 However, their tectonic origins are largely unexplained and are a matter of going research.When the Farallon Plate ruptured to create the Nootka Fault between five and seven million years ago, there were some apparent changes along the Cascadia subduction zone.At issue is the current plate configuration and rate of subduction but based on rock composition is for Silverthrone Caldera and Franklin Glacier Complex to be subduction related.