The Formation of the Rift System

Formation of the Rift System

Heat flow from the asthenosphere is causing bulges is Kenya and Ethiopia. It’s believed by geologists that these bulges formed because of mantle plumes under the earth’s surface that heat the continent so that it expands and fractures. When these bulges form, they stretch the crust into a series of normal faults. The rift opened about 65 million years ago, and while it's splitting the African continent in two, it's also caused the Red Sea to open into the Indian Ocean. The reasoning behind this occurence is that the Arabian Plate is drifting to the northeast. This drifting has also helped cause the formation of the volcanoes and mountains in East Africa.

Volcanic eruptions usually occur along these rifts, and the lava comes out of the fractures instead of individual volcanoes. This lava spreads around the land in floods. Two branches of this rifting have formed with this process. There is one that heads westward, and the rift filled with water which makes up the African Great Lakes. The other one is parallel to the latter and goes through Kenya to enter Tanzania. It is thought by geologists that the reasoning behind two parallel rifts is the Tanzania craton (ancient metamorphic rock) that was too hard for to be torn, so the rifts branched out and around the craton. The eastern branch of the rift has more volcanism and is characterized by a broad dome.

This photo shows both the eastern and western branches of the rift system. Both rifts surround Lake Victoria.