Major fault structures in East Africa Map from Ashley et al., 2004 2 2

Mau escarpment on the other side of the rift valley Volcanoes on valley bottom Rotational slip of escarpment Escarpment

Landforms of Tectonic Activity A narrow block dropped down between two normal faults is a graben A narrow block elevated between two normal faults is a horst Figure 13.16, p. 467

Cross-section of East African Rift Valley.

Landforms of Tectonic Activity rifting of continental lithosphere is the very first stage in the splitting apart of a continent to form a new ocean basin the process is illustrated by the East African Rift Valley system Figure 13.19, p. 469

The climate of the Early Pliocene differed from that of the Miocene primarily by the appearance of a cooling and drying trend across Africa, where early hominids evolved. It is likely that these climatic changes led to a decrease in the forest cover of large parts of the African continent. Some of the climatic conditions of the early Pliocene were indirect effects of tectonic activity on the African continent. The most important manifestation of Africa's geology, beginning some twenty million years ago, is the formation of the Great Rift Valley. The Great Rift is an ocean being born, as parts of East Africa pull away from the rest of the continent, leaving a sinking basin in their wake. This geology is not limited to Africa, but stretches into West Asia, causing the Dead Sea to occupy the lowest continental basin on Earth, and continuing to generate earthquake activity as far north as Anatolia.

NYIRAGONGO, Democratic Republic of Congo Unusual tectonic setting; a continental CPM Erupting basaltic magma Unusually high sulphur emissions and very high temperature, low silica lava. Flows move at 60 km/h + Erupted in 1977 (100-1000 deaths) and again in 2002 (45 deaths; possibly 100,000 homeless) Up to 500,000 potentially at risk.

East Africa Seismicity Figure by Andy Nyblade, Penn State 9 9

Volcanoes in Ethiopia Google Earth image http://i280.photobucket.com/albums/kk171/volcanism/ethiopia/ethvolc.jpg 11 11

4.Rift zone landscapes e.g. the East African Rift Valley

1-Magma chamber; magma intrudes towards the surface and is essentially ‘permitted’ because of crustal extension – this creates faults and areas of weaknesses allowing magma to rise 2&3-Intrusive dykes, which often have a surface expression i.e. a ‘wall’ like landscape feature. 4-Extensive lava flows / fields covering large areas 5-Volcanoes; in the African Rift Valley they are small, cone shaped volcanoes somewhere between a composite and shield type. 6-Rift valley lakes – drainage is constrained by the rift walls; many of these lakes have a high risk of lake overturn due to dissolved volcanic CO2 e.g. Lake Kivu. 7-Fumeroles and gas vents are common as rifting causes ground extension 8-Normal faults producing impressive fault scarps on the rift valley sides. 9-Fault scarps Combine with a study of Mount Nyiragongo in the DRC which erupted in 2002. TThere is an ongoing risk of eruption, plus a fear of a lake overturn in Lake Kivu which could have dire consequences.

http://www.youtube.com/watch?v=COuIZbUoVBY&feature=related 4 mins intro clip for rift valley scenery. start it at 6 mins 30 in