Where were the mountains and how big were they?

Constraining past topography and the shape of Earth’s surface is the next frontier in palaeogeography and full-plate tectonic modelling. Mountains are highly dynamic on geological time scales, growing in response to tectonic processes such as subduction and continent collision, and eroding as they are exposed to precipitation and time. Mountain ranges regulate atmospheric circulation and enforce a first order control on dissolved river loads and the transport of sediments to sedimentary basins. Because of this, mountains and the changing elevation of Earth’s surface are essential to understanding how the wider Earth system has evolved through time. Here we present a computational full-Earth, forward model of palaeotopography and palaeobathymetry from 1 Ga to present-day. We use an existing full- plate tectonic model, which traces the evolution of tectonic plate boundaries, to automatically isolate specific tectonic environments that are associated with mountain building, such as continental arcs, continental collisions, rifts and large igneous provinces. Our model separates Earth’s continental surface into a set of equally spaced nodes, so that each node can record its own unique topographic evolution, independent of the nodes around it. Once these regions have been identified, we simulate their growth, and decay, over the last 1 Ga, using parameters and limits derived from the present-day expression of topography on Earth. Our model produces a set of maps at 1° resolution and every Ma from 970 to 0 Ma. Despite the differences between our work and other existing Phanerozoic palaeotopographic models, our predicted Earth surface has a similar hypsometry to what we observe at present-day. Our model can provide a quantitative basis for palaeoclimate or landscape evolution modelling over the last 1 Ga.