(also geol)
11clay stone — Geol. argillite. Also, claystone. [1770 80] * * * …
12continental drift — Geol. the lateral movement of continents resulting from the motion of crustal plates. Cf. plate tectonics. [1925 30] * * * Large scale movements of continents over the course of geologic time. The first complete theory of continental drift was… …
13crustal plate — Geol. a large block or tabular section of the lithosphere that reacts to tectonic forces as a unit and moves as such. Also called plate. * * * …
14glacial drift — Geol. material, as gravel, sand, or clay, transported and deposited by a glacier or by glacial meltwater. Also called drift. Cf. till4. * * * …
15gravity fault — Geol. a fault along an inclined plane in which the upper side or hanging wall appears to have moved downward with respect to the lower side or footwall (opposed to reverse fault). Also called normal fault. * * * …
16ice age — Geol. (often caps.) the glacial epoch, esp. the Pleistocene Epoch. [1870 75] * * * or glacial age Any geologic period during which thick ice sheets cover vast areas of land. Such periods of large scale glaciation may last several million years… …
17index fossil — Geol., Paleontol. a widely distributed fossil, of narrow range in time, regarded as characteristic of a given geological formation, used esp. in determining the age of related formations. Also called guide fossil. [1895 1900] * * * any… …
18kettle hole — Geol. 1. a deep, kettle shaped depression in glacial drift. 2. pothole (def. 3). Also called kettle. [1880 85] * * * …
19mass wasting — Geol. downhill movement of soil and rock fragments induced by gravity. Also called wasting. * * * …
20remanent magnetism — Geol. magnetization in minerals induced by a former magnetic field and persisting after the field changes. Cf. paleomagnetism. [1865 70] * * * ▪ rocks also called Paleomagnetism, or Palaeomagnetism, the permanent magnetism in rocks,… …
