Lake George (New South Wales) - Geography / Geology

Geography / Geology

Lake George is an Endorheic lake, as it has no outflow of water to rivers and oceans.

The lake is believed to be more than a million years old. Originally, small streams drained its catchment into the Yass River, but then the Lake George Escarpment rose due to major crustal movement along a strong fault line, blocking this drainage and forming the lake. Lake George has in previous Ice Ages been much larger and deeper.

The thickness of sediment beneath the lake exceeds 250 metres (820 ft), according to a Bureau of Mineral Resources Canberra drilling program in the 1982/83 summer. The oldest sediments, which lie some distance above the bedrock, were dated at 3–5 million years using spore and pollen analysis and magnetic reversal stratigraphy.

At 25 km (16 mi) long and 10 km (6.2 mi) wide, Lake George is long, largely flat and extremely shallow, with a very small catchment. Resultant evaporation rates as well as a tendency for strong winds to blow the water back on itself explain the mysterious filling and drying episodes on both short term (hours) and long term (years) time scales that have been observed.

The lake's depth when full can range from 1.5–4.5 metres (4 ft 10 in–14 ft 9 in); however in many areas it is only around 0.8–1.0 metre (2 ft 7 in–3 ft 3 in) deep. Its deepest point has been measured as 7.5 metres (25 ft). When full, the lake holds about 500,000,000 cubic metres (1.8×1010 cu ft) of water. Between the late 1980s and mid 1990s, the lake lapped the Federal Highway on its western edge.