Key Terms for Exam 1, GEOL-G 110, Spring 2011, section 22330
Chapter 1 (p. 32 in 10th edition)
asthenosphere
atmosphere
biosphere
continental margin
convergent boundary
core
curst
divergent boundary
geology
geosphere
hydrosphere
hypothesis
igneous rock
inner core
lithosphere
magma
mantle
model
oceanic ridge
outer core
plate
plate tectonics
rock cycle
sediment
sedimentary rock
subduction zone
theory
fracture
hardness
ion
ionic bond
isotope
luster
metallic bond
mineral
Mohs hardness scale
neutron
nucleus
periodic table
proton
rock
silicates
streak
tenacity
valence electron
material names:
igneous rocks
granite
diorite
gabbro
rhyolite
andesite
basalt
volcanic tuff
volcanic breccias
lava
magma
melt
volitiles
compositional terms:
felsic
intermediate
mafic
ultra mafic
Chapter 2 (p. 56)
atom
chemical compound
cleavage
color
covalent vond
density
electron
element
ferromagnesian silicates
Chapter 3 (p. 79)
textures:
aphanitic
glassy
groundmass
phaneritic
phenocryst
porphyritic
pyroclastic
vesicular
extrusive vs. intrusive
volcanic vs. plutonic
assimilation
crystallization
crystal settling
decompression melting
geothermal gradient
magma mixing
partial melting
Chapter 4 (p. 110)
aa
caldera
cinder cone
composite cone
crater
dike
concordant
discordant
fissure
flood basalt
hotspot
laccolith
mantle plume
pahoehoe
pillow lava
pluton
pyroclastic material
shield volcano
sill
stratovolcano
viscosity
volcano
volcanic neck
exfoliation dome
frost wedging
soil horizon
leaching
parent material
sheeting
soil
spheroidal weathering
talus slope
sediment:
gravel
sand
mud
silt
clay
ions
sedimentary rocks:
breccia
conglomerate
sandstone
siltstone
shale
claystone
limestone
rock salt
rock gypsum
chert
coal
Chapter 5 (p. 134)
chemical weathering
physical weathering
eluviations
illuviation
erosion vs. weathering
Chapter 6 (p. 160)
biochemical origin
cementation
chemical sedimentary rock
clastic
compaction
crystalline texture
detrital sedimentary rock
diagenesis
evaporate
lithification
organic sedimentary rock
Chapter 1 Review Questions: 8, 9, 12, 13, 15, 16, 19, 20.
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How is a scientific hypothesis different from a scientific theory?
o A hypothesis is a tentative or untested explanation; a theory is a hypothesis that has
survived extensive scrutiny and competing models have been eliminated.
List and briefly describe the four spheres that constitute our natural environment
o Atmosphere – the life-giving gaseous envelope surrounding the earth; shallow layer
provides breathable oxygen, protection from the sun’s heat and UV rays, and the energy
exchange responsible for weather and climate.
o Hydrosphere - the dynamic mass of liquid that is continually on the move, evaporating,
precipitating, running.
o Geosphere – Solid Earth; extends from surface to the center of the planet; largest of
four spheres
o Biosphere - includes all life on Earth
What are the two sources of energy for the Earth system?
o The Sun – drives the external processes that occur in the atmosphere, hydrosphere, and
at the Surface.
o Heat from the Earth’s interior that powers the internal processes that produce
volcanoes, earthquakes, and mountains.
Using the rock cycle, explain the statement “One rock is the raw material for another”
o The rock cycle is a recycling mechanism of materials.
 Magma/Lava is crystallized to form Igneous rock
 Igneous rock is broken down/eroded into sediment by the process of
weathering/transportation
 Sediment is compacted through Lithification to form sedimentary rock.
 Sedimentary rock is buried and goes through metamorphosis into metamorphic
rock with the aid of increased stress/pressure
 Metamorphic rock melts under the surface to form Magma and the cycle begins
again.
List and Briefly describe Earth’s compositional layers.
o Crust: relatively thin, rocky, outer layer
 Continental
 25-40 miles
 Consists of many rock types; most common are granitic rocks
 Older and more dense rocks
 Oceanic
 5 miles thick
 Composed of Basalt
 Younger, less dense rocks
o Mantle: Solid rocky shell that extends 1800 miles
 Change in chemical composition
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82% of Earth’s mass
o Upper mantle mostly peridotite which is rich in magnesium and Iron
 Top portion of upper mantle part of stiff lithosphere
 Lithosphere: entire crust and uppermost mantle and forms
the relatively cool outer shell of the Earth
 Bottom portion Asthenosphere
 Asthenosphere: soft and weak layer compared to
lithosphere
o Lower Mantle – Mantle increases in strength as depth increases due to
increased pressure; however, they are still very hot and capable of gradual
flow
o Core: thought to be Iron/Nickel alloy with minor amounts of oxygen, silicon, and sulfur
 Outer core: liquid layer
o Movement of metallic iron int his zone that generates Earth’s magnetic field
 Inner core: solid due to immense pressure
Contrast the asthenosphere and the lithosphere
o Lithosphere: the entire crust and uppermost mantle; cool, ridged outer shell. Stiff,
relatively cool, outer layer
o Asthenosphere: weaker, upper portion has temperature/pressure regime that results in
some melting
o Both layers move independently of each other.
List the three basic types of plate boundaries and describe the relative movement each
exhibits.
o Divergent Boundaries – plates move apart causing an upwelling of material from the
mantle to create a new seafloor.
  Seafloor spreading: as plates pull apart fractures are filled with molten rock
producing new slivers of seafloor
o Convergent boundaries – plates move together resulting in the consumption of oceanic
lithosphere into the mantle
 Can also result in collision to create major mountain systems
 Old oceanic plates slide beneath the other along these boundaries returning them to
the mantle
 Plate margins where crust is being consumed – subduction zones
o Can lead to explosive volcanic eruptions; Mount St. Helens, but much of the
molten rock never reaches the surface
o [I suggest reading this section]
o Transform fault boundaries
 Where plates grind past each other without the production or destruction of
lithosphere
 Usually at ocean ridges but can happen mid continent like the san andres and the
alpine fault of new Zealand
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Which type of plate boundary:
o Subduction zone: Convergent boundary
o San Andreas Fault: Transform fault boundary
o Seafloor spreading: Divergent boundary
o Mount St. Helens: Convergent boundary
Chap 2, p. 56, questions: 1-3, 5-8, 10, 12, 14 (make it top 8), 15-19.
1. Q. List five characteristics an Earth material should have to be considered a mineral.
a. Naturally occurring, solid, orderly crystalline structure, well-defined chemical
composition, and generally inorganic
2. Q. Define the term rock.
a. A rock is any solid mass of mineral or mineral-like matter that occurs naturally as part of
our planet.
3. Q. List the three main particles of an atom, and explain how they differ from one another.
a. Proton, neutron, electron. Proton – very dense particles with positive electrical charges;
Neutron – have the same mass as a proton but lack an electrical charge; Electrons –
have negative electrical charges
4. Non-existent
5. Q. What is the significance of valence electrons?
a. They are important in chemical bonding.
6. Q. Briefly distinguish between ionic and covalent bonding.
a. Ionic bonding is when one or more valence electrons are transferred from one atom to
another; Covalent bonding is the bonding produced by the sharing of electrons. DUH!
7. Q. What occurs in an atom to produce an ion?
a. Producing an ion requires the atom to either gain or lose electrons, giving them a
negative or positive charge, respectively.
8. Q. What is an isotope?
a. Atoms with the same number of protons but different number of neutrons
9. Non-existent
10. Q. Why might it be difficult to identify a mineral by its color?
a. Use of color as a means of identification can be ambiguous or misleading because the
same mineral can have various hues, often occurring in the same sample
11. Non-existent
12. Q. Table 2.1 (p.52) lists a use for corundum as an abrasive. Explain why it makes a good abrasive
in terms of the Mohs hardness scale.
a. It is used as an abrasive because it is a 9 on the Mohs hardness scale, which is second
hardest only to diamond.
13. Non-existent
14. Q. What are the eight most common elements in Earth’s crust?
a. Silicon (Si), oxygen (O), aluminum (Al), Calcium (Ca), Sodium (Na), Potassium (K),
Magnesium (Mg), and iron (Fe)
15. Q. What do ferromagnesian minerals have in common? List examples of ferromagnesian
minerals.
a. They all contain iron and magnesium, and because of iron content, all are dark in color
and have greater specific gravity, between 3.2-3.6, than nonferromagnesian silicates.
Examples include olivine, the pyroxenes, the amphiboles, biotite, and garnet.
16. Q. What do muscovite and biotite have in common? How do they differ?
a. Common: both members of the mica family, which means they have excellent cleavage
in one direction. Difference: Muscovite is light in color and has a pearly luster and is
nonferromagnesian, biotite is darker and more iron-rich and has shiny black
appearance, and is ferromagnesian
17. Q. Should color be used to distinguish between orthoclase and plagioclase feldspar? What is the
best means of distinguishing between the two types of dickspar?
a. Color should not be used to distinguish between them. The best means is to look for a
multitude of fine parallel lines, called striations
18. Q. Each of the following statements describes a silicate mineral or mineral group. In each case,
provide the appropriate name.
a. The most common member of the amphibole group.
i. Hornblende
b. The most common nonferromagnesian member of the mica family.
i. Muscovite
c. The only common silicate mineral made entirely of silicon and oxygen.
i. Quartz
d. A high-temperature silicate with a name that is based on its color.
i. Olivine
e. Characterized by striations.
i. Plagioclase feldspar
f. Originates as a product of chemical weathering.
i. Clay
19. Q. What simple test can be used to distinguish calcite from dolomite?
a. They can be distinguished using dilute hydrochloric acid test; calcite reacts vigorously to
HCl, whereas dolomite reacts much more slowly.
Chapter 3 – Igneous Rocks
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What is Magma?
o Completely or partly molten material which on coolikng solidifies to form igneous rock
How does lava differ from Magma?
o Lava is magma that has reached the Earth’s surface; is no longer under the crust.
How does the rate of cooling influence the crystallization process?
o Slow cooling permits ions to migrate freely until they eventually join an existing
crystalline structure
 Slow cooling  fewer but larger crystals
o Rapid cooling – ions quickly lose mobility
 Rapid cooling  solid mass of small intergrown crystals
o Nearly instantaneous cooling – no time for ions to arrange in ordered crystalline
network
 Unordered ions  glass
In addition to the rate of cooling, what two other factors influence the crystallization process?
o The amount of silica present
o The amount of dissolved gases in the magma
The classification of igneous rocks is based largely on two criteria; name the criteria.
o Texture
o Mineral composition
The statements that follow relate to terms describing igneous rock textures. For each
statement, identify the appropriate term:
o Openings produced by escaping gas
 Aphanitic – crystals so small that they cannot be seen without a microscope
 Vesicular texture – voids left by gas bubbles that escape as lava solidifies
 Happens when lava cools very rapidly near the surface
 Obsidian exhibits this texture
 Glassy texture – when unordered ions are “frozen” before they are able
to unite into an orderly crystalline structure
o A matrix of fine crystals surrounding phenocrysts
 Porphyritic texture – large phenocrysts surrounded y a matrix of smaller crystals
called groundmass
 Form over tens of hundreds of thousands of years
 Termed porphyry
o Texture in which crystals are too small to be seen without a microscope
 Aphanitic
o A texture characterized by two distinctly different crystal sizes
o Coarse-grained texture, with crystals of roughly equal size.
 Phaneritic Texture – when large masses of magma slowly solidify far below the
surface
o Exceptionally large crystals exceeding 1 cm in diameter
 Pegmatitic texture  Pegmatites
 Form in the late stages of crystallization ; consequence of fluid rich environment
that enhances crystallization
What does a porphyritic texture indicate about an igneous rock?
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o That it was formed over a very long period of time and possibly changed environments.
How are granite and rhyolite different? In what way are they similar?
o Granite is Phaneritic or course grained whereas Rhyolite is Aphanitic or fine grained ;
Granite is plutonic or intrusive and rhyolite is extrusive or volcanic
o The are both Felsic or granitic rocks
Compare and contrast each of the following pairs of rocks:
o Granite and diorite
 Granite and Diorite are both phaneritic or coarse-grained rocks
 Granite is a Felsic or Granitic rock whereas Diorite is an Intermediate or
Andesitic rock
o Basalt and gabbro
 Basalt and Gabbro are both Mafic or Basaltic rocks
 Gabbro is a phaneritic or coarse-grained rock whereas basalt is an aphanitic or
fine grained rock.
 Gabbro is the intrusive or plutonic form of Basalt
o Andesite and rhyolite
 Andesite and Rhyolite are both Aphantic or fine-grained rocks
 Rhyolite is a Felsic or granitic rock whereas Andesite is an Intermediate or
Andesitic rock
How does tuff differ from other igneous rocks such as granite and basalt?
o It is pyroclastic or fragmental – composed of multiple types of rock/minerals.
What is the geothermal gradient?
o Increase of temperature with depth
Describe the three conditions that cause rock to melt.
o Heat – causes melting but at higher temperatures at greater depth because of a greater
confining pressure
o Pressure – decrease in pressure causes decompression melting
o Volatiles – Introduction of volatiles or water can lower a rocks melting point sufficiently;
melting is not complete so partial melting produces a melt made of the lowest melting
temperature minerals (higher in silica than original rock)
What is magmatic differentiation? How might this process lead to the formation of several
different igneous rocks from a single magma?
o It is the process of developing more than one magma type from a common magma
o Crystal settling causes previously formed denser to settle from the liquid portion at the
bottom of the magma chamber; remaining melt may solidify to form a rock with a
different chemical composition.
Relate the classification of igneous rocks to Bowen’s reaction series.
o The mineral makeup of an igneous rock is determined by the chemical composition of
the magma from which it crystallizes; minerals with higher melting points crystallize
before minerals with lower melting points and the reaction series illustrates the
sequence of mineral formation – those minerals that form at similar melting points will
typically be found in together in the same igneous rocks
What is partial melting?
o Partial melting produces a melt made of the lowest-melting temperature minerals
How does the composition of a melt produced by partial melting compare with the
composition of the original rock?
o
The composition of the partial melting material is much higher in silica than the original
rock; magmas generated by partial melting are nearer to the felsic end than the rocks
from which they formed.
Chap 4, p. 110, questions: 2-9, 14, 17, 20-27.
1. Non-existent
2. Q. List three factors that determine the nature of a volcanic eruption. What role does each
play?
a. Chemical composition, temperature, and the amount of dissolved gases it contains.
Temperature: The hotter the lava, the faster it flows, and vice versa. Composition: a
magma’s viscosity is directly related to its silica content, the more silica in the magma,
the greater its viscosity. Quantity of volatiles (gaseous components of magma) affect
mobility by having water dissolved in the magma, which tends to increase fluidity by
reducing polymerization (formation of long silicate chains) by breaking silicon-oxygen
bonds. This loss of gases renders magma more viscous.
3. Q. Why is a volcano that is fed by highly viscous magma likely to be a greater threat to life and
property than a volcano supplied with very fluid magma?
a. When viscous magma ascends, the developing gas bubbles do not easily escape, but
rather cause the molten material to expand resulting in a gradual increase in the
internal pressure. Increased pressure leads to fracturing, which lead to a further drop in
confining pressure which causes more gas bubbles to form. This reaction creates a
violent explosive eruption. Volcanoes supplied with fluid magma allow the expanding
gases to migrate upward and escape with relative ease.
4. Q. Describe pahoehoe and aa lava.
a. Aa flows: have surfaces of rough jagged blocks with dangerously sharp edges and spiny
projections. Pahoehoe flows: exhibit smooth surfaces that often resemble the twisted
braids of ropes (fig 4.7B). Pahoehoe means “on which one can walk”.
5. List the main gases released during a volcanic eruption. Why are gases important in eruptions?
a. Water vapor (70%), carbon dioxide (15%), nitrogen, sulfur dioxide (5% each), and
smaller amounts of chlorine, hydrogen and argon. These are important in eruptions
because they contribute significantly to the gases that make up our planet’s
atmosphere.
6. Q. How do volcanic bombs differ from blocks of pyroclastic debris?
a. Both are larger than 64 millimeters (2.5 inches) in diameter. However, if they are made
of hardened lava they are blocks. They are bombs when they are ejected as
incandescent lava.
7. Q. Compare a volcanic crater to a caldera.
a. A volcanic crater is the funnel-shaped depression, which is located at the summit of
most volcanoes. Some volcanoes have very large depressions called calderas. Craters
have a diameter ranging from a few tens to a few hundreds of meters, calderas have
diameters typically greater than one kilometer and in rare cases can exceed 50
kilometers
8. Q. Compare and contrast the three main types of volcanoes (size, composition, shape, and
eruptive style.
a. Shield volcanoes: usually modest in size, around 600 meters high and 10 km (6 miles) in
diameter. They emit fluid lava and have sides with gentle slopes that vary from 1 to 5
degrees. Have steeper flanks, while their summits are comparately flat. Most of the
lava (about 80%) flows through a well-developed system of lava tubes, which increases
distance lava reaches before it solidifies.
b. Cinder Cones: built from ejected lava fragments that take on the appearance of cinders.
Cinder cones are small, because of their short life span, usually between 30-300 meters
in height. They are found by the thousands all around the globe. They tend to shoot out
hot glowing rock fragments producing a fireworks display. Explosive discharges then
continue. They have a cone shape.
c. Composite Cones: Most picturesque and potentially dangerous volcano. Usually in the
middle in terms of size and conical shaped. Nearly symmetrical structure, product of
gas-rich magma. The silica-rich magmas of composite cones generate thick viscous lavas
that travel short distances, but ay generate explosive eruptions that eject huge
quantities of proclastic material.
9. Q. Name a prominent volcano for each of the three types.
a. Shield Volcano: Mauna Loa (Earth’s largest volcano) (1 of 5 shield volcanoes that
comprise Hawaii)
b. Cinder Cone: Parícutin, located 200 miles west of Mexico City
c. Composite Cone: Mount Shasta (in California, part of the Cascades)
10. Non-existent
11. Non-existent
12. Non-existent
13. Non-existent
14. Q. What is Shiprock, New Mexico, and how did it form?
a. Shiprock is a volcanic neck (neck is the rock occupying the volcanic pipe and remains
there long after most of the cone has vanished). It consists of igneous rock that
crystallized in the vent of a volcano that has long since been eroded away.
15. Non-existent
16. Non-existent
17. Q. Describe each of the four intrusive features discussed in the text (dike, sill, laccolith, and
batholith)
18.
19.
20.
21.
22.
23.
24.
25.
26.
a. Dike: tabular discordant bodies that are produced when magma is injected into
fractures. The force exerted by the emplaced magma can be great enough to separate
the walls of the fracture further.
b. Sill: Tabular plutons (structures that result from the emplacement of igneous material at
depth) formed when magma is injected along sedimentary bedding surfaces. Horizontal
sills are most common, although all orientations are known to exist.
c. Laccolith: Similar to sills because they form when magma is intruded between
sedimentary layers , but the magma that generates laccoliths is more viscous. It can be
detected because of the dome-shaped bulge it creates at the surface.
d. Batholith: By far the largest intrusive igneous bodies. Occur as linear structures several
hundreds of kilometers long and up to 100 kilometers wide. Consist of rock types
having chemical compositions toward the granitic end of the spectrum. Very thick.
Non-existent
Non-esistent
Q. Volcanism at divergent plate boundaries is associated with which rock type? What causes
rocks to melt in these regions?
a. Igneous rock. What causes rocks to melt is decompression melting, which is the process
of when rock rises, it experiences a decrease in confining pressure and undergoes
melting without the addition of heat.
What is the Ring of Fire?
a. An area within the circum-Pacific belt, where most of the 800 active volcanoes identified
are located, along the margins of the ocean basins.
What type of plate boundary is associated with the Ring of Fire?
a. Convergent plate boundary
Q. Are volcanoes in the Ring of Fire generally described as quiescent or violent? Name a volcano
that would support your answer.
a. They are generally described as violent. Mount Augustine, Alaska
Q. Describe the process that generates magma along convergent plate boundaries.
a. As the two plate boundaries converge, an oceanic trench develops. As the slab sinks
deeper into the mantle, an increase in pressure and temperature drives volatiles
upward into the piece of mantle located between the subtracting slab and the
overriding plate. The partially melting of mantle rock generates magma with a basaltic
composition. After a sufficient quantity of magma accumulates, it slowly migrates
upwards.
Q. What is the source of magma for intraplate volcanism?
a. Magma develops when a hotter-than-normal mantle called a mantle plume ascends
toward the surface. As the base of the lamp is heated, the denser liquid at the bottom
becomes buoyant and forms blobs that rise to the top. Once at the top, decompression
melting generates basaltic magma that may eventually trigger volcanism at the surface.
Q. What is meant by hot-spot volcanism?
a. A hot spot is a localized volcanic region a few hundred kilometers across. More than
100 hot spots have been identified, and most have persisted for millions of years. Land
surface is often elevated. By measuring heat flow in these regions, has been
determined that the mantle beneath hot spots must be 100-150 degrees Celsius hotter
than normal.
27. Q. How do geologists identify hot spots other than volcanism?
a. By measuring the heat flow in regions of hot spots, must be 100-150 degrees Celsius
hotter than normal.
Chapter 5 – Weathering and Soils
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If two identical rocks were weathered, one mechanically and one chemically, how would their
products differ?
o The rock that was mechanically weathered would form a product identical to the
original rock. Mechanical weathering merely breaks rock into smaller fragments
o The rock that was chemically weathered would form a product that is chemically
different than the original rock
How does mechanical weathering add to the effectiveness of chemical weathering?
o Mechanical weathering breaks the rock into smaller pieces thus creating more available
surface area for chemical attackers
Describe the formation of an exfoliation dome. Give an example of such a feature.
o The processes of sheeting and unloading form exfoliation Domes. Sheeting occurs when
large masses of igneous rock (granite) are exposed by erosion, slabs begin to break
loose. This sheeting happens because of unloading or a reduction in pressure when
overlying rock is eroded away. The outer layers expand more than the rock below and
separate. Weathering causes the slabs to fall of creating exfoliation domes like Liberty
Cap
Granite and basalt are exposed at the surface in a hot, wet region. Which type of weathering
will predominate? Which of the rocks will weather most rapidly? Why?
o Chemical weathering will predominate
o Basalt will weather more rapidly because it is lower in the stability scale
Heat speeds up a chemical reaction. Why then does chemical weathering proceed slowly in a
hot desert?
o There is a lack of available moisture
How is carbonic acid formed in nature? What results when this acid reacts with potassium
feldspar?
o Carbon dioxide is dissolved in water; rain dissolves some carbon dioxide as it falls
through the atmosphere and additional amounts released by decaying organic matter
are acquired as the water percolates through the soil
o It produces clay mineral, [potassium ions, bicarbonate ions, and silica ions] in solution
Relate soil to the earth system
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o
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It is an interface or a common boundary where different parts of a system interact
Soil forms where the geosphere, the atmosphere, the hydrosphere, and the biosphere
meet
o Soil is dynamic and sensitive to every aspect of its surroundings so any change in
environment results in a change in the soil characteristics until equilibrium is reached
again.
What factors might cause different soils to develop from the same parent material or similar
soils to form from different parent materials?
o Time – if weathering has been going on shortly, the soil will still greatly resemble the
parent material (and vice versa)
o Climate – variations in precipitation and temperature determine whether chemical or
mechanical weathering predominates as well as the rate and depth of weathering.
Controls leaching as well as plant and animal life
o Plants and Animals – the biosphere; types and abundance of organisms affect physical
and chemical processes.
Which control of soil formation is the most important? Explain.
o Climate is the most influential. Temperature and precipitation influence the
predominance of either chemical or mechanical weathering (thus the chemical
composition of the soil). Influences rate and depth of weathering (thick or thin layer of
soil) This also decides the degree to which materials are removed from the soil affecting
its fertility. Determines plant and animal life.
Chap 6, p. 161, questions: 1-18.
1. Q. How does the volume of sedimentary rocks in Earth’s crust compare with the volume of
igneous rocks in the crust? Are sedimentary rocks evenly distributed throughout the crust?
a. Igneous and Metamorphic rocks constitute 90-95% of the outer 10 miles of the crust,
however most of Earth’s solid surface consists of either sediment or sedimentary rock,
because they are concentrated at or near the surface. They are not evenly distributed,
they are concentrated across the ocean floor.
2. Q. List and briefly distinguish among the three basic sedimentary rock categories.
a. Detrital: Rocks that form from the accumulation of materials that originate and are
transported as solid particles derived from both mechanical and chemical weathering
b. Chemical: When ions in solution are precipitated by either inorganic or biological
processes, the material is known as chemical sediment
c. Organic: Ex. Coal, black combustible rock consisting of organic carbon from the remains
of plants that died and accumulated on the floor of a swamp.
3. Q. What minerals are most common in detrital sedimentary rocks? Why are these minerals so
abundant?
4.
5.
6.
7.
8.
9.
10.
11.
a. Clay minerals and quartz. Clay minerals are the most abundant product of the chemical
weathering of silicate minerals, especially feldspars. Quartz is abundant because it is
extremely durable and very resistant to chemical weathering.
b. Other common minerals are feldspars and micas
Q. What is the primary basis for distinguishing among various detrital sedimentary rocks?
a. Particle size
Q. Why does shale often crumble quite easily?
a. It is composed of silt and clay-sized particles, which are fine-grained detrital rocks. The
particles are so small that they cannot be readily identified without great magnification.
Q. How are the degree of sorting and the amount of rounding related to the transportation of
sand grains?
a. If sand grains are about the same size, the sand is considered well sorted, which means
it probably went a long distance by way of wind or waves. Waves are usually better
sorted than minerals deposited by streams. Likewise, if grains have rounded edges, it
implies that they have traveled a far distance. More angular edges are common for
shorter distances and by travel by glaciers. Therefore, degree of sorting and amount of
rounding can both estimate how far the minerals traveled, and by which method.
Q. Distinguish between conglomerate and breccia.
a. Conglomerate consists largely of gravels, may range in size from large boulders to
particles as small as garden peas. Particles usually large enough to be identified as
distinctive rock types. Poorly sorted and rounded.
b. Breccia is more angular. They did not travel far from their source area before they were
deposited. These characteristics describe clues to their history. Particle size reveals the
strength of the currents that transported them, degree of rounding indicates how far
they traveled.
Q. Distinguish between the two categories of chemical sedimentary rocks.
a. Inorganic Processes: evaporation and chemical activity can produce chemical sediments.
b. Organic (life) processes: water-dwelling organisms also form sediments, said to be of
biochemical origin.
Q. What are evaporite deposits? Name a rock that is an evaporite.
a. A sedimentary rock formed of material deposited from solution by evaporation of
water. Ex. Gypsum
Q. How is bituminous coal different from lignite? How is anthracite different from bituminous?
a. Deeper burial transforms lignite into a harder, more compact black rock called
bituminous coal. Bituminous coal metamorphoses into anthracite during folding and
deformation associated with mountain building, as heat and pressure cause further loss
of volatiles and water, thus increasing the concentration of fixed carbon.
Q. Each of the following statements describes one or more characteristics of a particular
sedimentary rock. For each statement, name the sedimentary rock that is being described.
a. An evaporite used to make plaster.
i. gypsum
b. A fine-grained detrital rock that breaks into chunks or blocks.
i. shale
c. Dark-colored sandstone containing angular rock particles as well as clay, quartz, and
feldspar.
i. graywacke
d. The most abundant chemical sedimentary rock.
i. limestone
e. A dark-colored, dense, hard rock made of microcrystalline quartz.
i. chert
f. A variety of limestone composed of small spherical grains.
i. Oolithic limestone
Chapter 6: 13-18
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What is Diagenesis? Give an example.
o Collective term for all of the chemical, physical, and biological changes that take place
after sediments are deposited and during and after lithification.
 Example: recrystallization- the development of more stable minerals from less
stable ones (aragonite the less stable form of calcium carbonate)
Compaction is most important as a lithificaton process with which sediment size?
o Fine grained sedimentary rocks because sands and other coarse sediments are less
compressible.
List three common cements for sedimentary rocks. How might each be identified?
o Calcite – effervesces with dilute hydrochloric acid
o Silica – forms the hardest sedimentary rocks
o Iron oxide – produces an orange or dark red color
Distinguish between clastic and nonclastic textures. What type of texture is common to all
detrital sedimentary rocks?
o Clastic: broken; rocks with a clastic texture consist of discrete fragments and particles
that are cemented and compacted together
 Some spaces between particles remain
 All detrital rocks are clastic
o Nonclastic/crystalline: minerals form a pattern of interlocking crystals (may be
microscopically small or visible) – ex: evaporates.
 Intergrown crystals
What is probably the single most characteristic feature of sedimentary rocks?
o Strata or beds since sedimentary rocks form as layer upon layer of sediment
accumulates.
Distinguish between cross-bedding and graded bedding.
o Cross bedding – sediments accumulate in layers that are inclined to the horizontal
o Graded beds – particles within a single sedimentary layer gradually change from coarse
at the bottom to fine at the top.