experience Nature
Jonathan Perret

The Ophiolitic Complex of Chamrousse

​

Only 30 minutes from Grenoble and 2 hours from the center of Lyon, the ski resort of Chamrousse is an easy and accessible starting point for organizing school outings to discover an ophiolite sequence .

During a day hike , plan between 4 and 7 hours of walking, we will be able to contextualize the notions of geology studied by the students in first and final class. In an easier (or faster) version  : 3h), the exit can also be done downhill only, with access to the summit by gondola .

As we progress, we come across metabasalts , dolerite veins, more or less foliated gabbros , and finally serpentinized peridotites , or even chromite . Occasionally, faults contain chrysotile asbestos.

The site therefore has the particularity of presenting a series of “  green rocks  reversed, returned. The opportunity to return to the notions of tectonic constraints, folding and faulting.

​

The pillow lavas have been recently updated and complement the site.

From the top of the Chamrousse cross, the view covers the sedimentary massifs of Chartreuse and Vercors where the Urgonian limestone bars take on their full extent.

Below, the bordering hills of the external branch make it possible to evoke the notions of glacial erosion , just like the stony rocks crossed on the way.

Depending on the descent route, we can discover other sedimentary rocks  : sandstones and cargneules (Triassic dolomite eroded by dissolution of gypsum). These rocks and the overall geographic configuration bear witness to the ancient peneplain which succeeded the Variscan ( Hercynian ) range. Perhaps we will then approach the Wilson cycle and Pangea .

A little further still, spilites will briefly evoke a volcanic episode.

​

The sedimentary massif of Vercors and karstic erosion

2h from Chamrousse, 1h30 from Grenoble and 2h30 from Lyon, the Vercors Sud offers magnificent possibilities for discovering the origins of a sedimentary massif and karstic erosion. During a 2 hour hike we will be able to cross lapiaz , glaciers and see sinkholes . On the road, we highlight synclinal folds, anticlines, faults , … We can also go in search of fossils , which will allow us to come back to the origin of the rocks and to approach the notions of geological stage. The outing can end with a private visit to a limestone cave with numerous concretions.

​

​

Facilities in Chamrousse:

Quick access to the starting point with buses and coaches

Accommodation options for school groups

Gondola to the top

Equipment  (even in nice and hot weather)  :

Waterproof jacket, warm layer (fleece, sweatshirt, ...), walking shoes, backpack for clothes and picnic.