The Little Blue Lake EarthCache

This Earthcache will bring you to The Little Blue Lake, a limestone sinkhole approximately 8 kilometres south of Mount Gambier.  The area around Mount Gambier contains many sinkholes such as this one.  It is more correctly known as a Collapse Doline in which underground water undermined the overlying limestone leading to the sinkhole we see before us today. The large boulders at GZ are actually basalt which has been brought to the site from the volcanic crater Mount Shank.

In the carpark at GZ, there are a series of large boulders that have obviously been brought to this site. They are basalt, a volcanic rock (notice the bubbles within the rock).  This is very different from the limestone that surrounds the Little Blue Lake.

Even though there are holes in the limestone, this is caused by the chemical process of solution and is not a sign of volcanic origin.  

To log this earthcache, you will need to email the answers of the questions below to the owner of this cache.  Feel free to log the cache and then send  the email with the answers.  However if your log is not supported with an email with the appropriate answers, your log may be deleted.

Question 1) Describe the difference in appearance of the basalt boulders and the limestone surrounding the lake.

Question 2) Near the top of the stairs at the lake, ie at the end of the fence line, describe the surface of the limestone.

Question 3) What is the approximate diameter of The Little Blue Lake?

Question 4) Provide a creative or scientific suggestion as to why the level of The Little Blue Lake changes.