Jurassic.—The middle one of the three periods of the Mesozoic era of geologic time.
Lava.—An igneous rock which in molten condition has poured out upon or close to the earth’s surface, e.g. basalt.
Limestone.—A sedimentary rock consisting essentially of carbonate of lime which generally represents accumulation of shells of organisms, but in some cases precipitates from solution. Often impure.
Loess (pronounced lurse with the r obscure).—A fine homogeneous silt or loam showing usually no division into layers and forming thick and extensive deposits in the Mississippi Valley and in China. It is generally regarded as in part at least a deposit of wind-blown dust.
Marble.—A crystalline limestone, usually a metamorphic rock, the limestone having been altered by heat, pressure, and moisture within the earth.
Meander.—To flow in serpentine curves. A loop in a stream. Most streams in flowing across plains develop meanders.
Mesa.—A flat-topped hill or mountain left isolated during the general erosion or cutting down of a region.
Mesozoic.—Next to the present era of geologic time.
Metamorphic Rock.—Any igneous or sedimentary rock which has undergone metamorphism, that is notable alteration from its original condition. (See [Metamorphism].)