Malawi

Geography

Malawi is a long narrow, landlocked country lying wholly within the tropics in south-eastern Africa. The country occupies a thin strip of land in between Zambia to the west and Mozambique to the east and protrudes southwards into Mozambique along the Shire River valley. In the north and north east it also shares a border with Tanzania. The western arm of the Great Rift Valley traverses the country from north to south and is occupied by Lake Malawi the third-largest lake in Africa. The total area of the country is 118,480 km², but this includes 24,400 km² of water surface, mainly corresponding to Lake Malawi but there are other sizeable lakes, such as Lake Malombe, Lake Chilwa and Lake Chiuta. The country is dominated by Lake Malawi, which drains into the Zambezi River through the Shire River. Lake Malawi is the ninth largest lake in the world and the second deepest in Africa after Lake Tanganyika. High plateaux, generally over 1000 metres, lies west of the Rift Valley. In the north, the Nyika Plateau rise as high as 2,600metres. The southern region is low-lying except for the Zomba Plateau (2130 metres) and the Mulanje massif which at 3002 metres is the highest mountain in south-central Africa.

Geology

A large proportion of Malawi is made up of igneous and metamorphic rocks of the Basement Complex of Precambrian, both Archean and Proterozoic, age comprising Archean charnockitic gneiss, granulites, meta-sediments and ultrabasics; Proterozoic sequences are dominated by meta-sediments and older granitoids. The complex geology of the crystalline basement is subdivided into northern and southern domains separated by the Chimaliro Fault.  Parts of the country comprise overlying volcano-sedimentary sequences, including coals, of Palaeozoic-Mesozoic Karoo strata and Late Jurassic-Cretaceous alkaline igneous intrusives are found in southern Malawi. Mesozoic and Cenozoic sedimentary rocks are found in narrow belts aligned parallel to Lake Malawi and extensive Quaternary alluvium and superficial deposits occur along the margins of the lake. The geological history of Malawi is summarised as a Precambrian basement and mobile belt overlain by Permo-Triassic sediments cut by Mesozoic intrusions and disrupted by Cenozoic faulting that led to the formation of the Malawi Rift a part of the western branch of the East African Rift System. In broad terms the geology can be divided into the (Precambrian) Basement Complex; the Karoo Supergroup; the Chilwa Alkaline province; Mesozoic sediments and Cenozoic cover rocks.