Abstract
One of the most fundamental insights for understanding how landscapes evolve is based on determining the extent to which topography was shaped by glaciers or by rivers. More than 104 years after the last major glaciation the topography of mountain ranges worldwide remains dominated by characteristic glacial landforms such as U-shaped valleys, but an understanding of the persistence of such landforms is lacking. Here we use digital topographic data to analyse valley shapes at sites worldwide to demonstrate that the persistence of U-shaped valleys is controlled by the erosional response to tectonic forcing. Our findings indicate that glacial topography in Earth's most rapidly uplifting mountain ranges is rapidly replaced by fluvial topography and hence valley forms do not reflect the cumulative action of multiple glacial periods, implying that the classic physiographic signature of glaciated landscapes is best expressed in, and indeed limited by, the extent of relatively low-uplift terrain.
Highlights
One of the most fundamental insights for understanding how landscapes evolve is based on determining the extent to which topography was shaped by glaciers or by rivers
We test whether the coupled fluvial and hillslope erosional response to tectonic forcing controls the timescale over which glacial topography persists into interglacial periods
We find that in Earth’s most rapidly uplifting mountain ranges the lifespan of glacial topography is on the order of one interglacial period, which prevents the glacial signal from evolving over multiple glacial cycles
Summary
One of the most fundamental insights for understanding how landscapes evolve is based on determining the extent to which topography was shaped by glaciers or by rivers. We quantify the degree of glacial imprint on topography by analysing valley cross-sectional shapes across spatial gradients in rock uplift and erosion rates in mountain ranges worldwide to assess how tectonic forcing has influenced valley morphology and the transition from glacial to fluvial topography. For this we assume a flux steady state, such that rock uplift and erosion rates remain in balance with the accretionary flux[17] throughout glacial– interglacial cycling. Glacial landscapes persist between glacial periods in relatively low-uplift b=1 b=1.7 b=1.3 b=2
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