GEOLOGY Chapters 6-10 Homework
__________________________________________________________ are pieces of rock that are contained within another rock.
inclusions
_______________________________ form when wet mud dries out and shrinks because it is exposed to air
mudcracks
The source of weathered mineral matter from which soils develop is called
parent material
Briefly describe the process that has led to the formation of intricate folding in solid rocks that now crop out at the surface of the Earth.
As solid rocks are subjected to intense heat and pressure, they become less rigid(pliable) and flow in response to stress. When the rock cools, the intricate folds remain.Weathering and erosion of the overburden can allow the intricately folded rocks to be exposed at the surface of the Earth.
Name and describe the two main ways that sedimentary rocks become lithified.
(1) Compaction occurs in old sedimentary layers as new layers pile on top and squeeze the old layers to a more compact and hard form. (2) Cementation occurs when mineral crystals crystallize in the pore spaces of bodies of sediment, where they "glue" together the grains of sediment.
Describe three settings in which metamorphism most often occurs.
(1) Metamorphism occurs in association with large-scale deformation (regional metamorphism) (2) where rock has been in contact with magma (contact metamorphism) (3) along fault zones.
Examine the illustration below (a cross section through the Earth as you might observe on the wall of a quarry or a road cut). Give two reasons why the granite must be older than the sedimentary layers. question #14 - chapter 9 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(1) One reason why the granite is older than the sedimentary layers is that the granite occurs beneath the sedimentary layers (i.e., it was there before the sedimentary layers were deposited on top of it). (2) Also, there are inclusions of granite in the oldest of the sedimentary layers, which means that parts of the granite were eroded and incorporated as sedimentary grains into the sedimentary layers.
Name three agents of metamorphism.
(1) heat (2)Pressure (3)chemically active fluids
What are the three main factors that determine how rocks will behave when subjected to stresses that exceed their strengths?
(1): the environment (pressure and temperature) (2): strength of the material to be deformed (3): length of time that the stress is to be applied
if the limbs of a fold diverge at the same angle from the axial plane, then the fold is said to be (a)_____________________________, but if the limbs of a fold diverge at different angles from the axial plane, then the fold is said to be (b)_____________________________
(a) symmetrical (b): asymmetrical
The numerical age of the Earth is about (a)_____________________ billion years, which is the same as (b)_____________________ million years.
(a): 4.5 (b): 4,500
Give a step-by-step description of how an angular unconformity can develop, starting with step a and proceeding through additional steps as needed.
(a): A sequence of horizontal strata is deposited. (b): The sequence of horizontal strata is folded or tilted, then partly eroded. (c): A second (younger) sequence of horizontal strata is deposited on the partly eroded and folded/tilted strata.
Carefully examine the cross section below of a subduction zone, and note the areas labeled A, B, and C. At which location (A, B, or C) would a metamorphic regime occur that is characterized by high temperature and high pressure? (a)________________ At which location (A, B, or C) would a metamorphic regime occur that is characterized by high temperature and low pressure? (b)________________ At which location (A, B, or C) would a metamorphic regime occur that is characterized by low temperature and low pressure? (c)________________ At which location (A, B, or C) would blue schist form? (d)________________ question #3 - chapter 8 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): B (b): C (c): A (d): A
Fill in the chart below with the correct name of a geologic era of time. question #15 - chapter 9 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): Cenozoic (b): Mesozoic (c): Paleozoic
How are slaty cleavage and schistosity related?(a)______________________________________________________________________________________ How are they different?(b)______________________________________________________________________
(a): They are both metamorphic features produced by the foliation process (and are both foliations) (b): They are two different kinds of foliations. Slaty cleavage is a foliation characterized by nearly perfect parallel alignment of mineral grains, has been caused by a low grade of metamorphism, and has undergone almost no recrystallization.Schistosity is a foliation characterized by less-parallel alignment of mineral grains, has been caused by a relatively high grade of metamorphism, and has undergone much recrystallization.
What kind of geologic structure is present in the photograph below? (a)____________________________________________________________________ Explain your answer. (b)____________________________________________________________________ question #3 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): fold (anticline) (b): The layers have been folded into an upfold.
On the blank provided beside each geologic cross section below, write the name of the specific type of unconformity that is labeled with an arrow. The v-pattern indicates igneous rock. All other patterns are different types of sedimentary rocks. question #9 - chapter 9 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): nonconformity (b): disconformity (c): angular unconformity
Carefully examine the photograph below of a rock sample. The sample is shown at its actual size. Also think of all of the different parts of the rock cycle that have to do with the formation of this rock. Now list all the steps of the rock cycle that were involved in the formation of this rock as it appears here and now. Start with step a, that is, weathering of pre-existing rocks at the surface of the Earth question #3 - chapter 8 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): Weathering of preexisting rocks occurred at the earth's surface. (b): Erosion,transportation, and rounding of weathered rock fragments caused them to develop spherical shapes. (c): The spherical rock fragments and associated clay, silt, and sand were deposited as a layer of gravel. (d): Burial of the gravel layer caused it to become lithified into a conglomerate. (e): Continued burial caused heating, so much that sedimentary grains became very pliable (nonrigid). (f): Shear and continued burial transformed the conglomerate into metaconglomerate (during which the rock became more dense, shortened in the vertical dimension, and lengthened in the horizontal dimension).
Fill in the chart below, which concerns common types of radioactive decay. question #10 - chapter 9 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): alpha emission (alpha decay) (b): 2 fewer (c): 4 fewer (d): beta emission (beta decay) (e): 1 more (f): No change (g): electron capture (h): 1 fewer (i): no change
An arch-like fold (upfold) having the oldest layers in its center is called a(n) (a)_____________________________, whereas a trough-like fold (downfold) having the youngest layers in its center is called a(n) (b)_________________________
(a): anticline (b): syncline
On the blanks provided below, write the name of the specific feature that has been labeled. What kind of fold is this? question #6 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): axial plane (b): axis (a): limbs (c????) (b): anticline (d????) *answer key listed a-b-a-b in sequencial order*
Rocks that fracture when deformed are said to undergo (a)_____________________________, whereas rocks that flow when deformed are said to be (b)_____________________________.
(a): brittle failure (b): ductile
Stress that causes shortening of a rock body is called (a)_____________________________. Stress that elongates rock bodies by pulling them apart is called (b)_____________________________. Stress applied unequally in different directions is called (c)_____________________________
(a): compressional stress (b): tensional stress (c): differential stress
Strata are said to be (a)___________________________________________ when they have been deposited one on top of the other without interruption. Wherever there has been an interruption in the deposition of layers (or wherever erosion has removed previously formed rocks), there are breaks in the rock record that are called (b)________________________________________________.
(a): conformable (b): unconformities
The task of matching up rocks of similar ages among different regions is referred to as (a)__________________________________. The (b)_________________________________________ states that fossil organisms (including plants) succeed one another in a definite and determinable order. Fossils that are associated with a particular span of geologic time are called (c)_____________________________________.
(a): correlation (b): principle of fossil succession (c): index fossils
Faults along which movements are primarily vertical are called (a)_____________________________. In such faults, the rock surface immediately above the fault is called the (b)_____________________________, and the rock surface immediately below the fault is called the (c)_____________________________.
(a): dip-slip faults (b): hanging wall (c): footwall
Each of the two block diagrams below portrays a specific kind of geologic structure. Write the name of the structure on the blank provided beside each block diagram. question #8 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): dome (b): basin
Rocks that return to their original shape after the stress is removed are said to deform (a)_____________________________. Deformed rocks that have folded and flowed and remain deformed even after the stress is removed are said to have undergone (b)_____________________________.
(a): elastically (b): ductile deformation
The largest standard division of geologic time is a(n) (a)__________________________________________, which can be subdivided into smaller standard subdivisions of time called (b)____________________________________. On the other hand, the smallest standard divisions of geologic time are called (c)____________________________________, which are commonly grouped together to form time divisions called (d)____________________________________.
(a): eon (b): eras (c): epochs (d): periods
(a)____________________________ is a clayey material formed by the pulverizing and grinding of rocks along fault surfaces. Striations or linear grooves that occur on the fault surfaces, as a result of the grinding, are called (b)_____________________________.
(a): fault gouge (b): slickensides
(a)_____________________________ are fractures along which displacement has occurred. When such features are very large, they generally consist of many closely spaced, interconnected surfaces in a broad belt of deformation known as a(n) (b)_____________________________.
(a): faults (b): fault zone
Carefully examine the photograph below of a metamorphic rock sample. The sample is shown at its actual size. Is this rock foliated or nonfoliated?(a)____________________________________________________________________ What is the name of this metamorphic rock?(b)____________________________________________________________________ Consider how this rock got its texture. Was it compressed from top to bottom or from side to side?(c)__________________________________________________________________ question #6 - chapter 8 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): foliated (b): gneiss (c): side to side
The rock pictured below is composed of large dark-colored garnet crystals set in a mass of small muscovite mica crystals that are aligned parallel to one another. Is this rock foliated or nonfoliated?(a)____________________________________________________________________ (b) What is the name of this kind of metamorphic rock?______________________________________________________________________ What other two names can be used to describe the textures of this rock?(c) ____________________________________________________________________ question #10 - chapter 8 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): foliated (b): schist (c): porphyroblastic and schistosity
(a)_____________________________ results whenever mineral crystals and structural features of a rock body are brought into parallel alignment, giving the rock body a layered texture. Rock bodies that have such a parallel alignment. of mineral crystals and structural features can be easily split along their layered texture. Such splitting is known as (b)____________________________ or (c)_________________________________
(a): foliation (b) / (c): slaty cleavage ; rock cleavage
On the blanks provided below, fill in the name of the specific type of geologic feature that has been labeled question #3 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): graben (b): horst (c): normal faults
On the blank provided beside each index mineral or rock type listed below, write low,intermediate, or high to indicate the grade of metamorphism that it represents. (a) migmatite:___________________________________________________________________ (b) chlorite:______________________________________________________________________ (c) sillimanite:______________________________________________________________________ (d) slate:______________________________________________________________________ (e) schist:______________________________________________________________________ (f) gneiss:______________________________________________________________________ (g) garnet:_____________________________________________________________________
(a): high (b): low (c): high (d): low (e): intermediate (f): high (g): intermediate or high
Uplifted, elongated blocks of crust that are bounded by normal faults are called (a)_____________________________, and elongated valleys between such features are called (b)_____________________________
(a): horsts (b): grabens
Hot ion-rich water released from bodies of magma is called (a)____________________________. It causes chemical alteration of rocks, which is known as (b)_______________________________ metamorphism.
(a): hydrothermal solution (b): hydrothermal
The two sides of a fold are called (a)_____________________________ and the imaginary plane that divides the fold in half as symmetrically as possible is called the (b)_____________________________. The line formed where this imaginary plane intersects a layer within the fold is called the (c)_____________________________ of the fold.
(a): limbs (b): axial plane (c): axis
The rock pictured below is composed of calcite. Is this rock foliated or nonfoliated?(a)____________________________________________________________________What is the name of this kind of metamorphic rock?(b)____________________________________________________________________ question #11 - chapter 8 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): nonfoliated (b): marble
Write a brief description for each of the metamorphic rock types listed below. (a) quartzite:________________________________________________________ (b) slate:________________________________________________________ (c) gneiss:________________________________________________________ (d) phyllite:_______________________________________________________ (e) marble:________________________________________________________
(a): nonfoliated, hard, dense, rock formed from the metamorphism of quartz and stone (b): fine-grained, foliated, metamorphic rock with nearly perfect rock cleavage (slaty cleavage) (c): foliated metamorphic rock with alternations in mineralogy that give the rock a banded appearance (d): fine-grained, foliated metamorphic rock with a metallic sheen and often having a wrinkled appearance (e): coarse-grained, nonfoliated metamorphic rock composed chiefly of calcite and often composed of equidimensional crystals
Carefully study each illustration below to determine the type(s) of geologic structure(s) it contains. On the blanks provided to the right of each illustration, write the name(s) of the structure(s) present int the illustration. question #2 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): normal (dip-slip) fault (b): reverse (dip-slip) fault (c): monocline developed over a normal (dip-slip) fault
What kind of geologic structure is present in the photograph below? (a)____________________________________________________________________ Explain your answer. (b)____________________________________________________________________ question #4 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): normal fault (b): The hanging wall has moved down relative to the foot wall.
Dip-slip faults are classified as (a)_____________________________ when the hanging side wall slides down relative to the footwall and are classified as (b)_____________________________ when the hanging wall slides upward relative to the footwall. If the latter type of fault is inclined to a nearly horizontal position, then the faults are instead called (c)____________________________
(a): normal faults (b): reverse faults (c): thrust faults
The era of ancient life is called the (a)_________________________________ Era, the era of recent life is called the (b)_________________________________ Era, and the era of middle life is called the (c)_________________________________ Era.
(a): paleozoic (b): cenozoic (c): mesozoic
The more than 4 billion years of time prior to the Cambrian Period is referred to as the (a)____________________________________. It is commonly subdivided into eons from the oldest (b)____________________________________ Eon to the (c)____________________________________ Eon to the youngest (d)____________________________________ Eon.
(a): precambrian (b): hadean (c): archean (d): proterozoic
The process by which nuclei of atoms spontaneously break apart, or decay, is called (a)____________________________________________________. It is the basis for a type of absolute dating called (b)___________________________________________.
(a): radioactivity (b): radiometric dating
What kind of geologic structure is present in the photograph below? (a)____________________________________________________________________ Explain your answer. (b)____________________________________________________________________ question #5 - chapter 10 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): recumbent fold (b): The layers have been folded, and the fold is lying on its side
When mica mineral crystals in slate are recrystallized to larger sizes, the rock develops a platy, or scaly, type of foliation called (a)_______________________________. This type of foliation is best developed in the metamorphic rock called (b)__________________________________
(a): schistosity (b): schist
a)_____________________________ is the amount of force acting upon a body of rock to change its shape and/or volume. (b)_____________________________ is the resulting change in shape and/or volume
(a): stress (b): straiin
(a)_____________________________ is the direction of the line that is produced by the intersection that an inclined layer of rock makes with an imaginary horizontal surface. (b)_____________________________ is the angle at which the surface is inclined, in a direction perpendicular to the line referred to in the preceding sentence.
(a): strike (b): dip
Broad, blister-like upwarps of rock layers are called (a)_____________________________, whereas broad, dimple-like downwarps of rock layers are called (b)_____________________________.
(a):domes (b): basins
A beta particle is composed of
1 electron.
What is the difference between a dome and a basin?
A dome is a blister-like upwarp of the crust, whereas a basin is a dimple-like downwarp of the crust.
How can rock bodies be bent into intricate folds without being crushed in the process?
At high confining pressures and temperatures, rocks deform plastically once their elastic limit is surpassed.
How do serpentine-rich and talc-rich rocks form on the seafloor?
Along ocean ridges and at oceanic hot spots, sea water circulates through still-hot basaltic rocks, transforming the iron-and magnesium-rich minerals into metamorphic minerals such as talc and serpentine.
What is an unconformity?
An unconformity is any break in the rock record caused by an interruption of deposition or by removal of previously formed rock.
What is confining pressure
Confining pressure is the pressure on rocks (equal in all directions) at great depth inside the Earth.
We are living in the
Cenozoic Era
Contact metamorphic rocks usually have a coarse-grained texture.
FALSE. Contact metamorphic rocks usually have a fine-grained texture.
In general, recrystallization causes new kinds of minerals to form.
FALSE. It generally encourages the growth of larger crystals of the same mineral(s)
The parent rock for marble is quartz sandstone.
FALSE. The parent rock for marble is limestone or dolostone (dolomite-rich rock). Quartz sandstone is metamorphosed into quartzite
Gneiss has no foliations
FALSE. Gneiss commonly develops its banded texture as a result of foliation
William Smith is credited with recognizing the law of superposition and the principle of original horizontality.
False. Steno is credited with recognizing these items
Archbishop Ussher estimated that the Earth was about 3 million years old.
False. He estimated that the earth is about 6,000 years old
The Mesozoic Era is composed of the Tertiary, Jurassic, and Cretaceous periods.
False. It is composed of the Triassic, Jurassic, and Cretaceous Periods
The KT extinction marks the end of the Paleozoic Era.
False. It marks the end of the Mesozoic Era.
The Black Hills of South Dakota are actually eroded remnants of a basin.
False. They are an eroded dome
In a technical sense, anticlines are simply upfolds.
False. They are upfolds that have the oldest rocks in the center of the structure
Steno made correlations based upon the principle of fossil succession.
False. William Smith made such correlations
___________________________________________ is the name of a metamorphic rock with banding caused by differences in mineralogy
Gneiss
Describe the metamorphic conditions that produce hornfels.
Hornfels is commonly formed in response to high-temperature, low-pressure contact metamorphism.
Explain briefly how impact metamorphism and tektites may be related.
Impact metamorphism has occurred when comets and asteroids impacted the earth.It may be that tektites are glass bodies that formed when such impacts melted rocks on impact, and the melted rock particles cooled into glass (tektites).
State the law of superposition.
In an undeformed sedimentary sequence of strata, each bed (layer) is older than the one on top and younger than the one below.
What is hornfels, and how does it form?
It is a hard, fine-grained, nonfoliated metamorphic rock commonly formed as a result of contact (thermal) metamorphism.
What is foliation?
It is a metamorphic texture characterized by the parallel alignment of mineral crystals and structural features.
Why is it that any eon, era, period, or epoch of geologic history can be recognized on the basis of its fossils?
It is because fossil plants and animals succeed one another in a definite and determinable order (the principle of fossil succession), which is the basis for subdividing and naming intervals of geologic time.
What is the task of correlation?
It is the task of matching up rocks of similar ages among different regions.
What is half-life?
It is the time required for half of a parent isotope to decay to its stable daughter products
State the principle of original horizontality.
Layers of sediment (strata) are generally deposited in a nearly horizontal position.
Imagine that the advertisement below appeared in your local newspaper. What are two scientific reasons why you should be suspicious about the validity of the ad?
Many fossils are much older than 100 million years (based on radiometric dating of the rocks in which they are found). Radiocarbon dating cannot be used to date fossils that are older than 75,000 years.
Name two early methods that were used to estimate the numerical age of the Earth, and give reasons why both methods were not accurate.
Method a: The total thickness of all sedimentary strata deposited during Earth's history was estimated, then divided by the estimated average rate at which sediments accumulate. Problems were that rates of sediment accumulation vary, estimates of the total thickness of strata were not consistent, and no corrections were made for compaction. Method b: The total salt content of the oceans was estimated and then divided by the amount of salt added to the oceans each year. Problems were that estimates of ocean volume and salt content were not consistent, the amount of salt added each year varies, and it is possible that salt is periodically removed from the oceans.
In terms of plate tectonics, where would you expect to find zones of high-pressure metamorphism?
One would expect zones of high-pressure metamorphism to occur wherever there is much compression of crust or lithosphere. This could occur wherever plates are colliding(at convergent plate boundaries).
The eon of visible life is called the
Phanerozoic
Give two distinctly different reasons why radiometric dates are sometimes unreliable (assuming that analytical laboratory techniques are totally reliable).
Possibilities include: (a): Ratios of isotopes in a rock unit may be altered by heating of the rock unit. (b): The material (wood, shell, crystal) containing the isotopes used in the radiometric dating process may have been moved from its original position and relocated in a new one.
In general, how was the geologic time scale constructed?
Relative age relationships determined from fossils and physical relationships of rock units were used to name time and rock subdivisions and place them in order of their relative ages. Much later,numerical dates were added to complete the time scale.
How are inclusions used for relative age dating?
Rock containing inclusions is younger than the inclusions.
Describe how black smokers and metallic ore deposits form along ocean ridge systems
Seawater migrates through cracks in hot, newly formed basaltic rocks of ocean ridges, where it is heated. This hot water removes metallic ions from the basalt and carries them back to the cooler seafloor, where they precipitate from black smokers to form metallic ore deposits.
What is strike?
Strike is the direction of the line produced by the intersection that an inclined rock layer makes with an imaginary horizontal plane.
Why is the Precambrian not subdivided into detailed time divisions as is the Phanerozoic Eon?
The Precambrian contains few fossils, if any.
What effect(s) do hydrothermal solutions have on a body of rock?
The hot water acts as a catalyst to speed up ion migration and cause recrystallization of minerals to larger sizes or to different kinds of minerals. Ions added from the hydrothermal solutions themselves may also change the composition of the rock body as new minerals form from the newly added ions.
When does the process of metamorphism begin, and when does it end?
The process begins when rock is subjected to conditions unlike those under which it formed. The process ends after the rock undergoes changes to reach a state of equilibrium with the new environmental conditions. .
How do migmatites form?
They form when partial melting of rocks occurs at very high temperatures. Light-colored minerals then melt to form bands of magma, while the dark-colored minerals remain relatively solid. Migmatite forms if the partially melted rock body slowly cools,and the magma bands crystallize into igneous rock bands within the dark-colored body of metamorphic rock.
Tree rings record information about
Time & environmental change
How does confining pressure affect the way rocks behave when deformed?
When confining pressure and temperature are low, rocks tend to fracture when deformed (i.e., are brittle), but when confining pressure is very high, rocks flow when a force is applied (i.e., they are ductile).
State the principle of cross-cutting relationships.
When rocks are cut by another feature (e.g., fault, fracture, dike), then they must be older than that feature.
Dome
a broad, blister-like upwarp on the crust
Plunging fold
a fold in which the axis is not horizontal (is inclined).
Recumbent fold
a fold that is "lying on its side"
Anticline
an upfold having the oldest rocks in its center
____________________________________________________________ occur where folded or tilted sedimentary rocks are separated from overlying strata that are flat-lying
angular unconformities
A(n)____________________________________________ is the specific name given to an unconformity formed between nonparallel strata
angular unconformity
During contact metamorphism, a zone of alteration (or halo) forms in the outer most edge of the emplaced body of magma. Such a zone, or halo, is called a(n)
aureole
__________________________________ metamorphism is a low grade of metamorphism that occurs beneath thick accumulations of sedimentary strata in a subsiding basin
burial
A radioactive isotope is referred to as a parent isotope, and it decays to form ______________________________________.
daughter products
____________________________ is the word used to refer to all changes in volume or shape of a rock body.
deformation
When the slopes of several adjacent normal faults decreases with depth and they join to form a single, nearly horizontal fault, the result is a _____________________________ fault
detachment
A(n)___________________________________________________ is an unconformity between parallel strata
disconformity
_____________________________ are low cliffs formed where fault displacements extend to the surface of the land
fault scarps
Mountains caused by the upward movements of huge blocks of lithosphere along normal faults are called
fault-block mountains
____________________________ are geologic structures formed when flat-lying rocks have been bent into wave-like undulations.
folds
An applied _____________________________ tends to put stationary objects in motion or change the motion of moving bodies.
force
Remains or traces of prehistoric life are called
fossils
Fractures, faults, and folds are three types of
geologic structures
Geologists have divided geologic history into a chart of dated and named eons, eras, periods, and epochs. This chart is called the
geologic time scale
The time required for one-half of the nuclei of an unstable isotope to decay is called
half-life
What landform or drainage feature is not characteristic of regions with active strike-slip faults?
hogback
___________________________ form when exposed ends of resistant inclined strata form conspicuous ridges that stand out above the more eroded, less resistant, adjacent strata.
hogbacks
Certain minerals are good indicators of the specific kind of metamorphic environment in which they formed. These minerals are called
index minerals
Rock fractures along which no appreciable movement has occurred are called
joints
an isolated remnant of an eroded thrust sheet is called a(n)
klippe
The __________________________________________________________ states that in an undeformed sequence of strata, each bed is older than the one above it and younger than the one below it.
law of superposition
__________________________________________ is a nonfoliated, crystalline metamorphic rock composed of calcite
marble
___________________________________________ are rock bodies of dark, foliated,highly metamorphosed rock having bands of light-colored crystalline igneous rock.
migmatites
Broad flexures that have just one limb and result from vertical displacement are called
monoclines
_________________________________________________ are breaks that separate older metamorphic or intrusive igneous rocks from younger sedimentary strata
nonconformities
Metamorphic rocks that do not have foliated texture are called __________________________________________________ metamorphic rocks
nonfoliated
____________________________ pinpoint the time in history when some event took place
numerical dates
Sites where bedrock is exposed at the Earth's surface are called
outcrops
A fold is said to be _____________________________ if one limb is tilted beyond vertical, so that it is upside down.
overturned
The eon of visible life is called the _______________________________________ Eon.
phanerozoic
A fold in which the axis is not horizontal is said to be
plunging
__________________________________________ texture is present in metamorphic rocks when large mineral crystals are set in a fine-grained mass of other minerals
porphyroblastic
The __________________________________________________________ states that when rocks are cut by another feature (fracture, fault, igneous intrusive body), the rocks are older than the cutting feature
principle of cross-cutting relationships
The ________________________________________ states that layers of sediment are generally deposited in nearly flat-lying position.
principle of original horizontality
_________________________________________ is a very hard, nonfoliated metamorphic rock formed from quartz sandstone
quartzite
_______________________________________________ is another name for C-14.
radiocarbon dating
A fold that has tilted so much that it is "lying on its side" is said to be
recumbent
In which of the following ways is the greatest volume of metamorphic rocks produced?
regional metamorphism
A layer of rock and mineral fragments produced by weathering is called
regolith
___________________________ means that rocks or events are placed in their correct sequence, or order
relative dating
A strike-slip fault is said to be _____________________________ if the crustal block on the opposite side of the fault seems to have moved to the right as you look across the fault.
right-lateral
Directional stresses can cause a rock body to break into slabs, which slide past one another. This is called
shear
Extensive, relatively flat areas of continents that are underlain by old metamorphic and igneous rocks are called
shields
_________________________________________ is a very fine-grained, foliated metamorphic rock with excellent rock cleavage.
slate
During compressional processes associated with mountain building or the burial of rocks, the rocks are subjected to force, or
stress
Faults along which movements are primarily horizontal (and parallel to the strike of the fault) are called
strike-slip faults
__________________________________________ is the size, shape, and distribution of particles that constitute a rock.
texture
Major strike-slip faults that cut through the lithosphere and accommodate horizontal motions between two major lithospheric plates are called
tranform faults
All isotopes of uranium are radioactive.
true
John Wesley Powell led a pioneering expedition down the Colorado River.
true
Lord Kelvin estimated the age of the Earth by assuming that it was once molten and that it had cooled to its present condition.
true
Low-grade metamorphism makes rocks more compact, so they are also made more dense.
true
Marble benches have been known to sag under their own weight over a period of a hundred years or so.
true
Phyllite represents a grade of metamorphism between that of schist and slate.
true
Plunging folds form V -shaped outcrop patterns as they are being eroded.
true
The Pennsylvanian Period is named for the state of Pennsylvania, where these rocks have produced much coal.
true
Numerical dating is
used to pinpoint the time in years when an event occurred & determined with radiometric dating techniques.
Name two ways that carbon is stored in sedimentary rocks, and describe how it got stored there
(1) Fossil fuels (coal, oil, gas, tar)-Organisms used carbon dioxide from the atmosphere and the process of photosynthesis to make their food and soft tissues. These soft tissues were fossilized as fossil fuels. (2) Limestone-Organisms used carbon dioxide from the atmosphere or hydrosphere to make their calcite and aragonite shells, which became sediment that was eventually cemented to form the limestone.
Name and describe five different types of sedimentary structures.
(1) bedding (strata): layers of sediment. (2)bedding planes: surfaces between layers of sediment. (3)cross-bedding: strata/beds deposited in an inclined position. (4)graded bedding: sedimentary layers with particle sizes that fine upwards. (5)ripple marks: small waves of sand.
Fill in the blanks with the correct names of the soil "layers" that are labeled. question #15 - chapter 6 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): 0 horizon (b): A horizon (c): B horizon (d): C horizon
Carefully observe each of the photographs below of sedimentary rocks. To the right of each sample, name the rock and describe its origin (how it formed) question #8 - chapter 7 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): Name:conglomerate (a clastic, detrital rock). Origin: A poorly sorted mixture of rounded grains of sand and gravel was lithified. (b): Name: biochemical limestone or coquina. Origin: A mass of calcareous seashells and broken shells was cemented together. (c): Name: breccia (a clastic, detrital rock). Origin: A poorly sorted mixture of angular grains of sand and gravel was lithified.
Sediments accumulate in layers called (a)_________________________________________________. These layers are separated from one another by surfaces called (b)___________________________________________________________.
(a): beds or strata (b): bedding planes
The rock-forming process by which sediments are "glued" together by chemical precipitates is the process of (a)_______________________________. The chemically precipitated material that acts as a "glue" in this process is called (b)_______________________________
(a): cementation (b): cement
(a)____________________________ is the process of decomposing rock, whereas (b)____________________________ is the process of fragmenting and disintegrating rock.
(a): chemical weathering (b): mechanical weathering
(a)_______________________________ is the ability of some rocks to split into thin layers along well-developed, closely spaced planes. The fine-grained sedimentary rock in which this property is best developed is (b)_______________________________.
(a): fissility (b): shale
The pictures below are cross sections through layers of sediment. Name the sedimentary structure that is present in each cross section. question #7 - chapter 7 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): graded bedding (b): cross bedding
Some sedimentary layers change from relatively large particles at their bases to finer particles at their tops. These layers are called (a)_______________________________. Other layers are deposited at a steep angle from the horizontal. Such layering is called (b)_______________________________.
(a): graded beds (b): cross-bedding
Give the particle size in millimeters for each kind of sediment: Gravel (a)_________________________ mm Sand (b)_________________________ mm Mud (c)_________________________ mm
(a): greater than 2 (b): 1/16 to 2 (c): less than 1/16.
Compare and fill in the chart below. question #8 - chapter 7 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): gypsum (b): halite
Soils are composed of layers called (a)____________________________. A vertical cross section through all of these layers is called a(n)(b)____________________________
(a): horizons (b): soil profile
Volcanism and mountain building are examples of (a)____________________________ processes. Weathering, mass wasting, and erosion are examples of(b)____________________________ processes
(a): internal (b): external
Complete the chart below. question #5 - chapter 6 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): iron, aluminum, clay minerals (b): calcium carbonate (calcite) (c): tropical (heavy rainfall) (d): brick red
The photo below was taken on a hilltop in Joshua Tree National Monument, California, by E. J.Tarbuck. What are these types of cracks called? (a)___________________________________________________________________What processes are enlarging these cracks?(b)___________________________________________________________________What process is causing the blocks of rock to become rounded?(c)___________________________________________________________________ question #3 - chapter 6 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): joints (b): frost wedging and chemical weathering (c): spheroidal weathering
What kind of sedimentary structure is pictured in the photograph below? (a)____________________________________________________ Explain how this kind of sedimentary structure forms. (b)______________________________________________________________________ question #7 - chapter 7 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): mudcracks (b): Mud shrinks and cracks as it dries (as in an evaporating mud puddle).
Complete the chart below. question #1 - chapter 7 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): nonclastic (b): any size (c): chemical (d): clastic (e): 1/16 to 2 mm (f): detrital (g): clastic (h): greater than 2 mm (i): detrital (j): clastic or nonclastic (k): any size (l): chemical or biochemical (m): nonclastic (n): any size (o): chemical
Soils rich in iron oxides and clay minerals are called (a)____________________________. Soils rich in calcium carbonate are called (b)____________________________
(a): pedalfers (b): pedocals
Metamorphism takes place on two different scales. When extensive portions of the crust are metamorphosed, then the rocks are said to have undergone (a)___________________________________. When rock is metamorphosed locally, because of direct contact with amass of magma, it is said to have undergone (b)___________________________________
(a): regional metamorphism (b): contact or thermal metamorphism
When water containing dissolved substances evaporates from the floor of an enclosed basin, a light-colored crust of mineral crystals is left behind on the surface of the ground. Such mineral-encrusted land surfaces are called (a)_______________________________ and the mineral deposits are called (b)_______________________________.
(a): salt flats (b): evaporites
(a)_______________________________ is any mass of particles of Earth materials that have been weathered, eroded, transported, and deposited. (b)_______________________________ is the process by which such a deposit of loose particles is transformed (hardened) into sedimentary rock.
(a): sediment (b): lithification
Large igneous bodies beneath the surface of the Earth are under great pressure from overlying rocks. When the overlying rocks are stripped away by weathering, erosion,and mass wasting, then layers of rock may break away from the exposed surface of the igneous body. Such a process is known as (a)____________________________ and the large exposed surfaces of such structures are called (b)__________________________________________.
(a): sheeting (b): exfoliation domes
What is the feature labeled "A" in the photograph below?(a)________________________________ How did it form?(b)______________________________________________________________________________________________________________________________________ question #7 - chapter 6 *** REFER TO HANDOUT - CANT UPLOAD IMAGE ***
(a): talus slope (b): Rocks fell from the adjacent rocky cliff and accumulated at the base of the cliff as a talus slope.
What is a facies?
A facies is a rock unit having distinctive characteristics that reflect the conditions of a particular environment in which it was formed.
What is acid precipitation, and why are people concerned about it?
Acid precipitation is precipitation that is more acidic than normal. It causes lakes and streams to be more acidic (which kills fish), promotes corrosion of metals, and promotes decomposition of stone structures and rocks.
How and why does the topography of arid regions generally differ from the topography of humid regions?
Angular topography is more common in arid regions, whereas subdued topography is more common in humid areas. This is because the effects of chemical weathering and soil development are greater in humid areas than in arid areas.
Briefly explain how sedimentary rocks form relative to the rock cycle.
As preexisting rocks weather at the Earth's surface, sedimentary particles are derived, eroded, transported, and deposited. The sedimentary deposits are then lithified to form detrital sedimentary rocks. Some earth materials are also dissolved and transported by water until they precipitate to form chemical sedimentary rocks or cement in detrital sedimentary rocks.
In which of the following areas are laterites best developed?
Brazil
Which soil horizon is composed mostly of weathered bedrock?
C horizon
What is caliche, and how does it form?
Caliche is a calcite (calcium carbonate) enriched layer in soil. It forms from the evaporation of soil water containing dissolved calcium carbonate. When the water evaporates, the calcium carbonate (calcite) precipitates as caliche.
How does carbonic acid form?
Carbonic acid forms when carbon dioxide is dissolved in water (such as a droplet of rain).
How does carbon move from sedimentary rocks (lithosphere) to the hydrosphere?
Carbonic acid in rainwater dissolves limestone and releases carbon to the hydrosphere. Also, when fossil fuels are burned or oxidize, they release carbon dioxide to the atmosphere. There, it mixes with water to make carbonic acid in rainwater, which falls to Earth's surface and enters the hydrosphere.
How does cementation occur?
Cementation occurs when cementing materials are carried into solution by water percolating through open spaces in sediment. Through time, the cement precipitates onto the sedimentary particles, fills the open spaces, and cements the particles together. The most common cementing materials are calcite, iron oxide, and silica.
What is chert?
Chert is a dense, hard rock made of microcrystalline silica (SiO2).
What is the compositional difference between limestone and dolomite (dolostone)?
Dolomite (dolostone) contains Mg [it is CaMg(CO3)2], and limestone does not [it is CaCO3].
If a detrital sedimentary rock is composed of angular, pebble-sized particles,then the rock is a conglomerate.
FALSE. If the pebble-sized particles have sharp edges (they are angular), then the rock is breccia
Calcite dissolves only in strongly acid solutions.
FALSE. It even dissolves in very weakly acidic solutions
The organic-rich layer at the very top of a soil profile is called the organicum.
FALSE. It is called humus, or the 0 horizon
Steep slopes typically have soils with well-developed soil profiles.
FALSE. Soil profiles on steep slopes are typically developed very poorly.
What are fossils?
Fossils are any remains or traces of prehistoric life.
Why are fossils important?
Fossils are important tools used to interpret the geologic past, including changes in environmental conditions and changes in life forms.
How does coal form?
If a great volume of plants accumulates in an oxygen-lacking environment (such as the bottom of a swamp or bog), then the plants do not decompose. As these plant deposits are buried by more plants, they turn into a brown spongy mass called peat. With additional burial and time, the peat undergoes chemical and physical changes that transform it into coal.
What is lithification?
It is a process by which unconsolidated (loose) sediment is transformed into solid sedimentary rock.
Explain how seafloor sediments can reveal how Earth's climate has changed.
Most seafloor sediments contain the remains of organisms that once lived near the sea surface. Their shells slowly settled to the sea floor as the numbers and types of these organisms changed with time and climate.
What is oxidation, and how does it occur?
Oxidation is the process by which rusting occurs because an element loses electrons to react with (bond with) oxygen
What are reefs, and how are they formed?
Reefs are massive biochemical limestone structures. They form by the joining of many external skeletons of colonial organisms like corals.
Briefly note why sedimentary rocks are important in the study of Earth history.
Sedimentary rocks contain much information about Earth history, and they contain many economically important materials like coal and oil.
What is sorting, and how does it occur?
Sorting refers to the degree of similarity in particle size in a sedimentary rock. It occurs as wind or water blow and wash the different sizes of particles apart.
What conditions led to the Dust Bowl of the 1930s?
Strong wind, drought, and the transformation of grass-covered prairies into farms all contributed to the Dust Bowl.
In general, how does time affect soil development?
The longer a soil has been forming, the thicker it becomes and the less it resembles its parent material
Explain why productive farmland is not produced by the clearing of tropical and subtropical rain forests.
The soils present beneath such rainforests are laterites: soils containing essentially no soluble materials. Laterites are very poor soils for farming.
What are chemical sedimentary rocks?
They are sedimentary rocks composed of materials that were physically or organically (biochemically) precipitated from solutions containing dissolved substances.
What are detrital sedimentary rocks?
They are sedimentary rocks composed of transported solid particles (grains of sediment)that were derived from both mechanical and chemical weathering.
soil developed from beach sands would be an example of a transported soil.
True
Ripple marks could form in a desert.
True (as they are made by wind)
Other sedimentary rocks are composed of interlocking crystals that were precipitated from solutions containing dissolved substances or are composed of materials formed during the life processes of animals and plants. Such rocks are called _______________________________ sedimentary rocks.
chemical
Sedimentary rocks consisting of discrete fragments of broken particles that have been compacted and cemented together display a(n)_______________________________ texture
clastic
As sediments accumulate through time, the weight of overlying material compresses the deeper sediments. This process is called
compaction
Some sedimentary rocks are composed of transported solid particles that were derived from both mechanical and chemical weathering of earth materials. Such rocks are called _______________________________ sedimentary rocks
detrital
_______________________________ is the term that refers to all of the physical, chemical, and biological changes that occur after sediment is deposited and during and after it is lithified.
diagenesis
The kind of weathering that forms unusual rock formations and landforms due to variations in mineral makeup, degree of jointing, and exposure to the elements, is called ____________________________ weathering.
differential
The process by which materials dissolve is called
dissolution
The process of washing fine-grained soil components from a soil, as water percolates downward through it, is called
eluviation
The incorporation and transportation of Earth material by water, wind, or ice is called
erosion
A(n)_______________________________ is a rock unit having distinctive characteristics that reflect the conditions of a particular environment in which it formed
facies
When water works its way into cracks and void spaces in rocks it may freeze. Upon freezing it expands and breaks the rock apart. This process is called
frost wedging
Name and describe four types of mechanical weathering.
frost wedging, unloading, thermal expansion, biological activity
A layer of decayed remains of plants and animals (organic matter) is called
humus
The reaction of any substance with water is called
hydrolysis
Which item below is not a mechanical weathering process?
hydrolysis
Rock fractures that form a definite pattern are called
joints
Depletion of soluble materials from the upper layers of soil is called
leaching
The transfer of rock material downslope under the influence of gravity is called
mass wasting
Sedimentary rocks composed of mineral crystals that form an interlocking pattern have a(n)_______________________________ texture.
nonclastic (or crystalline)
____________________________ is the process by which rusting occurs
oxidation
Metamorphic rocks are produced or transformed from preexisting igneous, metamorphic, or sedimentary rocks called
parent rocks
The two conditions that most favor the preservation of an organism as a fossil are
presence of hard parts and rapid burial.
_______________________________ are small waves of sand that develop on the surface of a sediment layer by the action of moving water or wind
ripple marks
A geographic setting where sediment is accumulating is called a(n)
sedimentary environment or environment of deposition
A layer of rock and mineral fragments, organic matter, water, and air covering the land is called
soil
The "true soil" is called the
solum
The degree to which particle size is the same among grains in a sedimentary rock is referred to as
sorting
In which of the following areas would a pedocal be most likely to form?
southwestern U.S.
The process by which rocks weather to a more rounded shape is called
spheroidal weathering
What is spheroidal weathering, and how does it occur?
t is the process by which blocks of rock weather to more rounded shapes, because the comers of blocks weather faster than the sides of the blocks.
Piles of fragmented rock at the base of steep rock outcrops are called
talus slopes
Which item below is not a chemical weathering process?
thermal expansion
As ocean water evaporates, gypsum (hydrous calcium sulfate) forms before halite (sodium chloride).
true
Limestone can have a clastic or nonclastic texture.
true
The B horizon of a soil profile is known as the "subsoil."
true
Chalk is a kind of limestone.
true (biochemical limestone)
Which item below does not influence rates of soil erosion?
type of bedrock
List five basic controls of soil formation.
type of parent material, climate, time, plants and animals, slope of the land
The disintegration and decomposition of rock at or near the Earth's surface is called
weathering