Geology

Wear-Resistant Rock

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Science  12 Jul 2002:
Vol. 297, Issue 5579, pp. 159
DOI: 10.1126/science.297.5579.159b

Long-term erosion rates of hills and mountains range from highs of centimeters or more per year in active mountain belts such as the Himalayas to lows of a millimeter per year in stable cratons. It has been suggested that, in parts of Australia, prominent granite domes known as inselbergs have persisted for 100 million years, during which almost no erosion has occurred, preserving a Mesozoic erosion surface.

Bierman and Caffee measured the accumulation of cosmogenic nuclides in several inselbergs to determine their long-term erosion rate. These nuclides accumulate in a rock when it is exposed on the surface and bombarded by cosmic rays. The data imply that the tops of the inselbergs are eroding at rates as low as 0.3 mm per year, one of the lowest rates in the world. Nonetheless, this process is still fast enough that it is unlikely that a Mesozoic erosion surface has been preserved, and thus inselbergs are indeed dynamic landforms. However, because the tops of the inselbergs are eroding no faster (or even slower) than their sides and the valleys, it is likely that the dramatic topography has persisted over that time. — BH

Geol. Soc. Am. Bull.114, 787 (2002).

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