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Explorer Ridge
The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer Plate, which together with the Juan de Fuca Plate and the Gorda Plate to its south, is what remains of the once-vast Farallon Plate which has been largely subducted under the North American Plate. The Explorer Ridge consists of one major segment, the Southern Explorer Ridge, and several smaller segments. It runs northward from the Queen Charlotte Triple Junction, a point where the Nootka Fault, the Sovanco Fracture Zone and the Juan de Fuca Ridge meet.
==Geology==
This divergent boundary first formed about 5-7 million years ago when the northern end of the Juan de Fuca Plate broke off along the Nootka Fault to form the Explorer Plate. This apparently had some important ramifications for regional geologic evolution. When this change was completed, Cascade Arc volcanism from Northern California to southwestern British Columbia returned and the present-day Cascade Range and Olympic Mountains started to form.〔(The Cascade Episode ) Retrieved on 2008-06-10〕
The oceanic crust is moving away from the Explorer Ridge to either side. On the eastern side the eastward moving Explorer Plate is being subducted under the North American Plate. The belt of volcanoes along the Pacific Ranges are the direct results of this collision. The western side of the Explorer Ridge is associated with the northwest trending Pacific Plate which has formed the Queen Charlotte Fault, an active transform fault along the coast of British Columbia and southeast Alaska.
The Explorer Ridge is also seismically active. Most seismicity recorded in this area occurred on or near the Explorer Transform Fault Zone. The relatively shallow depth of the Southern Explorer Ridge (up to 1800 m) in comparison with most other segments of the northeast Pacific spreading centers suggests that there has been considerable volcanic activity along this segment in the past 100,000 years.〔(NOAA Ocean Explorer: Submarine Ring of Fire ) Retrieved on 2008-06-16〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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