Castle Lake is reached by paved road. There is a parking lot that often gets busy on the weekends. Winter snows may make the EarthCache inaccessible.
Castle Lake was formed during a Pleistocene glaciation 10,000 years ago. A glacier likely formed in a preexisting depression and continued to expand the depression into a cirque (See Castle Lake – A Cirque
The material the glacier eroded out of the depression was transported downslope by the movement of the ice. At the end of the glacier where the ice melted, all the rock debris is deposited in a pile. This pile of glacial debris is called a moraine. Since a glacier carries a wide range of material, large boulders to fine rock powder, the pile reflects this range is grain sizes. Since it contains a wide range of grain sizes it is considered unsorted.
Moraines are given different names depending upon what the glacier was doing at the time the moraine was deposited. The moraine at the furthest extent the glacier ever reached is called the terminal moraine. As a glacier retreats, it may become stable for a period forming another moraine not as far as the terminal moraine, this is called a recessional moraine. If another glacial event extends the glacier out again, but not as far as the previous terminal moraine, the moraine that forms is called an end moraine.
By the erosional nature of glaciers, as a glacier advances, it will erase any earlier moraines that the glacier flows over. Thus only the youngest glacial advance is recorded by a moraine.
The road cut at this location is a moraine. The pile of material helps create Castle Lake by damming up the water behind it.
Send me a note with :
- The text "GC231X5 Castle Lake – Moraine" on the first line
- The number of people in your group (put in the log as well).
- Describe the layering in the road cut.
- How does the material in the road cut match the description of a moraine
The following sources were used to generate this cache:
- Castle Lake Geography; Copyright © 2008 Castle Lake Limnological Research Station; http://castlelake.ucdavis.edu/geography/castle_lake
- Garry Hayes, Glaciation of the Sierra Nevada; http://virtual.yosemite.cc.ca.us/ghayes/sierragla.htm
- BSG 1996-2008; last modified: 14th Sep 2009; Glacial Erosion Landforms (Large-scale); http://www.geomorphology.org.uk/pages/education/alevel/coldenvirons/Lesson%2011.htm Corrie or Cirque Formation; http://www.fettes.com/cairngorms/corrie%20formation.htm