the usambara mountains of northeastern tanzania in tropical east africa, comprise the easternmost ranges of the eastern arc mountains. the ranges of approximately long and about half that wide, are situated in the lushoto district of the tanga region. they were formed nearly two million years ago by faulting and uplifting, and are composed of precambrian metamorphic rocks. they are split into two sub-ranges; the west usambaras being higher than the east usambaras, which are nearer the coast and receive more rainfall.