Crawford Lake Earthcache EarthCache
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For park hours, visit this link:
http://www.conservationhalton.on.ca/ShowCategory.cfm?subCatID=1451
There is an admission fee to get into the conservation area.
Crawford Lake is a meromictic lake located in Crawford Lake
Conservation Area. Go back in time as you enjoy an educational
stroll along the boardwalk that encircles this rare lake. As an
added bonus, be sure to check out Mr. Twister and how it’s
formed.
Crawford Lake is small but deep with limited circulation and little
oxygen below 15 meters. Most living things cannot exist in the
bottom 9.4 meters of the lake and so the sediment lies unchanged in
its depths. A meromictic lake is one which lacks complete
circulation. In meromictic lakes the deepest water contains no
dissolved oxygen. Sediments are relatively undisturbed and
therefore offer a detailed record of the history of the lake.
Normally lakes in the temperate zone mix completely during the
spring and autumn when water temperatures are approximately the
same from top to bottom. In meromictic lakes there are no periods
of overturn or complete mixing because seasonal changes in the
thermal gradient are either small or overridden by the stability of
a chemical gradient, or the deeper waters are physically
inaccessible to the mixing energy of the wind. Most commonly, the
vertical stratification is stabilized by a chemical gradient in
meromictic lakes.
The upper stratum of water in a meromictic lake is mixed by the
wind and is called the mixolimnion. The bottom, denser stratum,
which does not mix with the water above, is referred to as the
monimolimnion. The transition layer between these strata is called
the chemocline. Of the hundreds of thousands of lakes on the Earth,
only about 120 are known to be meromictic.
In order to log a find on this cache, you will need to walk
along the boardwalk that surrounds this lake. Based on the
information given and using your own GPS to obtain measurements of
the lake, approximately how many litres or gallons of water are in
the bottom 9.4m of this meromictic lake. Additionally, based on
what was once in this area, what kind of things can one expect to
find in the lake sediment?
As a bonus, how was Mr. Twister formed?
Additional Hints
(No hints available.)
Treasures
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