Ch. 20, NSCI 1120
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
