the influence of climate on the tectonic evolution of mountain belts

In the mid‐1980s, advances in understanding the mechanics of the fold‐and‐thrust belts that flank many collisional mountain ranges set the stage for a fundamental change in our appreciation of the role of erosion in the tectonic evolution of mountain ranges. A combination of sandbox experiments, analytical treatments of stress state and field observations showed that fold‐and‐thrust belts form tapering wedges1–3. A growing wedge deforms internally until a critical surface slope (taper) — governed by its material properties and basal‐thrust geometry — is established. At this point, the wedge has sufficient internal strength to allow slip on the basal thrust, as required by ongoing tectonic convergence1–3. Erosion tends to thin orogenic wedges, changing the stress state and thereby inducing a deformational response to restore the critical taper. Thus, in such critical‐taper wedges, erosion is not simply a passive process occurring in response to tectonically driven rock‐uplift and relief‐ production; rather it exerts a direct first‐order influence on the tectonic evolution of the system. A few years after the advent of critical‐taper theory, researchers had demonstrated, at least qualitatively, that the rate and pattern of erosion of critical‐taper orogenic wedges effectively dictates many aspects of the tectonic and structural evolution of mountain belts. These aspects include the width of the mountain range, structural style, the longevity of exhumational structures, the rate and pattern of internal strain, near‐surface rock uplift rate, the pressure–temperature–time pathways of rocks and the spatial distribution of metamorphic facies in exposed rocks4–7. These pioneering researchers also evaluated the effects of asymmetry of erosional efficiency on orogenic evolution. Erosional efficiency determines the rate of erosion for a given topography, and depends on rock type, debris size and climate. The expected deformational and exhumational response to such asymmetry — induced by enhanced precipitation on windward slopes and rainshadow development on leeward slopes — is well matched by near‐surface rock‐uplift patterns and the metamorphic grade of exposed rocks in several active mountain ranges, such as the Southern Alps of New Zealand, the Olympic Mountains of Washington State, and the Himalaya4,7,8. Over the next decade, numerical experiments quantitatively demonstrated these concepts, the influence of climate on the tectonic evolution of mountain belts