Geo Exam 2
Gemstones are often found in pegmatites, which are igneous rocks that are
exceptionally coarse grained.
The blueschist facies form under which of these conditions:
high pressure but relatively low temperature
A pegmatite is a course-grained igneous rock that forms primarily because the melt
is water-rich
Because of its physical properties, magma tends to
move upward, away from where it formed.
Two common metamorphic rocks that typically lack foliation are ________ and ________.
quartzite; marble
In silicate minerals, the SiO4 tetrahedron can be chemically bonded to form all of the following EXCEPT
triple chains.
The majority of the rocks that form at the surface of the Earth are
sedimentary rocks.
________ commonly serves as a protolith in the formation of phyllite.
shale
________ commonly serves as a protolith in the formation of slate.
shale
Which of the following is a type of physical weathering?
thermal expansion
The photo shown below is a(n) ________ that geologists can use to study the minerals in the rock.
thin section
If the climate in an area has very little rainfall, what would be the characteristics of the soil in the area?
thin, with very little organic material
Igneous rocks are formed
through the freezing or crystallization of a melt.
Sea level rises locally, and marine sediments are deposited on top of terrestrial sediments during events termed
transgressions.
Grains become rounded primarily during
transportation
Chemically precipitated limestone that forms in caves or around hot springs is termed
travertine
The image below shows a series of graded beds. How many graded beds are shown?
3
Which of the following materials has been MOST altered from its original bedrock?
A
Which soil horizon is the most important to farmers for planting crops?
A
Which of the following is NOT true concerning the color of minerals?
A mineral's color reflects the wavelengths of light that are absorbed by the mineral.
Which of the following is NOT true about minerals
All minerals are compounds of more than one element.
Which letter corresponds to the regolith in the following picture?
B
Using the Mohs hardness scale below, which of the following statements is false?
Diamonds are twice as hard as apatite.
Why does differential weathering occur?
Different minerals have different resistances to weathering.
How would you tell if a rock is crystalline?
It contains interlocking crystals.
Which of the following statements cannot be applied to the extrusive igneous rock obsidian?
It cools very slowly.
Which of the following is true regarding biochemical chert?
It is made of cryptocrystalline quartz.
Which of the following is a primary difference between phyllite and schist?
Mica crystals within schist are larger than those within phyllite
What is the difference between a rock that is cemented together and a rock that has a crystalline texture?
Minerals are held together as interlocking pieces in a crystalline rock, whereas in a cemented rock the grains do not fit together like puzzle pieces and instead are held together by cement.
Which of the following is the most important characteristic used to identify minerals?
Multiple properties must be used to identify a mineral.
Which soil horizon contains the most organic material?
O
Why does physical weathering speed up the processes of chemical weathering?
Physical weathering produces more surface area for chemical weathering to attack.
________ metamorphism affects the greatest volumes of rock and produces the greatest variety in metamorphic rock
Regional
Pyrite (FeS2) is in which mineral class?
Sulfides
What is the difference in the formation of chalk versus chert?
They are made of different source materials.
Which of the following is true about regressions?
They occur when the land is uplifted by tectonic processes.
Which of the following describes a rock?
a collection of crystals that fit together like puzzle pieces
Minerals are all naturally occurring solid substances with a definable chemical composition. They must also possess
a fixed crystalline structure (spatial arrangement of atoms and ions)
Which of the following would NOT be considered a rock?
a natural pile of unconsolidated sand
If you find a tuff in the field, what type of geologic activity could you reasonably assume has occurred?
a volcanic eruption
Hydration occurs when minerals
absorb water and expand
Which environment would most likely produce sedimentary deposits characterized by poorly to moderately sorted, angular to subangular grains that consist of feldspar, quartz, and lithics (rock fragments)?
alluvial fan
The image below of Death Valley, CA, shows a road that curves around a(n)
alluvial fan.
Dissolution occurs when minerals
are dissolved into water
Most commonly, felsic igneous rocks
are lighter in color than mafic rocks.
Consult the figure below. Compared with low-grade metamorphic rocks, high-grade rocks
are produced at greater temperatures and pressures.
Of the ~4,000 known minerals, the vast majority
are rare
Silicate minerals are subdivided into six groups based on the way silica tetrahedra are
arranged and bonded.
Precambrian metamorphic rocks are exposed at the surface
at places in continental interiors (called shields).
In which of the following settings would you be most likely to find sedimentary rocks forming?
at the bottom of the Mediterranean Sea
Consult the figure below. The region of thermally metamorphosed rock surrounding a cooled pluton is called a (n)
aureole.
Mylonites, formed from dynamic metamorphism, typically do NOT display
bands of randomly oriented mica grains.
A vast, composite intrusive igneous body that covers hundreds of square kilometers (in a map view) is called a
batholith.
Differentiation of the Earth's iron core and collisions of planetesimals caused early Earth to
be much hotter than at present.
Because the velocity of sediment settling (deposition) is positively related to grain size for waterborne sediments, fluvial deposits are more likely than glacial deposits to
be well sorted.
Which environment would most likely produce sedimentary deposits characterized by very well-sorted, very well-rounded grains that are nearly pure quartz?
beach
Geologists call individual layers of sedimentary rocks ________, whereas several of them together are called ________.
beds; strata
Hardness refers to a mineral's ability to resist
being scratched
Cemented shells of marine organisms form which kind of sedimentary rock?
biochemical
The rapid, deep burial of sediments in an accretionary prism leads to the formation of a metamorphic rock termed
blueschist
Minerals can crystallize in all of the following ways EXCEPT
bonding carbon to oxygen atoms to form organic compounds
Volatiles refer to substances that
evaporate easily and exist as gases.
Marble and quartzite are nonfoliated metamorphic rocks because
both are dominated by minerals that produce equant grains.
A shale differs from a mudstone in that it
breaks into platy sheets
The image below shows a mineral with hydrochloric acid applied to it. Based on the reaction and presence of gas bubbles, which of the following minerals is this most likely to be?
calcite
Diamond and graphite are both polymorphs of
carbon
Calcite (CaCO3) is in which mineral class?
carbonates
Which of the following processes are NOT involved in metamorphism?
cementation and compaction of grains during diagenesis
Which of the following are NOT considered sediments?
cemented grains
Broadly, metamorphism involves
changes in mineralogy and texture in response to heat and stress
Precipitation of gypsum due to evaporation of seawater produces which kind of sedimentary rock?
chemical
Minerals are grouped into mineral classes primarily on the basis of
chemistry, specifically the anions within the chemical formula.
Lithified detritus (breakdown products of preexisting rocks) forms which kind of sedimentary rock?
clastic
hick accumulations of sediments and fossils in the deep ocean tend to be ___________-sized because of the low amount of energy in the environment.
clay
What type of sediment is typically found in lake bottoms?
clay/mud
The tendency for minerals to break along distinct planar surfaces that have a specific orientation in relation to the crystal structure called
cleavage
As compared to aphanitic igneous rocks, phaneritic rocks are
coarser grained.
Trace amounts of impurity can produce significant differences in ________ among individual crystals of a mineral species
color
Fewer than 50 minerals are
commonly found in rocks
Which of the following processes does NOT occur in the formation of metamorphic rock?
complete remelting of the rock, followed by solidification to form a new rock
Which of the following is NOT true? Sediments deposited in a beach environment are typically
composed of angular grains.
The image below shows a mineral specimen of quartz. What is the term for the smoothly curving, clamshell-shaped surface on the sample?
conchoidal fracture
Glass and quartz crystals exhibit a smoothly curving, clamshell-shaped fracture pattern termed
conchoidal fracture.
The image below shows an outcrop of coarse-grained sedimentary rock. Note the rock hammer for scale. What is the name of this rock type?
conglomerate
Consult the figure below. Compared with amphibolite metamorphic facies, greenschist facies
consist of lower-grade rocks.
The boundary formed between new intrusive igneous rock and the host rock around it is called a
contact
Which of the following common minerals is hardest?
quartz
A volcanic arc results from __________ tectonic movements and is associated with a __________.
convergent; subduction zone
As compared to coarse-grained igneous rocks, fine-grained igneous rocks
cool and solidify more quickly.
Intrusive rocks that form deep within the Earth ______________ than intrusive rocks that cool near the surface.
cool more slowly
What type of texture is shown in this photomicrograph?
crystalline
In the formation of gneiss from a granite protolith, distinctive compositional bands form because of
crystals dissolving, with atoms and ions migrating and reorganizing as new crystals.
A body of rock starts at location A in the graph below. The rock, over a period of time, moves to location B and begins to melt. This is an example of melting due to
decompression.
If the volatile content of magma is increased, its viscosity will
decrease
Vesicles in an igneous rock are evidence for which of the following?
degassing of volatiles
Topset, foreset, and bottomset beds are indicative of ________ environments.
delta
The mineral assemblage within metamorphic rock is
dependent on both the mineral content of the protolith and the temperature and pressure of formation
Large layers of cross-bedded sand can be indicative of a ____________ environment.
desert
The application of ________ during metamorphism causes elongated crystals to align parallel with each other. When this happens, the rock develops ________.
differential stress; foliation
In the figure provided below, what type of igneous intrusion is the vertical rock unit shown by letter A?
dike
Salt water is the end product of this weathering process.
dissolution
Naturally forming glass (such as obsidian) is NOT considered a mineral because it
does not have a fixed crystalline structure.
When limestone becomes chemically altered so that half of the calcium atoms are replaced by magnesium, the resultant rock is termed
dolostone
The Dust Bowl of the 1930s was created by which phenomenon?
drought
Which of the following is not typically associated with the eruption of a Large Igneous Province (LIP)?
emplacement of large granite batholiths
Differential stress will cause crystals to align in a preferred orientation unless the crystals are
equant
The removal of detritus from weathered rock at an outcrop is termed
erosion
Crystals that exhibit well-formed faces are referred to as
euhedral
The diamonds we typically see today in engagement rings do not display their natural crystal faces but rather ________,which are made by grinding the gem on a spinning lap.
facets
Which type of magma has the greatest silica content?
felsic
Large igneous provinces are formed by ________, which can flow tens to hundreds of kilometers.
flood basalts
Rocks resulting from thermal (contact) metamorphism will NOT possess
foliation
Slaty cleavage, schistosity, and compositional banding are all examples of
foliation
Basins that form on the continental side of mountain ranges are called _________ basins.
foreland
Which of the following statements is false? Hornfels facies rocks
form at high pressures and low temperatures.
Minerals that do not possess cleavage are said to possess
fracture
In which type of silicates are the greatest proportion of oxygen atoms shared by pairs of adjacent tetrahedra?
framework silicates
What type of weathering are you most likely to find occurring in areas with cold climates?
frost wedging
Which of the following minerals is more commonly known as table salt?
halite
As compared to mafic igneous rocks, felsic igneous rocks
have a higher proportion of silica relative to Mg oxide and Fe oxide.
Ore minerals, such as galena and hematite, tend to be different from typical minerals in that they have a
high specific gravity.
Consult the figure below. Hot water reacting with the crust is the basis for what type of metamorphism?
hydrothermal
Which transport medium carries the largest particles?
ice in glaciers
Which of the following is a mineral?
ice, which is water in the solid state
A body of gneiss is subjected to heat and forms a melt. Later, the melt cools and crystallizes to form a (n) ________ rock
igneous
What type of rock is being formed in the photo?
igneous
What type of rock would you expect to form from volcanic activity?
igneous
Which type of rock forms from the freezing (solidification) of a melt?
igneous
If a body of magma becomes more felsic, its viscosity will
increase
A mineral within a metamorphic rock that can be used to narrowly constrain the temperature and pressure of rock formation is termed a (n) ________ mineral.
index
Chemical weathering involves the breakdown of material due to
interaction with water or air.
Shiprock, New Mexico, seen in the photo below is a(n)
intrusion that represents the eroded remnant of an extinct volcano.
When magma solidifies below the surface of the Earth, ________ are formed.
intrusive igneous rocks
Regional metamorphism
is another name for dynamothermal metamorphism.
Within a single mountain range,
it is possible to find a variety of metamorphic rocks produced in distinct facies, including high-, low-, and intermediate-grade rocks
The following is a picture of what type of phenomenon?
jointing
What type of weathering has created the onion-like layers in the rocks in the picture?
jointing
Diamonds are usually found in a rock called
kimberlite
Differential weathering occurs when
layers of rock weather at different rates
________ commonly serves as a protolith in the formation of marble.
limestone
Compaction and cementation of grains occurs during
lithification
Which of the following processes is not responsible for the formation of magma within the Earth?
loss of volatiles to the atmosphere
The way a mineral scatters light is a diagnostic property termed
luster
A majority of the melts in the Earth form through the partial melting of ultramafic mantle rock. These newly formed magmas are
mafic
The difference between magma and lava is
magma is melt underground, whereas lava is melt that has emerged from the surface.
A protolith
may belong to any of the three primary rock types.
Injecting hot fudge into ice cream and causing the ice cream to melt is an appropriate analogy for which cause of magma melt
melting due to heat transfer from rising magma
If a rock is subjected to elevated levels of heat and pressure, a(n) ________ rock will form.
metamorphic
What type of rock is shown in the photo below?
metamorphic
What do geologists call the layering seen in this photo?
metamorphic foliation
A buried body of shale is subjected to differential stress, causing clay minerals to realign and produce slate. This is an example of
metamorphism.
Clay minerals within a buried body of slate are recrystallized at high temperatures and pressures to form mica, producing a rock called phyllite. This is an example of
metamorphism.
The net chemical change in a metamorphic rock induced by a reaction with hot groundwater is termed
metasomatism.
Chemical sedimentary rocks are classified primarily on the basis of
mineral composition.
Foliated metamorphic rocks possess
mineral grains in preferred orientations or patterns of association.
The zone of leaching is the area in which
minerals are dissolved and removed from soil
In general, when rock is partially melted, the chemistry of the melt is
more felsic than the original chemistry of the rock that was partially melted.
In general, if a body of igneous (source) rock is subjected to partial melting, the magma that is produced is expected to be
more felsic than the source rock.
During fractional crystallization of a magma body, the first rock that is expected to crystallize from the magma will be
more mafic than the magma.
The sedimentary rocks breccia and conglomerate most commonly form in a ________ environment.
mountain
Rocks are ________ and thus not human-made.
natural
Sedimentary rocks are most likely to form
near the Earth's surface.
Thermal (contact) metamorphism produces
nonfoliated rocks only
A heavy book is placed on top of a ball of pizza dough, causing the dough to flatten. This is an application of
normal stress.
In the discontinuous series of Bowen's reaction series, the first mineral to crystallize from a mafic melt is
olivine.
The most recently formed portion of any crystal is always found
on the outer edges.
For the majority of minerals, the streak obtained when the mineral is scratched against a porcelain plate is
only useful if the mineral is softer than the porcelain streak plate.
Two major sources of energy, coal and oil shale, are considered ________ sedimentary rocks.
organic
What type of weathering has altered the pyrite crystals in the picture?
oxidation
Which type of weathering process is happening to materials when they rust?
oxidation
Which common gemstone results from biomineralization?
pearl
An igneous rock with a mixed texture consisting of coarse crystals (phenocrysts) surrounded by fine crystals (groundmass) is termed
phaneritic.
Diagenesis refers to
physical and chemical alterations, including compaction and cementation, that occur as sediment is transformed into rock
The figure below shows mafic magma as it meets the seafloor, which cools to form an igneous rock called
pillow basalt.
The continuous series in Bowen's reaction series describes the crystallization behavior of which mineral?
plagioclase
A _________ is an irregular or blob-shaped intrusive body; a ___________ is a blister-shaped intrusion.
pluton; laccolith
When two different minerals have the same chemical formula but different crystal structures, they are said to be
polymorphs
Pegmatites, which often occur in dikes, are unusual among shallow intrusive rocks in that they
possess exceptionally coarse grains.
The primary difference between breccia and conglomerate is that conglomerate
possesses more rounded grains than breccia.
The transformation of low-grade metamorphic rocks into high-grade metamorphic rocks is termed ________ metamorphism.
prograde
Composition describes the
proportion of chemicals that make up a rock.
The preexisting rock that is subsequently altered to form a metamorphic rock is termed a
protolith
A felsic, highly-vesicular volcanic rock is termed
pumice
A fragmental, extrusive igneous rock is referred to as which of the following?
pyroclastic
Bombs, ash, and cinders are all examples of
pyroclastic debris.
Which of the following best explains how a metamorphic rock forms?
recrystallization due to changes in pressure and temperature
The transformation of high-grade metamorphic rocks into low-grade metamorphic rocks is termed ________ metamorphism.
retrograde
Granite, an intrusive igneous rock, is most similar in mineral composition to which extrusive equivalent?
rhyolite
Pulling a block of clay apart, resulting in the middle portion thinning and sinking, is an adequate analogy for
rift basins and subsidence.
Which of the following is NOT part of the process that leads to the exhumation of metamorphic rocks?
rising plumes of magma in the mantle
A well-sorted sandstone with asymmetric ripples was most likely deposited as sand by a
river (far from source).
Dynamothermal (regional) metamorphism occurs when
rock becomes deeply buried during continental collision and mountain building.
Why do geologists classify rocks?
rocks are the key to understanding how the Earth formed
What type of weathering are you most likely to find occurring on the coast?
salt wedging
What type of weathering has produced the honeycomb-like features shown in the following photo?
salt wedging
________ commonly serves as a protolith in the formation of quartzite.
sandstone
Which two gems are varieties of the mineral corundum (Al2O3)?
sapphires and rubies
A preferred orientation of large, flaky mica crystals within metamorphic rock is termed
schistosity
Granite is a type of rock that forms deep underground from magma that cools very slowly. What type of rock is granite?
sedimentary
Imagine you are holding a rock composed of small sand grains cemented together. What subclassification of sedimentary rock is this
sedimentary
What type of rock is shown in the photo? (bedding)
sedimentary
What type of rock would you most expect to find forming in a beach environment?
sedimentary
Which type of rock is formed by precipitation of minerals from a solution?
sedimentary
Which of the following are most likely to preserve conditions of ancient environments on the Earth?
sedimentary rocks
Which of the following describes the progression of rock types through increasing metamorphic grade from left to right?
shale → slate → phyllite → schist
Limestone is most likely formed in which of the following environments?
shallow-marine carbonate
The figure below shows the application of
shear stress
Spreading peanut butter on bread is an application of
shear stress.
The mineral class that makes up more than 95 percent of the continental crust is termed the
silicates.
In the figure provided below, what type of igneous intrusion is the horizontal rock unit shown by letter A
sill
Biochemical limestones are dominated by carbonate mud and fragments of
skeletons of marine invertebrates made of calcite and aragonite.
Which list properly orders foliated metamorphic rocks from lowest to highest grade from left to right?
slate, phyllite, schist, and gneiss
Weathering results in
smaller, more rounded pieces
A magma body with a ________ volume and a ________ shape cools fastest.
smaller; pancake
A mineral property defined as the density of the mineral sample divided by the density of water (1.0 g/cm3) is
specific gravity.
The color of a mineral in powdered form is termed
streak
The image below shows a mineral specimen of pyrite. What is the term for the thin parallel corrugations or stripes shown on the crystal faces below?
striations
Death Valley is currently sinking partly due to the weight of continuously accumulating sediment shed from the mountains that border the valley. What phenomenon is this an example of and what depositional environment is created
subsidence and alluvial fans
Flood basalts such as those found in the Columbia Plateau and the Deccan region are associated with
superplumes
As compared with metamorphism, diagenesis
takes place at lower temperatures and pressures
Which of the following common minerals is softest?
talc
Which of the following does not affect the cooling rate of magma?
tectonic setting
The geotherm is the rate of change of
temperature with depth in the Earth's interior.
Which of the following is a reliable characteristic that can be used to classify a rock?
texture
The electron microprobe, a commonly used analytical instrument in geology, focuses a beam of electrons on a sample to determine
the chemical composition.
Minerals in geodes (as seen below) form spectacular euhedral crystals because
the crystals have abundant room to grow in their hollow surroundings
Stratification refers to
the development of layering within sedimentary rocks
Viscosity does NOT depend on
the total volume of the magma body.
Fragments of material erupted from a volcano eventually settle and lithify to form an extrusive igneous rock called
tuff
When graded beds are observed in a rock outcrop, this tells geologists that a
turbidity current deposited these beds, depositing coarser material first
Which of the following is LEAST likely to affect soil thickness?
types of animals
If water is the transport mechanism of sediment, the grain size of sedimentary deposits most closely indicates the
velocity of the water at the moment the sediment settled to the bottom.
If a geologist found preserved mud cracks, he or she could conclude that the environment in which they formed
was once covered in wet mud.
Retrograde metamorphism will not occur unless an increased amount of ________ is added to the system.
water
Important volatiles in magmas include
water and carbon dioxide.
Symmetric ripples form when
water deposits sediment in layers, but the direction of flow periodically changes
Potassium feldspar reacts with water to form clay. This is an example of
weathering
Sediment formation is the result of __________ at the Earth's surface.
weathering
The breakdown of exposed rock into small fragments and dissolved ions is termed
weathering
What can geologists most easily determine by analyzing a thin section?
what minerals constitute the rock and how grains connect to one another
It is unusual for ________ to carry grains larger than sand.
wind
The pattern of atoms in a crystal can be detected using
x-ray diffraction.
