ERTH2404 Final Exam Lec 6-12
With Complete Solution
What is a strike? - ANSWER Intersection of planar structure with a horizontal
plane
What is a dip? - ANSWER Inclination of planar structure in respect to
horizontal level, measured at 90° from the strike line
What are the geological structures produced by deformation? - ANSWER
Faults
Joints
Folds
What is deformation? - ANSWER Alteration of size and/or shape of materials
What are normal stresses? - ANSWER Tension and compression
What is strain? - ANSWER Change in the shape and/or size of a body as a
result of stress
What is elastic deformation? - ANSWER When an object will return to its
original shape when the load is removed.
Strong rocks have a _________ modulus of Elasticity - ANSWER High
Weak rocks have a _________ modulus of Elasticity - ANSWER Low
Igneous rock's strength is ________ - ANSWER Strong
Sedimentary rock's and metamorphic rock's strength are_________ - ANSWER
,Variable
At shallow depth(low pressure), rocks behave? - ANSWER Elastically to elastic
limit before brittle failure
At middle to lower crust(higher confining pressure), rocks behave? -
ANSWER Elastically, materials soften with increasing temperature(depth)
Brittle rocks fail abruptly producing what? - ANSWER Fractures
Ductile rocks undergo plastic deformation producing what? - ANSWER
Undulations called folds
Factors controlling the brittleness of a rock are? - ANSWER Rock composition
and texture
Temperature and pressure
Presence of fluids
What are faults? - ANSWER Major fractures, showing movement between
rock blocks
What are joints? - ANSWER Minor fractures, showing little or no movement
between rock blocks
What is a hanging wall fault? - ANSWER Rock block above the fault; older
What is a footwall fault? - ANSWER Rock block below the fault; younger
What is a dip slip fault? - ANSWER Movement in the direction of dip, normal,
and reverse.
What movement type is a normal fault? - ANSWER Gravity does the work;
extension
,What movement type is a reverse fault? - ANSWER Compression
What movement type is a strike-slip fault? - ANSWER Lateral, along strike
What is a thrust fault? - ANSWER Low angle reverse fault; moves hanging
wall rocks over footwall rocks
What causes joints? - ANSWER Internal stresses
What causes expansive joints? - ANSWER Removal of overlying rocks by
erosin
What causes cooling joints? - ANSWER Thermal contraction/expansion in
relation to igneous processes
What are systematic joints? - ANSWER Parallel, regularly spaced fractures
What causes systematic joints? - ANSWER Regional uniform stress
What are non-systematic joints? - ANSWER Randomly orientated fractures
with irregular orcurved joint faces
What causes non-systematic joints? - ANSWER Local non-uniform stresses
What is a fold? - ANSWER Geological structure formed when rocks are bent
or curved as a result of plastic deformation
What is a anticline fold? - ANSWER Arched fold in which the central part
contains the oldest rock layer; convex upwards
What is a syncline fold? - ANSWER Arched fold in which the central part
contains the youngest rock layer convex downward
What is a neutral fold? - ANSWER Axial plane horizontal
How does the mantle melt? Case 1: - ANSWER Lower the pressure,
, decompression melting
How does the mantle melt? Case 2: - ANSWER Add volatile compounds(H2O,
CO2) dehydration melting
How does the mantle melt? Case 3: - ANSWER Hot mantle plume
(decompression dehydration)
What is the first step In a volcanic eruption? - ANSWER Creation of magma;
solid rock in the mantle melts
What is the second step In a volcanic eruption? - ANSWER Fractures; phase
change from solid to liquid leads to increase volume
What is the third step In a volcanic eruption? - ANSWER Volatiles; volatiles
gradually come out of solution, gas pushes magma upwards
What is the fourth step In a volcanic eruption? - ANSWER Magma fragments
are created; when bubbles are >75% volume magma gets expelled into the
atmosphere
Volcanoes at spreading centers have what properties? - ANSWER Peaceful
eruptions, magma directly derived from asthenosphere
Volcanoes at convergent zones have what properties? - ANSWER Little
volcanism, continent continent zones, volcanic mountains formed at the edge
of the continents where and oceanic plate subducts beneath another plate.
What is a stratovolcano? - ANSWER A large volcanic cone built of alternating
layers of viscous lava and pyroclastic debris.
What are hotspot volcanoes? - ANSWER Chain of volcanoes aligned in the
direction of the plate motion, age increasing with distance from hotspot.
With Complete Solution
What is a strike? - ANSWER Intersection of planar structure with a horizontal
plane
What is a dip? - ANSWER Inclination of planar structure in respect to
horizontal level, measured at 90° from the strike line
What are the geological structures produced by deformation? - ANSWER
Faults
Joints
Folds
What is deformation? - ANSWER Alteration of size and/or shape of materials
What are normal stresses? - ANSWER Tension and compression
What is strain? - ANSWER Change in the shape and/or size of a body as a
result of stress
What is elastic deformation? - ANSWER When an object will return to its
original shape when the load is removed.
Strong rocks have a _________ modulus of Elasticity - ANSWER High
Weak rocks have a _________ modulus of Elasticity - ANSWER Low
Igneous rock's strength is ________ - ANSWER Strong
Sedimentary rock's and metamorphic rock's strength are_________ - ANSWER
,Variable
At shallow depth(low pressure), rocks behave? - ANSWER Elastically to elastic
limit before brittle failure
At middle to lower crust(higher confining pressure), rocks behave? -
ANSWER Elastically, materials soften with increasing temperature(depth)
Brittle rocks fail abruptly producing what? - ANSWER Fractures
Ductile rocks undergo plastic deformation producing what? - ANSWER
Undulations called folds
Factors controlling the brittleness of a rock are? - ANSWER Rock composition
and texture
Temperature and pressure
Presence of fluids
What are faults? - ANSWER Major fractures, showing movement between
rock blocks
What are joints? - ANSWER Minor fractures, showing little or no movement
between rock blocks
What is a hanging wall fault? - ANSWER Rock block above the fault; older
What is a footwall fault? - ANSWER Rock block below the fault; younger
What is a dip slip fault? - ANSWER Movement in the direction of dip, normal,
and reverse.
What movement type is a normal fault? - ANSWER Gravity does the work;
extension
,What movement type is a reverse fault? - ANSWER Compression
What movement type is a strike-slip fault? - ANSWER Lateral, along strike
What is a thrust fault? - ANSWER Low angle reverse fault; moves hanging
wall rocks over footwall rocks
What causes joints? - ANSWER Internal stresses
What causes expansive joints? - ANSWER Removal of overlying rocks by
erosin
What causes cooling joints? - ANSWER Thermal contraction/expansion in
relation to igneous processes
What are systematic joints? - ANSWER Parallel, regularly spaced fractures
What causes systematic joints? - ANSWER Regional uniform stress
What are non-systematic joints? - ANSWER Randomly orientated fractures
with irregular orcurved joint faces
What causes non-systematic joints? - ANSWER Local non-uniform stresses
What is a fold? - ANSWER Geological structure formed when rocks are bent
or curved as a result of plastic deformation
What is a anticline fold? - ANSWER Arched fold in which the central part
contains the oldest rock layer; convex upwards
What is a syncline fold? - ANSWER Arched fold in which the central part
contains the youngest rock layer convex downward
What is a neutral fold? - ANSWER Axial plane horizontal
How does the mantle melt? Case 1: - ANSWER Lower the pressure,
, decompression melting
How does the mantle melt? Case 2: - ANSWER Add volatile compounds(H2O,
CO2) dehydration melting
How does the mantle melt? Case 3: - ANSWER Hot mantle plume
(decompression dehydration)
What is the first step In a volcanic eruption? - ANSWER Creation of magma;
solid rock in the mantle melts
What is the second step In a volcanic eruption? - ANSWER Fractures; phase
change from solid to liquid leads to increase volume
What is the third step In a volcanic eruption? - ANSWER Volatiles; volatiles
gradually come out of solution, gas pushes magma upwards
What is the fourth step In a volcanic eruption? - ANSWER Magma fragments
are created; when bubbles are >75% volume magma gets expelled into the
atmosphere
Volcanoes at spreading centers have what properties? - ANSWER Peaceful
eruptions, magma directly derived from asthenosphere
Volcanoes at convergent zones have what properties? - ANSWER Little
volcanism, continent continent zones, volcanic mountains formed at the edge
of the continents where and oceanic plate subducts beneath another plate.
What is a stratovolcano? - ANSWER A large volcanic cone built of alternating
layers of viscous lava and pyroclastic debris.
What are hotspot volcanoes? - ANSWER Chain of volcanoes aligned in the
direction of the plate motion, age increasing with distance from hotspot.
