Arthur C. Clarke. (2023, May 31). Wikiquote. Retrieved December 17, 2023 from https://en.wikiquote.org/w/index.php?title=Arthur_C._Clarke&oldid=3300288.
Much of the current topography was formed through the erosion of the depression by the Cordilleran Ice Sheet during the Vashon Glaciation, which lasted from about 19,000 – 16,000 BP.