It is believed by scientists taht the Great Rift Valley was created by _______.?

--B tectonic forces-- (divergent tectonic plate boundary.It is a linear feature that exists between two tectonic plates that are moving away from each other.--------------------------The name continues in some usages, although it is today considered geologically imprecise as it combines features that are today regarded as separate, although related, rift and fault systems. Today, the term is most often used to refer to the valley of the East African Rift, the divergent plate boundary which extends from the Afar Triple Junction southward across eastern Africa, and is in the process of splitting the African Plate into two new separate plates.a href="http://en.wikipedia.org/wiki/Great_Rift_Valley" rel="nofollow"http://en.wikipedia.org/wiki/Great_Rift_…/a ----------The East African Rift is part of the larger Great Rift Valley. It is a continental rift zone that appears to be a developing divergent tectonic plate boundary. The rift is a narrow zone in which the African Plate is in the process of splitting into two new plates called the Nubian and Somalian subplates or protoplates. a href="http://en.wikipedia.org/wiki/East_African_Rift" rel="nofollow"http://en.wikipedia.org/wiki/East_Africa…/a In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form in the middle of continents but eventually form ocean basins. a href="http://en.wikipedia.org/wiki/Divergent_boundary" rel="nofollow"http://en.wikipedia.org/wiki/Divergent_b…/a ----- GREAT RIFT VALLEY is depression, extending more than 4830 km (more than 3000 mi) from Syria in SW Asia to Mozambique in SE Africa. The valley is believed to have been formed by the sinking and tearing apart of the earth's crust along a 50-million-year-old zone of weakness a href="http://www.history.com/encyclopedia.do?vendorId=FWNE.fw..gr086300.a#FWNE.fw..gr086300.a" rel="nofollow"http://www.history.com/encyclopedia.do?v…/a ----------- Location of Great Rift Valley a href="http://upload.wikimedia.org/wikipedia/commons/thumb/c/c8/Great_Rift_Valley_map-fr.svg/465px-Great_Rift_Valley_map-fr.svg.png" rel="nofollow"http://upload.wikimedia.org/wikipedia/co…/a