GEOG 323 Regional Geography of Africa (East Africa) Lecture 2024 PDF

GEOG 323: Regional Geography of Africa (East Africa) The Physical Environment 1  Objectives To outline the major physical features (geology, relief, drainage and climate) of East Africa Discuss the socio-economic potential/significance of the different physical characte...

GEOG 323: Regional Geography of Africa (East Africa) The Physical Environment 1  Objectives To outline the major physical features (geology, relief, drainage and climate) of East Africa Discuss the socio-economic potential/significance of the different physical characteristics of the East African Region  East Africa- Geology Much of the East African physical landscape is defined by the Great Rift Valley. The East African Rift System is one the geologic wonders of the world. A wide variety of rock types are found in East Africa representing all three of the major groups: igneous, metamorphic, and sedimentary (Schlüter 1997).  East Africa has some of the highest mountains in Africa (Mount Kilimanjaro 19,340 ft.; Kenya 17,058 ft and the Ethiopian highlands - Ras Dashen 15,000ft above sea level) Kilimanjaro is a volcano of complex structure and alkaline lavas situated at an intersection of fault lines.  Mount Elgon is part of the Eastern Volcanics in Uganda, which consist of soda-rich lavas  Relief  East Africa is mainly a plateau region (comprises the low plateau, the Eastern and Western Highlands and the Central/Lake Victoria region).  Parts of the plateau are very old in origin while parts have been affected by faulting and warping or volcanic activity.  Faulting has produced the great depressions called the Rift Valley System (high mountains above the plateau surfaces and a number of lakes). (Asiedu,2013) The Great Rift Valley  The East African Rift System (EARS) is part of the Afro Arabian rift system that extends from the Red Sea through Ethiopian highlands, Kenya, Tanzania and Malawi to Mozambique in the South. Its total length is estimated to be 6,000 miles.  As the rift extends from the Ethiopian segment southwards it bifurcates at about 5°N into the Eastern and Western branches.  The western branch passes through Uganda, DRC and Rwanda; and a nascent south- western branch runs through Luangwa and Kariba rifts in Zambia into Botswana  EARS marks a place where the earth's tectonic forces try to create new plates by splitting apart old ones.  The volcanic and tectonic activity in the rift started about 30 million years ago and in the eastern branch the activity involved faulting and eruption of large volumes of mafic and silicic lavas.  The western branch, typified by paucity of volcanism, is younger and dominated by faulting that has created deep basins currently filled with lakes and sediments.  Geologists have named the new plate as the Nubian Plate. The Nubian Plate makes up most of Africa. The smaller plate that is pulling away has been named the Somalian Plate. These two plates are moving away from each other and away from the Arabian plate to the north as well.  The point where these three plates meet in the Afar region of Ethiopia forms what is called a triple- junction. The “Triple Junction” is where three plates are pulling away from one another.  Deep Cleavages in Rift Valley System in East Africa Some cleavages are 3,000+ feet deep It takes quite a feat to build a road across this!  The coastal belt East Africa borders the Indian Ocean for about 800 miles, and the coastlands form very distinctive zone. The coastal belt is a narrow plain but broadens in the Tana lowlands of Kenya and Rufiji lowlands in mainland Tanzania. The coastal belt includes the islands of Zanzibar and Pemba.  The coastal belt is straight and smooth with few indentations and natural harbours. There are major artificial harbours and railway terminals along the coast, Mombasa in Kenya and Dar es Salaam in Tanzania. Winds from the ocean bring high rainfall to most of the land along the coast. Densely populated and supports agriculture, tourism, manufacturing and service provision Drainage  East Africa is noted for mighty lakes and rivers. Rivers include the Kagera, Katonga, and Kyoga-Kafu. Ethiopia (Lake Abaya, Lake Chama, Lake Zway, Lake Shala) Kenya (Lake Baringo, Lake Bogoriua, Lake Turkana, Lake Nakuru) Tanzania (Lake Eyasi, Lake Makati, Lake Mayara, Lake Natron) (source: Carr 2017) Lake Tanganyika near Bujumbura, Murchison Falls on the Victoria Nile Burundi. Source: Kay River, northwestern Uganda. Source: Honkanen/Ostman Agency Oliver Sedlacek  The Nile: River of Life Nile is world’s longest river at 4,100 miles. White Nile starts at Lake Victoria in Uganda. Blue Nile flows from Lake Tana in the Ethiopian Highlands The concentration of population along the Nile River is due to the fertility this water resource brings to an otherwise desert area. Nile River flooding events deposit nutrients along the river banks to support agriculture for food and cash crops  Great Lakes Economic Activity: Cichlid Trade The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their watersheds support over 2000 species of cichlid fish, many of which are descended from single common ancestor within the past 25 million years (Twesigye, 2015) Cichlids fish from Rift Valley Lakes’ are found in Aquariums around the World Building Dams on the Rivers Aswan High Dam on the Nile River New dam on Nile River at location of Bujagali Falls Proposed & controversial Renaissance Dam under construction in Ethiopia will be largest dam in Africa when completed. CLIMATE  All parts of East Africa are within 12°C from the Equator. Places at sea level have high temperatures throughout the year. Varies due to differences in altitudes. Lowland coastal areas such as Mombasa and Dar es salaam have mean annual temperatures of about 27°C. The tops of Mounts Kilimanjaro and Kenya are permanently snow covered  “The Snows of Kilimanjaro” Snow-capped peaks at summit have polar-like temperatures below freezing. Vegetation and giraffes at base of Mt. Kilimanjaro show tropical temperatures. Schlüter 2006 Global warming may be causing reduction of the ice pack  There are large spatial variations in rainfall. Large parts of the region suffer extreme dryness. More than half of entire region has a mean annual rainfall of 800mm. The driest country is Kenya, while Uganda is the wettest.  Two main types of rainfall patterns: oThe equatorial pattern- Double maxima rainfall in areas near to the equator. oThe main rainfall season is from March-May while the minor season is around October- December. oThese seasons corresponds with the passage of the Inter-Tropical Convergence Zone (ITCZ), when the South Eastern and North Eastern winds converge.  The tropical pattern:- Realised in areas farther from the equator. oThe time between the northward and southwards passage of the Inter-Tropical Convergence Zone (ITCZ) becomes shorter, hence the two rainy seasons tend to merge into one. oOver much Central and Southern Tanzania, there is a single rainy season from November to April. oThere is little rainfall for about 5 - 6 months. Discussion Questions Identify the physical features of East Africa and elaborate on their roles/possible roles in the region’s socio-economic development What limitations may the physical environment place on economic growth & development?  References 1. Schlueter, T., (2006). Geological Atlas of Africa. Springer-Verlag Berlin Heidelberg. 123-129pp. 2. Twesigye, C. K. (2015). The Impact of Paleoclimate, Geologic History, and Human Influence on the Evolution of East African Cichlids. Quaternary International 369 : 67-77 3. Asiedu, A. 2013. Geography of Africa. In Manuh, T and E. Sutherland-Addy (eds) Africa in Contemporary Perspective: a textbook for undergraduate students. Pp.1-47