Ch. 20, NSCI 1120

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Streak

The name given to the color of a mineral in its powdered form.

Fracture

A break that does not occur along a plane of weakness

What is the difference between a dike and a sill

A dike intrudes across sedimentary layers, and a sill intrudes between sedimentary layers

Solubility

A measure of the ease with which a mineral can be dissolved. Low-solubility minerals are difficult to dissolve; high-solubility minerals are easier to dissolve.

Silicate

A mineral that contains both silicon and oxygen and (usually) other elements in its chemical composition; silicates are the largest and most common rock-forming mineral group.

Nonsilicate

A mineral that does not contain silica (silicon + oxygen)

Mineral

A naturally formed inorganic crystalline solid, composed of an ordered arrangement of atoms with a specific chemical composition.

Recrystallization

A process that occurs when rocks are subjected to high temperatures and pressures and go through a change in minerals; often accompanied by the loss of H2O or CO2.

Mohs scale of hardness

A ranking of a mineral's hardness, which is its resistance to scratching.

Rock cycle

A sequence of events involving the formation, destruction, alteration, and reformation of rocks as a result of the generation and movement of magma; the weathering, erosion, transportation, and deposition of sediment; and the metamorphism of preexisting rocks.

Rank these rock-forming minerals from most abundant to least abundant: (a) silicates, (b) carbonates, (c) sulfates, (d) oxides

A, B, C, D

Rank the magma types in order of increasing (low to high) silica content: (a) basaltic, (b) granitic, (c) andesitic

A, C, B

Rock

An aggregate of minerals. Some rocks are aggregates of fossil shell fragments, solid organic matter, or any combination of these components.

Rank the following properties used for mineral identification from most useful to least useful: (a) color, (b) hardness, (c) streak, (d) cleavage

B, D, C, A

What do freeze-thaw and salt weathering have in common

Both freeze-thaw and salt weathering require rain and force rocks apart physically

Rank the following stages of sedimentary rock formation from first to last: (a) erosion, (b) lithification, (c) weathering, (d) deposition

C, A, D, B

Rank these properties as to how much they are affected by chemical bonding: (a) color, (b) density, (c) hardness, (d) cleavage

C, D, B, A

Rank, from first to last, the episodes that brought about Earth's uneven distribution of elements: (a) gravitational attraction, (b) radioactive decay heating, (c) density segregation, (d) impact heating.

D, A, B, C

From hardest to softest, rank the following minerals: (a) apatite, (b) calcite, (c) quartz, (d) topaz

D, C, A, B

Why are mineral bands in metamorphic rocks light and dark colored

Dark minerals rich in iron and magnesium separate from light minerals rich in silica and aluminum

Why is oxygen the most common element in Earth's crust, but not in Earth as a whole

Density segregation - dense elements sank to Earth's center, and lighter elements rose to the surface

Weathering

Disintegration and/or decomposition of rock at or near Earth's surface.

In general, why does Earth's crust sit on top of the mantle

Earth's crust is less dense than the mantle

Volcanic rocks

Extrusive igneous rocks formed by the eruption of molten rock at Earth's surface. Basalt is a volcanic rock.

How are felsic magmas formed

Heat from the mantle melts part of the lower crust

Plutonic rock

Intrusive igneous rock formed from magma that cools beneath Earth's surface. Granite is a plutonic rock.

Which of these is a true statement about silicate minerals

Melting point decreases as silica percentage increases

Mechanical deformation

Metamorphism caused by stress, such as increased pressure

Why do bands of minerals form when rocks are put under normal stress

Minerals dissolve, atoms migrate to new locations, and minerals reform

Lava

Molten magma that moves upward from inside Earth and flows onto the surface. The term lava refers both to the molten rock itself and to the solid rocks that form from it.

Magma

Molten rock in Earth's interior

Could metamorphic rocks reach the surface of a planet without rock-uplifting processes

No, metamorphic rocks must be uplifted and exposed by erosion

Polymorph

One of two or more minerals that contain the same elements in the same proportions but have different crystal structures.

How are metamorphic rocks formed?

Preexisting rock is altered through heat and pressure

How do mafic volcanic rocks get to Earth's surface?

Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock

Igneous rocks

Rocks formed by the cooling and crystallization of hot, molten rock material called magma (or lava).

Metamorphic rocks

Rocks formed from preexisting rocks that have been changed or transformed by high temperature, high pressure, or both.

Sedimentary rocks

Rocks formed from the accumulation of weathered material (sediments) that has been eroded by water, wind, or ice.

Tectonic plates

Sections into which Earth's crust is broken up; they move in response to heat flow and convection in Earth's interior.

Chemical sediments

Sediments that form by the precipitation of minerals from water on Earth's surface

Metamorphism

The changes in rock that happen as physical and chemical conditions change.

Crystallization

The growth of a solid from a liquid or gas whose atoms come together in specific chemical proportions and crystalline arrangements.

Partial melting

The incomplete melting of rocks, resulting in magmas of various compositions.

Crystal form

The outward expression of the orderly internal arrangement of atoms in a crystal.

Erosion

The processes by which weathered rock particles are removed and transported away by water, wind, or ice.

Density

The ratio of the mass of a substance to its volume

Sedimentation

The stage of sedimentary rock formation in which deposited sediments accumulate and change (lithify) into sedimentary rock through the processes of compaction and, usually, cementation.

Deposition

The stage of sedimentary rock formation in which eroded particles come to rest

Cleavage

The tendency of a mineral to break along planes of weakness

Why are volcanic rocks often exposed at Earth's surface as hills, ridges, and mountains surrounded by areas of lower elevation

Volcanic rocks are often more resistant to erosion than surrounding rock

Why does water frozen in the cracks of a rock help to break down the rock

Water expands when frozen and physically forces the rock apart

Minerals are made up of different elements, and rocks are

a physical mixture of materials - minerals, fossils, fossil fragments, and/or organic matter

How about a piece of chromite

a piece of chromite sink in the liquid

Imagine that we have a liquid with a density of 3.5 g/cm3. Knowing that objects of higher density will sink in the liquid, will a piece of quartz sink or float in the liquid

a piece of quartz float in the liquid

In general, when will melted rock in the mantle rise

almost always

What is foliation

banding in metamorphic rocks that results from the reorientation of minerals

What is a magma chamber called after the conduit has solidified and been exposed by erosion

batholith

Where do most metamorphic rocks form

between a few and many kilometers beneath Earth's surface

A mineral's physical properties are dependent on

composition, structure, and bonding

Dark minerals rich in iron and magnesium separate from light minerals rich in silica and aluminum

dissolution followed by crystallization

What would you call a granite that has undergone metamorphism and now exhibits foliation

gneiss

Are the Hawaiian Islands made up primarily of igneous, sedimentary, or metamorphic rock

igneous rock

As magma cools, the first minerals to crystallize are those with a

low silica content

What lies underneath volcanic features at Earth's surface

magma chambers and volcanic conduits

Which two rock types would you expect to see sitting next to each other after a very long period characterized by only uplift and erosion

metamorphic and sedimentary rocks

If a magma contains molten forms of mineral A (30% silica) and mineral B (25% silica), which would crystallize last as the magma cools

mineral A

If a rock contains mineral A (30% silica) and mineral B (25% silica), which would melt first as temperature rises

mineral A

If a magma contains molten forms of mineral A (30% silica) and mineral B (25% silica), which would crystallize first as the magma cools

mineral B

If a rock contains mineral A (30% silica) and mineral B (25% silica), which would melt last as temperature increases

mineral B

In the process of crystallization, the remaining magma becomes

more and more silica enriched

Minerals with the same chemical composition will

not always have the same crystalline structure

If a magma contains molten forms of quartz and olivine (a silicate mineral), which crystallizes first as the magma cools

olivine

How will minerals orient when a rock is put under shear stress

parallel to the direction of the shear stress

How will foliation in continental metamorphic rocks formed during subduction be oriented

perpendicular to the direction of plate movement

How will minerals grow when a rock is put under normal stress

perpendicular to the direction of the greatest stress

How will minerals orient when a rock is put under normal stress

perpendicular to the direction of the greatest stress

If a rock contains both quartz and pyroxene (a silicate mineral), which melts first as the rock is heated

quartz

Do metamorphic rocks look like the preexisting rock from which they form

sometimes, but not always

What is salt weathering

the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart

What is rock texture

the way a rock looks

How do metamorphic rocks reach Earth's surface

through removal of overlying rocks

What is a volcanic conduit called after the conduit has solidified and been exposed by erosion

volcanic neck

When will magma rise to Earth's surface

when the magma is less dense than adjacent rock


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