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Earth 201 > Ch 4: Magma, Igneous Rocks & Intrusive Activity > Flashcards

Ch 4: Magma, Igneous Rocks & Intrusive Activity Flashcards

(104 cards)

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1
Q

Andesite

A

A gray, fine-grained igneous rock, primarily of volcanic origin and commonly exhibiting a porphyritic texture.

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2
Q

Assimilation

A

In igneous activity, the process of incorporating country rock into a magma body.

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3
Q

Asthenosphere

A

A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers (60 miles) and in some regions extends as deep as 700 kilometers (430 miles). The rock within this zone is easily deformed.

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4
Q

Basalt

A

A fine-grained igneous rock of mafic composition.

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5
Q

Batholith

A

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

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6
Q

Bed

A

See Strata

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7
Q

Biotite

A

A dark, iron-rich mineral and a member of the mica family with excellent cleavage.

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8
Q

Bowen’s reaction series

A

A concept proposed by N. L. Bowen that illustrates the relationships between magma and the minerals crystallizing from it during the formation of igneous rocks.

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9
Q

Breccia

A

A sedimentary rock composed of angular fragments that were lithified.

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10
Q

Caldera

A

A large depression typically caused by collapse or ejection of the summit area of a volcano.

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11
Q

Chemical bond

A

A strong attractive force that exists between atoms in a substance. It involves the transfer or sharing of electrons that allows each atom to attain a full valence shell.

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12
Q

Coarse-grained

A

See Phaneritic texture.

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13
Q

Coast

A

A strip of land that extends inland from the coastline as far as ocean-related features can be found.

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14
Q

Color

A

A phenomenon of light by which otherwise identical objects may be differentiated.

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15
Q

Columnar joints

A

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

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16
Q

Concordant

A

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

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17
Q

Confining pressure

A

Stress that is applied uniformly in all directions.

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18
Q

Convection

A

The transfer of heat by the mass movement or circulation of a substance.

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19
Q

Convergent plate boundary

A

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.

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20
Q

Country rock

A

See Host rock.

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21
Q

Crust

A

The very thin, outermost layer of Earth.

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22
Q

Crystal

A

Any natural solid with an ordered, repetitive atomic structure.

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23
Q

Crystal settling

A

A process that occurs during the crystallization of magma, in which the earlier-formed minerals are denser than the liquid portion and settle to the bottom of the magma chamber.

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24
Q

Crystalline

A

See Crystal.

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25
Dark silicate
A silicate mineral that contains ions of iron and/or magnesium in its structure. Dark silicates are dark in color and have a higher specific gravity than nonferromagnesian silicates.
26
Decompression melting
Melting that occurs as rock ascends due to a drop in confining pressure.
27
Dike
A tabular-shaped intrusive igneous feature that cuts through the surrounding rock.
28
Diorite
A coarse-grained, intrusive igneous rock primarily composed of plagioclase feldspar and amphibole minerals.
29
Discordant
A coarse-grained, intrusive igneous rock primarily composed of plagioclase feldspar and amphibole minerals.
30
Divergent plate boundary
A boundary in which two plates move apart, resulting in upwelling of material from the mantle to create new seafloor.
31
Element
A substance that cannot be decomposed into simpler substances by ordinary chemical or physical means.
32
Extrusive
Igneous activity that occurs at Earth’s surface.
33
Extrusive igneous rock
Igneous rock formed when magma solidifies at Earth’s surface.
34
Felsic composition
See Granitic composition.
35
Fine-grained
See Aphanitic texture.
36
Fissure
A crack in rock along which there is a distinct separation.
37
Fissure eruption
An eruption in which lava is extruded from narrow fractures or cracks in the crust.
38
Fracture
Any break or rupture in rock along which no appreciable movement has taken place.
39
Fragmental texture
See Pyroclastic texture.
40
Gabbro
A dark-green to black intrusive igneous rock composed of dark silicate minerals. Gabbro makes up a significant percentage of oceanic crust.
41
Geothermal gradient
The gradual increase in temperature with depth in the crust. The average is 30°C per kilometer in the upper crust.
42
Glass (volcanic)
Natural glass that is produced when molten lava cools too rapidly to permit recrystallization. Volcanic glass is a solid composed of unordered atoms.
43
Glassy
A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals.
44
Gradient
The slope of a stream, generally expressed as the vertical drop over a fixed distance.
45
Granite
An abundant, coarse-grained igneous rock composed of about 10–20 percent quartz and 50 percent potassium feldspar. Granite is used as a building material.
46
Groundmass
The matrix of smaller crystals within an igneous rock that has porphyritic texture.
47
Host rock
Pre-existing crustal rocks intruded by magma. Host rock may be displaced or assimilated by magmas.
48
Igneous rock
Rock formed from the crystallization of magma.
49
Intrusion
See Pluton
50
Ion
An atom or a molecule that possesses an electrical charge.
51
Joint
A fracture in rock along which there has been no movement.
52
Laccolith
A massive igneous body intruded between preexisting strata.
53
Lava
Magma that reaches Earth's surface.
54
Light silicate
A silicate mineral that lacks iron and/ or magnesium. Light silicates are generally lighter in color and have lower specific gravities than dark silicates.
55
Lithosphere
The rigid outer layer of Earth, including the crust and upper mantle.
56
Magma
A body of molten rock found at depth, including any dissolved gases and crystals.
57
Magma mixing
The process of altering the composition of a magma through the mixing of material from another magma body.
58
Magmatic differentiation
The process of generating more than one rock type from a single magma.
59
Mantle
One of Earth’s compositional layers. The solid rocky shell that extends from the base of the crust to a depth of 2900 kilometers (1800 miles).
60
Melt
The liquid portion of magma excluding the solid crystals.
61
Mineral
A naturally occurring, inorganic crystalline material with a unique chemical structure.
62
Mineralogy
The study of minerals.
63
Mountain belt
A geographic area of roughly parallel and geologically connected mountain ranges developed as a result of plate tectonics.
64
Muscovite
A common member of the mica family of minerals, with excellent cleavage.
65
Obsidian
A volcanic glass of felsic composition.
66
Olivine
A high temperature, dark silicate mineral typically found in basalt.
67
Parent material
The material on which a soil develops.
68
Partial melting
The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occurred, a melt with a higher silica content results.
69
Pegmatite
A 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.
70
Pegmatitic texture
A texture of igneous rocks in which the interlocking crystals are all larger than one centimeter in diameter.
71
Peridotite
An igneous rock of ultramafic composition thought to be abundant in the upper mantle.
72
Phenocryst
A conspicuously large crystal embedded in a matrix of finer-grained crystals.
73
Plagioclase feldspar
A relatively hard light silicate mineral containing both sodium and calcium ions that freely substitute for one another depending on the crystallization environment.
74
Plate
See Lithospheric plate.
75
Pluton
A structure that results from the emplacement and crystallization of magma beneath the surface of Earth.
76
Plutonic rock
Igneous rocks that form at depth. Named after Pluto, the god of the lower world in classical mythology.
77
Porphyritic texture
An igneous rock texture characterized by two distinctively different crystal sizes. The larger crystals are called phenocrysts, whereas the matrix of smaller crystals is termed the groundmass.
78
Porphyry
An igneous rock that has a porphyritic texture.
79
Potassium feldspar
An abundant, relatively hard light silicate mineral containing potassium ions in its structure.
80
Pumice
A light-colored, glassy vesicular rock commonly having a granitic composition.
81
Pyroclastic texture
An igneous rock texture resulting from the consolidation of individual rock fragments that are ejected during a violent volcanic eruption.
82
Quarrying
Removing loosened blocks from the bed of a channel during times of high flow rates.
83
Quartz
A common silicate mineral consisting entirely of silicon and oxygen that resists weathering.
84
Rhyolite
The fine-grained equivalent of the igneous rock granite, composed primarily of the light-colored silicates.
85
Rock
A consolidated mixture of minerals.
86
Scoria
Vesicular ejecta that is the product of basaltic magma.
87
Shield
A large, relatively flat expanse of ancient igneous and metamorphic rocks within the craton.
88
Silicate mineral
Any one of numerous minerals that have the silicon-oxygen tetrahedron as their basic structure.
89
Sill
A tabular igneous body that was intruded parallel to the layering of preexisting rock.
90
Stock
A pluton similar to but smaller than a batholith.
91
Tabular
A pluton similar to but smaller than a batholith.
92
Texture
The size, shape, and distribution of the particles that collectively constitute a rock.
93
Trigger
A factor or event, such as soil saturation, oversteepened slopes, removal of vegetation, or ground shaking, that initiates downslope movement of rock material.
94
Vent
The surface opening of a conduit or pipe.
95
Vesicles
Spherical or elongated openings on the outer portion of a lava flow that were created by escaping gases.
96
Vesicular texture
A term applied to aphanitic igneous rocks that contain many small cavities called vesicles.
97
Viscosity
A measure of a fluid’s resistance to flow.
98
Volatiles
Gaseous components of magma dissolved in the melt. Volatiles will readily vaporize (form a gas) at surface pressures.
99
Volcanic
Pertaining to the activities, structures, or rock types of a volcano.
100
Volcanic island
A seamount that has grown large enough to rise above sea level.
101
Volcano
A mountain formed from lava and/or pyroclastics.
102
Welded tuff
A pyroclastic deposit composed of particles fused together by the combination of heat still contained in the deposit after it has come to rest and the weight of overlying material.
103
Xenolith
An inclusion of unmelted country rock in an igneous pluton.
104
Igneous Rock Classification
See Chart

Earth 201 (9 decks)

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