Geology Exam #3

The most important characteristic of sediment that is used to classify a sedimentary rock is _____.

grain size

Detrital/clastic sedimentary rocks are classified (named) based on the

grain sizes of the particles

What type of metamorphism is caused by high temperature and high pressure imposed over a large volume of crust?

regional

In a ____ fault, the hanging wall block move up with respect to the footwall block.

reverse

Which type of faulting would be least likely to occur along the mid-Atlantic ridge?

reverse

clastic rock is...

rock formed from the cementation of transported grains

left lateral strike slip

shear stress

oblique slip fault stress type

shear stress and compression stress

What type of seismic waves are S waves?

shear waves

In a normal fault _____.

the hanging wall block above an inclined fault plane moves downward relative to the other block

For two earthquakes located the same distance away, the ground shaking produced by a Richter magnitude 4 earthquake would be ___ times greater than the ground shaking produced by a magnitude 3 earthquake.

10

The ground motion during a Richter magnitude 8 earthquake is ______ times greater than the ground motion during a Richter magnitude 6 earthquake.

100

The energy released during a magnitude 8 earthquake is approximately ______ times larger than the energy released during a magnitude 6 earthquake.

1000

How many seismograph stations are needed to locate the epicenter of an earthquake?

3

Earthquake A has a Richter magnitude of 7 as compared with earthquake B's 6.

A has 10X the shaking amplitude than B

Many people consider "locked" faults to be safe. Is this true or false? Why?

A locked fault is a fault that, for extended periods of time, does not slip. Contrary to many peoples' beliefs, locked faults are not safe. This is because, without small slips/earthquakes, pressure builds up in the fault and eventually, that pressure is released on a massive and catastrophic scale--resulting in one or more enormously damaging earthquakes.

Indicate which type of metamorphism is most likely to occur at each of the following: A) convergent boundary B) divergent boundary C) transform boundary

A) Regional metamorphism is most likely to occur at convergent boundaries. B) Hydrothermal and contact metamorphism are most likely to occur at divergent boundaries. C) Dynamic metamorphism is most likely to occur at transform boundaries.

Explain how grain size, rounding and sorting characteristics typically change as sediment is transported downstream. What is the exception to these trends?

As sediment is transported downstream, sorting becomes more uniform, grain size becomes smaller, and rounding becomes more prominent. As they travel downstream, rock fragments bump into one another and into the stream bed, breaking into pieces and smoothing along the way. Larger fragments are found closer to the source of the sediment, whereas smaller ones are found further downstream. The fragments' edges are further smoothed by rushing water. With increasing transport, grain characteristics go from jagged and angular to smooth and rounded.

Who developed the procedure used to measure the size of an earthquake?

Charles Richter

What role does climate play in chemical weathering? How will chemical weathering processes be different in the future as a result of climate change?

Chemical weathering describes the process of weathering that occurs when rocks come into contact with water and air. For that reason, the two most important aspects of climate that impact weathering include temperature and rainfall. In climates characterized by warm temperatures and significant rainfall, weathering happens at a faster rate than it does in climates with lower temperatures and less precipitation. So, in tropical climates rocks weather faster than those in cold, dry climates. As the global temperature gets warmer and rainfall increases, weathering of rocks will occur at a faster rate.

Which one of the following is consistent with deformation by folding?

Horizontal distance is shortened perpendicular to fold axes.

Measures an earthquake's intensity based on the observed effects on people and structures

Modified Mercalli Scale

measures an earthquake's intensity based on the observed effects on people and structures

Modified Mercalli Scale

Sedimentary rocks are...

Moved around by waves of flowing water. formed when water evaporates. formed when plant and anima debris pressurize and build up.

Why was building damage so extensive in the 1985 Mexico City quake?

Much of the city is built on filled-in, shallow lakes and swampland.

__________ is the maximum possible damage designation on the Mercalli scale.

XII

metasomatism

a change in the bulk composition of a rock during metamorphism

Which events can be triggered by an earthquake? -a tsunami -intense ground shaking -a landslide -all of the above

all of the above

T/F Conglomerates suggest deposition by strong winds in a desert.

false

T/F Foliated metamorphic rocks are composed largely of equidimensional grains of minerals such as quartz and calcite.

false

T/F Metamorphism happens only at depths greater than 5 km in Earth.

false

Sedimentary rocks provide clues about...

-Geologic activity at the time of deposition -Past climates -Surface conditions at the time of deposition

Which of the following foundation materials is most stable during earthquake shaking? -bedrock -unconsolidated and moist soil -water-saturated gravel -sand and mud

-bedrock

How are foliated rocks classified?

-crystal size -the degree to which the minerals are segregated into lighter and darker bands -metamorphic grade

Clastic sedimentary rocks...

-form from pieces of pre-existing rocks -form near Earth's surface -range from conglomerates to shales

The moment magnitude of an earthquake depends on all of the following except: -the area of the fault break -the strength of the rocks surrounding the fault -the displacement along the fault -the type of faulting

-the type of faulting

What can trigger a tsunami? a. undersea earthquakes b. undersea landslides c. the eruption of an oceanic volcano d. all of these

-undersea earthquakes -undersea landslides -the eruption of an oceanic volcano

A normal geothermal gradient is approximately _________ .

30 degrees C per KM

Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5?

30 times

How and why are weathering processes so vastly different on the Moon?

Because the atmospheric and climactic conditions on the moon are vastly different from those found on earth, so too are the weathering processes. Two important components that affect weathering include a rock's interaction with air and its interaction with water/rainfall--neither of which exist on the moon. Additionally, biological weathering cannot occur on the moon because there are no living organisms to facilitate the process. Physical changes or weathering on the moon's surface might instead occur as a result of meteorite impact.

How can an earthquake have more than one intensity, but only one magnitude?

Earthquake magnitude is a measurement of the amount of ground-shaking during a seismic event, whereas intensity measures the severity of observed damage. Although an earthquake can have only one magnitude, it can result in varying measurements of intensity. This is because unlike magnitude, intensity measurement is dependent upon a number of factors. Such factors include: proximity to the epicenter, rock type, structure type, and personality (of the individual reporting damage).

seismic waves

Energy waves that are released during an earthquake

T/F Because their energy dissipates rapidly in deep ocean waters, tsunamis seldom pose any danger to coastal areas far away from the causative earthquake.

False

T/F Unconsolidated, water-saturated soils or sediments provide good foundation materials for buildings and other structures.

False

The Mercalli Scale is a scale from _____.

I to XII that rates the structural damage due to an earthquake

Body waves consist of the...

P and S waves

list the different arrival times of waves from first to last

P waves ... S waves .... Surface waves

__________ are the first to arrive at distant receiving stations.

P-waves

Describe the conditions of contact metamorphism

Pressures are fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body.

__________, a common mineral found in igneous rocks, is the most abundant mineral in detrital/clastic sedimentary rocks.

Quartz

__________ is typically formed by metamorphism of a sandstone.

Quartzite

Where do sediments come from?

Rock weathering produces sediment

The ______ in California is the boundary between the North American and Pacific plates.

San Andreas strike slip fault

The pressure and heat that drive metamorphism result from which three forces?

The internal heat of the Earth, the weight of overlying rocks, and horizontal pressures developed as rocks become deformed

Sorting

The tendency for variations in current velocity to segregate sediments on the basis of particle size

T/F Earthquakes result from the sudden release of elastic strain energy previously stored in rocks surrounding a zone of fault movement.

True

T/F Following a major earthquake, aftershocks diminish in magnitude but may still be powerful enough to destroy or further damage weakened buildings.

True

T/F Horizontal, compressive deformation involves shortening and thickening of the crust.

True

T/F Partial melting is an important process in the formation of migmatites.

True

T/F The Richter earthquake magnitude scale is based on the total amount of energy released by the earthquake.

True

Assume that water filling a crack in a rock undergoes cycles of freezing and melting. What happens to the crack walls?

Water Expands as it freezes, causing the crack walls to expand

A graben is characterized by _____.

a hanging wall block that has moved down between two normal faults

A thrust fault is best described as _____.

a low-angle, reverse fault

conglomerate

a rock composed of cemented, rounded pebbles

Clastic Rock

a rock formed from the cementation of transported grains

A transform fault is __________.

a strike-slip fault that forms the boundary between tectonic plate

foliation

a strong, parallel alignment of coarse mica flakes and/or of different mineral bands in a metamorphic rock.

Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern. a. modified mercalli scale b. energy c. Richter d. amplitude

a. Modified Mercalli Scale

Which of the following is an organic sedimentary rock? a. coal b. sandstone c. basalt d. conglomerate

a. coal

Which of the following lists is written in order of decreasing particle size? a. conglomerate, sandstone, siltstone b. siltstone, sandstone, conglomerate c. sandstone, siltstone, conglomerate d. sandstone conglomerate siltstone

a. conglomerate, sandstone, siltstone

Which one of the following is consistent with deformation by folding? a. horizontal distance is shortened perpendicular to fold axes b. the crust is thinned c. horizontal distance perpendicular to fold axes is lengthened d. the crust is stretched and elongated

a. horizontal distance is shortened perpendicular to fold axes

What is the pressure on a rock at 15 kilometers depth?

about 5000 times atmospheric pressure

What are the smaller magnitude quakes that follow a major earthquake?

aftershocks

During metamorphism, what is the major effect of chemically active fluids?

aid in the movement of dissolved silicate constituents and facilitate growth of the mineral grains

frost wedging

an important, mechanical weathering process for enlarging fractures and extending them deeper into large boulders and bedrock

P waves __________.

are faster than S waves and surface waves

In which setting would regional metamorphism be most likely?

at great depths in the crust where two continents are colliding

Which statement below regarding the metamorphism of rocks is FALSE? a. during metamorphism the texture of a rock changes b. during metamorphism minerals crystallize from magma c. during metamorphism hydrothermal fluids can change rock chemistry d. during metamorphism the mineral composition of a rock can change

b. during metamorphism minerals crystallize from magma

Which of the following is not used to classify foliated rocks? a. crystal size b. the texture of the parent rock c. the degree to which minerals are segregated into lighter and darker bands d. the metamorphic grade

b. the texture of the parent rock

Which of the following statements is false? a. Most Earthquakes occur at plate boundaries b. the time and location of most major earthquakes can be predicted several days in advance c. earthquakes can be caused by normal, reverse, and strike-slip faulting d. P waves travel faster than both S waves and surface waves

b. the time and location of most major earthquakes can be predicted several days in advance

How do rock particles move during the passage of a P wave through the rock?

back and forth parallel to the direction of wave travel

What is probably the single most important, original, depositional feature in sedimentary rocks?

bedding or layering

Sedimentary rock that forms from the breakdown of organisms exhibits _____ texture.

bioclastic

A __________ forms at very high pressures but moderately low temperatures associated with subduction of oceanic crust and sediments.

bluechist

All of the following are stresses EXCEPT: a. compression b. shear c. brittle

c. brittle

Which one of the following features is NOT associated with sedimentary rocks? a. all may be associated with sedimentary rocks b. bedding c. foliation d. fossils

c. foliation

Which is not a type of sedimentary rock? a. chemical b. biochemical c. intrusive d. clastic

c. intrusive

Which statement concerning sedimentary rocks is NOT true? a. they may contain fossils that provide clues about ancient life forms b. they probably show some evidence of stratification c. they were originally deposited at depth below the bottom of the sea d. they are composed of particles and constituents derived from weathering and erosion

c. they were originally deposited at depth below the bottom of the sea.

Examine the words and/or phrases for each question below and determine the relationship among the majority of words. Choose the option which does not fit the pattern. a. cementation b. lithification c. weathering d. compaction

c. weathering

The mineral material precipitated in the empty or pore spaces between clasts in a detrital/clastic sedimentary rock is called _____.

cement

Texture of Detrital sedimentary rock

clastic

During lithification, the weight of overlying sedimetns will cause the sediments below to _____ by pushing the grains more tightly together.

compact

anticline stress type

compression

basin stress type

compression

reverse fault stress type

compression

syncline stress type

compression

What type of sedimentary rock would you expect to have originally been deposited by fast-moving streams?

conglomerate

Which of the following lists is written in order of decreasing particle size? -sandstone, siltstone, conglomerate -sandstone, conglomerate, siltstone -conglomerate, sandstone, siltstone -siltstone, sandstone, conglomerate

conglomerate, sandstone, siltstone

Brittle deformation would be favored over plastic deformation in which of the following conditions?

cooler temperatures

To which of the following groups does breccia belong? a. chemical sedimentary b. unfoliated metamorphic c. foliated metamorphic d. clastic sedimentary

d. clastic sedimentary

Normal and reverse faults are characterized mainly by _____.

dip slip

Where is the focus with respect to the epicenter?

directly below the epicenter

T/F Basin and range topography, like that in the western and southwestern United States, indicates that compressive folding is active today or was active very recently, geologically speaking.

false

Which types of sediments are most abundant?

fine clastics

The __________ is the point of origination for an earthquake.

focus

The point where movement occurred which triggered the earthquake is the _______ .

focus

The parallel alignment of mica in a metamorphic rock is an example of ______.

foliation

What is the most prominent textural feature of regional metamorphic rocks?

foliation

__________ is a strong, parallel alignment of coarse mica flakes and/or of different mineral bands in a metamorphic rock.

foliation

__________ is characterized by the segregation of light- and dark-colored minerals into thin layers or bands.

gneiss

What is the major source of heat for contact metamorphism?

heat from a nearby magma body

What type of pressure-temperature pathway represents subduction zone metamorphism?

high pressure and low temperature

Which stress situation results in folding of flat-lying, sedimentary strata?

horizontally directed; compressive stresses

How do rock particles move during the passage of a Rayleigh wave through the rock?

in a rolling circular motion

With increasing distance, the difference in arrival times between the P and the S waves _________

increases

Frost wedging is an important weathering process in which environments?

inland mountain ranges

In contact metamorphism there is a ____________ .

local heat source

Hydrothermal metamorphism is very common in which setting?

mid-ocean ridges

What type of metamorphic rock has undergone partial melting?

migmatite

Which of the following rocks can be considered transitional between an igneous and a metamorphic rock? -amphibolite -gneiss -migamtite -slate

migmatite

__________ is thought to form by partial melting and in situ crystallization of the melted portion.

migmatite

Shale refers to a rock formed from...

mud sized material

Which group represents that most abundant sedimentary rocks?

mudstones and shales

In a dip-slip fault, if the hanging wall block moved down relative to the footwall block, then the fault is classified as a _____.

normal fault

_____ are the products of horizontally directed, tensional stresses.

normal faults

Earthquakes can occur with _________ faulting.

normal, reverse, thrust

______ have the highest velocities.

primary waves

Flint, chert, and jasper are microcrystalline forms of...

quartz (SiO2)

During metamorphism, changes in the bulk composition of a rock occur primarily as a result of __________.

reaction with hydrothermal fluids

In a dip-slip fault, if the hanging wall block moved up relative to the footwall block, then the fault is classified as a ____.

reverse fault

Which types of currents can transport sand grains?

rivers, ocean waves, wind

Jointing in rocks is characterized by _____.

roughly parallel fractures separating blocks that show no displacement

The parent rock of quartzite is _______.

sandstone

Which low-grade metamorphic rock, composed of extremely fine-sized mica and other mineral grains, typically exhibits well-developed rock cleavage?

slate

Describe the metamorphic changes in shale with increasing metamorphic grade.

slate -> schist -> gneiss

describe the metamorphic changes in a shale with increasing metamorphic grade

slate -> schist -> gneiss

A _____ fault has little or no vertical movements of the two blocks.

strike slip

The epicenter of an earthquake is the ______.

surface location directly above the point where the fault slip initiates

In general, the most destructive earthquake waves are the __________ .

surface waves

On a typical seismogram, ______ will show the highest amplitudes.

surface waves

Which type of seismic waves are the slowest?

surface waves

normal fault stress type

tensional stress

The mountains and valleys of the Basin and Range Province of western United States formed in response to _____.

tensional stresses and normal-fault movements

The modified Mercalli intensity scale measures _______.

the amount of destruction caused by an earthquake

An earthquake's Richter magnitude is based on ______.

the amount of ground movement caused by seismic waves

What is the moment magnitude of an earthquake proportional to?

the area of the fault break and the seismic energy released during the earthquake

What does the elastic rebound theory describe?

the build-up and release of stress during an earthquake

In thrust faulting, _____.

the crust is shortened and thickened

Rounding is...

the grinding away of sharp edges and corners of rock fragments during transportation

A reverse fault is one in which _____.

the hanging wall block has moved up relative to the footwall block along an inclined fault

Erosion

the process by which weathered rock and mineral particles are removed from one area and transported elsewhere

liquefaction

the tendency for a foundation material to lose its internal cohesion and fail mechanically during earthquake shaking.

aureole

the zone of contact metamorphism surrounding an intrusive magma body

The __________ is a direct measure of the distance from a seismic receiving station to the focus of a distant earthquake.

time interval between the first P and S- wave arrivals

T/F Detrital/clastic sedimentary rocks are classified according to clastic particle size; chemical sedimentary rocks are named according to the most abundant minerals.

true

T/F During the 1906 San Francisco earthquake, fire destroyed many buildings that were otherwise undamaged or only slightly damaged by the ground shaking.

true

T/F If the P, S, and surface waves arrive almost simultaneously, the seismic recording station is virtually at the epicenter of the earthquake.

true

T/F In a reverse fault, the hanging wall block moves up relative to the footwall block.

true

T/F Oxidation of iron is an important chemical weathering process for ferromagnesian silicate minerals like olivine and biotite.

true

T/F Quartz is quite resistant to weathering and is an important component of sands in riverbeds and on beaches.

true

T/F Three major factors involved in metamorphism are elevated temperature, elevated pressure, and the chemical action of hot fluids.

true

T/F Tsunamis are caused by sudden displacement of large volumes of seawater.

true

__________ is the proper name commonly used by scientists to denote seismic sea waves induced by earthquakes.

tsunami

Coarse clastic material can be transported into a deep marine environment by ______ .

turbidity currents