Where were the mountains and how big were they?

Andrew Merdith, Nicky Wright, Simon Williams, Stephen Hunter, Jonathon Leonard, Morgan L. Blades , Fred Bowyer, Khushboo Gurung, Zhen Xu, Derrick Hasterok, Alan S. Collins , Benjamin Mills

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.