The evolution of mountains is written in the histories of the rocks that make up their ranges. Scientists have long used areas where rivers cut deep incisions in rock to study the patterns of how the Earth’s surface rose toward the sky—a geological process termed uplift—but this strategy assumes that there is very little lag time between uplift events and river-induced erosion.
A new study set out to test this assumption in the eastern Tibetan Plateau, where the Dadu and Min rivers carve deep gorges into the land. According to the authors, the relatively uniform rates of erosion in the region imply that the plateau was formed by a rapid uplift of rock in the late Miocene, but until now, the timing of river-induced erosion there had not been pinned down.
Tian et al. used fission track dating, which measures the number of fission events from the decay of uranium-238 in the mineral apatite, in two vertical rock profiles from areas where the two rivers have worn chasms into the plateau. These fission events are temperature sensitive, which makes the method a useful way to track the thermal history of rocks, and help scientists estimate when the rock became exposed at the Earth’s surface.
The authors found that river erosion rates increased fourfold to eightfold in the late Miocene, roughly 10 to 12 million years ago. The study indicates that the lag time between rock uplift and river erosion in the Tibetan Plateau was just 2 million years or so, making them relatively synchronous events—at least on geological timescales. (Geophysical Research Letters, doi:10.1002/2014GL062383, 2015)
—Kate Wheeling, Freelance Writer
Citation: Wheeling, K. (2015), Dynamics of the Earth’s surface in the eastern Tibetan Plateau, Eos, 96, doi:10.1029/2015EO030019. Published on 22 May 2015.