The Rift Margins and the Great Western Escarpment

Abstract

Although the margins of the Rift Valley and Afar are often shown as distinct black lines on geological maps, including those in this book, they are in reality much more complex. On the ground, indeed, they are often difficult to decipher. It is easy to be certain when you are in the highlands, or when you are in the Rift Valley or Afar, but it is less clear just where one ends and the other begins. This is because the rift margins are not formed of single, simple faults but are in most cases broad, complex belts of faults and flexures, extending over widths of up to 80 km. Sometimes the original faults have been obscured by later flows of lava or ignimbrite . Finally, they have been subject to millions of years of erosion by rivers and streams cutting across them, wearing them back and blurring their original features.