From introduction: Much of the ground surface around Mount Rainier volcano is directly underlain by loose geologic deposits that veneer the hard rock formations. Examples of these deposits are sand and gravel bars along the rivers, ridges of loose rock debris beside the glaciers, and sloping aprons of rock fragments beneath almost every cliff. Even though they are generally thin and inconspicuous when compared with the rock formations, these surficial deposits are clues to geologic events that. have profoundly influenced the shape of the park's landscape. Thus, from the character and extent of glacial deposits one can judge the age and size of former glaciers that carved the cirques and deep canyons of the park; from the mudflows which streamed down nearly every valley one can infer the age and size of huge landslides of the past that helped determine Mount Rainier's present shape; and from the pumice deposits some of the volcano's recent eruptive activity can be reconstructed.

Introduction: This report was started as part of a study of the North Cascade Primitive Area, an area of about 830,000 acres, which adjoined the Canadian border on the north and which extended from Mount Shuksan on the west to Rock Mountain on the east. In the fall of 1968, Public Law 90-544, 90th Cong., reclassified the North Cascade Primitive Area and certain other national forest lands and created the North Cascades National Park, the Ross Lake National Recreation Area, and the Pasayten Wilderness. Ross Lake National Recreational Area, a corridor 21/2-4 miles wide along the Skagit River and its dammed portions, Ross, Diablo, and Gorge Lakes, separates the park into two parts and separates the northern part of the park from the Pasayten Wilderness. The present study concerns those parts of North Cascades National Park and the Ross Lake National Recreation Area that are north of Skagit River and west of Ross Lake (fig. 1), as well as part of the Mount Baker National Forest west of the park (pl. 2).

This report studies the several aspects of the basalts in the Columbia River Basalt Group in the Spokane quadrangle, Washington, Idaho, and Montana.

This report follows the geological field studies of dolomite deposits near Marble Stevens county, Washington.