How do deformation, orographic precipitation, and erosion coordinate during orogenic growth?

Crustal thickening associated with orogenic growth elevates topography, causing the orographic enhancement of precipitation, which in turn facilitates local erosion and possibly intensifies the localization of deformation. The orographic climate-tectonics-erosion feedback exists in small orogens such as the Southern Alps of New Zealand and Olympic Mountains of Washington State, USA, and may be even stronger under some circumstances in active orogens on the margins of large, high-elevation plateaus such as the Himalayas, the Tibetan Plateau, and the Central Andes. How these three processes—deformation, precipitation, and erosion—coordinate during orogenic growth remains unknown. Here, we present a new numerical model where tectonics, surface processes, and orographic precipitation are tightly coupled, and explore the impact on low, intermediate, and high erodibility orogens. We show that, for the intermediate erosion models, rock uplift rates and precipitation rates correlate well with erosion rates for the formation of orogenic plateaus with high correlation coefficients of ~0.9 between rock uplift and erosion rates, and ~0.8 between precipitation and erosion rates. We propose that three processes (deformation, precipitation, and erosion) take place successively as a consequence of the lateral orogenic growth, and demonstrate a cyclicity of correlation evolution among uplift, precipitation, and erosion rates through the development of new faults propagating outward. These results shed new insights into the relative tectonic or climatic control on erosion in active orogens (e.g., the Himalayas, the Central Andes, and the Southern Alps of New Zealand), and provide a plausible explanation for several conflicting data and interpretations in the Himalayas, which we propose are due to the youthful, mature, or old stage of faults and different locations relative to the old faults. Studies using similar approaches with more detailed geological parameters could shed more insights into the growth of mountain belts co-evolving with spatiotemporally tectonic and climate change, and help more quantitatively establish links between tectonics, climate, erosion, topography, and biodiversity.