Geology or Related Geological Terms +

(a glossary, or dictionary, of terms used in geology; the science of the earth including its origin, composition, structure, and history)

A naturally occurring fine-grained white or light-colored translucent form of gypsum that is often streaked or mottled (spotted or blotched with different shades or colors).

A soft material which is easily carved but seldom used for outdoor sculpture.

alga (s), algae (pl)
Aquatic protistan organisms that include many lime-secreting kinds.
Pertaining to algae; such as, algal limestones and reefs, largely formed by algae; algal structure, generally laminated crusts, ooids, and pisoids; some of which may be inorganic.
Precambrian granite of the Canadian Shield region, post-Timiskamingian in age, classified as Archean.
The main division of late Precambrian time and rocks (equivalent to Proterozoic).
allochthonous coal
A type of coal arising from accumulations of plant debris moved from their place of growth and deposited elsewhere.
1. A rock that was transported a great distance from its original deposition by some tectonic process; generally related to over thrusting, recumbent folding, or gravity sliding.
2. A large displaced body of rocks; such as, a rock mass that has moved a considerable distance by thrust faulting; the opposite of autocthon.
1. A reference to rocks whose primary constituents have not been formed in their natural or original places.
2. Material that is formed or introduced from somewhere other than the place it is presently found.
Pertaining to alluvium (relating to, consisting of, or formed by sediment deposited by flowing water); such as, alluvial cones, fans (gravel and associated sediments deposited), plains, etc.
alluvium (s), alluvia (pl)
Unconsolidated detrital deposits ranging from clay to gravel sizes, generally poorly sorted, typically fluviatile (river or stream) in origin.
alternation of generations
Succession of sexually and asexually formed groups of offspring belinging to a given species of organisms; such as, microspheric and megalospheric foraminifers, polyps, and medusa stages of some coelenterates (invertebrate lacking a backbone or spinal column), etc.

Coelenterates are radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms.

Moderately large early Paleogene hoofed mammal with blunt, elephant-like feet, small brain case, and unspecialized teeth.
A variety of quartz, colored violet by the presence of small quantities of impurities; such as, manganese or iron; used as a semiprecious stone.

Amethysts are found chiefly in the Ural Mountains, India, the United States, Uruguay, and Brazil.

Extinct late Paleozoic or Mesozoic cephalopod distinguised mainly by the complexity of the suture pattern of the shell.
Externally shell-covered cephalopod characterized by strongly curved, angulated, or complex suture patterns and generally by the position of the siphuncle inside the shell differing from that of nautiloids; includes ammonites, ceratites, and goniatites.

Index of additional Scientific and Technological Topics.