Definition of atom. 1  1a : the smallest particle of an element that can exist either alone or in combination an atom of hydrogenb : the atom considered as a source of vast potential constructive or destructive energy â¦ a largely forgotten legacy of this country's conquest of the atom.
The mountain, a part of the Cascade Range, is a volcano that has not erupted for 2,000 years. It is also the highest mountain in the state of Washington. English explorer George Vancouver named Mount Rainier in honor of another navigator, Peter Rainier. Some people, however, prefer to call the mountain by its Indian name, Mount Tacoma.
More recently, researchers have charted its mudflows and traced the ash around it. Mount Rainier's new scientific profile lacks the mysticism of legend, but it retains much of its mystery and power. Unlike Mount St. Helens, a young spud of the Cascade range at 40,000 years of age, Rainier is a half-million years old. St. Helens is a tidy mountain, a nearly symmetrical cone until 1980, having been built by alternating layers of lava, ash and volcanic debris.