Geology Test 2 Vocabulary (Ch3-5)

Front 1

Mineral

Back 1

solid inorganic substance of natural occurence

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streak

Back 2

powdered form of mineral

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fracture

Back 3

breaks along irregular boundaries (smooth, curved edges)

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Mohs' hardness scale

Back 4

a numerical value of hardness 1 (softest; talc) 10 (hardest; diamond)

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Silicates

Back 5

any one of numerous minerals that have the silicon-oxygen tetrahedron as their basic structure

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silica-oxygen tetrahedron

Back 6

silicon atom with four surrounding oxygen atoms arranged to define the corners of a tetrahedron; basic building blocks of silicates

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Pyroclastic

Back 7

Pyro=fire; clastic=broken

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Intrusive

Back 8

crystallizes inside the crust from magma

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Extrusive

Back 9

crystallizes outside the crust from lava

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Aphanitic

Back 10

Microscopic crystals-not visible

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Ultramafic

Back 11

Lowest silica, Fe and Mg rich

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Felsic

Back 12

highest silica, quartz and feldspar rich

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fractional crystallization

Back 13

magma changes composition continually

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pyroclasts

Back 14

fragments of lava that fall to the ground after volcanic explosions, smaller bits travel farther

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Volcanic Ash

Back 15

smallest bits: fine, light colored

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fissure

Back 16

a crack in rock along which there is a distinct separation

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volcanic dome

Back 17

form of viscous felsic lavas, steep-sided and small, grow slowly

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stratovolcano

Back 18

-mainly alternating pyroclastic deposits and andesitic lava flows

-slopes are intermediate in steepness

-large

-intermittent eruptions over long time span

-eruptions often highly explosive

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Andesitic lava

Back 19

intermediate in composition and viscosity between mafic and felsic magmas

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Bond types

Back 20

-Ionic

-Covalent

-Metallic

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Hardness

Back 21

resistance to scratching

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cleavage

Back 22

breaks along definite planes of weakness (straight edges)

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Index minerals

Back 23

-talc (softest)

-gypsum

-calcite

-fluorite

-apatite

-feldspar

-quartz

-topaz

-corundum

-Diamond (hardest)

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Sialic

Back 24

light colored with silicon and aluminum

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chemical bonds

Back 25

form mineral compounds

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composition

Back 26

what minerals the rock contains

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magma/lava

Back 27

magma-underground

lava-above ground

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Phaneritic

Back 28

crystals visible with the naked eye

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mafic

Back 29

low silica

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decompression melting

Back 30

melting at divergent plate boundaries and hot spots

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pegmatite

Back 31

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

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lahars

Back 32

water, gas & pyroclastic debris

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volcanic bombs

Back 33

rounded fragments of ejected magma

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crater

Back 34

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

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shield volcano

Back 35

-formed mainly of basltic lavas

-gentle sides

-huge; wide

-long duration of activity

-non-violent eruptions

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basaltic lava

Back 36

low-viscosity mafic lavas, typically erupt at 1000-1200 degrees C

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Viscosity

Back 37

resistance to flow

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color

Back 38

how mineral interacts with light

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luster

Back 39

how mineral scatters light

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cleavage types

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-basal: one direction

-prismatic: two directions at right/non-right angles

-cubic-three directions at right angles

-rhombohedral-three directions at non-right angles

-octahedral-four directions

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mineral classification

Back 41

silicates vs. nonsilicates

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Ferromagnesium

Back 42

darker with more iron (Fe) and magnesium

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texture

Back 43

size & shape of the minerals; look & feel of the rock

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glassy

Back 44

no crystals

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porphyitic

Back 45

two sizes of crystals

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intermediate

Back 46

moderate silica

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flux melting

Back 47

adding water-melting at convergent plate boundaries:addition of water as wet ocean crust is subducted

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types of basalt flows

Back 48

-flood: thick widespread accumulations of basalt, typically fed by fissures

-pahoehoe: low viscosity basaltic lava with ropy texture

-Aa: low viscosity basaltic lava characterized with jagged, blocky texture

-pillow: forms beneath the water, characterized by glassy pillows filled with crystalline basalt

-vesicular: trapped gases form bubbles (vesicles)

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pyroclastic flow

Back 49

gas & pyroclastic debris

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lapilli

Back 50

little stones: dark lapilli-cinders or scoria; light lapilli-pumice

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caldera

Back 51

large depression; formed by collapse of a volcano into a partially drained magma

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magma chamber

Back 52

large underground pool of liquid rock beneath the surface of the earth

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Cinder-cone volcano

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-formed mainly of basaltic pyroclastic material

-steep sides

-relatively small

-short-lived: typically a single event

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rhyolitic lava

Back 54

High-viscosity felsic lavas, typically erupt at 800-1200 degrees C; most explosive