Geology Lab Midterm Review

Moh's Hardness Scale

from softest to hardest: 1 talc, 2 gypsum. 3 calcite, 4 fluorite, 5 apatite, 6 orthoclase feldspar, 7 quartz, 8 topaz, 9 corundum, 10 diamond.

North American Plate

main plate containing North American and Canada continents

Microcrystalline texture

nonfoliated metamorphic texture; a fine-grained aggregate of intergrown crystals; hornfels.

Glassy texture

nonfoliated metamorphic texture; a homogenous texture with no visible grains or other structures and breaks along glossy surfaces; anthracite coal.

Sandy texture

nonfoliated metamorphic texture; a medium/coarse-grained aggregate of fused, sand-sized grains that resemble sandstone; quartzite.

Crystalline texture (nonfoliated)

nonfoliated metamorphic texture; medium/coarse-grained aggregate of intergrown, usually equigranular, visible crystals; marble.

Metamorphic Rock

A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions.

Sedimentary Rock

A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together.

Bowen's Reaction Series - Minerals

From highest temperature/first to crystallize to lowest/last: olivine, pyroxene, amphibole, biotite mica, k-spar, muscovite mica, quartz.

Bowen's Reaction Series - Rocks

From highest temperature/first to crystallize to lowest/last: peridotite/komatite, gabbro/basalt, diorite/andesite, granite/rhyolite.

Bowen's Reaction Series - Magma

From highest temperature/first to crystallize to lowest/last: ultramafic magma, mafic magma, intermediate magma, felsic magma.

Biochemical sediment

a compositional classification of sedimentary rocks; made mostly of grains that are fragments or shells of organisms (plants or animals).

Chemical sediment

a compositional classification of sedimentary rocks; made mostly of mineral crystals precipitated from aqueous solutions and/or chemical residues (rust).

Detrital sediment

a compositional classification of sedimentary rocks; made mostly of rock fragments, quartz grains, feldspar grains, or clay minerals.

Mineralogical composition

a description of the kinds and relative abundances of mineral crystals that comprise the rock.

Rhyolite

a felsic, aphanitic igneous rock, extrusive equivalent of granite. Usually light gray or pink.

Pumice

a glassy extrusive igneous rock, generally white to dark gray, very abundant adjacent vesicles.

Basalt

a mafic, aphanitic igneous rock, the extrusive equivalent of gabbro, dark gray.

Gabbro

a mafic, phaneritic igneous rock, comprised cheifly of ferromagnesian and plagioclase mineral crystals.

Recrystallization

a process whereby small crystals of one mineral will slowly convert to fewer, larger crystals of the same mineral, without melting of the rock.

Igneous Rock

a type of rock that forms from the cooling of molten rock at or below the surface.

Volcanic breccia

an extrusive igneous rock comprised chiefly of pyroclasts more than 2mm in diameter.

Scoria

an extrusive igneous rock with mafic color index and an abundance of adjacent vesicles.

Tuff

an extrusive, pyroclastic igneous rock comprised chiefly of volcanic ash (pyroclasts <2mm).

Andesite

an intermediate, aphanitic igneous rock, extrusive equivalent of diorite. Usually medium-to-dark gray.

Peridotite

an intrusive, phaneritic igneous rock of very high color index (>95%), comprised essentially of ferromagnesian mineral crystals.

Granite

an intrusive, phaneritic igneous rock with light color index, comprised chiefly of quartz and feldspar mineral crystals.

Diorite

an intrusive, phaneritic igneous rock, intermediate color, comprised chiefly of plagioclase feldspar and ferrmagnesian mineral crystals.

Grain shapes

angular, rounded, well-rounded.

Lignite

biochemical sedimentary rock; dull, dark brown, brittle rock; fossil fragments may be visible; intermediate between peat and bituminous coal

Calcarenite

biochemical sedimentary rock; type of limestone (fossilferous), mostly sand-sized shell fragments; often contains a few larger whole fossil shells.

Coquina

biochemical sedimentary rock; type of limestone, mostly gravel-sized shells or shell or coral fragments.

Micrite

biochemical sedimentary rock; type of limestone, no visible grains in most of the rock. May break with conchoidal fracture, may contain a few visible fossils; limestone composed of very tiny calcite particles - solidified lime mud

Peat

bioclastic sedimentary composition; made mostly of plant fragments; loose, unconsolidated, brownish mass of partially decayed plant matter; a precursor to coal

Biochemical/bioclastic limestone

bioclastic sedimentary composition; made mostly of shells and shell fragments.

Coal

bioclastic sedimentary composition; made of carbon/charcoal from plants.

Chemical limestone

chemical sedimentary composition; made mostly of calcite (or aragonite) mineral crystals.

Dolostone

chemical sedimentary composition; made mostly of dolomite mineral crystals; Chemical sedimentary rock composed of calcium-magnesium carbonate, a converted form of calcite, and fizzes when in contact with hydrochloric acid

Rock gypsum

chemical sedimentary composition; made mostly of gypsum mineral crystals; sedimentary rock in the class known as chemical sedimentary rocks. It is formed by the evaporative deposition of gypsum from solution.

Rock salt

chemical sedimentary composition; made mostly of halite mineral crystals; A rock: sedimentary, composed of halite with a find to coarse crystalline structure.

Ironstone (hematite)

chemical sedimentary composition; made mostly of iron-bearing mineral crystals, like hematite.

Ironstone (limonite)

chemical sedimentary composition; made mostly of iron-bearing residues, like limonite.

Chert

chemical sedimentary composition; made of microcrystalline quartz varieties; A sedimentary rock made up of chemically or biochemically precipitated silica.

Oolitic limestone

chemical sedimentary rock; type of limestone, comprised of spherical grains that resemble minature pearls, called ooliths and ooids.

Breccia

detrital sedimentary composition; made up of rock fragments, angular shaped gravel.

Wacke

detrital sedimentary rock; type of sandstone, sand is mixed with much mud.

Shale metamorphosed

depending on the the grade (intensity): low-grade (slate), to medium-grade (phyllite and schist), to high-grade (gneiss).

Mudstone and Shale

detrital sedimentary composition; made mostly of clay minerals.

Arkose

detrital sedimentary composition; made mostly of feldspar grains; hard; coarse; quartz and feldspar; usually very coarse

Conglomerate

detrital sedimentary composition; made mostly of rounded gravel and sand grains (usually quartz grains).

Parent rock

every metamorphic rock has this, protolith, the rock type that was metamorphosed. Can consist of any of the three main rock types: igneous, sedimentary, and metamorphic.

Obsidian

extrusive igneous rock comprised of dark glass (volcanic glass).

Muscovite mica

felsic mineral; brown, red, or colorless mica, short opaque prisms, splits along 1 excellent cleavage into thin flexible transparent sheets. Hardness of 2-2.5.

Quartz

felsic mineral; light gray, clear; the most widely distributed and common rock-forming mineral; composed of silicon dioxide.

Potassium feldspar

felsic mineral; pink, opaque, 2 cleavages at nearly right angles.

Plagioclase feldspar

felsic mineral; white or gray, opaque, 2 cleavages at nearly right angles, striations, Hardness of 6.

Crystalline

grain size; aggregate of visible crystals.

Microcrystalline

grain size; crystals not visible, feels smooth, shiny luster on freshly broken surface.

Gravel-sized

grain size; grains are visible, larger than sand.

Silt-sized

grain size; grains barely visible, feels gritty.

Clay-sized

grain size; grains not visible, feels smooth, dull luster on freshly broken surface.

Sand-sized

grain size; grains visible, like within a sandbox.

Metamorphic texture

is a description of its constituent parts and their sizes, shapes, and arrangements.

Serpentinite

mafic and ultramafic igneous rocks were metamorphosed to this type of rock.

Biotite mica

mafic mineral; black mice, short opaque prisms, splits easily along 1 excellent cleavage into thin sheets. Hardness of 2-2.5.

Amphibole (hornblende)

mafic mineral; dark gray to black, 2 cleavages at about 56 and 124 degrees, Hardness of 5.5-6.

Pyroxene (augite)

mafic mineral; dark green to black, 2 cleavages nearly right angles. Hardness of 5.5-6.

Olivine

mafic mineral; green, transparent or translucent, conchoidal fracture. Hardness of 7.

Foliated metamorphic rock

metamorphic rocks with layering and parallel alignment of platy (flat) mineral crystals, such as micas.

Schistosity

metamorphic texture; a scaly glittery layering of medium/coarse-grained platy minerals and/or linear alignment of long prismatic crystals; schist.

Slaty rock cleavage

metamorphic texture; a very flat foliation, developed along flat, parallel, closely spaced shear planes in tightly folded clay or mica-rich rocks; slate.

Phyllite texture

metamorphic texture; a wavy and/or wrinkled foliation of fine-grained platy minerals, gives rock a metallic luster; phyllite.

Gneissic banding

metamorphic texture; alternating layers or lenses of light and dark medium/coarse-grained minerals; gneiss.

Neomorphism

one way that mineralogical composition actually changes during metamorphism. In this process, minerals not only recrystallize but also form different minerals from the same chemical elements.

Grain arrangements

poorly sorted, moderately sorted, well sorted.

Phaneritic

rock texture; crystals 1-10mm, slow cooling, viscous magma, and/or good nucleation.

Aphanitic

rock texture; crystals <1mm, rapid cooling, fluid lava, and/or good nucleation.

Pegmatitic

rock texture; crystals >1cm, very slow cooling, viscous magma, and/or good nucleation.

Porphyritic

rock texture; large and small crystals within, slow, then rapid cooling, and/or change in magma viscosity or composition.

Pyroclastic/Fragmental

rock texture; particles emitted from volcanoes.

Glassy

rock texture; rapid cooling and/or very poor nucleation.

Vesicular

rock texture; rapid cooling of gas-charged lava. Gas-bubbles are present in lava.

Metaconglomerate, quartzite, and marble

sedimentary rocks of conglomerate, sandstone, and limestone, respectively, metamorphosed into these three rocks.

Current ripple marks

sedimentary structure; asymmetrical ripple marks, the steep slope faces down current, and the gentle slope faces up current; form in any environment where wind/water travels in one direction for some of the time.

Cross-bedding

sedimentary structure; inclined beds or laminations; forms wherever there are wind or water currents.

Horizontal strata

sedimentary structure; relatively flat beds (>= 1cm thick) and laminations (<1cm thick); occur where sediments settle from a standing body of water or air, or where currents travel parallel to the surface on which sediments are accumulating.

Bimodal cross-bedding

sedimentary structure; sequence of cross-bedding in which cross-bedding is inclined in opposite directions; forms in environments where currents of wind or water flow back and forth in opposite directions, common with tides.

Graded bed

sedimentary structure; stratum that contains different sizes of sedimentary grains arranged from largest at the bottom to smallest at the top; form when a turbulent body of water full of sediment (flood, wave, river) suddenly loses energy and calms down. Large particles settle out before small.

Raindrop impressions

sedimentary structure; tiny craters formed by impact bedding plane surfaces; occur on muddy land surfaces.

Mudcracks

sedimentary structures; polygonal patterns of cracks that develop in mud as it dries; form in muddy environments that wet or dry sometimes, like tidal mudflats or land surfaces exposed to rain.

Oscillation ripple marks

sedimentary structures; symmetrical ripple marks; form in any body of water where gentle waves barely touch bottom, or where weak currents move back and forth (oscillate) in shallow water.

Features of foliated and nonfoliated metamorphic rocks

stretched/sheared grains, porphyroblastic texture (an arrangement of large crystals), hydrothermal veins, folds, lineations.

Metasomatism

the most significant mineralogical changes occur here; in this process, chemicals are added or lost.

Contact metamorphism

type of metamorphism; igneous intrusions and along fractures that are in contact with watery hot (hydrothermal) fluids.

Regional metamorphism

type of metamorphism; occurs over a very large areas (regions), such as deep within the cores of rising mountain ranges. Cause by large igneous intrusions that form and cool over long periods, the moderate to extreme pressure and heat associated with deep burial or tectonic movements of rock, and/or the very widespread migration of hot fluids from one region to another along rock fractures and pore spaces.

Varieties of quartz

types of common mineral; milky, crystal, rose, jasper.