HomeGeography and Geology

Geography and Geology

The Republic of Sierra Leone is located on the West Coast of Africa, between latitudes 7 and 10 north and longitudes 10.5 and 13 west. The Republic of Guinea is to the north and northeast; Liberia is to the east and southeast, and the Atlantic Ocean on the west and south. It has 300 miles of coastline.

From an approximate 70-mile coastal belt of low-lying land, the country rises to a mountain plateau near the eastern frontier rising 4000 to 6000 feet with a rich timber forest region. The Western Area encompasses the Sierra Leone Peninsula, on which the capital and main commercial centre of Freetown stands; is 24 miles long and 10 miles wide.

A mountainous promontory, it rises in places to 300 feet above sea level - one of the few parts of the West African Coast where there is high land so near the sea. Where the lush green forest spills down hillsides to meet the most beautiful white sandy beaches along the Atlantic Ocean.

This 27,925 square mile (73,326 sq km) country has a population of approximately 4.5 million people. Sierra Leone is divided into four main Provinces, West, North, East and South. There are twelve Districts in the entire country.

Most of the country is underlain by rocks of Precambrian age (Archaean and Proterozoic) with a coastal strip about 50 km in width comprising marine and estuarine sediments of Tertiary and Quaternary to recent age. The Precambrian (mainly Archaean) outcrops over about 75% of the country and typically comprises granite-greenstone terrain. It represents parts of ancient continental nuclei located on the edge of the West African Craton. Regional reconnaissance mapping indicates that the Archaean basement can be subdivided into infracrustal rocks (gneisses and granitoids); supracrustal rocks (containing greenstone belts); and basic and ultrabasic igneous intrusions. The infracrustal gneisses and granitoids were formed and reworked during two major orogenic cycles, an older Leonean episode (~2,950-3,200 Ma) and a younger Liberian episode (~2700 Ma).

The Leonean orogenic episode commenced with the intrusion of a basic igneous suite (the Pre-Leonean amphibolites) and by the formation of a greenstone belt represented by the Loko Group which is now deeply eroded. The Loko Group comprises amphibolites, silimanite quartzites and ironstones. It appears to have formed on a gneiss/granitoid basement in which several granitoid bodies related to an earlier plutonicorogenic episode have been distinguished mainly in the northern part of the country. Only the main deformational phase of the Leonean orogenic episode which resulted in folds and fabrics trending