In a study published in GSA Today, University of Vermont geologists Paul Bierman and Eric Portenga collated estimates of erosion rates generated using measurements of a rare radioactive element, beryllium-10, that appears in quartz bombarded by cosmic rays in the top metre or so of the Earth’s surface.

The results allowed the scientists to begin to identify the environmental factors that drive erosion rates in drainage basins and outcrops of bedrock. Using several statistical tests, they were able to explain about 60 per cent of what controls differing erosion rates in drainage basins around the world and about 30 per cent of the variability between outcrops of bedrock. ‘It turns out that the greatest control on erosion isn’t mean annual precipitation,’ Bierman said. Instead, the data showed that slope was more important.

The scientists’ long-term goal is to create a global model that can predict the background rate and patterns of erosion across the whole planet – and how these erosion rates will respond to changes such as human-induced climate change. ‘We want a predictive model,’ said Bierman. ‘We want to be able to have somebody say, “Here’s my drainage basin, here’s the climate, here’s the rock type, here’s the slope, here’s the mean annual precipitation: how quickly is this eroding?” That’s what you need for land management.’

September 2011