Viewing All Flashcards for Geology Test 3
Questions
Answers
100,000’s to millions
Sudden movement along a
fault is the cause of most earthquakes
Crust and upper mantle.
Not many greater than 400 miles in depth (4000 miles to the center of
Earth)
1. If a rock is stressed it can store up the energy elastically. •2.) When the strength of the rock is exceeded
the rock breaks (brittle deformation)•3.) The rocks on either side of the fault
snap back to their original shape and release the stored energy.
The amount of energy stored up determines the
size of the earthquake.
Elastic, brittle
8)
An instrument that can
detect vibrations and shaking
Inertia (The resistance to stationary movement)
10)
Waves that travel through rock
11)
An energy transfer mechanism
12)
Distance from crest to crest
13)
The height of the wave
High amplitude
Low amplitude
16)
Time it takes for one
wavelength to pass.
17)
Periods
(cycles) per second (Hertz)
Higher the frequency
Elastic disturbances
Elastic disturbances
22)
The point of energy
release.
23)
The position vertically
above the focus on the Earth’s surface
1. Pass through the Earth
and travel outward in all directions from the
focus2. Travel along the surface of the Earth.
P-Waves and S-Waves
A.) Consist of alternating pulses of
compression and expansion (slinky)
b.) Produce changes in volume and density
c.) Travel through solids, liquids, and
gasses
d.) Has the fastest velocity (about 6km/s)
e.) Motion of the wave is parallel to its
direction
A.) Shear waves
b.) Deform material by changing shape but not
volume
c. ) Because gasses and liquids cannot change
shape, S-waves cannot pass through them
d.) Arrive at the seismograph last (about
3Km/s)
e.) Motion of the wave is perpendicular to
direction
28)
The recording produced by the seismograph
Determined by measuring the time interval
between the P and S-wave arrival.
31)
Travel along the surface of the Earth
•Travel more slowly than P and S-waves
•Last wave to be detected
Type of material
Increase
Based on what people experience during an
earthquake
1.) A qualitative measure based on earthquake
effects in populated areas
•2.) Intensity ratings are expressed as Roman
numerals between I at the low end and XII at the high end. (p. 52 Table 3-2)
I. People do not feel any Earth movement.
•II. A few people might notice movement if they
are at rest and/or on the upper floors of tall buildings.
•III. Many people indoors feel movement. Hanging
objects swing back and forth. People outdoors might not realize that an
earthquake is occurring.
•IV. Most people indoors feel movement. Hanging
objects swing. Dishes, windows, and doors rattle. The earthquake feels like a
heavy truck hitting the walls. A few people outdoors may feel movement. Parked
cars rock.•V. Almost everyone feels movement. Sleeping
people are awakened. Doors swing open or close. Dishes are broken. Pictures on
the wall move. Small objects move or are turned over. Trees might shake.
Liquids might spill out of open containers.
•VI. Everyone feels movement. People have trouble
walking. Objects fall from shelves. Pictures fall off walls. Furniture moves.
Plaster in walls might crack. Trees and bushes shake. Damage is slight in
poorly built buildings. No structural damage.
•VII. People have difficulty standing. Drivers
feel their cars shaking. Some furniture breaks. Loose bricks fall from
buildings. Damage is slight to moderate in well-built buildings; considerable
in poorly built buildings.•VIII. Drivers have trouble steering. Houses that
are not bolted down might shift on their foundations. Tall structures such as
towers and chimneys might twist and fall. Well-built buildings suffer slight
damage. Poorly built structures suffer severe damage. Tree branches break.
Hillsides might crack if the ground is wet. Water levels in wells might change.
•IX. Well-built buildings suffer considerable
damage. Houses that are not bolted down move off their foundations. Some
underground
The Intensity Scale differs from the Richter
Magnitude Scale in that the effects of
any one earthquake vary greatly from place to place, so there are many Intensity values (e.g.: VI, VIII) measured from one earthquake.
Shows the intensity ofshaking over an area thathas experienced anearthquake
- Quantitatively measures the amount of
energy released from an earthquake
- Needs instrumentational measurement
- Only one magnitude for an earthquakeMagnitude
The magnitude is calculated by measuring the
height of the largest S-wave
Logarithmic
1.) Ground motion (destroys buildings)2.) Faults – breaks
the ground surface3.) Fire – gas lines
break4.) Landslides,
avalanches – shaking causes movement on unstable slopes*5.) Liquefaction
*6.) Tsunami
7.) Flooding – dams
and levees break
8.) Differential
ground settlement
43)
The transformation of a granular material
from a solid state into a liquid state.
Liquefaction
1. Lateral Spread2. Flow failure 3. Ground Oscillation
47)
Low slope 0.3 to 3 degrees
Liquefaction of a subsurface layer
Gravity causes the mass to move down slope
Movement is from meters to 10’s of meters
Damages pipelines, utilities, bridges
48)
Occurs on slope > 3 degrees
•Blocks of soil or intact rock slide on a
liquefied subsurface layer
•Material moves 10’s of meters to 10’s of
miles (velocities of 10’s mph)
Slope is too gentle to permit lateral
movement
•Blocks of soil may decouple and begin to
shake
•Fissures open and close
•Sand boils up out of the ground
A loss of bearing strength.
Building can settle or tip over.
Buoyant objects (septic tanks) will rise to
the surface.
51)
A series of
sea-waves generated by an undersea disturbance.
Earthquakes, landslides, volcanic eruptions,
explosions, and meteorite impacts can all cause tsunamis.
vertical displacement of the
seafloor caused by movement
on a fault. *Epicenter must be
under water!
Must be a dip slip
fault!
Long periods (on the order of hours)
•Long wavelengths (60 miles)
•Speed – FAST - >400mph
•Height – changes as it approaches land
1.) Slow down
2.) Amplitude increases – unnoticeable at sea
to > 100 feet at shore
Tsunamis may appear as a rapidly rising
tide -
a wall of water
They can strip beaches of sand•Cause flooding•Destroy homes and buildings
Detects, locates, and sends out warnings to
locations around the Pacific Ocean
Consists of tide gauges and seismic stations
December 26, 2004
1.) 80% of all earthquakes originate in the cirum-pacific belt - The ring of fire2.) 15% of earthquakes originate in the
Mediterranean-Asiatic belt.
3.) The remaining
earthquakes occur on ridges and scattered through
the plates.
Although we know where
earthquakes will occur, there is currently no reliable way to predict when they will occur.
•
Earthquake prediction is a popular pastime
for psychics and pseudo-scientists
1.) Identifying patterns of small earthquakes
as precursors to large ones (foreshocks)
2.) Increase in ELF (extremely low
frequencies) waves
3.) Changes in land elevation and ground
water levels
4.) Unusual animal behavior
Convergent
Plate Boundary
Subduction Zone –
Java Trench
8 minutes long
Magnitude:9Location: off the west coast of northern Sumatra
1.) Convergent
boundary off the coast of Alaska, Washington and Oregon2.) Transform
boundary in
California.
1.) As the Atlantic basin opened, North
America moved westward into the Pacific basin.•2.) This resulted in subduction of
oceanic lithosphere under Alaska, Canada, Washington, Oregon and California•3.) A portion of the East Pacific Rise
(spreading center) was subducted under California.
This resulted in a transform fault.
In 1964, major subduction movement created the second largest
earthquake in recorded history.
5-7 centimeters per year
1.) Magnitude – 9.2 (Richter scale) second
largest
Largest recorded earthquake was in Chile in
1960 M 9.5
•2.) Epicenter – Prince William Sound120 km east of Anchorage, Alaska•5.) After shocks (small earthquakes following
a large earthquake)•3.) Intensity - III through X on the modified Mercalli
intensity scale. Felt over 700,00 square
miles of Alaska and Canada•4.) Duration of shaking
About 4 minutes!
Thousands of
after shocks were recorded in the months following the main shock.
In the
first day, there were 11 smaller earthquakes > M 6 !!
NW
motion of the Pacific plate of about 5
to 7 cm/year causes the coast of Alaska to become compressed and warped –
Tremendous stresses build up.The compression was
relieved by the sudden SE motion of portions of the Alaskan coast back over the
subducting
slab.
The Pacific plate moved under the North
American plate by about 30 feet in four minutes.•The rapid subduction was accompanied by vertical movement
The area around Montague Island was raised by
25 feet
9 feet
Area of significant damage covered about
130,000 sq km
The four minutes of shaking triggered landslides, avalanches,
liquefaction, tsunamis, and extreme ground shaking.
76)
131 people were killed.
122 of these were killed by the tsunami.
(16 were killed in Oregon and California)
Low population density, Holiday, Wooden
buildings survived shaking.
Tsunami- Maximum height reported was 120 feet.
Villages were destroyed, boats washed away,
people drowned.
Flow failure (slope > 3 degrees) occurred
in the city of Seward.
A large section of the city slid into the
ocean
80)
Long period
surface waves traveled around the Earth for several weeks.
The whole
Earth was ringing like a bell. Texas experienced vertical motions of 4 inches
Boats in a
Louisiana bay were sunk due to waves caused by ground shaking
1906 San Francisco
Vs.
1989 San Francisco (Loma Prieta,
World Series)
North American plate is
sliding (to the SE) by the Pacific plate
1. Some parts are locked and some parts are
creeping.•In the parts that are “weak” (creeping) many
earthquakes occur.
•These earthquakes typically have magnitudes
of about 5 to 6.•Other segments are “strong” (locked) and can
store up energy elastically to generate earthquakes with magnitudes > 7
1.) Location – Epicenter near San Francisco
-However, 265 miles of the fault ruptured
-This is part of the “locked” segment
The entire crust was breached to a depth of
12.5 miles
About 8 on the
Richter scale
Intensity – VII to IX experienced along the
length of the rupture.
Shaking was much more intense in areas of
weak unconsolidated materials around the
bay.
4.) Duration of shaking – about 60 seconds.
•5.) Foreshock – 30 seconds before the major
shaking, a smaller earthquake was felt throughout San Francisco.
The surface of the Earth had many fractures
Offset on the surface was about 20 feet
Deaths > 3,000
Homeless
225,000
Buildings
Destroyed 28,000
1.) Location – Epicenter was about 60 miles
south of San Francisco
•
•This was the first major rupture on the San
Andres since the 1906 earthquake
•
•About 25 miles of the fault ruptured
(southern end of the 1906 break)
93)
7.1
94)
VI to IX reported in
central California. Shaking more intense
around the bay.
4. ) Aftershocks – M 5.2 aftershock
occurred 2.5 minutes after the main
shock. Thousands of smaller quakes
occurred in the next two weeks.
•5.) Duration of shaking – about 11 seconds
Deaths – 67
Injured
– 4000
Homeless
– 12,000
Buildings
Destroyed – thousands
Fire
– 22 fires reported
Liquefaction around the bay area
Most of the people killed were on a section
of highway I-880 that collapsed.
1.) Surface Waters – Streams and Lakes
a.Originates from precipitation
Very little natural surface water in Texas –
Caddo Lake
Why do rivers flow when it stops raining?
2.) Ground Water
a. Originates from precipitation
99)
All the water contained in spaces within
rocks and soil
100)
The parts of rock or soil that are not
occupied by solids.
Groundwater occupies porosity.
Solution cavities –formed
by the dissolution of rock - usually forms in limestones.SINK HOLES – solution
cavitity that opens to the
surface
Space between sedimentary
grains.
103)
Cracks in the rocks
104)
The ability of material to transmit water.
105)
A body of permeable rock saturated with
water.
106)
An impermeable body of rock
1. Confined Aquifer2. Unconfined Aquifer
108)
An aquifer with an impermeable layer above it.
Unconfined aquifer
110)
The top of the saturated (phreatic)
zone – Unconfined Aquifer
A. Mimics the ground surface
b.
Moves up and down depending on rain
112)
Places where water enters
the aquifer (environmentally sensitive)
113)
Places where groundwater flows out of the aquifer.
Groundwater
Pressure
Potential surface
Unconfined
Down
120)
A place where groundwater discharges at the Earth’s surface
121)
A place where groundwater discharges at the Earth’s surface
122)
A well drilled into a confined aquifer with enough hydraulic pressure for the water
to flow to the surface without pumping. The pressure surface of the aquifer is
above the land surface.
A conical depression in the potential surface – water table
Streams
Water and sediment
126)
A network of connecting channels through
which water is transmitted back to the oceans.
1. Tributaries- The collection systemA dendritic pattern of smaller streams that feed water into the main trunk.
128)
Transport the water
129)
The dispersing system. River water flows into a standing body of
water.
1.) The number of tributaries decreases down
stream•2.) Tributaries “V” downstream•3.) The stream gradient (relief of the land,
slope) decreases down stream.•4.) Stream competence (grain size) decreases
down stream.•5.) Velocity decreases down stream.•6.) Discharge increases down stream.
131)
The volume of water per
time that passes though a stream.
Velocity X Cross sectional area = Discharge
Hydrograph