An upland area, such as the Alps or Andes, formed by the buckling of the Earth’s crust. Many fold mountains are associated with destructive or collision margins of plates. Young fold mountains, such as the Caucasus and Alps, were formed by the Alpine orogeny of 65 million years bp, and reach elevations of 10 000 m. Old fold mountains, such as the Grampian mountains of Scotland, were created by earth movements pre-dating the Alpine orogeny but have been extensively eroded. Some old fold mountains have been uplifted and re-eroded.