Sisters Country Geologic History

Global subduction, rifting and movement of plates has continued through all Earth history and continues today. Off the coast of the Pacific Northwest , a spreading ridge (red) separates the Pacific Plate moving to the northwest from the Farallon Plate , moving to the southeast. The once immense Farallon Plate is now almost completely subducted beneath Oregon. Three trailing remnants remain—the Gorda, Juan de Fuca, and Explorer microplates. The melting, assimilation, and subsequent eruption of subducted slab material has influenced Oregon geology for millions of years.

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