1. The land and its features

The United States offers a varied mosaic of landform types— broad plains, rolling hills, rugged plateaus, and majestic moun­tains. Such diversity offers many opportunities for different types of land use and economic development.

1. Mountains and Valleys of the Pacific Region

The Pacific region extends from California to Alaska and includes Hawaii. It is home to the country’s greatest mountain ranges, its highest (and “tallest”) mountains, and some of the continent’s most stunning scenery. Here, all three of nature’s land-building processes—volcanism, faulting, and folding—are at work. It is also a region in which the agents of erosion—gla­ciers and swift-flowing streams, in particular—have sculpted spectacular physical landscapes.

Volcanic activity created the Hawaiian Islands; Alaska’s Aleutian Islands and many of its mountains; and the Cascades of northern California and western Oregon and Washington. Volcanism is an ongoing process in each of these regions. Hawaii’s highest peak, Mauna Kea, rises about 20,000 feet (6,096 meters) from the Pacific floor and reaches an elevation of 13,796 feet (4,205 meters) above sea level. Measured from base to peak, it spans a distance of almost 34,000 feet (10,360 meters), making it the world’s “tallest” mountain.

On the mainland, hills and low mountains form a series of coastal ranges. Many of these features are the result of geologic folding, formed by the colliding Pacific and North American tectonic plates. Moving inland, uplands give way in several locations to fertile valleys that rank among the country’s most productive agricultural areas. They include the Imperial Valley and Central Valley (formed by the combined San Joaquin and Sacramento valleys) in California, Oregon’s Willamette Valley, and the lowlands that border Washington’s Puget Sound.

A series of high mountain ranges that are part of the Pacific “Ring of Fire” extend from California northward to Alaska and continue into Asia. This region is a zone of geologic instability that includes all lands bordering the Pacific. As the Pacific and other tectonic plates crunch and grind away, they are respon­sible for more than 80 percent of the world’s seismic and volcanic activity.

The Sierra Nevada, central California’s towering “back­bone,” is an excellent example of an uplifted fault block range. From its crest, the forest-covered western slope drops gradually over a distance that averages about 80 miles (130 kilometers). The upward-thrust eastern edge of the range features majestic Mount Whitney, a 14,494-foot (4,418-meter) peak that is the highest point in the adjoining 48 states. The eastern slope of the Sierra offers spectacular scenery as it drops more than 14,000 feet (4,267 meters) in a distance of only several miles. Incredibly, about 60 miles (100 kilometers) east of Mount Whitney, Death Valley plunges to a depth of 282 feet (86 meters) below sea level. This is not only the lowest spot of dry land in the Western Hemisphere; it is the third-lowest point of dry land on Earth!

Many of Alaska’s towering mountains also are of fault block origin, including the Alaska Range. Here, buried beneath a mantle of snow and glacial ice, Mount McKinley (also called Denali) is North America’s highest peak. No mountain can match McKinley’s local relief, thereby making it the world’s “tallest” (although not the highest) and one of the most imposing peaks above sea level. From a base near sea level, it soars to an elevation of 20,320 feet (6,194 meters) in a distance of about 20 miles (32 kilometers).

Beginning in northern California and extending northward into Washington are the volcano-formed Cascades. The highest peak is spectacular snowcapped Mount Rainier, which rises 14,410 feet (4,392 meters) above the surrounding lowlands. In 1980, the violent eruption of Washington’s Mount St. Helens was a stark reminder that the Cascades remain a very active volcanic range.