Game of Stones: how does rock strength control the shape of Earth's surface?

The 'hardness' of a rock is a problematic concept where our intuition is based on the temporally and spatially limited human experience. While theory suggests that rock strength should be a fundamentally important factor in controlling the pattern of topographic relief, the pace of changes due to climate or tectonic variation, and magnitude of natural hazards, the scientific community is still a long way from being able to parameterize rock strength in a way that can be used to accurately forward model the evolution of natural landscapes.  For example, how rivers respond to different rock types is poorly constrained and difficult to isolate from other confounding factors such as climate and tectonic influences in natural landscapes, and laboratory experiments have yet to reveal well-described relationships between material properties and erosion.

To isolate the material properties of rocks we have developed a new device for quantifying the erodibility of rocks which allows us to fully quantify all aspects of the abrasion process.   This project will focus on three primary tasks. 1) Develop methods for estimating the erodibility of rock samples using the new experimental machine. 2) Measuring the mechanical properties of synthetic and natural samples. 3) Capitalizing on the lessons learned in the laboratory to create a scaled relationship between rock mechanical properties and bedrock erodibility in a river channel.