Thirty years or so ago a number of French geologists took part in what was then called the International Deep Sea Drilling Project carrying out the first seismic acquisition and drilling on the world’s continental margins. Some of these men were also experts on the geology of the Western Alps and started to see clear parallels between the geology of their mountains and the geology that was beginning to be visualised on the continental margins of Galicia and Newfoundland.

In recent years, mostly because of available high resolution deep seismic data, there has been an explosion of ideas about the structure of the continental margins and the continent - ocean transition, and, thanks to a new generation of researchers, the Alps has become even better known as the outcrop analogue for rifting, continental separation and the development of an ocean.

This talk reviews some of the older Alpine work, explores passive margin geometry as we are now able to see it with the aid of that modern seismic imagery, and examines the French Alps in that context. We will travel from Grenoble to Briancon along a geological transect which, although it lies high in a mountain belt, probably illustrates passive margin evolution better than anywhere else on the planet.