The Aleutian Islands lie near a convergent plate boundary where the Pacific Plate meets the North American Plate. The location where the plates converge is marked on the ocean floor by the Aleutian Trench. The Pacific Plate dives beneath the North American Plate along the Aleutian subduction zone which extends for approximately 4,000 km. The subduction zone is a large thrust fault capable of generating large megathrust earthquakes, sometimes tsunamigenic. The 1946 Aleutian Islands earthquake and 1964 Alaska earthquake, measuring 8.6 and 9.2 respectively.