Page 87 - 4567

Cinder cone A rather small volcano built primarily of pyroclastics ejected from a single vent.
Cleavage The tendency of a mineral to break along planes of weak bonding.
Compaction A type of lithification in which the weight of overlying material compresses more
deeply buried sediment. It is most important in fine-grained sedimentary rocks such as shale.
Composite cone A volcano composed of both lava flows and pyroclastic material.
Conduit A pipelike opening through which magma moves toward Earth’s surface. It terminates
at a surface opening called a vent.
Continental slope The steep gradient that leads to the deep ocean floor and marks the seaward
edge of the continental shelf.
Continental volcanic arc Mountains formed in part by igneous activity associated with the
subduction of oceanic lithosphere beneath a continent. Examples include the Andes and the
Cascades.
Convergent plate boundary A boundary in which two plates move together, resulting in
oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the
mantle. It can also involve the collision of two continental plates to create a mountain system.
Core Located beneath the mantle, it is Earth’s innermost layer. The core is divided into an outer
core and an inner core.
Crater The depression at the summit of a volcano, or that which is produced by a meteorite
impact.
Craton That part of the continental crust that has attained stability; that is, it has not been
affected by significant tectonic activity during the Phanerozoic eon. It consists of the shield and
stable platform.
Creep The slow downhill movement of soil and regolith.
Cross-bedding Structure in which relatively thin layers are inclined at an angle to the main
bedding. Formed by currents of wind or water.
Cross-cutting A principle of relative dating. A rock or fault is younger than any rock (or fault)
through which it cuts.
Crust The very thin, outermost layer of Earth.
D
Dark silicate Silicate minerals containing ions of iron and/or magnesium in their structure. They
are dark in color and have a higher specific gravity than nonferromagnesian silicates.
Debris flow A relatively rapid type of mass wasting that involves a flow of soil and regolith
containing a large amount of water; also called mudflows.
Deep-ocean basin The portion of seafloor that lies between the continental margin and the
oceanic ridge system. This region comprises almost 30 percent of Earth’s surface.
Deflation The lifting and removal of loose material by wind.
Deformation General term for the processes of folding, faulting, shearing, compression, or
extension of rocks as the result of various natural forces.
Density The weight per unit volume of a particular material.
Desert One of the two types of dry climate; the drier of the dry climates.
Dike A tabular-shaped intrusive igneous feature that cuts through the surrounding rock.
Disconformity A type of unconformity in which the beds above and below are parallel.
Discordant A term used to describe plutons that cut across existing rock structures, such as
bedding planes.
Distributary A section of a stream that leaves the main flow.
Divergent plate boundary A boundary in which two plates move apart, resulting in upwelling
of material from the mantle to create new seafloor.
Dry climate A climate in which the yearly precipitation is less than the potential loss of water by
evaporation.
E
Earthquake The vibration of Earth produced by the rapid release of energy.