Geology or Related Geological Terms +

A substance used for cutting and polishing or for removing small amounts of the surface of hard materials. There are two types of abrasives, natural and artificial.

The hardness of abrasives is measured using the Mohs scale (available in this list), a scale used to measure the hardness of minerals, with talc at zero and diamond at ten. Each mineral on the scale is hard enough to scratch the one below it in the scale.

Time before the present stated in years; referring to geologic events; actual age: Absolute age is generally based on measurement of radioactive decay rates and products of minerals or rock substances, such as the uranium lead method, carbon-14 method, etc.

1. Referring to the depth within the Earth: An abyssal deepness generally signifiesg an extent of some miles.
2. Pertaining to the depth in oceans or lakes, well beyond depth of light penetration: An abyssal deepness commonly refers to 1,000 feet or more in lakes and 6,000 feet or more in oceans.

Descriptive of igneous rocks having silica (SiO₂) content greater than two-thirds of total constituents. Feldspars and granite are acidic rocks and have a low content of magnesium, iron, and calcium.

The magnetic equator which is an imaginary line near the Earth's equator: At the aclinic line, a compass needle balances horizontally, the attraction of the north and the south magnetic poles being equal.

Adjustment of structures or modes of living (including methods of reproduction) that better fit an organism to its environment Through adaptation, successful competition with other organisms can lead to or ensure survival.

Differentiation of related organisms by adaptation to dissimilar environments or modes of living: Many animals, like horses, wolves, seals, whales, and all mammals have gone through stages of adaptive divergence. .

The process of diversification of a single species into multiple new species: Adaptive radiation is very important in creating biodiversity patterns throughout a variety of geographical areas and ecosystems.

A term applied to coast line, drainage pattern, or individual stream with placement controlled by rock hardness or structure or both; such as, so-called subsequent streams of Appalachian Mountains flowing in weak rocks parallel to strike.

A reference to air or atmosphere; subaerial conditions or processes on land, because of being directly under the atmosphere: Aerial actions move, operate, or occur in the air.

1. Banded or cloudy quartz with a waxy appearance: An agate is a semiprecious stone revealing different tints or colors, and are displayed quite artistically.
2. Cryptocrystalline with crystals that are too small to be seen with an optical microscope: An agate contains silica that is composed of cloudy and banded chalcedony (translucent or grayish semiprecious stone), sometimes mixed with opal, which forms in rock cavities.

Applied to silicified fossilized wood; a species of hornstone: Agatized invertebrate shells, and vertebrate bones have an appearance of agate.

Time represented by the time-stratigraphic unit called Stage (initial capital letter used in formal nomenclature): A series of rock strata formed in a single age on the geological timescale that signifies millions of years of deposition.

A certain stage of rock and the equivalent age of time have the same name and the same boundary.

Any time span in Earth history: Age can refer to the absolute existence of rocks or minerals, or the relative age of one rock unit compared with another.

The "age of reptiles" refers to the time when reptiles were dominant animals on the Earth.

Accumulation of coarse, angular or subangular pyroclastics: Agglomerates is a rock that has been created by an exploding volcano and consists of fragments of volcanic debris that have been ejected.