The Big Drift is in Glacier National Park, 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 Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

 and is an area along the Going-to-the-Sun Road

Going-to-the-Sun Road

Going-to-the-Sun Road is the only road through the heart of Glacier National Park in Montana, USA. It was completed in 1932, and it is the only road that crosses the park, going over the Continental Divide at Logan Pass. A fleet of 1930s red tour buses "jammers", rebuilt in 2001 to run on propane...

 where a large amount of winter snow can accumulate to depths of 80 feet (24.4 m). Located immediately east of Logan Pass

Logan Pass

Logan Pass is located along the Continental Divide in Glacier National Park, in the U.S. state of Montana. It is the highest point on the Going-to-the-Sun Road....

, the westerly winds push snow over the crest of the Continental Divide onto the eastern flank of a long arête

Arete

Areté is the term meaning "virtue" or "excellence", from Greek ἈρετήArete may also be used:*as a given name of persons or things:**Queen Arete , a character in Homer's Odyssey.***197 Arete, an asteroid....

 which extends south from Pollock Mountain

Pollock Mountain

Pollock Mountain is located in the Lewis Range, Glacier National Park in the U.S. state of Montana. Pollock Mountain is situated along the Continental Divide and is one of the peaks along the Garden Wall and is approximately south of Bishops Cap....

. West of the divide, this arête is known as the Garden Wall

Garden Wall

The Garden Wall is a steep alpine area within Glacier National Park well known during the summer months to be heavily covered in dozens of species of flowering plants and shrubs...

.

As spring approaches, the region is surveyed by helicopter in preparation for snow removal

Snow removal

Snow removal is the job of removing snow after a snowfall to make travel easier and safer. This is done by both individual households and by governments and institutions.-De-icing and anti-icing:...

 that will be needed in order to reopen the Going-to-the-Sun Road for the summer season. By early April, snow removal crews working from either end of the 53 miles (85.3 km) roadway have begun to ascend the steeper east and west slopes of the Lewis Range

Lewis Range

The Lewis Range is a mountain range located in the Rocky Mountains of northern Montana, U.S. and extreme southern Alberta, Canada. Formed by the Lewis Overthrust beginning 170 million years ago, an enormous slab of Precambrian rocks 3 miles thick, wide and long faulted and slid over newer...

. The area of the Big Drift is usually reached by late May, and it often can take a month to clear this one stretch of road that is slightly more than 1 miles (1.6 km) in length. Survey crews identify avalanche

Avalanche

An avalanche is a sudden rapid flow of snow down a slope, occurring when either natural triggers or human activity causes a critical escalating transition from the slow equilibrium evolution of the snow pack. Typically occurring in mountainous terrain, an avalanche can mix air and water with the...

 hazards and help to locate the road using global positioning equipment. Large cornices

Cornice (climbing)

A snow cornice or simply cornice is an overhanging edge of snow on a ridge or the crest of a mountain. They form by wind blowing snow over the crest of the mountain, so they often form on the leeward sides of mountains...

 are usually removed using explosives, then excavators and front-end loaders move the snow over the cliffsides or into dump truck

Dump truck

A dump truck is a truck used for transporting loose material for construction. A typical dump truck is equipped with a hydraulically operated open-box bed hinged at the rear, the front of which can be lifted up to allow the contents to be deposited on the ground behind the truck at the site of...

s. The entire Going-to-the-Sun Road takes about ten weeks to plow, even with equipment that can move 4000 short tons of snow an hour. By the first of June of each year, the Logan Pass visitor center can usually be reached by vehicle from at least one side of the Continental divide. In 2011, due to abnormally heavy late winter and early spring snowfall, the Going-to-the-Sun Road did not open until July 13th, the second latest opening ever.