.
continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of
in the east. Varying sources have limited it to the countries of
, a region that was known by the French during colonial times as "Afrique du Nord" and is known by Arabs as the
("West", The western part of Arab World). The most commonly accepted definition includes
, the 6 countries that shape the top North of the African continent. Meanwhile, "North Africa", particularly when used in the term
(MENA), often refers only to the countries of the Maghreb. North Africa also includes the
.
Since probably
3500 BCE, the Saharan and sub-Saharan regions of Africa have been
separated by the extremely harsh climate of the sparsely populated Sahara, forming an effective barrier interrupted by only the
Nile in Sudan, though navigation on the Nile was blocked by the river's
cataracts. The
Sahara pump theory explains how
flora and
fauna (including
Homo sapiens) left Africa to penetrate the
Middle East and beyond. African
pluvial periods are associated with a
Wet Sahara phase, during which larger lakes and more rivers existed.
The
Sahara ('the Greatest Desert') is a desert on the
African continent. With an area of 9,200,000 square kilometres (3,600,000 sq mi), it is the largest hot
desert in the world and the third largest desert overall, smaller only than the deserts of
Antarctica and the northern
Arctic.
The desert comprises much of
North Africa, excluding the fertile region on the
Mediterranean Sea coast, the
Atlas Mountains of the
Maghreb, and the
Nile Valley in
Egypt and
Sudan. It stretches from the
Red Sea in the east and the Mediterranean in the north to the
Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the
Sahel, a belt of
semi-arid tropical savanna around the
Niger River valley and the
Sudan Region of
Sub-Saharan Africa. The Sahara can be divided into several regions, including the western Sahara, the central
Ahaggar Mountains, the
Tibesti Mountains, the
Aïr Mountains, the
Ténéré desert, and the
Libyan Desert.
For several hundred thousand years, the Sahara has alternated between desert and savanna grassland in a 20,000 year cycle caused by the
precession of the Earth's
axis as it rotates around the Sun, which changes the location of the
North African Monsoon. The area is next expected to become green in about 15,000 years (17,000 CE).
The Sahel ("coast, shore") is the ecoclimatic and
biogeographic realm of
transition in
Africa between the
Sahara to the north and the
Sudanian savanna to the south. Having a
semi-arid climate, it stretches across the south-central latitudes of
Northern Africa between the Atlantic Ocean and the
Red Sea.
The Sahel part of Africa includes from west to east parts of northern
Senegal, southern
Mauritania, central
Mali, northern
Burkina Faso, the extreme south of
Algeria,
Niger, the extreme north of
Nigeria, the extreme north of
Cameroon and
Central African Republic, central
Chad, central and southern
Sudan, the extreme north of
South Sudan,
Eritrea and the extreme north of
Ethiopia.
Historically, the western part of the Sahel was sometimes known as the
Sudan region ("lands of the Sudan"). This belt was roughly located between the Sahara and the
coastal areas of West Africa.
Sub-Saharan Africa is, geographically and ethnoculturally, the area of the continent of
Africa that lies south of the
Sahara. According to the
United Nations, it consists of all
African countries and territories that are fully or partially south of the Sahara. While the
United Nations geoscheme for Africa excludes Sudan from its definition of sub-Saharan Africa,
the African Union's definition includes Sudan but instead excludes
Mauritania.
It contrasts with
North Africa, which is frequently grouped within the
MENA ("
Middle East and North Africa") region, and most of whose states are
members of the
Arab League (largely overlapping with the term "
Arab world"). The states of
Somalia,
Djibouti,
Comoros, and the
Arab-majority
Mauritania (and sometimes
Sudan) are, however, geographically considered part of sub-Saharan Africa, although they are members of the Arab League as well. The
United Nations Development Program lists 46 of Africa's 54 countries as "sub-Saharan", excluding
Algeria,
Djibouti, Egypt, Libya, Morocco, Somalia, Sudan and Tunisia.
