Asbog 4

Different Tops of beds

Different Tops of beds

graded beds, truncated cross-bedding, ripple marks, sole marks, basal conglomerate, rip-up clasts, scouring or channeling, mud cracks, solution surfaces, pebble dents, brachiopod shells, coral, pelecypod shells, worm trails, burrows, baked zone, lava flows, pillow lavas.

Correlation of units

physical continuity 2. lithology 3. sequence of strata 4. rock properties (radioactive properties as measured on a well log) 5. key beds (layers deposited over large areas) 6. index fossils 7. fossil assemblages

types of unconformities

Angular Unconformity: strata below the unconformity are cut off and are overlain at an angle by the beds above the unconformityNonconformity: sedimentary deposits rest upon older igneous or metamorphic rocsParaconformity: unconformity is parallel to the strata above and below itDisconformity: beds above and below an unconformity are parallel, but the unconformity is not parallel to the bedding

Nonconformities in map view

are obvious if the rock type is show on the map. sedimentary & plutonic rocks show vastly different patterns in map view.

Rule of Vs

V made by a geologic unit crossing a stream valley will point in the direction that the formation underlies the valley

types of V's made by different dipping beds

Horizontal bedding: V upstream parallel to topographyDip upstream: V upstream, outside topographyVertical bedding: straight lines cutting across valley topographyDip downstream greater than valley gradient: V downstreamDip downstream equals valley gradient: parallel lines along valley sidesDip downstream less than valley gradient: V upstream inside topography

Evidence of faulting

Repetition or omission of unitsDiscontinuity of structuresJuxtaposition of noncontiguous sedimentary faciesGeomorphic StructuresPresence of slickensides, grooving, drag, gouge, breccia, or myolinitesilicification or mineralization along faults

magnetic declination

azimuthal difference between true North and magnetic North

3 types of plate boundaries

divergent (ex: Mid-Atlantic Ridge) transform (ex: San Andreas) convergent (ex: Chile)

The assemblage of albite, chlorite, actinolite and calcite would be most characteristic of the

greenschist facies

__________________ is now used as an industrial substitute for asbestos

wollastonite

The assemblage of hornblende, plagioclase, epidote, garnet and biotite would be most characteristic of the

amphibole facies

The assemblage of wollastonite, anorthite, diopside cordierite and tridymite would be most characteristic of the

sanidinite facies

The assemblage of glaucophane, lawsonite glaucophane and lawsonite would be most characteristic of the

blueschist facies

Asthenosphere

A region of Earth's outer shell beneath the lithosphere. The asthenosphere is of indeterminate thickness and behaves plastically. (Begin Chapter 1)

continental drift

A concept suggesting that continents move over Earth's surface.

convergent boundary

A boundary between two plates that are moving toward each other.

core

The central zone of Earth.

crust

The outer layer of rock, forming a thin skin over Earth's surface.

data

Observations or measurements used by scientists to test hypotheses.

divergent boundary

Boundary separating two plates moving away from each other.

equilibrium

Material is in equilibrium if it is adjusted to the physical and chemical conditions of its environment so that it does not change or alter with time.

erosion

The physical removal of rock by an agent such as running water, glacial ice, or wind.

hypothesis

A tentative and testable theory. Usually written as an if/then statement.

igneous rock

A rock formed or apparently formed from solidification of magma.

isostatic adjustment

Concept of vertical movement of sections of Earth's crust to achieve balance or equilibrium.

lithosphere

The rigid outer shell of Earth, 70 to 125 or more kilometers thick.

magma

Molten rock, usually mostly silica. The liquid may contain dissolved gases as well as some solid minerals.

mantle

A thick shell of rock that separates Earth's crust above from the core below.

metamorphic rock

A rock produced by metamorphism.

mid-oceanic ridge

A giant mountain range that lies under the ocean and extends around the world.

plate tectonics

A theory that Earth's surface is divided into a few large, thick plates that are slowly moving and changing in size. Intense geologic activity occurs at the plate boundaries.

scientific method

A means of gaining knowledge through objective procedures.

sediment

Loose, solid particles that can originate by (1) weathering and erosion of preexisting rocks, (2) chemical precipitation from solution, usually in water, and (3) secretion by organisms.

sedimentary rock

Rock that has formed from (1) lithification of any type of sediment, (2) precipitation from solution, or (3) consolidation of the remains of plants or animals.

subduction zone

Elongate region in which subduction takes place.

tectonic forces

Forces generated from within Earth that result in uplift, movement, or deformation of part of Earth's crust.

theory

An explanation for observed phenomena that has a high possibility of being true.

transform boundary

Boundary between two plates that are sliding past each other. (End Chapter 1)

Amphibole group

Mineral group in which all members are double chain silicates. (Begin Chapter 2)

atom

Smallest possible particle of an element that retains the properties of that element.

atomic mass number

The total number of neutrons and protons in an atom.

atomic number

The total number of protons in an atom.

atomic weight

The sum of the weight of the subatomic particles in an average atom of an element, given in atomic mass units.

biotite

Iron/magnesium bearing mica.

bonding

Attachment of an atom to one or more adjacent atoms.

calcite

Mineral with the formula CaCO3.

chain silicate structure

Silicate structure in which two of each tetrahedron's oxygen ions are shared with adjacent tetrahedrons, resulting in a chain of tetrahedrons.

clay mineral group

Collective term for several clay minerals.

cleavage

The ability of a mineral to break along preferred planes.

covalent bonding

Bonding due to the sharing of electrons by adjacent atoms.

crystal form

Arrangement of various faces on a crystal in a definite geometric relationship to one another.

crystalline

Describing a substance in which the atoms are arranged in a regular, repeating, orderly pattern.

density

Weight per given volume of a substance.

earthy luster

A luster giving a substance the appearance of unglazed pottery.

electron

A single, negative electric charge that contributes virtually no mass to an atom.

element

A substance that cannot be broken down to other substances by ordinary chemical methods. Each atom of an element possesses the same number of protons.

feldspar group

Group of most common minerals of Earth's crust. All feldspars contain silicon, aluminum, and oxygen and may contain potassium, calcium, and sodium.

ferromagnesian mineral

Iron/magnesium-bearing mineral, such as augite, hornblende, olivine, or biotite.

fracture

The way a substance breaks where not controlled by cleavage.

framework silicate structure

Crystal structure in which all four oxygen ions of a silica tetrahedron are shared by adjacent ions.

glassy (vitreous) luster

A luster that gives a substance a glazed, porcelainlike appearance.

hardness

The relative ease or difficulty with which a smooth surface of a mineral can be scratched; commonly measured by Mohs' scale.

ion

An electrically charged atom or group of atoms.

ionic bonding

Bonding due to the attraction between positively charged ions and negatively charged ions.

isolated silicate structure

Silicate minerals that are structured so that none of the oxygen atoms are shared by silica tetrahedrons.

isotope

Atoms (of the same element) that have different numbers of neutrons but the same number of protons.

luster

The quality and intensity of light reflected from the surface of a mineral.

magnetite

iron oxide that is attracted to a magnet.

metallic luster

Luster giving a substance the appearance of being made of metal.

mica group

Group of minerals with a sheet silicate structure.

mineral

A naturally occurring, crystalline solid that has a specific chemical composition.

Mohs'

hardness scale Scale on which ten minerals are designated as standards of hardness.

muscovite

Transparent or white mica that lacks iron and magnesium.

neutron

A subatomic particle that contributes mass to an atom and is electrically neutral.

nonmetallic luster

Luster that gives a substance the appearance of being made of something other than metal (e.g., glassy).

nucleus

Protons and neutrons form the nucleus of an atom. Although the nucleus occupies an extremely tiny fraction of the volume of the entire atom, practically all the mass of the atom is concentrated in the nucleus.

olivine

A ferromagnesian mineral with the formula (Fe, Mg)2SiO4.

ore mineral

A mineral of commercial value.

plagioclase feldspar

A feldspar containing sodium and/or calcium in addition to aluminum, silicon, and oxygen.

potassium (orthoclase) feldspar

A feldspar with the formula KAlSi3O8.

proton

A subatomic particle that contributes mass and a single positive electrical charge to an atom.

pyroxene group

Mineral group, all members of which are single chain silicates.

quartz

Mineral with the formula SiO2.

sheet silicate structure

Crystal structure in which each silica tetrahedron shares three oxygen ions.

silica

A term used for oxygen plus silicon.

silicates

A substance that contains silica as part of its chemical formula.

silicon-oxygen tetrahedron

Four-sided, pyramidal object that visually represents the four oxygen atoms surrounding a silicon atom; the basic building block of silicate minerals. Also called a silica tetrahedron or a silicon tetrahedron.

specific gravity

The ratio of the mass of a substance to the mass of an equal volume of water, determined at a specified temperature.

streak

Color of a pulverized substance; a useful property for mineral identification.

striations

On minerals, extremely straight, parallel lines. (End Chapter 2)

Andesite

Fine-grained igneous rock of intermediate composition. Up to half of the rock is plagioclase feldspar with the rest being ferromagnesian minerals. (Begin Chapter 3)

basalt

A fine-grained, mafic, igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar.

batholith

A large discordant pluton with an outcropping area greater than 100 square kilometers.

Bowen's reaction series

The sequence in which minerals crystallize from a cooling basaltic magma.

chill zone

In an intrusion, the finer-grained rock adjacent to a contact with country rock.

coarse-grained rock

Rock in which most of the grains are larger than 1 millimeter (igneous) or 2 millimeters (sedimentary).

contact

Boundary surface between two different rock types or ages of rocks.

country rock

Any rock that was older than and intruded by an igneous body.

crystal settling

The process whereby the minerals that crystallize at a high temperature in a cooling magma move downward in the magma chamber because they are denser than the magma.