Mount St. Helens Before 1980

Even before its recent loss of height, Mount St. Helens was not one of the highest peaks in the Cascade Range. Its summit altitude of 9,677 feet made it only the fifth highest peak in Washington. It stood out handsomely, however, from surrounding hills because it rose thousands of feet above them and had a perennial cover of ice and snow. The peak rose more than 5,000 feet above its base, where the lower flanks merge with adjacent ridges. The mountain is about 6 miles across at its base, which is at an altitude of about 4,400 feet on the northeastern side and about 4,000 feet elsewhere. At the pre-eruption timberline (upper limit of trees), the width of the cone was about 4 miles.

Mount St. Helens is 34 miles almost due west of Mount Adams, which is in the eastern part of the Cascade Range. These "sister and brother" volcanic mountains are each about 50 miles from Mount Rainier, the giant of Cascade volcanoes. Mount Hood, the nearest major volcanic peak in Oregon, is about 60 miles southeast of Mount St. Helens.

Mount St. Helens was named for British diplomat Alleyne Fitzherbert (1753-1839), whose title was Baron St. Helens. The mountain was named by Commander George Vancouver and the officers of H.M.S.Discovery while they were surveying the northern Pacific coast from 1792 to 1794.

Mount St. Helens was recognized as a volcano at least as early as 1835; the first geologist apparently viewed the volcano 6 years later. James Dwight Dana of Yale University, while sailing with the Charles Wilkes U.S. Exploring Expedition, saw the peak (then quiescent) from off the mouth of the Columbia River in 1841. Another member of the expedition later described "cellular basaltic lavas" at the mountain's base.

Although Mount St. Helens is in Skamania County, the best access routes to the mountain run through Cowlitz County on the west. State Route 504, ... connects with the heavily traveled Interstate Highway 5, about 34 miles to the west. That major north-south highway skirts the low-lying cities of Castle Rock, Longview, and Kelso along the Cowlitz River and passes through Vancouver, Washington - Portland, Oregon, metropolitan area less than 50 miles to the southwest. The community nearest the volcano is Cougar, which is in the Lewis River valley about 11 miles south-southwest of the peak. Guifford Pinchot National Forest surrounds Mount St. Helens, but some land on the mountain and much of the area adjacent to the national forest are Washington State lands or are privately owned.

Streams that head on the volcano enter three main river systems -- the Toutle River on the north and north-west, the Kalama River on the west, and the Lewis River on the south and east. The streams are fed by abundant rain and snow that dump an average of about 140 inches of water on Mount St. Helens a year, according to National Weather Service data. The Lewis River is impounded by three dams for hydropower generation. The southern and eastern sides of the volcano drain into an upstream impoundment, the Swift Reservoir, which is directly south of the volcano. The streams that drain the mountain also are somewhat regulated naturally by the mountain's perennial snowfields and glaciers. Water is stored as snow and ice during the cool, wet periods and is released as melt water during warmer, drier periods.

Water-related recreation has been one of the major activities in the area. All three reservoirs on the Lewis River have been used extensively for recreation, as was Spirit Lake before 1980. Before the eruption, Spirit Lake was impounded in the North Fork Toutle River valley by a natural dam formed chiefly of deposits from one or more ancient mudflows. The principle resource of the region is timber, and many areas near the volcano had been logged recently and were still being logged at the beginning of the 1980 eruptive activity.

Mount St. Helens, like most other Cascade volcanoes, is a great cone of rubble consisting of lava rock interlayered with pyroclastic and other deposits. Volcanic cones of this internal structure are called composite cones or stratovolcanoes. Mount St. Helens includes layers of basalt and andesite through which several domes of dacite lava have erupted. The largest of the dacite domes formed the previous summit; another formed Goat Rocks on the northern flank.