward for a season or two, bulldozing some material in front of it. Then it resumes retreating leaving a small moraine. Thus these types of moraines are also called resessional moraines.
It appears that in this valley, the climate warmed up in stages as there are a series of end moraines as you move up the valley. Each time the climate stabilized for a period of time, an end moraine formed. Then the climate warmed relatively quickly and the glacier retreated a ways back up the valley leaving only erratics on the valley floor.
These end moraines have acted like small dams to the creek. Upstream of each end moraine is a relatively flat valley that the creek meanders across.
Logging questions:
- The text "GC3JN0E Lee Vining River End Moraines" on the first line.
- The number of people in your group (put in the log as well).
- Count the number of resessional moraines in the valley along your direction of travel, thus if you are going up the valley you only need to count from the coordinates westward and if you are going down the valley count from the coordinates eastward.
- What geomorphologial feature is described on the informational panel at the coordinates?