A volcanic arc forms along the northwest coast of North America due to subduction

When the Mountain Dwarfs Danced: Aboriginal Traditions of Paleoseismic Events along the Cascadia Subduction Zone of Western North America. 2002. https://doi.org/10.1215/00141801-49-1-41

Geological evidence demonstrates that recurrent great earthquakes have been generated at the Cascadia subduction zone, off the west coast of North America, throughout the Holocene. Such major earthquakes and associated tsunamis would have had devastating impacts on Native villages along this coastline. Native oral traditions of such disasters, along with earthquake figures in myth and ceremony, are examined for evidence of the nature of such past geological events and the impact they had on human populations.

Sr-Nd-Hf-Pb isotope and trace element evidence for the origin of alkalic basalts in the Garibaldi Belt, northern Cascade Arc. 2014. https://doi.org/10.14288/1.0075981

In the Garibaldi Belt, the northern segment of the Cascade arc, basalts at Bridge River Cones, Salal Glacier, and Mt. Meager (BSM volcanic centers) are alkalic, atypical for an arc setting. Subduction signatures are negligible or absent from primitive alkalic basalts from Salal Glacier and Bridge River, while altered oceanic crust may have contributed a minimal amount of fluid at Mt. Meager. More evolved BSM basalts display trace element signatures considered typical of arc lavas, but this is a consequence of deep crustal assimilation rather than primary input from the subducted slab. Primary BSM basalts represent 3–8% melts that segregated from enriched garnet lherzolite at significantly higher temperatures and pressures (70–105 km) than calc-alkaline Cascade arc basalts. The BSM mantle source is significantly more incompatible element-enriched than the depleted mantle tapped by calc-alkaline Cascade arc basalts. The BSM basalts are also isotopically distinct from calc-alkaline Cascade arc basalts, more similar to MORB and intraplate basalts of the NE Pacific and NW North America. The relatively deep, hot, and geochemically distinct mantle source for BSM basalts is consistent with upwelling asthenosphere. The BSM volcanic centers are close to the projected trace of the Nootka fault, which forms the boundary between the subducting Juan de Fuca plate and the near-stagnant Explorer plate. A gap or attenuated zone between the plates may promote upwelling of enriched asthenospher

Proceedings of Workshop XLIV: Geological, Geophysical, and Tectonic Setting of the Cascade Range. 1989. http://cdm17267.contentdm.oclc.org/cdm/ref/collection/geoheat/id/4554

The Cascade Range is an active volcanic arc that is formed by the continuing subduction of the Juan de Fuca plate system beneath North America. Understanding of the Cascade Range and its tectonic setting is not only of broad scientific interest, but also is important for the assessment of geothermal resources and the evaluation of volcanic and seismic hazards

Episodic Tremor and Slip on the Cascadia Subduction Zone: The Chatter of Silent Slip. 2003. https://doi.org/10.1126/science.1084783

We found that repeated slow slip events observed on the deeper interface of the northern Cascadia subduction zone, which were at first thought to be silent, have unique nonearthquake seismic signatures. Tremorlike seismic signals were found to correlate temporally and spatially with slip events identified from crustal motion data spanning the past 6 years. During the period between slips, tremor activity is minor or nonexistent. We call this associated tremor and slip phenomenon episodic tremor and slip (ETS) and propose that ETS activity can be used as a real-time indicator of stress loading of the Cascadia megathrust earthquake zone.