Transcript here
THE EAST AFRICAN RIFT VALLEY TECTONICS • The East African rift system is formed at a conservative plate margin involving three continental sub -plates • The pull-apart is not vigorous enough to create a clean, single break through the thick plate material • The thick continental plate is arched upwards from the convection currents, pulled thin by the stretching of the crust, and fractured into a rift-shaped structure • Normal faults develop on both sides of the rift as the plates move apart and the central grabens (displaced rock between plates) slide downwards • Earthquakes occur as a result of this fracturing and movement. -The Somalian plate is gradually moving away from the Nubian, causing a series of rifts to form along east Africa. EARTHQUAKES • The East African rift system is a zone of shallow earthquakes with a 20 km average focal depth • The Western branch is more seismically active than the Eastern branch, with the Kenya rift almost devoid of seismic activity, although the rift floor is seismically active. • The seismic activity along the East African rift system is, although higher than elsewhere in the continent, still low. Many frequent but low magnitude earthquakes occur but pose no significant hazard HTTP://WWW.GEO.ARIZONA.EDU/GEO5XX/GEOS5 77/PROJECTS/MOONEY/HAZARDS.HTM This map shows that the earthquakes occurring along the African rift tend tor range from 30.2 on the Richter scale, indicating the the quakes along this rift are very minor and cause little to no damage to human settlements or activity VOLCANOES • As the plates pull apart, the crust thins, cracks, and settles—sometimes violently. Magma rises to the surface putting tremendous pressure on the thinning, fragmented crust • Fissure eruptions may occur • The central volcanoes of the rift are underlain by crustal magma chambers during some stages of their active periods. • They erupt silicic magma, which when under lots of pressure breaks their roof – either as large volume pyroclastic flow or smaller volumes of lava flows. • Central volcanic activity also includes long lasting eruptions or lava activity in the central crater of the basaltic lava lake. • Some of the volcanoes formed are very large and iconic, including Mount Kilimanjaro and Mount Kenya, which have become popular attractions for adventuring tourists. VOLCANOES ACROSS THE RIFT PRESERVATION • The volcanic conditions in the East African rift system are favourable for fossil preservation, with ash deposits favouring fossilisation of organic remains. • Lucy, a famous 3.2 million-year-old Australopithicus afarensis, was found in Ethiopia's Afar Depression. • The fossils have been vital in reconstructing the history of the human species and explaining the link between us and modern apes. AFRICAN RIFT GEOTHERMAL DEVELOPMENT FACILITY ARGEO • ARGEO claims that: Geothermal energy is one of the most promising energy options for countries in Africa’s Rift Valley. According to the US Geothermal energy Association, using present-day technology, the region’s geothermal potential is in the 2.5 to 6.5 GW range. Not only does geothermal energy present a sustainable, low-cost compliment to the region’s hydropower and diesel-based thermal electricity, but it is also unaffected by drought and petroleum price fluctuations. • ARGEO aims to: • Set-up a Regional Network providing support for the development of a geothermal energy-old knowledge sharing database, as well as capacity building and awareness raising. • Provide Technical Assistance programme focusing on surface investigation, risk minimization, policy frameworks, and presenting bankable proposals to local or international financing sources. • Officially launched in November 2010, the six countries are in the process of selecting potential geothermal sites to be considered for support under the project. Additional co financing is provided by BGR (Germany) and ICEIDA (Iceland). • The organisation targets six African Rift countries: Kenya, Eritrea, Djibouti, Ethiopia, Tanzania, and Uganda, all of which lie on the rift MORE INFO. • http://education.nationalgeographic.co.uk/media/file/Africa_Great_Rift_Valley_Art.pdf • http://www.volcano.20m.com/catalog.html • http://www.unep.org/energy/Activities/ARGeo/tabid/79467/Default.aspx