**Author details**

Dereje Ayalew1 \*, David Pyle2 and David Ferguson3

1 School of Earth Sciences, Addis Ababa University, Addis Ababa, Ethiopia


\*Address all correspondence to: dereayal@yahoo.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
