In what climate region can cacti be found

In 1915 the german geologist and meteorologist alfred wegener first proposed the theory of continental drift, which states that parts of the earth's crust slowly drift atop a liquid core. the fossil record supports and gives credibility to the theories of continental drift and plate tectonics.

In the diagram below, ab and bc are tangent to o. what is the measure of

What was the great rift valley formed by