2/23/08
Saturday, February 23rd - Day 7
Back in Nairobi! The evening after my last post was filled with elephant activity. Everytime we tried to sleep, a mama elephant would begin trumpeting just outside the hotel. She would chase a couple of hyenas around the water hole, followed by two baby elephants. The noise was incredible! Eventually she was joined by some of her family, and the persistant hyenas were finally chased off. The next day we traveled on to Lake Nakuru, a national park within the East African Rift Valley. The lake is long, relatively narrow, and one of the few freshwater lakes within the rift. We set off on our first game drive that evening, and we saw: greater flamingoes, lesser flamingoes, pelicans, waterbuck, bushbuck, zebra, warthogs, cape buffalo, black-faced vervets (monkeys), white-faced vervets, baboons (surprisingly cute), white rhinos, black rhinos, and a hippo... The next day we did another game drive before heading out to Malewa River Lodge in Kigio. It's amazing how many animals there are - you can see them all - hundreds of them - everywhere you look! The lodge at Malewa River is a sustainable, environmentally friendly lodge - all materials are local - energy is solar, etc., etc. We stayed in a thatched cabin overlooking the river - amazing! At the lodge I had the chance to take a nature walk with the local naturalist - he's very interested in learning more about geology, so I had a chance to describe the rocks to him, and we plan to stay in contact. Anyway, he showed us the obsidian deposits that come from nearby Mount Longonot. After Malewa, we went to the Maasai Mara - more game drives, a visit to a local village (cannot begin to describe), and more game drives. We finally saw a pride of lions, and we found a cheetah! Friday morning we took a hot air ballon ride over the plains and had a champagne breakfast under an acacia tree - we've been completely spoiled! Now we're back in Nairobi, getting for our last couple of days - we're going to Amboseli National Park. Geologists - tell me about the plate tectonic setting in the rift valley - what type of volcanoes do you think I've found?
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The Rift Valley is made up of divergent boundaries. Part of the Mid- ocean ridge of the Indian Ocean, the Arabian Peninsula used to be attached to Africa. The Great Rift Valley is split into the Western and Eastern Rift Valleys. The Rift Valley is still forming because of geothermal activity that could possibly create a mid ocean ridge by splitting Eastern Africa off into its own landmass. Volcanic activity and many hot spots have created volcanic mountains such as Mount Kilimanjaro. The island Jabal al-Tair contains a basaltic stratovolcano.
Divergent plate boundaries make up the plate tectonic setting in The Rift Valley in Africa. When the plates split apart, it creates a lot of geothermal activity that results in many hot spots which can lead to volcanoes. Volcanoes in the area include volcanic mountains such as Mount Kilimanjaro, Mount Kenya, Mount Karisimbi, along with some others. Although these volcanic mountains are not "active," The Ol Doinyo Lengai volcanoe in the Rift Valley is the only natrocarbonatite volcano in the world!
Mount Longonot and Mount Kenya are both Stratovolcanoes. The Rift Valley has divergent tectonic boundaries.
The East African Rift is an active continental rift approximately 3000km long. The rift has divergent boundaries. This rift is the beginning of the splitting of a continent. Lots of basaltic lava is present and magma is produced through decompression melting. Mount Kilimanjaro, a composite cone, is one volcano that is part of the rift. - Andrew Bartolucci
In geology a rift means a place where the Earth's crust is being pulled apart. It is common to find volcanic rocks and active volcanism just like the many volcanos that currently exist in Africa. Rifts are different from mid-ocean ridges in the sense that no new crust is formed when the Earth is pulled apart like in a mid-ocean ridge. It is stated that the transition from rifting to spreading develops as three converging rifts over a hotspot. Because we know this, we can assume that the types of volcanoes found along the Great Rift Valley are Shield Volcanoes. Shield Volcanoes are very broad topped with gradually sloping peaks. They form by mid-ocean ridges or hot spots which is what exists along the Great Rift Valley in Africa.
-Nicole Grant
The East African Rift Valley is a divergent boundary. This type of boundary in Africa is also a triple junction, where three plates are pulling away from one another causing the splitting along the East African Rift Zone. The Arabian Plate and the two parts of the African Plate (the Nubian and the Somalian) split along the East African Rift Zone. The types of volcanos you would find in this area would be shield volcanos and more commonly stratovolcanos.
The African Rift Valley is located on a divergent tectonic boundary. Both shield and stratovolcano's can be found in this rift.
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