There are few natural landscapes more inspiring than a lone peak or isolated cluster of mountains that tower above the surrounding terrain. In some cases, this topography results from an especially hardened rock formation that has resisted the erosive forces of water, wind and ice. Mt. Monadnock, in southwest New Hampshire, provides an excellent example; composed of metamorphosed sediments from the Silurian and Devonian Periods, this mountain has withstood the advance and retreat of the Pleistocene Glaciers.
Many of our isolated peaks are volcanic in origin, rising above expanding chambers of magma and coated by recurrent lava flows or explosive eruptions. The massive volcanic domes of the Cascades are best known but volcanic peaks are also widespread in the Southwest; Sierra Grande, a dormant stratovolcano in northeast New Mexico, Mt. Taylor, west of Albuquerque, and the San Francisco Mountains, north of Flagstaff, are a few examples.
Finally, many of our natural monoliths developed beneath the surface, extruded as magma within layers of sedimentary rock. Later, as the terrain was lifted and the encasing sediments eroded away, these plutons or laccoliths were uncovered and now tower above their surroundings; Stone Mountain, near Atlanta, and Devil's Tower, in eastern Wyoming, are famous examples. Laccolithic mountains are especially common across the Colorado Plateau; these include Sleeping Ute Mountain in southwest Colorado and the La Sals, Abajo Mountains and Henry Mountains of southeast Utah. Shiprock, in northwest New Mexico, also developed from a column of underground magma before it rose with the Plateau and was unveiled by erosion.
