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