The removal of the north side of the mountain reduced St. Helens ' height by about 1,300 feet ( 400 m ) and left a crater 1 mile ( 1.6 km ) to 2 miles ( 3.2 km ) wide and 0.5 miles ( 800 m ) deep , with its north end open in a huge breach .
The collapse of the north side of the volcano shortened St. Helens ' height by about 1,300 feet ( 400 m ) and left a volcanic crater one to two miles ( 1.6 to 3.2 km ) wide and half of a mile ( 800 m ) deep .