Blue Lake EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Did you know that Blue Lake is the only lake in the whole world that changes from a brilliant blue each summer through to a cold grey colour in the winter?
Mount Gambier's Blue Lake, situated in an extinct volcanic crater exposes crystal clear water that has been filtered underground as it passes slowly under the city of Mount Gambier through the limestone. The blue lake itself forms one of four lakes around Mt Gambier, but is only one of two that still remain today.
The crater which formed during two closely spaced periods of eruption is one of the youngest volcanoes in Australia. This eruption is thought to have occured only 28000 years ago.
From December to March, the lake turns to a vibrant blue colour, returning to a colder steel grey colour for April to November.
During winters of high rainfall surplus water seeps down through the limestone recharging the underground water system. Making its way gradually to the ocean, the underground water has contributed to the dissolution of the limestone forming many caves beneath the City of Mount Gambier and surrounding areas.
The Blue Lake was formed when the volcano erupted through the limestone allowing the underground water to fill the crater, creating the lake that we see today. The lake itself is thought to be between 72 and 75m deep., and provides the town with drinking water.
There have been various studies on the lake over time, with the first major one being listed as occuring in 1967 when surveys of the lakes depth were conducted. Further temperature and visibility studies have been completed since, with one exploration finding a Stromatolite Field, a collection of hollow rock formations, located along the north eastern perimeter at a depth of just 40m.
Stromatolites are among the oldest evidence of life on the Earth. Stromatolites are the fossilized remains of microbial life forms, primarily algae and cyanobacterial mats.
Cyanobacteria growing in tidal flats tend to form thick, wavy mats that are then preserved and fossilized, forming “stromatolites”.
To log this Earth cache go to S 37°51.007 E140°46.904 and answer the following questions:
A= The lava cooled and solidified to form a layer of dark basalt up to “A” metres thick.
B= Large blocks or bombs of basalt and limestone, weighing up to “B” tonnes, were thrown out.
C= The water level has dropped two meters in the last “C” years.
Send an Email to me through my GC profile to confirm your answers.
Include an answer in your log of your made up opinion that somehow explains, why the blue lake turns its colour from blue to grey or the opposite way (grey to blue). There are many crazy theories as to why Blue Lake changes colour each year, but which one is yours???
Make sure to add your Geocaching name and the names of all cachers in your group to your email.
3 (optional). Take a picture somewhere around the lake showing you with your GPSr and the Blue Lake on it and add it to your log.
Sources - Wikipedia, Evolutionary Research & Mt Gambier tourism.
Additional Hints
(No hints available.)