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