Geology of Kenya in brief
Kenya, like all of its East African neighbors, lies on one of the great fractures in the earth's crust. The slow ballet of tectonic plates on the surface of the Earth produces zones of friction, privileged places of intense seismic activity. These numerous earthquakes generate faults. There are three types of faults: reverse faults (or thrust faults), which create mountain ranges, horizontal faults (or strike-slip faults), which displace existing landforms, and finally, so-called normal faults, which create collapse trenches also called rifts.
The spectacular relief that characterizes Kenya is due to its specific location at the heart of tectonic activity: the country is indeed located on the meeting line between the African plate and the so-called Somali plate, which covers the western Indian Ocean. The fissure zone between these two plates constitutes a major rift (a fault), the Rift Valley, an endoretic zone. In addition to the Rift Valley, which stretches for more than 6,500 km between the Red Sea in the north and Mozambique in the south, repeated tectonic movements have been the source of a tormented relief and important volcanism.
The formation of the country's eastern highlands, where the capital, Nairobi, is located, and the western highlands, which slope down to Lake Victoria, originated from plate collisions, which caused lava flows (mainly basalt). The latter gradually formed vast plateaus, dominated by dizzying escarpments. Many volcanic cones were built and are still visible today: Mount Elgon, Menengai, Longonot or Mount Kenya and the famous Kilimanjaro, emblematic of the region.
The bottom of the Rift Valley is a zone of levels, which rise from Lake Turkana (which stretches in the north over 250 km long and 40 km wide, up to the Ethiopian border) to Lake Naivasha (central region), passing through Lakes Bogoria, Baringo, Nakuru, and Elementaita, before descending to Lakes Magadi and Natron, on the Tanzanian border. Recent volcanoes have appeared there (Suswa, Longonot, Menengai).
It is this geomorphological history that has shaped Kenya's present relief and, indirectly, its climate. The relief has indeed a considerable influence on rainfall. This largely explains why this region, located in the middle of a tropical zone, is less hot, drier and therefore less forested than other regions located at the same latitudes, particularly in West Africa.
A divisive rift
What if Africa was splitting in two? This is what is evoked in 2018, when an impressive fault of 20 km long, up to 20 meters wide and 50 meters deep, emerges in Mai Mahiu, southwestern Kenya. This suddenly appeared continental wound divided the scientific community. Some evoked the premises of the separation of the continent. Wouldn't Africa be splitting, between the Nubian plate and the Somali plate, in the east of the continent? This immediate interpretation is quickly swept away. The fault is not of tectonic origin and has nothing to do with the East African Fault, but rather a subsidence of the soil eroded by heavy rains, in a context of numerous earthquakes and landslides. The volcanic activity of the region remains monitored by geologists around the world, because at the Great Rift Valley, inexorably, the African tectonic plate continues to slowly separate from the Somali plate. A geological phenomenon that extends from the Red Sea to the Zambezi, over 6,000 km and 40 to 60 km wide. The Kenyan Great Rift Valley could then become, in 50 million years, a vast ocean.
Geographic clusters
There are five main geographical zones in Kenya. Each with its own landscape, vegetation and climate: the coastal belt, the central highlands cut in two by the Rift Valley, the west and finally the north and east of the country.
The coastal belt.
For about 500 km, between Somalia and Tanzania, there are fine sandy beaches, protected by coral reefs. In the extreme north, a string of islands border the coast, the main ones being Manda, Pate and Lamu. The coastal plain, interrupted by the estuaries of the Tana (the country's main river) and the Galana, is a fairly fertile area, overlooked by the central plateau which rises rapidly, giving way to desert and savannah trees. The inhabitants, mostly Swahili, grow cassava, banana, sisal, sugar cane as well as coconut and fruit trees. This narrow strip of land enjoys a relatively hot and humid climate, far from a true equatorial climate, since rainfall (concentrated between March and May) rarely exceeds 1,000 mm per year. The heat mitigated by the trade winds of the Indian Ocean allows the coastal belt to enjoy pleasant temperatures throughout the year.The central highlands.
These are located on either side of the Great Rift Valley. This is a very mountainous region that includes Mount Kenya (5,199 m) and the Aberdares Mountains (4,000 m) on the eastern side and the Mau Escarpment (3,100 m) and the Cherangana Hills (3,500 m) on the western side. The highlands receive high rainfall and are intensively cultivated by the Kikuyu as well as the Meru and Embu. The climate in the highlands is subtropical, with two distinct rainy seasons (November and May-August) and pleasant, sometimes cool, temperatures at high altitudes (around 0°C at 3,000 m in the evening).
The Rift Valley.
The Rift Valley, a huge trench installed in the junction of the African and Somali tectonic plates, and which stretches from the Red Sea to the Zambezi, passes through Kenya in the middle of the highlands and extends over the entire length of the country, from Lake Magadi in the south to Lake Turkana in the north. The bottom of this vast depression is occupied by a series of shallow lakes that attract hundreds of species of birds and offer a unique bird show in the world. The volcanic activity, still latent (numerous geysers and hot springs), has covered the ground with volcanic ashes rich in soda which, little by little, have been dragged into certain lakes. Thus, lakes Magadi, Bogoria, Elmenteita and Nakuru have particularly alkaline waters favoring the development of algae on which thousands of pink flamingos feed. On the contrary, lakes Baringo, Naïvasha and Turkana contain fresh water and therefore rich in fish. The Rift Valley, too protected and below the relief, suffers from a föhn effect: the dry seasons are more marked there and the rainfall (November, from April to May) lower. This explains the semi-desert, even desert character of the southern and northern areas, where semi-nomadic and pastoral peoples such as the Turkana live.
The West.
This region consists of a hilly plateau that stretches along the border with Uganda (interrupted only by the enormous mass of Mount Elgon, 4,321 m) and ends on the shores of Lake Victoria. Country of the Luo (third ethnic group of Kenya), this region is well irrigated and very fertile: intensive agriculture is practiced there (tea, sugar cane...). Lake Victoria enters through the Kano Fault over a depth of 80 km, forming the Gulf of Winam, at the bottom of which is the city of Kisumu. The southern part towards Tanzania suffers regularly from drought and the green hills give way to savannah. The western plateau is hot and humid. It reaps the benefits of the humid equatorial west flow of the Congo, the presence of the huge body of water of Lake Victoria and the altitude. This allows it to be the region with the highest rainfall (everywhere more than 1,000 mm per year) and the most regular rainfall (it rains throughout the year, most often in the evening). The West is the domain of tea, coffee and horticulture.North and East. The north of Kenya is occupied by vast arid interior plains. Their monotony is broken by Lake Turkana (6,405 km²), north of the Rift Valley, and by numerous volcanic cones. Only the Marsabit massif benefits from significant humidity. The eastern part of the country consists of a dry and unglamorous plateau that descends from 1,300 m to 300 m and extends to the southeast to the coastal plain. It is dotted with inselbergs (isolated hills in the middle of plains) including the amazing Taita Hills (2,208 m) and Chyulu Hills. These two regions cover almost two thirds of the country with alternating bush and desert (the Chalbi Desert in the north is the driest area in Kenya). Only the breeding of a few species, such as camels or goats, is possible. This area suffers in fact from subsidence and wind divergence phenomena that limit rainfall (no more than 250 mm or 300 mm per year). The rains are therefore rare but very violent (November is the wettest month). After a big storm, the numerous luggas (dry river beds) turn into real torrents of mud and sand. The tribes living in these regions (the Samburu, the Turkana, the Rendille, the Gabbra, the El Molo and the Boran) are mostly nomadic pastoralists. The limited contact with the modern world has allowed them to preserve until today a large part of their traditions and their secular way of life
A grandiose and varied nature
Kenya offers just about the entire range of landscapes that one would expect from an African country: savannahs, equatorial forests, high plateaus, deserts and semi-deserts, immense beaches of fine sand with turquoise waters, coconut groves... From the mountains to the immense depression of the Rift Valley, passing by the charismatic silhouette of Kilimanjaro and the coast of the Indian Ocean, travelers will be fascinated by a quantity of grandiose and striking landscapes. With a relatively low density of human settlement and a rich, diverse, and surprising wildlife, Kenya is definitely a destination for those who love the great outdoors. We have mentioned the relief, but the colors and the lights that are spread out are just as amazing, as well as the flora that varies greatly from one region to another, as well as the depth of the skies, of which our eyes never tire.
