Earth materials Chpt 2

Elements

A chemical substance consisting of atoms of the same atomic number that cannot be decomposed into simpler materials by chemical reactions

From where do mantle plumes derive their heat?

Accreation heat, at the DD' layer

Dikes

An igneous sheetlike body that cuts across the layering in the surrounding rocks. Most dikes have steep dips.

fossil fuels

Any fuel derived from rocks that are formed from fossil organisms

Divergent plate boundary

Boundary at which tectonic plates move part and new crust is created between them, as occurs at a mid-ocean ridge.

How are shallow epeiric seas related to plate tectonics?

Get eroded by plate tectonics, they are close by

crystalline

Having an ordered internal crystal structure. Applies to well-developed (euhedral) crystals as well as poorly formed (anhedral) mineral grains.

Magma

Molten rock. Most magma is not totally molten but contains some solids that are carried along in the liquid.

On what basis are minerals classified into different chemical groups, and of those, which forms the largest group?

Silicates are the largest. They are classified by anion / cations in chemical groups

Soil

The unconsolidated materials above the bedrock but also the medium for growth of plants.

Passive margins

a continental margin created when plate divergence rifts a continent apart. As the plate cools on moving away from the divergent boundary, the passive continental margin slowly subsides

subhedral

a crystal that is only partly bounded by good crystal faces. The remaining faces are less well developed because of crowding by adjacent mineral grains

Slate

a fine-grained metamorphic rock characterized by a prominent foliation resulting from the preferred orientation of platy minerals such as Muscovite and chlorite

isotherm

a line on a map, cross-section, or phase diagram joining points of equal temperature

Granite

a medium to coarse grained igneous rock composed of approximately one-third quartz and two-thirds alkali feldspars

anhedral

a mineral grain that lacks well-formed crystal faces as a result of having grown against adjacent minerals

halides

a mineral with halogen anions such as F, Cl, or I

migmatite

a mixed metamorphic and igneous rock formed when the rock was raised to a temperature at which partial melting occurred. The melt tends to be granitic in composition and forms light-colored layers in the darker refractory metamorphic rock

mantle plumes

a narrow column of rock that is hypothesized to rise buoyantly form deep in the mantle and on reaching the lithosphere mushrooms out to form a plume head. Hot spots are believe to be located above mantle plumes.

travertine

a porous boundstone formed by precipitation of calcite from hot springs

Epeiric seas

a shallow sea formed by the flooding of a continent during periods of high sea-level stand

vugs

a small cavity in rock, or in a vein, usually lined with crystals

Amorphous

a solid that lacks an ordered crystalline structure

Ions

an atom that as a result of gaining or losing one or more electrons has acquired a positive or negative electric charge

Shale

an extremely fine-grained sedimentary rock that is characterized by a prominent foliation or fissility parallel to the bedding

Batholiths

an extremely large intrusive igneous body with an outcrop area exceeding 100 km2. Usually composed of granite and granodiorite

What common igneous rock forms above sub-ducting tectonic plates, and what role does water play in its origin?

andesite, water lowers its melting point

Synthetic

applies to a substance produced in a laboratory and having the same crystal structure and chemical and physical properties as the naturally occurring equivalent

Where does the largest production of new rock take place?

at midocean ridges, where divergent plates cause basltic magma to rise from the mantle

Forearc basin

basin formed between an oceanic trench and volcanic arc at a convergent plate boundary

Although the cation-anion ratio in garnet is fixed, what allows it to have a wide compositional range, and why are such widely different compositions still classified as the same mineral?

because they have same size or charges so they can be interchangeable

Rapakivi granite

common decorative facing stone in which large pink alkali feldspar phenocrysts are rimmed by gray or white plagioclase

Euhedral

crystal bounded by well-developed crystal faces

phenocrysts

crystals in igneous rocks that are significantly larger than most of the crystals in the rock. Igneous rocks containing phenocrysts are described as porphyritic

What plate tectonic process deflects isotherms up or down in the Earth?

divergent, any plate tectonic associated with magma

pegmatites

exceptionally coarse-grained igneous rock, usually of granitic composition and forming irregular dikes and lenses

Basalt

fine grained igneous rock composed predominantly of equal proportions of plagioclase feldspar and pyroxene (or olivine). It is the most common igneous rock and forms most of the ocean floor

groundmass

fine-grained crystals that surround phenocrysts in a porphyritic rock

mudflows

flow of debris with particles of various size carried along in a mud matrix

Veins

fracture that is filled with a mineral, which is commonly quartz or calcite, but can include minerals of economic value

graded layers

layer in which mineral grains gradually change size and or density form bottom to top of the layer. In sedimentary rocks, graded beds result from settling of grains in turbidity currents

Schist

metamorphic rock in which medium to coarse grained platy minerals, such as micas, or needle-like minerals, such amphiboles, create a prominent foliation or schistosity.

Gneiss

metamorphic rock in which prominent layers are produced by variations in the abundance of minerals. often platy minerals, such as micas, alternate with more granular minerals, such as quartz and feldspar

rock-forming minerals

mineral that is a common constituent of various rock types found in the earth's crust

radiolarian

minute pelagic organisms that build their tests of silica

Trap rock

name given to massive flat-lying basaltic lava flows that are quarried from the rock's durability, which makes it particularly desirable for highway construction. Its name comes form the step-like topographic expression of the lave flows, trap being the Dutch word for stairs

Magma ocean

name given to the huge body of molten rock that is believed to have covered the outer part of the earth early in its history

Rocks

naturally occurring consolidated mixture of minerals. It is the sold material that makes up the earth.

Mineral

naturally occurring solid, with an ordered atomic arrangement and a definite( but commonly not fixed) chemical compositon. Almost all minerals are formed by inorganic chemical processes

foliation

property of a rock to break into thin sheets that are bounded by planes along which typically platy minerals are aligned. this alignment may result form sedimentation of clay minerals or from the growth of micas in a preferred orientation in metamorphic rocks.

turbidity currents

rapidly moving suspension of sedimentary particles. he suspension travels as a coherent body, and when it comes to rest, the larger and denser mineral grains settle first to produce a graded sedimentary bed.

Hot spots

region on the earth's surface marked by a lengthy period of igneous activity. they have been interpreted to be located above plumes that have sources deep in the mantle.

Marble

rock formed from the metamorphism of limestone and composed predominately of calcite, but it may also contain dolomite

Pillows

rounded sacklike bodies of lava that are erupted beneath water. They have a glassy shell but their interiors cool slowly enough to form fine-grained rock. Much of the ocean floor is underlain by pillowed basalt

Conglomerate

sedimentary rock composed of gravel-sized particles

Limestone

sedimentary rock composed predominantly of calcite or more rarely aragonite

Coal

sedimentary rock composed predominantly of fossilized plant remains.

Sandstone

sedimentary rock composed predominantly of sand-sized grains, which are usually made of quartz

Rock factories

specific places where rocks are made in response to plate tectonic-related processes

Hydrothermal alteration

the process by which minerals in a rock are altered, usually to hydrous minerals, by reaction with hot water

mid-ocean ridge

topographic high produced by the creation of new hot oceaninc crust at a divergent plate boundary. Ridges are often located near the center of an ocean, as in the case of the Mid-Atlantic ridge, but they need not be , as in the case of the E. pacific rise

mid ocean ridge basalt (MORB)

type of basalt erupted at midocean ridges and forming most of the ocean floor

flood basalts

type of basalt that is erupted in large volumes form long fissures and tends to form large flat lava flows. They are commonly associated with large igneous provinces.

karst

type of topography characterized by solution features that develops on carbonate rocks

structure

used for features that are on a larger scale than the relations between individual mineral grains, which is referred to as texture

Texture

used to indicate how individual mineral grains are related to one another

rift valleys

valley or basin formed by the down faulting of a block along normal faults as a result of crustal extension

andesite

volcanic rock that characterizes composite volcanoes formed along island arcs above subduction zones. It is composed of approximately equal proportions of pyroxene and plagioclase

Convergent plate boundary

where two tectonic plates converge, with one sub-ducting beneath the other