Geo Chp 4

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Aa flow

Back 1

A type of lava flow that has jagged, blocky surface. is slow

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Batholith

Back 2

A large mass of igneous rock that formed when magma was emplaced at depth, crystallized, and was subsequently exposed by erosion.

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Block lava

Back 3

Lava having a surface of angular blocks associated with material having andesitic and rhyolitic compositions

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Caldera

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A large depression typically caused by collapse of the summit area of a volcano following a violent eruption

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Cinder cone

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A rather small volcano b uilt primarily of pyroplastics ejected from a single vent.

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Columnar joints

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A pattern of cracks that forms during cooling of molten rock to generate columns.

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Composite cone

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A volcano composed of both lava flows and pyroclastic material

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Condcordant

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A term used to describe intrustive igneous masses that form parallel to the bedding of the surrounding rock

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Conduit

Back 9

A pipelike opening through which magma moves toward Earths surface. It terminates at a surface opening called a vent.

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Continental volcanic arc

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Mountains formed in part by igneous activity associated with the subjuction of oceanic lithosphere beneath a continent.

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Crater

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The depression at the summit of a volcano, or that which is produced by a meteor impact.

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Dike

Back 12

A tabular shaped instrusive igneous feature that cuts through the surrounding rock

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Discordant

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A term used to describe plutons that cut across existing rock structures, such as bedding planes.

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Eruption column

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Buoyant plumes of hot ash-laden gases that can extend thousands of meters into the atmosphere.

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Fissure

Back 15

A crack in rock along which there is a distinct separation.

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Fissure eruption

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An eruption in which lava is extruded from narrow fractures or cracks in the crust.

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Flood basalt

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Flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thicknesses of hundreds of meters.

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Fumarole

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A vent in a volcanic area from which fumes or gases escape.

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Hot spot

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A proposed concentration of heat in the mantle capable of introducing magma that in turn extrudes onto Earths surface.

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Intraplate volcanism

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Igneous activity that occurs within a tectonic plate away from plate boundaries.

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Laccolith

Back 21

A massive, concordant igneous body intruded between preexisting strata.

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Lahar

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Mudflows on the slopes of volcanoes that result when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels.

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Lava dome

Back 23

A bulbous mass associated with an old age colvano, produced when thick lava is slowly squeezed from the vent.

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Lava tube

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tunnel in hardened lava that acts as a horizontal conduit for lava flowing from a volcanic vent.

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Mantle plume

Back 25

A mass f hotter than normal mantle material that ascends toward the surface, where it may lead to igneous activity.

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Nuee ardente

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Incandescent volcanic debris that is buoyed up by hot gases and moves downslope in an avalanche fashion.

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Pahoehoe flow

Back 27

A lava flow with a smooth to ropy surface

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Parasitic cone

Back 28

A volcanic cone that forms on the flank of a larger volcano

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Pillow lava

Back 29

Basaltic lava that solidifies in an underwater environment and develops a structure that resembles a pile of pillows

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Pipe

Back 30

A vertical conduit through which magmatic materials have passed.

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Pluton

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A structure that results from the emplacement and crystallization of magma beneath Earths surface.

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Pyroclastic flow

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A highly heated mixture, largelyt of ash and pumice fragments, traveling down the flanks of a volcano or along the surface of the ground.

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Pyroclastic material

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The volcanic rock ejected during an eruption.

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Shield volcano

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A broad, gently sloping volcano built from fluid basaltic lavas.

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Sill

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A tabular igneous body that was intruded parallel to the layering of preexisting rock.

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Tabular

Back 36

Describing a feature such as an igneous pluton having two dimensions that are much longer than the third

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Viscosity

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A measure of a fluids resistance to flow.

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Volatiles

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Gaseous components of magma dissolved in the melt.

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Chemical weathering

Back 39

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

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Eluviation

Back 40

The washing out of fine soil components from the A horizon by downward percolating water

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Erosion

Back 41

The incorporation and transportation of material by a mobile agent, such as water, wind, or ice.

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Exfoliation Dome

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

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External processes

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Process such as weathering, mass wasting, or erosion that is powered by the Sun and transforms solid rock into sediment.

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Frost wedging

Back 44

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

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Internal process

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A process such as mountain building or volcanism that derives its energy from Earths interior and elevates Earths surface.

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Leaching

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

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Mass wasting

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the downslope movement of rock, regolith, and soil under the direct influence of gravity

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Mechanical weathering

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the physical disintegration of rock, resulting in smaller fragments.

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Parent Material

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the material upon which a soil develops

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Regolith

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The layer of rock and mineral fragments that nearly everywhere covers Earths land surface

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Secondary Enrichment

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The concentration of minor amounts of metals that are scattered through unweathered rocks into economically valuable concentrations by weathering processes

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sheeting

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

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Soil

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

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Soil profile

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

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Soil taxonomy

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A soil classification system consisting of six hierarchical categories based on observable soil characteristics.

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solum

Back 56

The O, A, and B horizons in a soil profile. Living roots and other plant and animal life are largely confined to this zone.

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Talus

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An accumulation of rock debris at the base of a cliff

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Weathering

Back 58

The disintegration and decomposition of rock at or near the surface of the Earth.