Harrow and Hillingdon Geological Society

Geothermal Exploration

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The rise in oil prices in the 1970s made it imperative to find an alternative power source in East Africa. The countries included in this research were, Tanzania, Uganda, Kenya, Ethiopia and Djibouti, all of which are associated with the rift valley. Uganda has hydroelectric power but there is only a little in Kenya, which is why this country became the forerunner in geothermal prospecting.

The East African rift valley is not a single entity and comprises the east and west rifts. The west side is lacking in volcanicity except in the Virunga Mountains and hence the rift valley filled with water instead of lava. The eastern rift valley, which runs from Tanzania through Kenya and Ethiopia to Djibouti, has many volcanic centres and a number of lakes. The area is comprised of two major domes, the result of mantle upwelling. The main Ethiopian Rift area is surrounded by plateau basalts, which are many km thick. The major influences on the geothermy are the lakes and volcanoes. Some of the lakes are fresh water while others are sumps of salt. They vary in colour and may be blue, green, pink or brown. Kilimanjaro is still active.

Geothermal Systems require a source of heat and water. Magma provides the heat while the water is in the form of rain, and together these form a hot spring, which is accessed by a vent. Exploration is normally on foot, or by boat, Land rover or helicopter depending on the topography.

Central Island fumarole
Cental Island fumarole * measuring the temperature of a small, sulphur-depositing steam vent on the volcanic Central Island of Lake Turkana.
Abaya fumarple
Abaya fumarole * On the way to sampling a boiling spring and associated steam vent near Lake Abaya, southern Ethiopia. The boiling waters are rising to the surface on the side of a small graben on the floor of the main Rift Valley.
Bogoria Spring
Bogoria spring * A boiling spring on the west side of Lake Bogoria, Kenya Rift Valley. In the background, flamingos feed in the shallows of the highly alkaline lake.


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