Northern Washington shows them well. The purple, medium green, red, and light blue are all terranes of Paleozoic and Mesozoic age that began their existence thousands of kilometers to the south and west. The Pleistocene ice ages affected Washington strongly, covering the north part of the state deep in glaciers. The ice dammed some of the rivers that flow through here, creating large lakes. Those account for the streaky pattern of the rocks there, with flood channels in the cream-colored areas of recent sediments stripping clean the underlying Columbia River Basalt and laying down huge sand and gravel deposits in the stippled areas.
More glacial sediments fill the basin where Seattle sits.
This is a reduced image of U.S. Geological Survey Map I-593 by A. E. Weissenborn, published in 1969. The explanation is legible, but not all the map labels are, which is OK if you know your landmarks already. Low, discount pricing. Over 200 earth science software solutions. Over 200 earth science software solutions.