GLY 150-002 Exam 4 Review Sheet
Topics and concepts
that may appear on the exam
Lecture Topic 1 – Earth
in the Solar System
-
What is the Big Bang theory?
o Astronomers
have concluded that the expansion began at a specific time
-
When was the big bang thought to have occurred?
o 13 billion years ago
-
When was our Sun thought to have formed?
o 5 billion years ago
-
What is the current theory of how the moon
formed? (the theory developed after the Apollo
space mission)
o the
Moon formed when a nearby Mars-sized protoplanet collided with the Earth
Lecture Topic 2 –
Development of the Earth
-
When did the Earth first form?
o About
4.6 billion years ago
-
When the Earth first formed, was it homogeneous
or differentiated?
o Homogeneous
-
Since solid materials are immobile, to become differentiated,
the earth must have become what?
o Partially molten
-
For partial heating, and therefore partial
melting of the Earth, to occur, an enormous amount of heat had to be created.
What are the three processes that created the heat?
o
The kinetic energy of colliding meteorites
transforms into heat energy
§ This
energy is absorbed into the rocks
o Radioactively
generated heat accumulated deep within the Earth
o As
material accumulated at the surface, the weight on underlying materials would
have generated more heat by gravitational compression
Lecture Topic 3 – The
Earth’s Interior, Heat Sources and Convection
–
What does the velocity of seismic waves depend on?
o
Velocity
depends on the density and elasticity of the
intervening material
–
Abrupt changes in seismic-wave velocities that occur at
particular depths helped seismologists conclude that Earth must be composed of
what?
o
Composed
of distinct shells
–
With increasing depth, Earth’s interior is
characterized by gradual increase in what three things?
o
Temp,
press, density
–
Depending on the temperature and depth a particular
Earth material may behave in what three ways?
o
behave like a brittle solid,
o
deform in a plastic–like manner,
o
or melt and become liquid
–
What does the lithosphere consist of?
o
Crust,
upper mantle
–
What layer is below the lithosphere (in the upper
mantle)?
o
atmosphere
–
What allows the lithosphere to move independently of
the asthenosphere?
o
Small
amount of melting
–
The fact that S waves do not travel through the core
provides evidence for the existence of what beneath the rocky mantle?
o
a liquid layer beneath the rocky mantle
–
What are the major processes that have contributed to
Earth’s internal heat?
o
Heat emitted by radioactive decay of isotopes
of uranium (U), thorium (Th), and potassium (K)
o
Heat released as iron crystallized to form the
solid inner core
o
Heat released by colliding particles during the
formation of Earth
–
Heat flow in the crust occurs through a process called
what?
o
Conduction
Lecture Topic 4 –
Plate Tectonics
o Who
put forth the theory of continental drift?
§ wegner
o What
were Wegner’s geological arguments based on?
§ based
on the apparent continuity of some mountain ranges, coal beds, and other
geological structures from one continent to another
o What
did Wegner’s biological arguments depend on?
§ based
on observations in geology, biology, and climatology
Plate Tectonics
o Who
came up with the theory of seafloor spreading?
§ Harry
Hess
o The
theory of seafloor spreading was aided by what?
§ Mapping ocean floor
o What
did the navy magnetometers record on the seafloor?
§ Magnetic field variations
o What
does the theory of Plate Tectonics help to explain?
§ geologic
processes and events
§
-
What are the three forces that cause the
tectonic plates to move?
o
Mantle plume convection
o
Ridge-push force
o Slab-pull
force
-
Why are mid-ocean ridges high topographically?
-
Lithosphere is very young and hot
-
Why does the ridge-push force develop?
o mid-ocean
ridges lie at a higher elevation than the adjacent abyssal plains
-
What causes the slab-pull force?
o Caused
by the tendency of the colder and denser lithosphere to sink into the
underlying mantle. convergent
What are the three types of plate boundaries?
§ Con, div, trans
A divergent plate boundary is defined by what geologic
feature?
§ volcano
What are divergent boundaries on land called?
§ rifts
A convergent plate boundary is characterized by what
geologic features?
§ Volcanic mountains or islands
What are the three types of convergent plate boundaries?
§ Ocean/ocean, continent/ocean,
continent/continent
What is a transform plate boundary defined by?
§ Transform fault zone
Lecture Topic 5 –
Subduction Zones and Convergent Plate Boundaries
-
According to the plate tectonics theory, the
creation of new oceanic crust at mid-ocean ridges is matched by what?
o
matched by the destruction of old oceanic crust
at subduction zones
‒
Why are subduction-zone volcanoes highly
explosive?
o
their magmas contain large quantities of
volatiles and gases that escape when reaching the surface
-
What are the seaward boundaries of subduction
zones marked by?
o
marked by the deepest trenches in the world
‒
What determines which plate is subducted?
o
When two lithospheric plates converge,
generally the oceanic plate is bent and pushed under the thicker, more buoyant
continental plate
Lecture Topic 6 –
Rifting and Seafloor Spreading
–
Along what type of plate tectonic boundary do rifts
form?
o
divergent
‒
Typically the transition from rifting to
spreading develops where?
o
triple junction where three converging rifts
meet over a hotspot.
‒
Because the crust in an aulacogen region remains
weakened by previous rifting activity, what type of geologic activity may
subsequently re-occur from time to time?
o
Volcanic
Activity
Lecture Topic 7 – Volcanoes
and Igneous Rocks
-
Where do the majority of magmas originate?
o in
the upper mantle at depths between 50-250 km
-
At the depths of 50-250 km, what two conditions
exist that allow the rock to melt?
-
Magma is typically generated at what three
tectonic settings?
o Divergent
plate boundaries
o
Convergent plate boundaries – subduction zones
o Hot
spots
-
What is the relationship between viscosity and
temperature?
o Viscosity
increases with decreasing temperature
-
What is the relationship between viscosity and
silica content?
o Increase with silica
-
How do low viscosity mafic magmas erupt?
§ mafic
magmas tend to erupt quietly, with relatively gentle outpouring of degassed
lava
-
How do high viscosity felsic magmas erupt?
§ Explosively
Lecture Topic 9 – Types
of Volcanoes
-
What type of volcano typically forms over a hot spot?
Shield Volcano
-
Where do stratovolcanoes (composite volcanoes) form?
subduction zones
-
What volcanic hazard can be produced by the collapse of a steep-sided
lava dome?
pyroclastic flows
-
How do calderas form?
Explosive
disintegration of the top of a volcano
Lecture Topic 10 –
Stratovolcanoes – Cascade Volcanoes
– In a subduction zone, what
determines the location of magma formation?
Temperature and depth
– What determines the horizontal
distance from the trench to the volcanic arc?
dip angle of the
subducting plate
– At steeply dipping subduction
zones, is the arc and trench close together or farther apart?
the arc and trench are
close together
– At gently dipping subduction
zones, is the arc and trench close together or farther apart?
Further apart
– What are the five signs of an
impending eruption of a volcano?
Seismicity
Inflation
Increased gas emissions
Increased temperatures as magma approaches surface
Changes in density/gravity and magnetic signature
Lecture Topic 11 –
Hot Spot Volcanism
- Where are the mantle plumes that
create hot spots thought to arise from?
The mantle plume rises
toward the surface via convection
- A kink in a line of volcanic
islands/seamounts formed over a mantle plume documents past changes in what?
Kinks in the
island/seamount chain document past changes in direction of plate motion
(typical) OR movement of
the hot spot itself (rarely).
- Seismicity (earthquakes) in a
hot spot volcano is solely driven by what two things?
volcanic activity and
gravitational collapse of the volcanic edifice
Lecture Topic 8 –
More on Volcanoes
–
Along which types of convergent plate boundaries do
volcanoes occur?
o
Along rifts
–
Along which type of convergent plate boundary do
volcanoes NOT occur?
o
No
volcanism at continent-continent
collision zones or transform boundaries
–
Along which type of convergent plate boundary does a
volcanic island arc form?
o
Ocean-ocean
subduction zones
–
Along which type of convergent plate boundary does a
narrow mountain belt with volcanoes form?
o
Oceanic-continental
subduction zones
–
What percentage of volcanoes are located at convergent
plate boundaries?
o
80%
–
What percentage of volcanoes are located along
mid-ocean ridges and spreading centers?
o
20%
–
What affect do volatiles have on the melting
temperature of materials in the subducting wedge?
o
decrease
the melting temperature of materials in wedge
–
Do volatiles increase or decrease explosivity?
o
Increase
–
Is the erupted magma derived from the subducted oceanic
plate or the overriding plate?
o
Subducted
–
What two things does magma viscosity depend on?
o
Silica Oxygen
–
What are the four factors that affect magma
explosivity?
o
Volatile (a.k.a. gas) Content, Viscocity,
Nucleation sites, Suddenness of the pressure release
–
Where do effusive eruptions occur? (What type of
tectonic boundary?)
o
oceanic
–
Where do explosive eruptions occur? (What type of tectonic
boundary? – i.e., the type of tectonic boundary that has a subduction zone)
o
–
Why is ash more of a problem? (5 reasons)
o
It can
take several months or years for the dust to settle
o
In the
meantime, the floating dust and ash partially blocks out the incoming sunlight
– causing measurable cooling
–
What is a lahar?
o
Volcanic
mud-flow or debris-flow
–
During a volcanic eruption, what causes a lahar to be
generated?
o
when large
volumes of ice and snow melt during an eruption
–
How can a lahar be generated when there is no eruption?
o
when heavy
rainfall saturates weathered volcanic deposits
–
When do pyroclastic flows form?
o
when the
amount of pyroclastic material expelled by a volcano is so great that gravity
almost immediately pulls it down onto the volcano slope
–
Why are pyroclastic flows buoyant?
o
flow also
contains trapped air and magmatic gases
–
What do the gases create between the base of the flow
and the ground?
o
a
frictionless barrier
–
Can a single volcanic eruption have a global impact on
climate?
o
yes
–
In what way can the large amounts of volcanic ash
erupted affect the climate?
o
Can create
ashfalls that, when combined with rainwater, can cause buildings and structures
to collapse
Lecture Topic 14 –
Earthquakes – Part 2
-
What are the four causes of earthquakes?
o
Tectonic,
Volcanic, Explosion, Collapse
-
What is the Benioff zone?
o
narrow
zone of earthquakes that marks the position of the descending slab at
subduction zones
-
Depth of earthquakes:
o
At convergent boundaries WITH subduction zones,
are the earthquakes deep, shallow, or both?
§
both
o
At convergent boundaries WITH subduction zones,
what causes the deep earthquakes?
§
o
At convergent boundaries WITH subduction zones,
what causes the shallow earthquakes?
o
At continental collision zone convergent
boundaries, are the earthquakes deep, shallow, or both?
§
Shallow
o
At continental collision zone convergent
boundaries, what causes the shallow earthquakes?
§
intense
compression at the plate boundary
-
Intraplate earthquakes
o
The New Madrid Seismic Zone is made up of
reactivated faults that formed when?
§
North
America began to split or rift apart during the breakup of the supercontinent
What are two ways that seismic activity can be induced by
human activities?
Injection & Reservoir
Why do geothermal fields have naturally high seismicity rates?
Because of volcanic & geothermal characteristics
How are additional earthquakes induced in a geothermal
field?
by extraction and re-injection of fluids
-
What are the five factors that affect earthquake
damage?
o
Distance
to epicenter
o
Depth of
earthquake
o
Geology
o
Density
o
Building
codes
-
Along which type(s) of tectonic boundaries do
the highest percentage of earthquakes occur?
o
Transform
or Convergent
-
Why are there fewer earthquakes along divergent
plate boundaries?
o
hotter
rocks there: more plastic and less brittle
Lecture Topic 13 –
Earthquakes – Part 1
-
What is the most common cause of an earthquake?
-
What does the elastic rebound theory describe?
-
What type of stress is found at divergent plate
boundaries?
-
What type of stress is found at convergent plate
boundaries?
-
What type of stress is found at transform plate
boundaries?
-
Divergent plate boundaries
o
What happens to the lithosphere?
o
What type of faulting occurs at divergent plate
boundaries?
o
Are the faults and earthquakes shallow or deep?
-
Convergent plate boundaries
o
What happens to the lithosphere?
o
What type of faulting occurs at divergent plate
boundaries?
-
Transform plate boundaries
o
What happens to the lithosphere?
o
What type of faulting occurs at divergent plate
boundaries?
o
Are the faults and earthquakes shallow or deep?
-
Seismic waves
o
What type of stress do P-waves create –
compressional, shear, or tensional?
o
What materials within the Earth can P-waves pass
through?
o
What type of stress do S-waves create –
compressional, shear, or tensional?
o
What materials within the Earth can S-waves NOT
pass through?
o
Which type of seismic waves cause the most
damage?
-
What information can seismologists get from the
distribution of aftershocks?
-
What is liquefaction?
-
What term is incorrectly used to describe a
tsunami?
-
What do tsunamis originate from?
-
What is a warning sign along the coast that a
tsunami is forming?
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