24. Superimposed Drainages, Macdonnell Ranges, Australia

The Macdonnell Ranges lie right at the center of Australia — the only mountain range between the east and west coasts. Upper Precambrian/Lower Paleozoic sedimentary rocks were folded on east-west trending axes about 300 million years ago. The ranges as we see them today are probably the result of relatively recent uplift. This is suggested by the fact that the Finke and Palmer Rivers included in this photograph appear to cut right across the folded strata rather than being deflected into courses parallel with the ridges. From this we deduce that the rivers probably existed before the ranges and simply continued to carve downward as the mountains rose, thereby retaining their existing course.

Central Australia is very arid at the present day. The mountains yield a little extra rainfall (Mt. Zeil, the highest mountain in the range, is 1510 meters or 4954 feet), but the area remains very dry. Rivers are seasonal and water shortages limit development of the area

STS-41D, August-September 1984. Picture #14-41-033.

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