Unlike most subduction zones worldwide , there is no oceanic trench present along the continental margin in Cascadia . Instead , terranes and the accretionary wedge have been uplifted to form a series of coast ranges and exotic mountains . 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
Cascadia earthquake of 1700
1700 Cascadia earthquake
Cascade Volcanoes