Great Rift Valley. also Rift Valley is part of an intra-continental ridge system that runs through Kenya from north to south. It is part of the Gregory Rift, the eastern branch of the East African Rift, which starts in Tanzania to the south and continues northward into Ethiopia. Approximately 6,000 kilometres (3,700 mi) in length, that runs from Lebanon’s Beqaa Valley in Asia to Mozambique in Southeastern Africa. The region is marked by vulcanism and by a series of faults caused by tectonic action. The formation and evolution of the African Rift Valley are shaded in mystery, but geoscientists at Penn State are mapping the history of the Rift through space and time by analyzing the chemistry of ancient lava from Lake Turkana, northern Kenya. Geologists know that the Rift Valley was formed by violent subterranean forces that tore apart the earth’s crust. These forces caused huge chunks of the crust to sink between parallel fault lines and force up molten rock in volcanic eruptions. The eastern branch of the rift passes through Ethiopia and Kenya, and the western branch forms a giant arc from Uganda to Malawi.
The East African Rift Valley, as the region is known, formed where the Somalian and Nubian plates are pulling away from the Arabian Plate. The eastern branch of the rift passes through Ethiopia and Kenya, and the western branch forms a giant arc from Uganda to Malawi. The eastern branch formed around 25 to 30 million years ago, whereas the western branch formed only 10 to 15 million years ago — or at least that’s what scientists thought. Now, new evidence points to an earlier birth date for the western branch, too.
“We now believe that the western portion of the rift formed about 25 million years ago, and is approximately as old as the eastern part, instead of much younger as other studies have maintained,” said Michael Gottfried, a geologist at Michigan State University who co-authored the study. To piece together the story, Gottfried and his colleagues, including Nancy Stevens, a paleontologist from Ohio University, collected rock samples, zircons (a rare crystalline mineral that can be used to pinpoint geological ages) and fossils, which they correlated with similar specimens from other regions to determine the ages of the rocks encasing them.
A video and photos showing deep chasms opening in Kenya’s Narok and Suswa County quickly went viral on the internet this year. One tear in the earth, stretching several miles, is reportedly fifty feet deep and sixty feet wide. Local geologists have explained the chasms in part as fossil faults, covered previously by volcanic ash from the nearby Mount Longonot. Strong rainfalls have washed the material filling the faults away. Likely the faults, if confirmed as such, are associated with tectonic stress or a magma intrusion in the underground. This area is part of the Great Rift Valley, where Africa is slowly pushed and pulled apart by uprising material in earth’s mantle. Eventually, the rift will become deep enough to host a new ocean, separating Eastern Africa from the rest of the continent.
The Great Rift has also been home to hominids such — Australopithecus afarensis that lived fin the Great Rift Valley: much farther than previously thought. An international team of paleontologists led by Emma Mbua of Mount Kenya University and Masato Nakatsukasa of Kyoto University report findings of fossilized teeth and forearm bone from an adult male and two infant A. afarensisfrom an exposure eroded by the Kantis River in Ongata-Rongai, a settlement in the outskirts of Nairobi.