Chris Hedeen, Oregon City High School, developed this classroom activity that features a hands-on model of crustal block motions within the Pacific Northwest active continental margin. (The accompanying PDF by Philip Dinterman, Chris DuRoss, and Ray Wells describes construction of the model itself.) Through this activity, students can investigate the motions of crustal blocks in the Pacific Northwest and relate these to the tectonics of western North America. Ray Wells, a US Geological Survey geologist who is an expert on the tectonics and earthquake hazards of the Pacific Northwest, used paleomagnetic and GPS observations to determine how crustal blocks of this region slide past each other along boundaries marked by earthquake zones and how rocks of some blocks are faulted and folded as they are squeezed between blocks of stronger crust. The resulting earthquakes that occur on crustal faults near or immediately beneath densely populated cities of Oregon, Washington, and British Columbia are a major risk.