Seasonal Almanac

Minor heat: hawk studies and learns (1 of 5)

January 16th, 2009

minor heat 11 of 15On a whim we drove to Canberra today to visit the Charles Darwin exhibition (that commenmorates the bicentennial of his birth and the 150th anniversary of the publication of The Origins of Species) at the National Museum of Australia. The last (and only) time we traveled this route was June 2007 when we drove across from Perth. The 237 kilometer Canberra to Wollongong stretch was the final leg of our journey.

Today’s shorter trip provided an opportunity to observe the surrounding landscape. Not long after we entered the Federal Freeway we were confronted by the strange landform of Lake George. With cattle and sheep grazing in the dried lake it looked like any other field but for its vastness and flatness.

The great lake is flanked by an escarpment on the Western side and from the road we could see a distant wind farm along its southern edge. The lake’s extreme fluctuation of water levels (from full to completely dry) despite having no outlet watercourse is explained by the rate of precipitation versus the rate of evaporation. Due to the basin’s large size when the lake is filled it tends to be very shallow (with depth ranging from 1 to 4.5 meters with only one part measuring up to 7.5 meters). The waterbody’s large surface area results in fast evaporation, together with porous slit soil on the lakebed that absorbs a sizeable quantity of water, the lake seems to drain mysteriously.

This ancient lake arose 5 million years ago from tectonic activity of uplift along the fault under the Lake Geroge range. An enornouse area rose and formed the lake’s basin. This uplifted area blocked drainage from the Great Diving Range to river systems such as the Yass. It has been at its present state (dry) since 2002.

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