 The changes are the result of a drop in elevation of about 1,400 feet from the summit of Snoqualmie Pass to Thorp, and a significant drop in precipitation of about 107 inches average a year at the summit of Snoqualmie Pass, to 42.94 inches average a year at Thorp.At the bottom of the Thorp Drift moraine the view opens up into the Kittitas Valley which is deeply buried in river gravel deposited by the ancient Yakima River.This valley is a syncline that creates the Ellensburg Basin located between Mission Ridge to the north and Manastash Ridge to the south.