The Zigzag Glacier is an alpine glacier located on the upper southwest slopes of Mount Hood

Mount Hood

Mount Hood, called Wy'east by the Multnomah tribe, is a stratovolcano in the Cascade Volcanic Arc of northern Oregon. It was formed by a subduction zone and rests in the Pacific Northwest region of the United States...

 in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

.
It ranges in elevation from 7,200 to 10,200 ft (2,200 to 3,100 m) with fingers in canyons extending to about 6,400 ft (1,953 m), and lies almost entirely within Mount Hood Wilderness

Mount Hood Wilderness

The Mount Hood Wilderness is a protected wilderness area inside the Mount Hood National Forest which is located in the U.S. state of Oregon. The area, covering , includes the peak of Mount Hood and its upper slopes, and ranges from temperate rain forests at the lower elevations, to glaciers and...

. The upper extent is divided from Reid Glacier by Illumination Rock. The top of the glacier is at the foot of Crater Rock.

The glacier is bounded on the east by a slight rise shared with the Palmer Glacier

Palmer Glacier

The Palmer Glacier is a glacier located on the upper slopes of Mount Hood in the U.S. state of Oregon. It is on the south side of the mountain ranging in elevation from about 6,200 to 9,300 ft , and was named for Joel Palmer, an Oregon pioneer...

 (a popular skiing area north of Timberline Lodge since the 1930s) and on the northwest by Reid Glacier. It is the source of the Zigzag River

Zigzag River

The Zigzag River is a tributary, about long, of the Sandy River in the U.S. state of Oregon. The Zigzag and one of its major tributaries, the Little Zigzag River, drain the Zigzag Glacier on Mount Hood, a high volcanic peak in the Cascade Range. Their waters flow westward to meet the Sandy River...

 which has eroded

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 a large, steep canyon

Canyon

A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...

 named Zigzag Canyon. Below the glacier, its snowfield varies significantly seasonally, varying in length by almost two miles (3.2 km).

In 1922, a Jökulhlaup

Jökulhlaup

A jökulhlaup is a glacial outburst flood. It is an Icelandic term that has been adopted by the English language. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland which are triggered by geothermal heating and occasionally by a volcanic subglacial...

originating from Zigzag Glacier as a flow of dark debris came out of a crevasse high on the glacier. It flowed on the surface more than 650 m (2100 ft) before entering another crevasse, and precipitated a minor panic by those who thought Mount Hood was erupting.