Algeria is located in Northern Africa, bordering the Mediterranean Sea, between Morocco and Tunisia. Inland it shares borders with the Western Sahara, Mauritania and Mali in the southwest, Niger in the southeast and Libya in the east. Algeria covers a total area of 2,381,741 km2 and is the second largest country in Africa, after Sudan, and the eleventh largest country in the world. The Sahara desert makes up more than 80 per cent of the country. The northern portion between the Sahara and the Mediterranean Sea, known as the Maghreb, is a region of the Atlas mountain ranges with intervening valleys and plateaus. The lower Tell Atlas forms the coastal hinterland and the larger sub-parallel Saharan Atlas runs further south. These ranges coalesce further east in the Aurés Mountains. Plateaus between the Tell and Saharan Atlas average 1100-1300 m ASL in the west and drop to 400 m in the east. The Algerian portion of the Sahara is a region of great diversity. Immense areas of sand dunes or ergs occupy about one-quarter of the territory. Much of the remainder comprises rocky platforms and almost the entire southeastern quarter is taken up by the Ahaggar and Tassili-n-Ajjer highlands which rise to over 2,000 m. Mount Tahat in the Ahaggar Mountains, at 3,003 m is the highest peak in Algeria.
Geologically, Algeria is divided into three contrasting tectono-stratigraphic domains: the West African Craton, consisting of Precambrian granitic basementand surrounding Neoproterozoic mobile belts, outcrops in the south and west of the country. The limit of the Craton is broadly defined by the Tuareg Shieldwhich comprises the Hoggar, Adrar des Iforas and Air sub-shields affected by Pan African tectono-thermal events. In the north a series of folded and thrust-bound strata belonging to the younger Alpine Chain extend over the entire length of the Maghreb region.