On the west side of the Cascade Mountains, two lobes covered the Puget Lowlands. Along the north side of the Olympic Mountains the Juan de Fuca Lobe moved west, and between the Olympics and the Cascades the Puget Lobe moved south.
As the Puget Lobe advanced, it deposited hundreds of feet of Lawton Clay, Esperance Sand, and Vashon Till. Meltwater flowing below the ice carved out troughs that we know as valleys.