Brooks Range
The Brooks Range is a rugged mountain chain spanning approximately 700 miles (1,100 km) east-west across northern Alaska, from the Chukchi Sea coast to the Yukon Territory border, serving as a physiographic divide between the Arctic coastal plain to the north and the Yukon River basin to the south.[1][2] Its highest peak, Mount Isto in the Romanzof Mountains, reaches 8,976 feet (2,736 m).[3] Named in 1925 by the U.S. Board on Geographic Names after Alfred Hulse Brooks, a pioneering USGS geologist who surveyed Alaska's mineral resources, the range features sharp glacial cirques, U-shaped valleys, and exposed bedrock from extensive Pleistocene glaciation, which covered much of the area unlike the ice-free interior lowlands.[4] Much of the Brooks Range lies within protected areas, including Gates of the Arctic National Park and Preserve, where its central and eastern segments exhibit diverse sedimentary rocks, granitic intrusions, and metamorphic terrains shaped by tectonic compression during the Mesozoic era.[4] Ecologically, the range supports Arctic tundra vegetation and serves as a critical corridor for wildlife migrations, notably the Porcupine caribou herd that traverses its slopes annually, alongside grizzly bears, Dall sheep, and wolves adapted to the short summers and prolonged winters with average elevations rising from 3,000 feet (900 m) in the west to over 8,000 feet (2,400 m) eastward.[1][5] The region's remoteness and harsh climate, with permafrost underlying vast areas, limit human access primarily to bush planes and foot travel, underscoring its role in preserving intact boreal and Arctic ecosystems amid broader debates over resource extraction in adjacent areas like the Arctic National Wildlife Refuge.[4][5]
Geography
Location and Extent
The Brooks Range is situated in northern Alaska, United States, forming the northernmost segment of the Rocky Mountains system in North America. It extends eastward from the northwestern Alaskan interior near the Chukchi Sea coast to the Alaska-Yukon Territory border, spanning approximately 700 miles (1,100 km) in an east-west orientation. This positioning places the range primarily between latitudes 67° N and 70° N, with longitudes ranging from about 168° W in the west to 141° W at the eastern boundary.[6] The range serves as a critical physiographic divide, separating the northward-draining Arctic Slope—which feeds rivers like the Colville and Canning into the Arctic Ocean—from the southward-flowing systems of the Yukon River basin. Its northern foothills transition into the flat Arctic coastal plain, while the southern slopes descend into broader plateaus and lowlands. Significant portions of the Brooks Range fall within protected areas, including Gates of the Arctic National Park and Preserve in the central section and the Arctic National Wildlife Refuge along the eastern flank.[2] In terms of width, the Brooks Range varies but generally measures 100 to 200 miles (160 to 320 km) north-south, with elevations rising abruptly from surrounding tundra and creating a formidable barrier to cross-range travel. The central and eastern sectors are more dissected and higher, while the western portions integrate with other ranges like the Baird Mountains.[6]Topography and Major Peaks
The Brooks Range displays rugged topography defined by jagged peaks, steep escarpments, and deeply incised valleys shaped by Pleistocene glaciation. U-shaped glacial valleys and cirque basins dominate the landscape, with persistent valley glaciers up to 6 miles (10 km) long originating from high cirques in the eastern sectors.[7] [4] Small ice caps and rock glaciers further characterize the higher elevations, particularly where permafrost underlies talus slopes and moraines.[8] Spanning roughly 700 miles (1,100 km) east-west from the Alaska-Yukon border to the Chukchi Sea coast, the range averages 100-150 miles (160-240 km) in north-south width and acts as a major physiographic divide between northward-draining Arctic rivers like the Colville and southward-flowing tributaries of the Yukon River.[1] Elevations rise progressively eastward, from 3,000-5,000 feet (900-1,500 m) in the western Endicott Mountains to over 8,000 feet (2,400 m) in the eastern Romanzof and Franklin Mountains, with broad plateaus dissected by river canyons in intervening areas.[9] The highest peaks cluster in the eastern Brooks Range. A 2015 airborne photogrammetry survey using fodar technology remeasured elevations, confirming Mount Isto in the Romanzof Mountains as the tallest at 8,975 feet (2,736 m).[10] This corrected prior USGS maps, which listed it at 9,050 feet and erroneously ranked Mount Chamberlin higher. The survey identified Mount Hubley at 8,916 feet (2,718 m) as second and Mount Chamberlin at 8,899 feet (2,714 m) as third, with no peaks exceeding 9,000 feet even accounting for annual snowpack variations of up to 3 feet.[10]| Peak | Elevation (ft) | Subrange |
|---|---|---|
| Mount Isto | 8,975 | Romanzof Mountains |
| Mount Hubley | 8,916 | Romanzof Mountains |
| Mount Chamberlin | 8,899 | Franklin Mountains |