Chapter 2: Geographic Patterns of the Physical Environment

Alaska is part of four general physiographic regions, the Interior Plains, Rocky Mountains, Intermontane Basins and Ranges, and the Pacific Mountains and Valleys.The Pacific Mountains and Valleys adjoin the Pacific Ocean and constitute the area where most Alaskans live. This region is part of a greater North American system that extends from Mexico through the conterminous US and Canada and then arcs to form the northern boundary of the Pacific Ocean. Here we find the great mountains of Alaska, dominated by Mt. McKinley (20,320 feet; 6,194 meters) in the Alaska Range.


Between the two great mountain systems is the Intermontane Basin and Plateau region. This area contains highlands such as the Yukon-Tanana Uplands, the Kuskokwim Mountains, and the Ahklun Mountains. It also contains the largest river systems in Alaska—the Yukon, as well as the vast Yukon-Kuskokwim coastal lowlands that forms the delta region of the two rivers. 

Most of Alaska lies north of 600 meaning that sun angle (degrees above the horizon) is going to be fairly low. Consequently, incoming solar radiation will be limited making Alaska cold. Northern latitudes also experience great seasonal differences with long periods of summer light and long periods of little winter sunlight. In the case of our two examples, at Barrow the sun does not rise above the horizon from mid-November to late January whereas Ketchikan has over six hours of sunlight on December 21, its “shortest” day. On June 21, the sun reaches approximately 42 degrees above the horizon whereas in Ketchikan it is about 58 degrees above the horizon.

Figure PS.3 - Climatic Regions

The Mendenhall Glacier Alaska, which is located 13 miles from downtown Juneau, plays an important role in Alaska history. It was named after Thomas Corwin Mendenhall who served as Superintendent of the U.S. Coast and Geodetic Survey from 1889 to 1894.


The Mendenhall Glacier, Alaska extends for 12 miles from the Juneau Icefield to Mendenhall Lake. The ice from the glacier flows forward at an average rate of 2 feet per day. This impressive glacier was formed during a period known as the Little Ice Age, which began about 3,000 years ago. Fortunately, the unique climate and geography of Alaska allows glaciers to survive long after they began receding from other parts of North America.

Caribou at Mount McKinley, Denali National Park and Reserve, Alaska. (Jeff Vanuga/Corbis)

A mountain reflected on a small lake with wildflowers in the foreground. Wrangell - St. Elias National Park near Nebesna, Alaska.