The father of geology, James Hutton, in the late eighteenth century provided the insights which led nearly a century later to the first understandings of how mountains are constructed and what causes them. In the nineteenth and early twentieth centuries Lapworth, Peach and Horne, and Clough in Britain, and Argand, Bertrand, Heim and others working in the Swiss Alps, revolutionised our understanding of what the German geologist Kober called ‘orogens’ and of the process of orogenesis, the building of mountains.

To understand the significance of orogens, it is necessary to know something about plate tectonics, which has been remarkably successful in explaining many of the features of the Earth. In particular it deals with large-scale dynamic processes in the planet. Plate tectonics developed from the preceding ideas of continental drift, but in essence originated from an idea put forward in the 1960s by H. H. Hess. Hess postulated a surprising concept: that the ocean floor is in motion and is older as one moves away from submarine mountains known as mid ocean rises: for this reason the model became known as sea-floor spreading. The ocean floor is like a giant conveyor belt, and the interesting question is, where does it go? What this idea meant was that, for the first time in the history of geology, attention was turned on the oceans rather than the continents.