Ch 5 Vocabulary

Front 1

Aa flow

Back 1

a type of lava flow that has a jagged, blocky surface

Front 2

composite volcano/cone

Back 2

composed of both lava flows and pyroclastic material

Front 3

crater

Back 3

the depression at the summit of a volcano or a depression that is produced by a meteorite impact

Front 4

flood basalts

Back 4

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

Front 5

volcanic island arc

Back 5

a chain of volcanic islands generally located a few 100km from a trench where there is active subduction of one oceanic plate beneath another

Front 6

mantle plume

Back 6

a mass of hotter-than-typical mantle material that ascends toward the surface, where it may lead to igneous activity. these plumes of solid, yet mobile material may originate as deep as the core-mantle boundary

Front 7

pipe

Back 7

a vertical conduit through which magmatic materials have passed

Front 8

pyroclastic material

Back 8

the volcanic rock ejected during eruption. pyroclastics include ash, bombs and blocks

Front 9

stocks

Back 9

smaller plutons -- many appear to be portions of much larger intrusive bodies that would be classified batholiths if they were fully exposed

Front 10

volatiles

Back 10

gaseous components of magma dissolved in the melt. volatiles will readily vaporize (form a gas) at surface pressures

Front 11

batholith

Back 11

a large mass of igneous rock that formed when magma was emplaced at depths, crystallized and subsequently exposed by erosion

Front 12

concordant

Back 12

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

Front 13

dike

Back 13

a tubular-shaped intrusive igneous feature that cuts through the surrounding rock

Front 14

fumarole

Back 14

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

Front 15

laccolith

Back 15

a massive igneous body intruded between preexisting strata

Front 16

nuee ardente

Back 16

incandescent volcanic debris buoyed up by hot gases that moves downslope in an avalanche fashion

Front 17

pluton

Back 17

a structure that results from the exmplacement and crystallization of magma beneath the surface of earth

Front 18

scoria

Back 18

vesicular ejecta that is the product of basaltic magma

Front 19

composite cone aka stratovolcano

Back 19

a volcano composed of both lava flows and pyroclastic material

Front 20

volcanic breccia

Back 20

pyroclastic rocks composed mainly of particles larger than ash

Front 21

pegmatites

Back 21

very coarse-grained igneous rock (typically granite) commonly found as a dike associated with a large mass of plutonic rock that has smaller crystals,

crystallization in a water-rich environment is believed to be responsible for the very large crystals

Front 22

caldera

Back 22

a large depression typically caused by collapse or ejection of he summit area of a volcano

Front 23

conduit

Back 23

a pipelike opening through which magma moves toward earth's surface. it terminates at a surface opening called a vent

Front 24

discordant

Back 24

a term used to describe plutons that cut across existing rock structures, such as bedding plumes

Front 25

hot spot

Back 25

a concentration of heat in the mantle, capable of producing magma, that in turn, extrudes onto earths surface

Front 26

lahar

Back 26

a debris flow on the slopes of a volcano that results when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels

Front 27

pahoehoe flow

Back 27

a lava flow with a smooth to ropy surface

Front 28

pumice

Back 28

a light colored glassy vesicular rock commonly having a granitic composition

Front 29

shield volcano

Back 29

a broad, gently sloping volcano built from fluid basaltic lavas

Front 30

vent

Back 30

the surface opening of a conduit or pipe

Front 31

volcanic neck

Back 31

an isolated steep sided erosional remnant consisting of lava that once occupied the vent of a volcano

Front 32

xenolith

Back 32

an inclusion of unmelted country rock in an igneous pluton

Front 33

cinder cone

Back 33

a rather small volcano built primarily of ejected lava fragments that consist mostly of pea-walnut size lapilli

Front 34

continental volcanic arc

Back 34

mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent

exa the andes and the cascades

Front 35

fissure eruption

Back 35

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

Front 36

intraplate volcanism

Back 36

igneous activity that occurs within a tectonic plate, away from plate boundaries

Front 37

lava dome

Back 37

a bulbous mass associated with an old age volcano, produced when thick lava is slowly squeezed from the vent. lava domes may act as plugs to deflect subsequent gaseous eruptions

Front 38

pillow lava

Back 38

interior lava moves forward by breaking through hardened surface on ocean floor. composed of numerous tube like structures

like toothpaste

useful in geologic history because presence indicates the lava flow formed below surface of a water body

Front 39

pyroclastic flow

Back 39

highly heated mixture, largely of ash and pumice fragments, that travels down the flanks of a volcano or along the surface of the ground

Front 40

sill

Back 40

a tubular igneous body that was intruded parallel to the layering of preexisting rock

Front 41

viscosity

Back 41

a measure of a fluid's resistance to flow

Front 42

volcanic tuff

Back 42

pyroclastic igneous rock, composed of compacted and cemented volcanic ash, from explosive volcanic eruptions