| Glossary |
| Alluvial
fan | A fan-shaped deposit of
sediment when a stream slope is reduced, often at the base of mountains. |
| Bentonite | An
elastic, soapy-textured clay material that swells extensively in water to
form a gelatinous mass several times its original volume. |
| Chaparral | A
close growth of low evergreen oaks or other dense thicket. |
| Concretion | A
concentricity of mineral growth around a central nucleus, resulting in a more
highly cemented area within the surrounding rock matrix. |
| Differential
erosion | A variation in the decomposition
rate of a rock, caused by variations in cement strength and resulting in varying
surface textures and features. |
| Deposition | The
coming to rest of eroded material, from a higher place to a low place. |
| Erosion | The
transportation of weathered material by wind, water, ice, or gravity. |
| Fault | A
break or crack in the earth's crust along which movement has occurred. |
| Folds | Wavelike
undulations in rock beds caused by compressional stresses. |
| Foraminifera | Small,
single-celled organisms which float on the ocean surface (planktonic foraminifera)
or live near the ocean bottom (benthonic foraminifera). |
| Formation | A
distinct type of rock that covers an area large enough to show on a map. |
| Fossilization | The
preservation in rock of the remains or traces of organic material. |
| Fractures | Cracks
in rock. |
| Graded
beds | A depositional rock structure
characterized by larger grains at the bottom and fining upward to smaller grains
at the top; also called a fining upward sequence. |
| Laminar
bedding | Thin parallel layers
of sedimentary rock caused by repeated similar depositional action. |
| Lithification | The
formation of rock by compaction and cementation. |
| Matrix | The
fine-grained portion of a rock that encompasses the larger grains. |
| Mineral | A
naturally occurring, inorganic crystalline solid with a definite internal structure
and a specific chemical composition. |
| Oxidation | In
rocks, the chemical breakdown of rock material by exposure to air and water. In
chemistry, the removal of one or more electrons from an atom or ion, commonly
causing elements to combine with oxygen. |
| Permineralization | The
preservation in rock of organic material when it is permeated by a resistant substance
that hardens and cements the material as a fossil. |
| Redbeds | Any
group of oxidized sedimentary rocks characterized by a red or maroon color. |
| Rock | An
aggregate of minerals. |
| Sandstone | A
sedimentary rock formed from sand-sized grains. |
| Savannah | A
plain characterized by coarse grasses and scattered tree growth where rainfall
is seasonal. |
| Sedimentary
rock | Rock formed from the weathered
products of pre-existing rocks which have been transported, deposited, compacted,
and cemented. |
| Shale | A
fine-grained sedimentary rock formed from clay-sized grains. |
| Silt | A
sediment with very fine grains between 1/16 and 1/256 milimeters in diameter. |
| Spheroidal
Weathering | A weathering process
that produces a spherical shape from a blocky shape. |
| Subside | To
sink to a lower level. |
| Tectonic
plate | A large, rigid section
of earth crust that moves as a unit on the surface of the earth. |
| Tectonics | The
study of the major structural features of the earth's crust, and of the large-scale
processes that deform it. |
| Transgressing
sea | The onland movement of shoreline
caused by a rise in sea level. |
| Trace
fossils | Impressions left in
rock by living things. |
| Weathering | The
disintegration and compositional breakdown of rock at the earth's surface. |
