Small+mantle
51Pearl — For other uses, see Pearl (disambiguation). Pearl Pearls General Category Mineral Chemical formula Ca …
52dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or …
53igneous rock — Any of various crystalline or glassy, noncrystalline rocks formed by the cooling and solidification of molten earth material (magma). Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary …
54metamorphic rock — Any of a class of rocks that result from the alteration of preexisting rocks in response to changing geological conditions, including variations in temperature, pressure, and mechanical stress. The preexisting rocks may be igneous, sedimentary,… …
55Plate tectonics — The tectonic plates of the world were mapped in the second half of the 20th century …
56Superior craton — in the west. The western margin extends from northern Minnesota through eastern Manitoba to northwestern Ontario.The formation of the Superior craton is best explained within the context of 2.72 2.68 Ga accretion of small continental plates and… …
57geology — /jee ol euh jee/, n., pl. geologies. 1. the science that deals with the dynamics and physical history of the earth, the rocks of which it is composed, and the physical, chemical, and biological changes that the earth has undergone or is… …
58moon — mooner, n. moonless, adj. /moohn/, n. 1. the earth s natural satellite, orbiting the earth at a mean distance of 238,857 miles (384,393 km) and having a diameter of 2160 miles (3476 km). 2. this body during a particular lunar month, or during a… …
59Moon — /moohn/, n. Sun Myung /sun myung/, born 1920, Korean religious leader: founder of the Unification Church. * * * Sole natural satellite of Earth, which it orbits from west to east at a mean distance of about 238,900 mi (384,400 km). It is less… …
60mountain — mountainless, adj. /mown tn/, n. 1. a natural elevation of the earth s surface rising more or less abruptly to a summit, and attaining an altitude greater than that of a hill, usually greater than 2000 ft. (610 m). 2. a large mass of something… …
