The major geographical features of the county are determined by a series of ridges running from west to east across the county. These ridges are the remains of the Wealden dome, a denuded anticline across Kent, Surrey and Sussex, which was the result of uplifting caused by the Alpine movements between 10-20 million years ago. The dome was formed of an upper layer of Chalk above subsequent layers of Upper Greensand, Gault, Lower Greensand, Weald Clay and the Hastings Beds. The top of the dome eventually eroded away through weathering and ridges and valleys resulted across Kent and Sussex due to the exposed clay eroding at a faster rate than the exposed chalk, greensand and red sandstone and normal sandstone. The following ridges and the valleys have formed across Kent, listed from north to