Brooks Range

The Brooks Range, known in Gwich'in as Gwazhał, is a massive mountain range in far northern North America.

It stretches from west to east across northern Alaska and into the Yukon Territory of Canada. In the United States, these mountains are classified as a subrange of the Rocky Mountains. However, Canadian geography views them as a separate entity. This is because the official northern border of the Rocky Mountains is considered to be the Liard River in British Columbia. The range is incredibly ancient, with an estimated age of approximately 126 million years.

Geologically, the Brooks Range serves a critical role as a drainage divide. It is the northernmost drainage divide in North America. This means the mountains separate streams that flow into the Arctic Ocean from those that flow toward the North Pacific. The range also acts as a physical boundary for the Arctic front during the summer. It represents the northern limit of the tree line. Most trees cannot grow north of this continental drainage divide. You might find isolated stands of balsam poplar or black spruce in certain areas. However, trembling aspen and white spruce are usually limited to sites disturbed by human activity.

The mountains are a vital habitat for many species of wildlife. They are home to Dall sheep, grizzly bears, black bears, gray wolves, and moose. The range is also a major corridor for caribou migrations. The Western Arctic Caribou herd, which numbered 490,000 in 2004, traverses these mountains every year. The Central Arctic herd, numbering 32,000 in 2002, also uses the range. Additionally, the Porcupine Caribou herd, consisting of 123,000 animals, migrates through the mountains. The migration path of the Porcupine Caribou is the longest of any terrestrial mammal on Earth.

Because the rocks in the range were once part of an ancient seabed, they contain many fossils. These marine organisms provide a record of the region's deep history. You can find fossilized corals in the sandy limestones of the Central Brooks Range.

Scientists have also discovered trilobites and brachiopods from the middle Cambrian period. In the western part of the range, near the Wulik River, lies the Red Dog mine. This is currently the largest zinc mine in the world. Other fossils, such as the remains of a woolly mammoth that died 17,100 years ago, have been found north of the range.

Human history in the range involves both exploration and industry. The range was officially named in 1925 by the United States Board on Geographic Names. It was named after Alfred Hulse Brooks, who was the chief USGS geologist for Alaska from 1903 to 1924. Before this, the mountains were known by several names, including the Arctic Mountains and the Meade Mountains. In 1929, explorer Bob Marshall traveled through the North Fork Koyukuk River area. He named Mount Doonerak, using an Eskimo word meaning "spirit" or "devil." He described the peak as a towering, black, unscalable-looking giant.

While much of the range is uninhabited, there are small pockets of human activity. The Dalton Highway and the Trans-Alaska Pipeline System run through the Atigun Pass. This pass sits at an elevation of 1,415 meters. These routes provide access to the oil fields at Prudhoe Bay on Alaska's North Slope. The only permanent settlements are the Alaska Native villages of Anaktuvuk and Arctic Village. There are also very small communities at Coldfoot, Wiseman, Bettles, and Chandalar. In the United States, much of the land is federally protected. This includes the Gates of the Arctic National Park, the Arctic National Wildlife Refuge, and the Noatak National Preserve.

The climate in the Brooks Range is changing due to global warming. Between 1969 and 2018, the Eastern and Western portions of the range saw a 17.2% increase in annual precipitation. This region experiences polar amplification, meaning it warms faster than other areas. The northern and western parts of Alaska are warming at twice the rate of southeastern Alaska. In the Brooks Range, average summer temperatures rose between 4.2 °F and 5.8 °F during that same period. This warming has a visible impact on the landscape. In 1985, there were 34 square miles of perennial snowfields. By 2017, that area had dropped to less than four square miles.