The Glaciers Come and the Glaciers Go…
Written by Bert Pschunder
Introduction
The action of glaciers in recent geologic time has had a significant influence on the shape of the land at Ames Lake and the surrounding region. Lake topography, along with nearby deeply incised drainage channels and steepened hillsides, are the result of the repeated movement of glaciers and subsequent large quantities of glacial meltwater flowing across the uplands we know today as Tolt Hill and Union Hill. The lake itself owes its very existence to dynamic processes that closed out the most recent glacial episode in the Puget Sound region.
Also, our Ames Lake region is within a very seismically active zone as evidenced by faults and earthquakes, some of which have been recently mapped around Ames Lake and in the nearby Snoqualmie Valley.
The recent mapping and an accompanying report are presented for the Carnation, Washington quadrangle by Dragovich et al., (2010). An excerpt from their map showing the lake area is included as Figure 1.

Figure 1: Excerpt from Carnation quadrangle geologic map (from Dragovich et al. (2010)
The Glaciers Leave Their Mark
Glaciers are large masses of ice that can be thousands of feet thick. They can move as the ice thickness increases, albeit very slowly. There is evidence that the Puget Sound region has experienced several large-scale glacial advances originating from up north in British Columbia, Canada and reaching as far south as the Olympia, Washington area.