TEST 3 Geology

The major discontinuity that occurs at a depth of 2,900 km below Earth's surface is the

core-mantle boundary.

asymetric anticlines and syncline

different directions

dome

dome A rather circular geologic structure in which all rock layers dip away from a central point and the oldest exposed rocks are in the dome's center.

Which of the following is most likely to occur at deep crustal levels?

ductile behavior

Which of the following correctly lists metamorphic mineral assemblages in order of decreasing temperature/pressure of formation?

e.sillimanite, kyanite, staurolite, garnet, biotite, chlorite

What type of structure is shown in this figure?

syncline

What type of stress formed the structure shown in this figure

tension

When an isolated mountain range occurs in the interior of a continent, one may infer that the range formed by:

the collision of two continents

The magnitude of an earthquake measures

the energy released.

In adjacent rocks that show a gradual increase in metamorphic intensity, the first appearance of a particular index mineral indicates

the location of the minimum pressure and temperature conditions needed for the formation of that mineral.

Understand strike and dip—

the orientation of deformed rock layers. Strike and dip are used to define the orientation of deformed rock layers. This same concept applies to other planar features such as fault planes.

Metamorphism is a physical and chemical change that occurs in such a way that:

the rock reaches equilibrium with its new environment.

surface waves

travel around the surface slower than body waves rolling motion (boat movement) R waves( slower) L waves (like s wave) back and forth movement

Body Waves

travel through the solid body of Earth, are somewhat like sound waves

syncline

u shapes oldest rx outside youngest in middle dip towards the center rx always dip towards the youngest rx

Presence of water

wet rx more elastically or ductile dry rx more likely break

Surface Waves

which travel along the ground surface, are analogous to undulations or waves on water surfaces

Love wave (L-wave)

• A surface wave in which the individual particles of material move only back and forth in a horizontal plane perpendicular to the direction of wave travel.

The special geologic terms used to represent the direction of a horizontal line on an inclined surface (like in a fault) and the angle of that surface to the horizontal are

strike and dip

Plunging anticlines and synclines

- axial plaine plunging down(dipping) -

Dip slip faults

- has movement along the dip (veritcal Movement) - Normal Fault -hanging wall down footwall going up. (tensional Stress Thins Crust) - reverse Fault - HW goes up FW goes down.(compressional Stress- thicken crust) - Low Angel reverse Fault <15 degrees. (occur stress on large area, convg plate Bounadries)

Strike Slip Faults

- movement along the strike (horizontal movement) - look across the fault to determine direction of fault - san andreas fault, anatolian fault - transform boundaries. Sheer Stress

Which location on this diagram would most likely record contact metamorphism in shallow levels of the crust?

1

Which of the numbers on this figure indicates low pressure/high temperature metamorphic conditions?

1

Which location on this diagram would result from burial to moderate depths accompanied by normal heating of rocks (regional metamorphism)?

2

Which of the numbers on this figure indicates high pressure/low temperature metamorphic conditions?

3

Which location on this diagram would most likely record metamorphism along a subduction zone

3

Which location on this diagram would most likely record hot conditions deep within the continental crust?

4

Which of these conditions could form rocks that are partly metamorphic and partly igneous

4

Shale is metamorphosed into three rock types: (1) a banded gneissic rock; (2) a rock with small mica crystals with a shiny aspect; (3) a very shiny rock with large mica crystals; and (4) a dull slate with cleavage. Which of the following lists these rocks in order of increasing metamorphic grade?

4, 2, 3, 1

fracture

A break in rock resulting from intense applied pressure.

anticline

A circular fold in which all strata dip inward toward a central point and the youngest exposed strata are in the center.

P waves (body waves)

A compressional, or push-pull, wave; the fastest seismic wave and one that can travel through solids, liquids, and gases; also called a primary wave.

Fault

A fracture along which rocks on opposite sides of the fracture have moved parallel with the fracture surface.

Modified Mercalli Intensity scale

A scale with values from I to XII used to characterize earthquakes based on damage

S Waves (body waves)

A shear wave that moves material perpendicular to the direction of travel, thereby producing shear stresses in the material it moves through; also known as a secondary wave; travel only through solids.

Rayleigh wave (r-wave)

A surface wave in which individual particles of material move in an elliptical path within a vertical plane oriented in the direction of wave movement.

elastic strain

A type of deformation in which the material returns to its original shape when stress is relaxed.

fold

A type of geologic structure in which planar features in rock layers such as bedding and foliation have been bent.

Ductile Deformation

AKA plastic deformation beyond elastic limit it will change shape permenantly

What is true of reflection versus refraction?

All of these are true. Answers: Reflection sends a portion of the wave energy back away from the encountered boundary. Both may happen to a seismic wave as it encounters boundaries between materials of different physical properties. Refraction bends a portion of the wave energy as the wave either slows or speeds up as it crosses the encountered boundary.

P-wave shadow zone

An area between 103 and 143 degrees from an earthquake focus where little P-wave energy is recorded by seismographs.

San Andreas Fault Zone

An example of a region where mylonites are formed is the

What type of structure is shown in this figure

Anticline

1 out of 1 points Which of the following is most likely to occur at shallow crustal levels

Brittle deformation

Folds are ductile

Caused by compressional stress - axial plane divides center of fold - sides are called limbs - hinge where fold bends

What type of stress is the cause of most folding

Compression

The composition of the core is:

Correct iron and nickel metal.

Most earthquakes occur along:

Correct plate boundaries

how many faults

Dip Slip strike-slip

Domes and Basins

Dome - circular anticline beds dip away oldest rock in center Basins - circular synclines beds dip towards center. youngest rocks in center

Which of the following is most likely to occur at deep crustal levels

Ductile behavior

3 stages of stress on rock

Elastic deformation (elastic limit) Ductile deformation (rock cant hold any more energy ) then it Fractures (Brittle deformation)

Fault Block Mountains

Form from tensional stress pulling apart, thins crust normal faults upthrown ranges ( top of mountain) Down thrown valleys Horst and Graben system

Horst and Graben

Horst upthrown Graben - down thrown valley

Isostasy

Isostatic rebound - erosion crustal root will rise up youngest mountain belts are the tallest oldest mountain belts are the lowest

Fold thrust Mountains

Largest mountains form cont- cont convergent

What type of fault is shown in this figure

Normal Fault

When a seismic wave hits an interface and some of the energy is sent back toward the surface, that wave is said to have been:

Reflected

At the San Andreas fault, the Pacific Plate is moving northwest relative to the southeast moving North American Plate. Therefore, movement along the San Andreas is:

Right-Lateral

Tsunami may be generated by:

Selected Answer: all are correct IAnswers: earthquakes that cause the seafloor to shift activity associated with volcanic eruptions landslides that displace large amounts of water

What type of stress formed the structure shown in this figure?

Shear

The refracted wave shown in the diagram has passed into a material that caused it to:

Slow Down

Stress and Strain

Stress: Pressure being placed on rock Strain: change and shape of the rock

What does the horizontal line along the intersection of the plane and the water represent?

Strike of the surface

What type of fault is shown in this figure

Strike slip fault

What type of structure is shown in this figure?

Syncline

types of strains dependent on:

Temperature higher temps cause elastic or ductile deformation. Lower temps will break Confining pressure (less Pressure)- the more pressure the more likely to behave elastically or ductility. (less likely to break)

Moho

The boundary between Earth's crust and mantle

How would the force and stress on the wooden pillar in this figure change if the stone weight was the same size but the wooden pillar was narrowe

The force would remain the same, but the amount of stress would increase

intensity

The subjective measure of the kind of damage done by an earthquake, as well as people's reaction to it.

Which of the following are true for horsts and graben

These are all true of horsts and grabens. A horst is a block that is uplifted relative to blocks on either side. May form associated with multiple normal faults. A graben is a block that is dropped down relative to blocks on either side.

S-wave shadow zone

Those areas more than 103 degrees from an earthquake focus where no s-waves are recorded.

Continents grow and evolve by addition of crust⎯a process known as:

accretion

Brittle deformation (fracture)

accumulation of strain breaks the rock

Shaking during an earthquake can

all of these Answers: generate a tsunami trigger landslides liquefy unconsolidated sediments, causing destruction of buildings on top of them cause rigid buildings to collapse

How would this diagram change if the seismic station was farther from the earthquake?

all of these Answers: the S-waves would arrive later there would be a larger gap between the arrives of the P- and S-waves the P-waves would arrive later

Which of the following is a characteristic of S-waves?

all of these Answers: they shear rock from side to side or up and down they cannot travel through liquids they displace the rock in a direction that is perpendicular to their travel direction

Which of the following does NOT match a sedimentary rock with a possible metamorphic equivalent

all of these are correct matches Answers: sandstone-quartzite shale-schist limestone-marble shale-gneiss

Which of the following rocks cannot be metamorphosed?

all of these can be metamorphosed Answers: sandstone limestone shale granite

Foliated metamorphic rocks form when pressure is applied

as compression or tension.

In what site on this figure would you expect low pressure/high temperature metamorphism?

c

Elastic deformation

changes shape of the rock but will return original shape if stress is removed.

Majority of earthquakes occur

circum-Pacific belt

When an isolated mountain range occurs in the interior of a continent, one may infer that the range formed by:

collision of two continental plates

When a rock is buried deep in the Earth and experiences the same force from all sides, it is unde

confining pressure

Volcanic island arcs are characteristic of which type of convergent plate boundaries

continental-oceanic AND oceanic-oceanic

elastic rebound theory

elastic rebound theory An explanation for the sudden release of energy that causes earthquakes when deformed rocks fracture and rebound to their original undeformed condition

Earthquakes may be caused by

explosions and human activity volcanic eruptions and magma movement landslides movement along faults Correct all of these may be caused by earthquakes

Rate of Strain:

faster the rate rx will break slower rates like to behave elastically and ductility

Divergent plate boundaries are characterized by

hydrothermal alteration and contact metamorphism

Metamorphic rocks may form from

igneous, sedimentary or metamorphic rocks

Metamorphic rocks may form from:

igneous, sedimentary or metamorphic rocks

Anticline

make a shapes erode away and cut top off oldest rx are in center youngest on outsides beds dip away from center

In the map to the right, areas of significant earthquake risk are shaded. Most high risk areas will be located

near a boundary between tectonic plates

In what environments does low pressure/high temperature metamorphism occur?

near magma but at shallow levels

Volcanic Mountains

not formed from deformation built up of volcanic material occur at volcanic arc, above subduction zones, divergent boundaries, and hotspots, rise in magma.

A seismic wave is refracted to a steeper angle when it

passes from a faster material into a slower one

The composition of the mantle is:

peridotite

Terranes

pieces of crust that form continents. added to continents through subduction process

What type of structure is shown in this figure?

plunging anticline

What type of structure is shown in this figure?

plunging syncline

When a seismic wave hits an interface and some of the energy is bent as it crosses that boundary, the wave has been:

refracted

What type of fault is forming here?

reverse fault

What type of fault is shown in this figure

reverse fault

When do rocks along a fault have the highest amount of stress and stored elastic strain?

right before an earthquake

What kind of metamorphic rock is formed where rocks have been heated but not deformed?

rock with metamorphic minerals but no foliation or lineation

According to the elastic rebound theory:

rocks will bend before they break, will snap back to their original shape after faulting, AND will break when their capacity to store energy of deformation has been exceeded

composition of rx:

rx behave brittally(limestone) behave eleastically or ductie (muscovite, biotites, clays)

Which of the following matches a sedimentary rock with a possible metamorphic equivalent?

shale-slate

What type of stress could form the fault in this figure?

shear

The cause of the P-wave shadow zone includes:

some P-waves are refracted upward before they reach this zone