Blue Lake / Warwar (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 volcanic crater lakes originally on Mount Gambier maar. Of the four lakes, only two remain, the other one being Valley Lake / Ketla Malpi; the other two, Leg of Mutton Lake / Yatton Loo and Brownes Lake / Kroweratwari, have dried up as the water table has dropped. History Conflicting dates have been estimated for the last eruption of the volcano: of 4,300 years ago, of 28,000 years ago, and 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. The Boandik (or Bungandidj) people occupied the area before the colonisation of South Australia. Description Blue Lake / Warwar is one of four lakes in the extinct volcano complex. Sites of cultural significance to the Boandik people were assigned dual names by the City of Mount Gambier in February 2022, and the renaming included the four lakes in the Bungandidj language. These are as follows: Blue Lake / Warwar, meaning "crow country" Leg of Mutton Lake / Yatton Loo Brownes Lake / Kroweratwari, meaning "emus, [or] their tracks" Valley Lake / Ketla Malpi, meaning "sacred talking tree" Blue Lake is thought to be of an average depth of , but in places reaches deep (but some unconfirmed values mention a maximum depth due to a natural cave section). The crater rim measures , but the lake itself measures . The surface of the lake is below the level of the main street of the nearby town. The Blue Lake supplies the town with drinking water. Browne's Lake / Kroweratwari (sometimes spelt Browns Lake) dried up in the 1980s, and is now a picnic spot. There is a road and walking track around the circumference of Blue Lake / Warwar, with an underpass between it and Leg of Mutton Lake / Yatton Loo. Annual colour change Each November, the lake turns to a deep turquoise colour, gradually returning to a duller blue colour in late February to March. The exact cause of this phenomenon is still a matter of conjecture, but likely it involves the warming of the surface layers of the lake