Zimbabwe covers an area of some 390,580 square kilometres, consisting of a central highveld area, a raised granite shield known as the Zimbabwe Plateau, with an average elevation of just over 1,000m. In the north the plateau drops dramatically towards the Zambezi Valley, forming the Zambezi Escarpment. In the southwest a broad area of the country slopes down towards the Limpopo. From the western border with Botswanna, windblown sands from the Kalahari Desert extend into the country. To the east a range of rugged mountains, the Eastern Highlands, forms a natural border with Mozambique.