Orogeny – or mountain building – occurs when continental plates collide, forcing land upwards, and while there are mountain chains all over the planet, the highest peaks are found in regions near the equator.

Using satellite images captured by NASA in 2001, David Egholm from Aarhus University in Denmark and colleagues set out to explain this pattern by mapping all of the major mountain ranges located between 60°N and 60°S, noting the elevation, average altitude of the snow line and latitude. They also created a model of the effects of erosion by glaciers.

They demonstrated that, in general, mountains only rise to around 1,500 metres above their snow lines, suggesting that it’s the altitude of these lines – which depends on climate and latitude – that ultimately decides their height. The model then suggested that it was glacial erosion that was keeping the mountains’ height in check.

‘What we show is that, once the mountain is pushed up across the snow line, a very effective erosion agent comes into play and that is represented by glaciers,’ said Egholm. ‘It’s so effective that it can keep pace with any tectonic uplift rate that we have on the Earth today.’

October 2009