The Cascadia Depression connects the two halves of the Blanco Transform Fault Zone . The depression is elongated , around 20 km in the NE-SW direction , but only about 8 km in the NW-SE direction . Roughly 500 m of sediments line the floor of the depression , mostly turbidites . Channels cut through the southern end of the depression are remnants of turbidity flows originating from the Missoula floods , but there are also signs of more recent , local turbidity currents . There is also evidence of active seafloor spreading in this zone , indicating that the Cascadia Depression likely became separated from one of the spreading ridges that border the Blanco Transform Fault Zone
Missoula floods
Missoula Floods
Blanco Fracture Zone