Eritrea is located in the Horn of Africa and is bordered to the northeast and east by the Red Sea, to the west and northwest by Sudan, to the south by Ethiopia, and to the southeast by Djibouti. The total area of the country including the Dahlak Archipelago and other islands along the Red Sea coast is 121,320 km². The border between Eritrea and Ethiopia is disputed. The terrain is dominated by extension of Ethiopian highlands; a high central plateau that varies from 1,800 to 3,000 meters above sea level. Other regions include a narrow eastern lowland desert strip along the Red Sea coast that accounts for around 33% of the land area and the semi-arid flat-to-rolling western plains that extend to the Sudanese border. The Danakil depression extends from Ethiopia into Eritrea where the lowest point is Lake Kulul at 75 m below sea level. Rivers flow to the north and west; none have perennial flow.


Eritrea is underlain by Precambrian meta-sediments and older gneissic basement, Neoproterozoic terranes illustrating the effects of the Pan-African event, and locally extensive Tertiary to Recent volcanic rocks. Numerous thin basalt flows are found in the Miocene sediments of the Red Sea coast; the Aden Series basalts range in age from Pliocene to Holocene and were probably extruded contemporaneous with the major Pleistocene phase of uplift and rifting. Marine sediments of Mesozoic to recent in age are exposed in the coastal area along the Red Sea.