Blue Lake

The Blue Lake is a large monomictic crater lake located in a dormant volcanic maar associated with the Mount Gambier maar complex. The lake is situated near in the Limestone Coast region of South Australia and is one of four crater lakes on Mount Gambier maar. Of the four lakes, only two remain, as the other two (Leg of Mutton and Brown) have dried up over the past 30 to 40 years as the water table has dropped.Conflicting dates have been estimated for its last eruption, of 4,300 years ago, of 28,000 years ago, and, most recently, a little before 6,000 years ago. If the youngest date is correct, this could be the most recent volcanic eruption on the Australian mainland.Blue Lake is thought to be of an average depth of, but in places reaches deep. The crater rim measures by, however, the lake itself measures by. The bottom of the lake is below the level of the main street of the nearby town. The Blue Lake supplies the town with drinking water, providing approximately 3500ML per year from its 36000ML store.StudiesBathymetric surveys located the deepest point in the lake at in 1967. Major diving exploration of the lake first occurred in 1985. Cave diver Peter Horne conducted temperature and visibility studies and made discoveries of a fresh water sponge species and other invertebrates. This exploration also discovered "The Stromatolite Field", a collection of hollow rock formations that are found along the north-eastern perimeter down to a depth of. In 2008, permission was granted by SA Water for another diving exploration of the central and deepest parts of the lake. On this dive core samples from the calcite-silt covered lake bed were collected where water temperature drops to 14C.