The Largest Mountain Belt of the Last Billion Years: The East African Orogen, its tectono-topographic evolution and global significance

Hutton's Principle of Uniformitarianism suggests that the present is the key to the past, and in the present, Earth's topography is dominated by the Himalaya. The geological record clearly preserves past mountain ranges, but few have purported to have the effect on Earth's surface systems (such as the atmosphere, hydrosphere, biosphere and ocean chemistry) that the Himalaya does today. The Neoproterozoic East African Orogen is an exception. Not only is it the scale of the modern Himalaya, but it affected ocean chemistry in a similar manner to the Himalaya. Here we posit that the East African Orogen is the only other Himalayan-scale mountain range, and the only orogen that contends with the Himalaya as the largest mountain range of the last billion years. In this manuscript we review and reconstruct the orogen. We then use existing metamorphic data triaged to exclude subduction-zone metamorphism, to estimate the elevation-time evolution of the orogen. We demonstrate that the available metamorphic record supports our assertion that the East African Orogen is amongst the largest orogens in the geological record. We also integrate spatially-located metamorphic data with a full-plate tectonic reconstruction of the evolving orogen to show how different plate interactions created the evolving topography.