As if huddled in self-defense, a massive group of domes rises at the center of a vast encircling plain. In the heart of the central Australian desert, a cluster of massive, humpbacked rocks looms against the horizon. They create a slightly eerie spectacle—some 30 giant, smoothly rounded domes huddled in the midst of a vast empty plain. The highest of the group is Mount Olga, rising some 1,500 feet (460 meters) above its surroundings and 3,507 feet (1,069 meters) above sea level.
Named for the Queen of Spain by the Australian explorer Ernest Giles, who first sighted them in 1872, Mount Olga and its massive companions are known collectively as the Olgas. The group occupies an area of about 11 square miles (28 square kilometers).
From a distance the Olgas at first appear only as a vague, bluish silhouette obscured by haze on the horizon. From closer vantage points, however, the individual rocky masses take form, and their true red and reddish-yellow colors become apparent. Fringed by meager vegetation, they are especially beautiful in spring, when they are set off by a brief but brilliant display of wildflowers.
Along with famed Ayers Rock, located some 20 miles (32 kilometers) to the east, the Olgas are protected in an Australian national park and are visited by people on holidays by the thousands. And like Ayers Rock, they are spectacular examples of what geologists call inselbergs (from a German term meaning “island mountains”).
The Olgas are composed of durable conglomerate, which is a type of rock made up of pebbles and boulders that are fused together much like cemented gravel. Formed approximately 400 million years ago, the mass of rock was subsequently uplifted and folded by movements in the earth’s crust. It was then subjected to alternating periods of moist and dry climates and was gradually dissected into its present pattern of freestanding domes by wind and water erosion.
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