Geology Test 2 Terms

Front 1

The physical disintegration of rock, resulting in smaller fragments.

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mechanical weathering

Front 2

The process by which internal structure of a mineral is altered by the removal and/or addition of elements.

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chemical weathering

Front 3

Any weathering process that tends to produce a spherical shape from an initially blocky shape.

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spheroidal weathering

Front 4

uneven weathering

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differential weathering

Front 5

The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices.

Back 5

frost wedging

Front 6

A mechanical weathering process characterized by the splitting off of slablike sheets of rock.

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sheeting

Front 7

Large, dome-shaped structure, usually composed of granite, formed by sheeting.

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exfoliation dome

Front 8

The layer of rock and mineral fragments that nearly everywhere covers Earth's land surface.

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regolith

Front 9

A combination of minerals and organic matter, water, and air; that portion of the regolith that supports plant growth.

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soil

Front 10

A vertical section through a soil showing its succession of horizons and the underlying parent material.

Back 10

soil profile

Front 11

The depletion of soluble materials from the upper soil by downward-percolating water.

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zone of leaching

Front 12

The part of a glacier characterized by snow accumulation and ice formation. The outer limit of this zone is the snowline.

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accumulation zone

Front 13

rocks that form from the accumulation of materials that originate and are transported as solid particles derived from both mechanical and chemical weathering.

Back 13

detrital sedimentary rock

Front 14

sedimentary rock consisting of material that was precipitated from water by either inorganic or organic means.

Back 14

chemical sedimentary rock

Front 15

sedimentary rock composed of organic carbon from the remains of plants that died and accumulated on the floor of a swamp.

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organic sedimentary rock

Front 16

A geographic setting where sediment is accumulating.

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sedimentary environment

Front 17

A sedimentary rock texture consisting of broken fragments of preexisting rock.

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clastic texture

Front 18

The degree of similarity in particle size in sediment or sedimentary rock.

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sorting

Front 19

A sedimentary rock formed of material deposited from solution by evaporation of water.

Back 19

evaporite

Front 20

The process, generally by cementation and/or compaction, of converting sediments to solid rock.

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lithification

Front 21

one way in which sedimentary rocks are lithified. As material precipitates from water that percolates through the sediment, open spaces are filled and particles are joined into a solid mass.

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cementation

Front 22

A type of lithification in which the weight of overlaying material compresses more deeply buried sediment. Most important in fine-grained sedimentary rocks.

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compaction

Front 23

Parallel layers of sedimentary rock.

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strata (beds)

Front 24

structure in which relatively thin layers are inclined at an angle to the main bedding. Formed by currents of wind or water.

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cross-bedding

Front 25

a sediment layer characterized by a decrease in sediment size from bottom to top.

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graded bed

Front 26

Small waves of sand that develop of the surface of a sediment layer by the action of moving water or air.

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ripplemark

Front 27

A feature in some sedimentary rocks that forms when wet mud dries out, shrinks, and cracks.

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mud crack

Front 28

Changes in rock caused by the heat of a nearby magma body.

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contact metamorphism

Front 29

Metamorphism associated with large-scale mountain building.

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regional metamorphism

Front 30

Near the surface, rock behaves like a brittle solid.

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fault-zone metamorphism

Front 31

Buried rocks, which is analogous to water pressure, where the forces are applied equally in all directions.

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confining pressure

Front 32

The forces that deform rocks are unequal in different directions.

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differential stress

Front 33

A term for a linear arrangement of textural features often exhibited by metamorphic rocks.

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foliation

Front 34

The type of foliation characteristic of slates in which there is a parallel arrangement of fine-grained metamorphic minerals.

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slaty cleavage

Front 35

A type of foliation characteristic of coarser-grained metamorphic rocks. Such rocks have a parallel arrangement of platy minerals such as the micas.

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schistosity

Front 36

The texture displayed by the metamorphic rock in which dark and light silicate minerals have separated.

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gneissic texture

Front 37

A texture of metamorphic rocks in which particularly large grains are surrounded by a fine-grained matrix of other minerals.

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porphyroblastic texture

Front 38

A significant change in the chemical composition of a rock, usually by the addition or removal of icons in solution.

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metasomatism

Front 39

A zone or halo of contact metamorphism found in the host rock surrounding an igneous intrusion.

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aureole

Front 40

A mineral that is a good indicator of the metamorphic environment in which it formed. Used to distinguish different zones of regional metamorphism.

Back 40

index mineral

Front 41

A rock exhibiting both igneous and metamorphic rock characteristics. Such rocks may form when light-colored silicate minerals melt and then crystallize, while the dark silicate minerals remain solid.

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migmatite

Front 42

Rocks are placed in their proper sequence or order. Only the chronological order of events is determined.

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relative dating

Front 43

Layers of sediment are generally deposited in a horizontal or nearly horizontal position.

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original horizontality

Front 44

In any undeformed sequence of sedimentary rocks or surface-deposited igneous materials, each layer is older that the one above it and younger than the one below.

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law of superpostion

Front 45

A principle of relative dating. A rock or fault is younger than any rock through which it cuts.

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cross-cutting relationships

Front 46

Establishing the equivalence of rocks of similar age in different areas.

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correlation

Front 47

A surface that represents a break in the rock record; caused by erosion or nondeposition.

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unconformity

Front 48

An unconformity in which the older strata dip at an angle different from that of the younger beds.

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angular unconformity

Front 49

A type of unconformity in which the beds above and below are parallel.

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disconformity

Front 50

An uncomformity in which older metamorphic or intrusive igneous rocks are overlain by younger sedimentary strata.

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nonconformity

Front 51

Fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content.

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fossil succession

Front 52

A fossil that is associated with a particular span of geologic time.

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index fossil

Front 53

Geologic history divided into units of varying magnitude.

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geologic time scale

Front 54

A time span on the geologic time scale between the Proterozoic and Mesozoic eras from about 542 million to 251 million years ago.

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paleozoic era

Front 55

A time span on the geologic time scale between the Paleozoic and Cenozoic eras from about 251 million to 65.5 million years ago.

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mesozoic era

Front 56

A time span on the geologic time scale beginning about 65.5 million years ago following the Mesozoic era.

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cenozoic era

Front 57

All geologic time prior to the Paleozoic era.

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precambrian

Front 58

The procedure of calculating the absolute ages of rocks and minerals containing certain radioactive isotopes.

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radiometric dating

Front 59

The time required for one half of a radioactive substance to decay.

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half-life