By regressing simple, independent variables that describe climate and
tectonic processes against measures of topography and relief of 69
mountain ranges worldwide, we quantify the relative importance of these
processes in shaping observed landscapes. Climate variables include
latitude (as a surrogate for mean annual temperature and insolation, but
most importantly for the likelihood of glaciation) and mean annual
precipitation. To quantify tectonics we use shortening rates across each
range. As a measure of topography, we use mean and maximum elevations
and relief calculated over different length scales. We show that the
combination of climate (negative correlation) and tectonics (positive
correlation) explain substantial fractions (>25%, but <50%) of mean
and maximum elevations of mountain ranges, but that shortening rates
account for smaller portions, <25%, of the variance in most measures of
topography and relief (i.e., with low correlations and large scatter).
Relief is insensitive to mean annual precipitation, but does depend on
latitude, especially for relief calculated over small (similar to 1 km)
length scales, which we infer to reflect the importance of glacial
erosion. Larger-scale (averaged over length scales of similar to 10 km)
relief, however, correlates positively with tectonic shortening rate.
Moreover, the ratio between small-scale and large-scale relief, as well
as the relative relief (the relief normalized by the mean elevation of
the region) varies most strongly with latitude (strong positive
correlation). Therefore, the location of a mountain range on Earth with
its corresponding climatic conditions, not just tectonic forcing,
appears to be a key factor in determining its shape and size. In any
case, the combination of tectonics and climate, as quantified here, can
account for approximately half of the variance in these measures of
topography. The failure of present-day shortening rates to account for
more than 25% of most measures of relief raises the question: Is active
tectonics overrated in attempts to account for present-day relief and
exhumation rates of high terrain?