<P> The Aleutian Trench (or Aleutian Trough) is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands . The trench extends for 3,400 km from a triple junction in the west with the Ulakhan Fault and the northern end of the Kuril--Kamchatka Trench, to a junction with the northern end of the Queen Charlotte Fault system in the east . It is classified as a "marginal trench" in the east as it runs along the margin of the continent . The subduction along the trench gives rise to the Aleutian arc, a volcanic island arc, where it runs through the open sea west of the Alaska Peninsula . As a convergent plate boundary, the trench forms part of the boundary between two tectonic plates . Here, the Pacific Plate is being subducted under the North American Plate at a dip angle of nearly 45 ° . The rate of closure is 3 inches (76 mm) per year . </P> <P> The north side of the trench slopes 3 °--4 ° and the south side 1 °--4 ° . The deepest part of the Aleutian trench has been measured at 7,822 metres (25,663 ft) at 51.21 ° N, 174.83 ° E., located about 145 km SSW of Buldir Island . </P>

What type of plate boundary is the aleutian islands