Stroll under the watchful gaze of giant Mont Aiguille

4 points of interest

• 

  Back to the past

  Compare with what you can see today! 150 years ago, the forest was sparse and confined to very steep slopes. 
  Crops dominated the meadows, the plots of land showed a more complex field pattern and hedges were rare. The slopes of Mont Aiguille were bare or studded with rough moorland that hardly covered the large gashes caused by erosion.

• 

  The Mont Aiguille, tectonic ans erosion

  Mont Aiguille is really an isolated piece of the Vercors massif situated within the Trièves mountains! This can be largely explained by the tectonic history.
  The Vercors is the result of compression of the earth’s crust due to closure of an ocean basin during Alpine mountain building over almost 40 million years. As a result, the rocks were folded and fractured, leading to anticlines, synclines and faults.
  While anticlines are more easily attacked by erosion, synclines remain resistant for longer.

• 

  Work to contain the torrent's energy

  The torrent of Les Fraches runs in a debris flow channel which joins the Donnière stream. 
  The Mountain Land Restoration services carried out flood protection measures. The Allée Royale is a succession
  of 23 small dams built between 1987 and 1992 to limit the scouring effect and break the energy of the torrent.

• 

  An underwater channel?

  Limestone is formed on the seabed through an accumulation of skeletons and shells of sea creatures. The limestone of Mont Aiguille was fashioned in a shallow sea in a tropical climate and close to the continent. This limestone is “stratified” like a millefeuille cake or a pile of plates, each sheet representing a period of sedimentation.
  
  You can see this stratified limestone on the south-east face of Mont Aiguille in front of you. However, on the its upper section you can very clearly make out one level that cuts through the stratification at an angle. This is almost certainly an old underwater channel that created ravines in the sediment that was already there.
  
  Once established, sedimentation was able to restart and plugged this channel.