Exploratory Archeological Survey For Glassy Volcanic Rock Sources in the Silver Creek Watershed, 1997

Glassy volcanic rocks such as obsidian were used by prehistoric peoples to make tools whenever it was available. Such materials fracture easily and in the predictable "conchoidal" pattern most often recognized by the characteristically smooth, curving fracture surfaces.

Exploratory Archeological Survey For Glassy Volcanic Rock Sources in the Silver Creek Watershed, 1997

by Robert R. MIerendorf, North Cascades NPS Complex

The investigation consisted of a field survey centered in the watershed of Silver Creek, a tributary of the upper Skagit River. Today, Silver Creek drains into Ross Lake, a reservoir operated by the Seattle City Light Department (SCL).