It grew to be this large by sinking of the caldera floor. The caldera floor is very level and holds a lake.
Streams run down the caldera walls into the lake.
Ngorongoro is full of pastureland of red and white clover. Over 75,000 wild animals live in this caldera. Ngorongoro is now extinct . It once erupted trachytic flows and large quantities of pyroclastic materials. Tephra from this volcano helps scientists put ages on early human fossils found there.