During the Pleistocene Age, one to three million years ago, rock and ash from the volcanoes of the Ngorongoro area covered what is today the Serengeti Plains. The volcanic ash on the plains produced a very particular type of soil. The fine-grained ash contained many salts, such as potassium, sodium, and calcium, much of which is still present on the surface today. During the seasonal rains, these salts are washed down into the soil where they precipitate, or come out of solution.

After spending the dry season in the wetter northern woodland of Serengeti, the wildebeest follow the seasonal rains south and move onto the Serengeti Plains. The shallow, water-holding soil and over a million grazing mouths maintain the plains in a super-productive growing state. With ample food, the wildebeest females produce and suckle their calves. The wet season is also the time of year for predators to fatten up. With an abundance of young and inexperienced herbivores, lions, cheetahs, and hyenas have an endless supply of food.