The Great Rift Valley is a massive valley in Africa.  Formed where Earths crust is being pulled apart by the action of convection currents beneath the surface, rift valleys are long, deep valleys bounded by parallel faults, or fractures, in Earths crust (MSN Encarta® Quote).  The Great Rift Valley begins in Syria, it then extends southward down the length of the Red Sea.  From the Red Sea it eventually enters Africa at the Afar Depression on the coast of Eritrea and Djibouti, and from there travels a distance about 5,600 kilometers (3,500 miles) to the coast of Mozambique.  In the middle section of the Great Rift Valley it breaks into two main areas.  These two areas are called the Eastern Rift Valley and the Western Rift Valley.  These two rift valleys are divided by towering escarpments that are up to 1,000 meters (4,900 feet) in southern Ethiopia , 1,500 meters (4,900 feet) along the Eastern Rift in the central area of Kenya, and 1,300 meters (4,300 feet) in the northern part of the Western Rift along the Democratic Republic of Congos border with Uganda, Rwanda, and Burundi.  The extreme south of the rift system is much less spectacular in size and appearance.

Several major lakes, typically long and narrow, are located on the floors of the Western and Eastern rift valleys. The Western Rift contains Lake Albert, Lake Edward, and Lake Kivu to the north, Lake Tanganyika in the middle, and Lake Malawi (Lake Nyasa) to the south. The lakes of the Eastern Rift tend to be smaller and include Lake Naivasha, Lake Natron, and the southern part of Lake Turkana. (MSN Encarta® Quote.)

Africa has the worlds largest desert, the Sahara.  It reaches from the Atlantic Ocean to the Red Sea, and also from the Mediterranean Sea and Atlas Mountains southward for 2,000 kilometers (1,000 miles) until it meets imperceptibly into the semi-desert Sahel region.  Most of the Sahara desert consists of extensive plains covered with loose gravel and boulders, those are called reg.  The rest of the Sahara has areas of shifting sand dunes, called erg, mixed with wide and long areas of bare and rocky areas which are known has hamada.

There is also the Namib and Kalahari deserts of Southern Africa are much smaller than the Sahara in size.  The Namib stretches along the Atlantic coast for 1,500 kilometers (930 miles).  The Namib starts in southern Angola ,stretches over the entire length of Namibia, and into western South Africa.  Nearby the Namib Desert is the Kalahari desert in Botswana, Namibia, and South Africa which is sort of a semiarid region in the center of the Kalahari Basin.

Africas coastline is generally very even, spotted with a few good natural harbors.  There is a costal plain around most of the continent, but it is usually narrow.  It is especially narrow in the south and east.  Major escarpments run parallel along the coast in many areas.  Lots of the Red Sea and Indian Ocean coastline is fringed with coral reefs.  These coral reefs do pose an obstacle to ships trying to access the harbors along the coast.  The reason that most of the coral reefs are on the east coast is because the Atlantic Ocean on the west coast is generally to cool for coral to be created.  The best natural harbors of Africa are found in the deep costal inlets along the coast, especially in Senegal and Liberia.  These natural harbors are even better at the mouths of rivers.  Lagoon coasts, with a coastal barrier beach that is backed by lagoons.  This to is common between Liberia and Nigeria.

Most scientists believe and use the theory of plate tectonics to explain how Africa was formed, along with the other 6 continents.  According to this theory, the crust of Earth consists of 14 rigid plates floating (barely touching) on an underlying mantle.  These plates are in constant motion.  This motion includes colliding, moving, or thrusting beneath one another.  Africa sits at the center of the African Tectonic Plate., one of the Earths largest tectonic plates.

Earth is believed to have only had one actual continent called Pangaea.  Around 220 million years ago, some tectonic plate movement broke Pangaea into the two supercontinents  named Gondwanaland and Laurasia.  Gondwanaland broke apart later as well:  First broke of Antarctica, the Australia, then Madagascar, and the Indian subcontinent broke away, later South America broke off as well.  Africa was at the center of Gondwanaland and formed its present day shape around 15 million years ago when the formation of the Red Sea split off the Arabian Peninsula.

Africas geological structure is very complex.  It reflects many stages of over 3.5 Billion years.  Most of the continent of Africa consists of rock dating back from the Precambrian Period (over 570 years ago).  These rocks are either ingenious or metamorphic.  These ancient rocks, along with some new sedimentary rocks, is what makes up the basement complex of Africa.

In much of the continent, younger deposits of igneous and sedimentary rock were laid down on top of the basement complex. The largest of the sedimentary deposits formed in northern and western Africa during the Paleozoic Era (between 570 million and 240 million years ago). Later in the Paleozoic, sediments were deposited in parts of present-day South Africa. In the Mesozoic Era (between 240 million and 65 million years ago) this area was also covered with igneous basalt from major lava flows. Sedimentary limestone was deposited during the Mesozoic on Africas northern edge. More recent sedimentary deposits dating from the Cenozoic Era (from 65 million years ago to the present) occupy the bottoms of the continents large, shallow interior basins and some coastal areas.  (MSN Encarta® Quote.)  

Africas surface, like many other areas in the world, suffer from weathering and erosion.  Weathering is the processes of physical disintegration and chemical decomposition of solid rock materials above, or near, the earths surface.  Erosion refers to the removal (getting rid of) weathered rock or materials by natural processes.  The general flatness of the African landscape is the result of chemical weathering along with prolonged erosion.

Although Africa is now generally warm and tropical, glaciation played a significant role in the continents development millions of years ago during the ice ages. When it was still a part of Gondwanaland, areas of Africa were covered in massive continental glaciers. They left behind deep deposits of tillite (rock formed from sediments deposited by glaciers) in southern Africa. Other tillite deposits are found in the Congo River Basin and in the northwestern Sahara. Glaciers are still found at the summits of some of Africas highest peaks, including Mount Kenya and Kilimanjaro. These glaciers are all above 4,500 m (14,800 ft) today, but extended as low as 3,000 m (10,000 ft) during the most recent ice age.  (MSN Encarta® Quote.)

Africa is an area that is very rich in minerals.  Especially in the south.  In South Africa, in the Witwatersrand region and the province of Free State, gold is extracted from rich reefs.  The reefs contain layers of old metamorphosed sediments that have been tilted upwards throughout time.  This formation is like other formations of minerals, some examples of this is copper, platinum,  chromium, iron ore, and coal.

Some of these mineral deposits were created when magma poured from into the older geological formations, it cooled slowly, that allowed the minerals to concentrate.  This process  created the rich deposit of chromium at the Great Dyke, which is a 520 kilometer long (320 mile long) ridge which bisects Zimbabwe from the northeast to the southwest.

A similar process created diamond-bearing kimberlite deposits in countries such as Botswana, the Democratic Republic of the Congo, South Africa, and Angola.  In other places of Africa diamonds have been washed downstream in a river and people could find them, some of this happens more frequently in Sierra Leon and parts of the Democratic Republic of the Congo.

Guinea contains large reserves of bauxite, the commercial source of aluminum.  Processes of chemical weathering and leaching formed deposits of high concentrations of aluminum oxide.  Several of Africas sources, most of them are major sources,  of iron ore were created similarly as residual deposits associated with chemical weathering.

Africa contains large pockets of natural gas and petroleum.  The natural gas and petroleum are located in two main areas, North Africa, Libya and Algeria, found in sedimentary basins in the south and east of the Atlas Mountains.  The other main area is along the Atlantic Coast between Cote dIvoire and Angola.  Between Cote dIvoire and Angola the wells are located off and onshore.  The regions most important area of production is the Niger River Delta.  The central Nile Valley in southern Sudan is emerging as a new center of petroleum production, the first significant one in the African interior.

Africas water systems are extremely diverse.  This diversity helps to reflect upon the physical geography and climate.  These water systems vary from season to season, region to region, and even year to year.

Africa contains many of the worlds greatest rivers.  The Congo, which alone in Africa is 38% of Africas discharge into the ocean, drains an area more than 4.1 million square kilometers (1.6 million square miles), ranking only second in the world. First being the Amazon River in terms of discharge and size of the drainage basin.   The Nile which extends a total of 6,695 kilometers (4,160 miles), is the worlds longest river.  The Nile also occupies the worlds fourth largest drainage basin.  Two other important rivers in Africa is the Niger in West Africa, and the Zambezi in southern Africa.

Because of Africas two main seasons, a dry season and a wet season, Africas rivers have rare constant rates of flow, height, and floods that could occur at almost any time at the beginning of the dry season and in the wet season. In the dry season and the very beginning of the wet season a river might have no discharge or any flooding.  But when the wet season and the beginning of the dry season come there is flooding and damage done to areas.  Very few of Africas rivers have the year-round constant rate of the Congo.  There are challenged with flooding because of great changes in the heights of some rivers, some challenges have been trying to limit the waters height, but use it for irrigation.   Several major dams have been built all over Africa to stop this problem, especially in the 1960s and 1970s. Today, dams regulate a greater portion of total river discharge in Africa than they do on any other continent.

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