ERRATIC BEHAVIOUR
EARTHCACHE
On the road to another fine Alberta earthcache
(end shameless plug) there is
an interesting rock by the side of the road. (The right side, if
you’re headed west.) This rock is another one of the wonderful
features in Alberta known as a “glacial erratic.” In 1956,
Dr.
A. MacS. Stalker mapped out this group of erratics in
Southern Alberta, and it gave scientists a keen insight into the
events of the last ice age in Alberta. Unlike rocks that have
been run over by glaciers, erratics land on top of the ice
sheets and get carried to their new location when the ice sheet
melts.
A standard rock that has been run over by a
glacier looks something like this:
[image courtesy of Fettes College Edinburgh]
Notice particularly the smooth surface and the sratches in the
rock, known as glacial striations. These scratches are caused by
the glacier's movement over the rock surface, the same way sliding
something over sand on a hardwood floor scratches it.
A glacial erratic looks like this:
This particular erratic is also split in half.
This is caused by water seeping into the rock and the freezing,
causing the two halves to separate. Of course, this process took
many, many years.
TO LOG THIS EARTHCACHE:
- Email the owner the approximate height of the
erratic between the two halves.
- Email the owner the approximate length (on
the longest axis) of this erratic.
- Email the owner the name of the erratic group
to which this one belongs, or alternatively, email the owner the
name of the person who is connected with the First Nations legend
regarding this erratic.
- OPTIONAL: post a photo of yourself at the
erratic, but please, do not post one taken of yourself on the
inside. Keep to the outside of the rock.
Enjoy!