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hogback

(Encyclopedia)hogback, sharp-crested ridge with steep slopes on both sides, formed by the erosion of steeply tilted rock layers. Hogbacks are commonly formed along the eroded flanks of large, tightly folded anticli...

feldspar

(Encyclopedia)feldspar fĕlˈspär [key], an abundant group of rock-forming minerals which constitute 60% of the earth's crust. Chemically the feldspars are silicates of aluminum, containing sodium, potassium, iron...

amphibole

(Encyclopedia)amphibole ămˈfəbōlˌ [key], any of a group of widely distributed rock-forming minerals, magnesium-iron silicates, often with traces of calcium, aluminum, sodium, titanium, and other elements. The ...

Breuil, Henri

(Encyclopedia)Breuil, Henri äbāˈ [key], 1877–1961, French archaeologist, paleontologist, and cleric. He taught at the Institut de paléontologie humaine, Paris, after 1910. During much of his lifetime, Breuil ...

alpine plants

(Encyclopedia)alpine plants, high-altitude representatives of various flowering plants (chiefly perennials) that because of their dwarf habit, profuse blooming, and the preference of many for shady places are culti...

chromite

(Encyclopedia)chromite krōˈmīt [key], dark brown to black mineral. It is an iron-chromium oxide, FeCr2O4, with traces of magnesium and aluminum. Its crystals are octahedral, but rare; it usually occurs as irregu...

kame

(Encyclopedia)kame kām [key], low, steep, rounded hill or ridge of layered sand and gravel drift, developed from glacial deposits. Kames were probably formed by streams of melting glacial ice that deposited mud an...

Natural Bridges National Monument

(Encyclopedia)Natural Bridges National Monument, 7,636 acres (3,093 hectares), SE Utah; est. 1908. Located in an area of colored cliffs and box canyons, the monument contains three huge natural sandstone bridges: O...

Turner, Tina

(Encyclopedia) Turner, Tina 1939- , African American R&B and rock singer, b. Brownsville, Tn., as Anna Mae Bullock. Turner had a turbulent childhood, with her par...

Ashokan Reservoir

(Encyclopedia)Ashokan Reservoir əshōˈkən [key], 13 sq mi (34 sq km), SE N.Y., completed 1912. It is supplied by the Esopus and Schoharie watersheds and provides part of New York City's water supply. Water is ca...