Western Oregon 's mountainous regions , home to three of the most prominent mountain peaks of the United States including Mount Hood , were formed by the volcanic activity of the Juan de Fuca Plate , a tectonic plate that poses a continued threat of volcanic activity and earthquakes in the region . The most recent major activity was the 1700 Cascadia earthquake . Washington 's Mount St. Helens erupted in 1980 , an event visible from northern Oregon and affecting some areas there
erupted in 1980
1980 eruption of Mount St. Helens
Oregon