Chapter 5: Igneous Rocks & Volcanoes

Front 1

Andesite

Back 1

An intermediate igneous rock with a composition between that of dacite and that of basalt

Front 2

Basalt

Back 2

A dark, fine-grained, mafic igneous rock composed largely of plagioclase feldspar and pyroxene

Front 3

Batholith

Back 3

A great irregular mass of intrusive igneous rock that covers at least 100 km2 that largest of pluton

Front 4

Bomb

Back 4

A pyroclast 2mm or larger, usually consists of blobs of lava that cools in flight and becomes rounded or a chunk torn loose from previously solidified volcanic rock

Front 5

Breccia

Back 5

A volcanic rock formed by the lithification of large pyroclasts

Front 6

Caldera

Back 6

A large, steep-walled, basin-shaped depression formed by a violent volcanic eruption in which large volumes of magma are discharged rapidly form a large magma chamber, causing the overlying volcanic structure to collapse catastrophically through the roof of the emptied chamber

Front 7

Country Rock

Back 7

The rock surrounding an igneous intrusion

Front 8

Crater

Back 8

A bowl- shaped it found at summit of most volcanoes centered on the vent, or caused by meteorite

Front 9

Dacite

Back 9

A light-colored, fine-grained, intermediate igneous rock with a composition between that of rhyolite and andesite

Front 10

Decompression Melting

Back 10

The spontaneous melting of rising mantle material as it reaches a level where pressure decreases below a critical point, without the introduction of any additional heat

Front 11

Dike

Back 11

A sheetlike discordant igneous intrusion that cuts across layers of bedded country rock

Front 12

Diorite

Back 12

A coarse-grained intermediate igneous rock with a composition between that of grandiorite and gabbro

Front 13

Felsic Rock

Back 13

Light-colored igneous rock that is poor in iron and magnesium and rich in silica minerals such as quartz or orthoclase, feldspar

Front 14

Fluid-Induced Melting

Back 14

Melting of rock induced by the presence of water, which lowers its melting point

Front 15

Fractional Cyrstallization

Back 15

The process by which the crystals formed in cooling magma are segregated from the remaining liquid rock, usually by settling to the floor of the magma chamber

Front 16

Gabbro

Back 16

A dark gray, coarse-grained igneous rock containing an abundance of mafic minerals, proxene

Front 17

Granite

Back 17

A felsic, coarse-grained igneous rock composed of quartz, orthoclase feldspar, micas

Front 18

Granodiorite

Back 18

A light-colored, coarse-grained intermediate igneous rock that is similar to granite in containing a lot of quartz but is mostly feldspar that is plagioclase

Front 19

Hot Spot

Back 19

A region of intense, localized volcanism found far from a plate boundary, hypothesized to be the surface expression of a mantle plume

Front 20

Intermediate Igneous Rock

Back 20

An igneous rock midway in composition between mafic and felsic, neither rich in silica nor as poor as mafic

Front 21

Lahar

Back 21

A torrential mudflow of wet volcanic debris

Front 22

Lava

Back 22

Magma that flows out onto Earth's surface

Front 23

Mafic Rock

Back 23

Dark-Colored, igneous rock containing minerals such as pyroxenes and olivines that are rich in iron and magnesium and relatively poor in silica

Front 24

Magma Chamber

Back 24

A large pool of magma that forms in the lithosphere as rising magmas melt and push aside surrounding solid rock

Front 25

Magmatic Differentiation

Back 25

A process by which rocks of varying composition arise from a uniform parent magma as various minerals are withdrawn from it by fractional crystallization as it cools, changes its compostion

Front 26

Mantle Plume

Back 26

A narrow, cynlindrical jet of hot, solid material rising from deep within the mantle, thought to be responsible for intraplate volcanism

Front 27

Obisidian

Back 27

A dense, glassy volcanic rock, usually felsic composition

Front 28

Partial Melting

Back 28

Incomplete melting of a rock that occurs because the minerals that compose it melt at different temperatures

Front 29

Pegmatite

Back 29

A vein of extremely coarse-grained granite, crystallization from a water-rich magma in the late stages of solidification, that cuts across much finer grained country rock and may contain rich concentrations of rare minerals

Front 30

Peridiotite

Back 30

A coarse-grained, dark greenish gray, ultramafic igneous rock, intrusive, composed primarily of olivine with smaller amounts of pyroxene and other minerals such as spinel or garnet, the dominant rock in Earths Mantle and the source rock of Basaltic magmas

Front 31

Pluton

Back 31

A large igneous intrusion, ranging in size from a cubic kilometer to hundreds of cubic kilometers, formed deep in the crust

Front 32

Porphyry

Back 32

An igneous rock of mixed texture in which large crystals " float" in a predominantly fine-grained matrix.

Front 33

Pumice

Back 33

A volcanic rock, usually rhyolitic in composition, containing numerous cavities ( vesicles) that remain after trapped gas has escaped from solidifying lava

Front 34

Pyroclast

Back 34

A rock fragment ejected into the air by a volcanic eruption

Front 35

Pyroclastic Flow

Back 35

A glowing could of ash ash, dust, and gases ejected by a volcanic eruption that rolls downhill at high speeds

Front 36

Rhyolite

Back 36

A light brown to gray, fine- grained felsic igneous rock

Front 37

Shield Volcano

Back 37

A broad, shield -shaped volcano many tens of kilometers in circumference and more than 2 km high, built by successive flows of basaltic lava from a central vent

Front 38

Sill

Back 38

A sheetlike concordant igneous intrusion formed by the injection of magma between parallel layers of bedded country rock

Front 39

Stock

Back 39

A pluton less than 100 km2 in area

Front 40

Stratovolcano

Back 40

A concave-shaped volcano formed from alternating layers of lava flows and beds of pyroclasts

Front 41

Tuff

Back 41

A volcanic rock formed by the lithification of small pyroclasts

Front 42

Ultramafic Rock

Back 42

An igneous rock consisting primarily of mafic minerals and containing less than 10 percent feldspar

Front 43

Vein

Back 43

A sheetlike deposit of minerals precipitated in fractures or joints in country rock often by hydrothermal solution

Front 44

Viscosity

Back 44

A measure of a fluids resistance to flow

Front 45

Volcanic Ash

Back 45

Pyroclasts less than 2mm in diameter, usually glass, that form when escaping gases force a fine spray of magma from a volcano

Front 46

Volcano

Back 46

A hill or mountain constructed from the accumulation of erupted lava and pyroclasts