Origin and Evolution of the Great Lakes of Africa

Great Lakes of Africa

Introduction

The Great Lakes of Africa are a set of lakes that make up a remarkable section of the Rift Valley lakes around and in the East African Rift System which is an active continental rift zone in the eastern portion of the continent. The East African Rift System itself is believed to have started formation during the beginning of the Miocene which is about 25 million years ago. In the times past, this rift system was seen to be a section of the bigger Great Rift Valley that stretched northward to as far as Asia Minor. 

The Great Lakes of Africa (also called Maziwa Makuu in Swahili) is made up of Lake Victoria, the second biggest freshwater lake in the world by surface area, and also Lake Tanganyika which is the second biggest freshwater lake by depth and volume. Then it is also made up of Lake Malawi which is the eighth biggest freshwater lake by area, overall these lakes have 31,000 km3 of water which makes them bigger than Lake Baikal or the Great Lakes system of North America. This makes up around one-quarter of the unfrozen surface fresh water on the planet. These massive African rift lakes are domains of expansive biodiversity and one-tenth of the fish species found on earth – it is a place rich in natural resources. 

Origin and Evolution of the Great Lakes of Africa

Scientists have been able to ascertain that the East African rifts adopted the form that they have today because of the tectonic movements during the Pleistocene Epoch which is about 2,600,000 to around 12,000 years ago. The understanding is that the formation of the lakes must have been established in the landscapes that they are eventually set. 

 The relatively shallow depths of the lakes like Albert where the maximum depth that has been recorded is less than 200 feet and Edward with 367 feet came about because of the solid sedimentary layers they rest upon. 

In some other lakes too, the activities of the volcanoes constituted the blockage of drainage and also influencing the shorelines. The elevated beaches showed that the levels of the lakes were higher with the surface even more extensive during the rainy periods of the Pleistocene Epoch. In the Eastern Rift, to illustrate, Lakes Baringo and Rudolf were initially belonging to a single lake from which there was a link across the Sobat River alongside the White Nile. Dry conditions, later on, led to the eastern lakes becoming reduced in size eventually leading to current sizes. 

There have also been remarkable changes in the geology of the lakes of the Western Rift systems. Scientists believe that the drainage of Lake Kivu was down in a northward direction towards the Nile before the geological activity as evidenced by the Virunga Mountains eruption. Records of fossils state that the organic content of Lakes George and Edward was decreased following severe volcanic activity in the shorelines even though several fish species managed to survive through all the phases. 

A rise in the shoulders of the Western Rift led to the reversal in the direction of the flow of rivers like Katonga, Kagera, and Kyoga-Kafu while Lakes Kyoga and Victoria were formed via diversion of water from the northern portion of the rift. This is believed to have happened around 100,000 years ago. Later on, much of the drainage of most of what is now Uganda was redirected to the Western Rift and then the Nile. This led to a series of reductions in the depth of Lake Victoria. 

The lakes of East Africa that are situated in the inland troughs at heights of around 2,000 feet or below have a dry and hot climatic environment with a lot of evaporation. In the upper portions of the rift floors, the climate remains similar to the surrounding highlands. Today, the moist air predominating the Western Rift from the Congo Basin is a source of the wetter conditions that prevail over Lakes Kivu and Tanganyika. 

It is known that massive lakes either influence or creates their climates and this is most seen on the northern and western portions of the massive Lake Victoria. A similar phenomenon is seen with Lake Nyasa and others like Lakes Nakuru, Chilwa, and Rukwa. In summary, the Great Lakes of Africa have evolved via a series of complex geological events which keep shaping the planet as we know it today. 

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