what is the shape of the Rift Valley
http://www.google.com/search?q=rift+valley&es_sm=119&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMIq6eMiaXAyAIVSaweCh0oXQWF&biw=1440&bih=712
Do you mean as on a map or when you're standing somewhere close, looking at it?
Look at the different images in the search results linked above. Let us know what you think.