Aleutian subduction zone

[4] Debris flows and turbidity currents transported igneous materials from volcanic source to shallow marine basins.

There are Quaternary volcanoes on the north of the Aleutian Islands structural axis, which is composed of andesite mostly, mixed with olivine basalt to rhyolite.

[6] A hypothesis suggests that the northward movement of the Pacific Plate ended ~66-56 my, and the underthrusting of oceanic crust created the Aleutian trench.

The tensional hypothesis suggests that island arc loading caused the oceanic crust to create downward faulting.

In other words, the trench was a part of oceanic crust once, but faulted down at depth due to the loading of island arc.

The compressional hypothesis suggests that mantle convection or drag prevented oceanic crust from reaching isostatic equilibrium, because the imbalance was not adjusted in a relatively short amount of time.

[6] There is a high supply of sediment from turbidity currents, slumps, and creeps into the eastern portion of the Aleutian trench.

[9] Most of the major crustal faults found in the overriding Aleutian island arc are pre-Pleistocene, although precise dating has not been achieved.

This may be because the depths at which the hydrous minerals release water and produce tremors are greater when the plate is older, colder, and subducting faster.