Rift Valleys: Formation, Pictures, and Examples Geology In Africa's Rift Valley and the Creation of SRIRAM's IAS Divergent Boundary, The Great Rift Valley (African Rift Valley) PMF IAS Riftvallei Diagram East African Rift Valley is caused by tectonic forces on earth Rift Valley formation.pptx. Follows a week by week, letter by letter progression. Engages learners who prefer factual content. Uses strictly controlled text so only known letter sounds appear. Includes tricky words only after they have been introduced. Builds confidence as children master the phonics code. Features full color photography throughout. Provides book banded reading levels for use with other schemes. Library contains 72 reader titles, 12 at each phase level. Recommended for ages 46 (Pre K to Grade 2).