 A high rate of sedimentation from the outflow of the three major rivers (Fraser River, Columbia River, and Klamath River) which cross the Cascade Range contributes to further obscuring the presence of a trench.However, in common with most other subduction zones, the outer margin is slowly being compressed, similar to a giant spring.When the stored energy is suddenly released by slippage across the fault at irregular intervals, the Cascadia subduction zone can create very large earthquakes, such as the 8.7–9.2 Cascadia earthquake of 1700.