Lake Chisholm Sinkhole EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
There are numerous sinkholes around the greater area of Lake Chisholm and there is evidence of at least two others near the lake.
Sinkholes are holes that appear in the ground after a cave has formed below and eventually the crust falls away, exposing the cave. This process takes a very long time.
What is special about this sinkhole? It is a lake. This sinkhole lake is the only one of its type here in Tasmania and similar lakes can be found in Finland.
But how did the sinkhole form? That is what you need to find out. At the posted coords is an information board. From that, you can learn how the sinkhole is formed and why this one has water in it. When you get down to the lake, you will realise that it is quite a large sinkhole (larger than those I’ve seen in SA!)
To log this earthcache, email me the answers to the following questions. In addition, upload a photo of you and your GPS in front of the lake at the far end of the loop track.
1. How long does it take to form a sinkhole?
2. Through what process is the sinkhole formed?
3. Name the rock in the area?
4. Why is this sinkhole a lake instead of a hole?
5. Upload your photo.
Other interesting facts about this sinkhole.
Lake Chisholm is a warm monomictic forest lake which means it nevers freezes. In addition, because of the depth of water and the surrounding sheltering forest, the lake has water temperature layers for 9 months of the year. During winter the temperature of the lake top cools and the water layers mix thoroughly from top to bottom. Another lake that is similar in this regard is the Blue Lake at Mt Gambier in South Australia.
The lake has a high humic content which causes the brown water colour. This also causes a red wavelength underwater climate. The humus comes from the surround soils, being manly peat.
There are also sporadic monospecific blooms of chromophyte flagellates which are the dominant algae in the water.
Additional Hints
(No hints available.)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures