Lake Natron (pink color results from the billions of iron oxide bacteria that inhabit it), approximately 35 miles (56 kilometers) long and 15 miles (24 kilometers) wide, has its northern end on the Tanzania-Kenya border; the summit of the small volcano, 5130 feet (1560 meters) above sea level at the northern end of the lake, is in Kenya. The north-south-trending lines on either side of Lake Natron help to establish the width of the Rift Valley at this point as approximately 20 miles (32 kilometers). Although this part of Africa has a humid, equatorial classification, this area has a definite dry winter season and varying rainfall amounts averaging approximately 40 inches (100 centimeters) annually. Lake Natron and its flamingo population are very sensitive to rainfall amounts—both suffer during drought.