Tower Hill is a volcanic formation believed to have erupted about 32,000 years ago. Its formation is known as a "nested maar" and it is the largest example of its type in Victoria. During formation, molten lava pushed its way up through the Earth’s crust and encountered a layer of water-bearing rock. Violent explosions followed creating a shallow crater which later filled with water to form the lake. Further eruptions occurred in the centre of this crater, creating the islands and cone shaped hills. In 1892 Tower Hill became Victoria’s first National Park. In 1961, Tower Hill became a State Game Reserve under the then Fisheries and Wildlife Department and a major re-vegetation program began. (https://www.towerhill.org.au/index.php/about-reserve/history, accessed 23 December 2019)
Colour photographs of a lake in a volcanic crater at Tower Hill, Victoria.