Queen Charlotte Triple Junction

The Queen Charlotte Triple Junction is a geologic triple junction where three tectonic plates meet: the Pacific Plate, the North American Plate, and the Explorer Plate. The three plate boundaries which intersect here are the Queen Charlotte Fault, the northern Cascadia subduction zone, and the Explorer Ridge. The Queen Charlotte triple junction is currently positioned adjacent to the Queen Charlotte Sound near the Dellwood Knolls off the coast of Vancouver Island.^[1] 10 Ma to 1.5 Ma prior to the triple junction's current location, it was located southwest of Vancouver Island ^[1] The movements of the triple junction have been characterized by two major shifts in the Pacific-North American Tertiary plate tectonic record. First, at approximately 40 Ma the relative plate motions switched from orthogonal convergence to right-lateral strike slip. The variance in location of the triple junction may have also been related to the formation of an independent basin block.^[1] This formation could have been produced by fore-arc bending of the Pacific Plate, due to oblique underthrusting prior to 1 Ma which produced stresses sufficient to break the Pacific Plate and isolate the block. Transpression of 15–30 mm/yr since 5 Ma has been taking place, as well as varying amounts of both transpression and transtension occurring before then.^[2] To the northwest of the triple junction the Pacific plate currently has 15 degrees of oblique convergence, passing under the North American plate along the Queen Charlotte transform fault zone.^[3] The Explorer plate is a small chunk of the Juan de Fuca plate that broke away from the Juan de Fuca Plate about 3.5 Ma and has moved much slower with respect to North America.^[3]