They were formed over 21,000 years ago as the result of an underground steam explosion.[4] The Killeak Lakes and White Fish Lake are also volcanic maar lakes of notable size on the northern Seward Peninsula. Four mountain ranges line the southern side of the peninsula, the most prominent being the Kigluaik (or Sawtooth) Mountains. The highest point in the range and the peninsula is the peak of 4,714-foot (1,437 m) Mount Osborn.