TrapRock Valley

Portage Lake
Traprock Valley
Keweenaw Fault

The Traprock Valley lies parallel to the Keweenaw Fault. The Traprock River is located about a half mile east of the Fault, and like the Pilgrim River, the Traprock is downcut into the softer Jacobsville, even though it location is strongly influenced by the fault.  Glacial scouring was more intense into the Jacobsville, so a valley was present as the glacier withdrew.  The valley fill derived from glacial deposits and post glacial lakes, much of it fine unconsolidated silts. Thus the valley is agriculturally more productive than most of the Keweenaw.