Zigzag Glacier is an alpine glacier on Mount Hood’s upper southwest slopes in Oregon, lying mostly within the Mount Hood Wilderness. It extends from about 10,200 feet down to 7,200 feet, with lower fingers reaching nearby canyons at roughly 6,400 feet. Beginning at the foot of Crater Rock, it is separated from Reid Glacier by Illumination Rock and also adjoins Palmer Glacier. Its seasonal snowfield can vary greatly, changing in length by nearly two miles. The glacier feeds the Zigzag River, which carved steep-walled Zigzag Canyon, and in 1922 a sudden debris-laden outburst flow on its surface briefly raised fears that Mount Hood was erupting.