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joint, in geology

(Encyclopedia)joint, in geology, fracture in rocks along which no appreciable movement has occurred (see fault). Nearly vertical, or sheet, joints that result from shrinkage during cooling are commonly found in ign...

sandstone

(Encyclopedia)sandstone, sedimentary rock formed by the cementing together of grains of sand. The usual cementing material in sandstone is calcium carbonate, iron oxides, or silica, and the hardness of sandstone va...

Fletcher, John Gould

(Encyclopedia)Fletcher, John Gould, 1886–1950, American poet, b. Little Rock, Ark., educated (1903–7) at Harvard. After traveling throughout Europe, he became a leader of the imagists in England. His early coll...

Arches National Park

(Encyclopedia)Arches National Park, 76,519 acres (30,979 hectares), E Utah; est. as a national monument 1929, designated a national park 1971. Located in red-rock country and overlooking the gorge of the Colorado R...

Tiruchirapalli

(Encyclopedia)Tiruchirapalli trĭchĭnŏˈpəlē [key], city (1991 pop. 711,862), Tamil Nadu state, SE India, on the Kaveri River. It is a district administrative center and an important educational, religious, and...

Pennebaker, D. A.

(Encyclopedia)Pennebaker, D. A. (Donn Alan Pennebaker), 1925–2019, pioneering documentary filmmaker, b. Evanston, Ill. His first film, Daybreak Express (1958), is a five-minute short detailing New York's doomed T...

concretion

(Encyclopedia)concretion, mass or nodule of mineral matter, usually oval or nearly spherical in shape, and occurring in sedimentary rock. It is formed by the accumulation of mineral matter in the pore spaces of the...

Cashel

(Encyclopedia)Cashel kăˈshəl [key] [Irish,=castle], town, Co. Tipperary, S central Republic of Ireland. ...

talus

(Encyclopedia)talus tāˈləs [key], deposit of rock fragments detached from cliffs or mountain slopes by weathering and piled up at their bases. A talus is a common geologic feature in regions of high cliffs. The ...

quartzite

(Encyclopedia)quartzite, usually metamorphic rock composed of firmly cemented quartz grains. Most often it is white, light gray, yellowish, or light brown, but is sometimes colored blue, green, purple, or black by ...