GEOL 306 FINAL
Arrange the following materials in order of increasing viscosity, with 1 being the lowest viscosity and 5 being the highest.
1. Water 2. Basalt lava 3. Andesite lava 4. Rhyolite lava 5. Mantle rocks
Conditions that affect the amount of damage caused by an earthquake include:
- Building design - Distance from the epicenter of the earthquake - Type of surface material (rock or dirt)
A cross-section of the Earth from the surface to the interior is as follows:
- Crust, mantle, core - Lithosphere, asthenosphere, mesosphere, outer core, inner core.
In order to generate magma, part of the mantle must melt. What causes melting in the mantle?
- DECREASE in PRESSURE - INCREASE in TEMPERATURE - Introduction of water (or more accurately, introduction of hydrogen and oxygen)
Which of the following tectonic features are associated with volcanic activity?
- Divergent plate boundaries - Convergent plate boundaries - SUBDUCTION ZONES - Hot spots
Which of the following can trigger landslides on volcanoes?
- Intrusion of magma below the volcano - Explosive eruptions of the volcano - Large earthquakes directly beneath or nearby the volcano - Heavy rainfall that saturates the slopes of the volcano
Earthquakes can occur along which of the following types of faults?
- Normal faults - Reverse faults - Strike-slip faults
Which of the following were precursor events to the 1980 eruption of Mt. St. Helens?
- Steam eruptions - Earthquakes - A bulge on the volcano's flank - Fissure development
Which of the following describes EXTRUSIVE igneous rocks?
- They cooled from lava that erupted onto the surface of the Earth - They cooled quickly - They have very small crystals - Volcanoes and lava flows are made of them - Rhyolite, andesite, and basalt are all examples
Which of the following describes INTRUSIVE igneous rocks?
- They cooled from magma that never made it to the surface of the Earth - They cooled very slowly - They have large crystals - They can be found underneath volcanoes - Granite, diorite, and gabbro are all examples
What parts of the U.S. are at the highest risk for earthquakes?
- Western states, especially Washington, Oregon, Nevada, and California - Most of Alaska - Hawaii, especially the big island of Hawaii - The region near the borders of Kentucky,Tennessee, Arkansas, and Missouri
How did scientists in the 1800s deduce that the interior of the Earth is mostly solid?
1. If the interior of the Earth was liquid, then the surface of the planet would rise and fall in response to gravitational pull from the moon (the surface of the Earth would experience tides). 2. This would cause the surface of the Earth AND the oceans to rise and fall together, there would be no observable tidal sea level change. 3. This is not the case - there IS an observable tidal sea level change, so the interior of the Earth cannot be liquid (or at least most if it isn't liquid, they did not yet know about the liquid outer core). Smart scientists!
What four steps do scientists take in the process of alerting the public about possible tsunamis?
1. Locate the earthquake 2. Determine tsunami travel time 3. Check sea level gauges for evidence of a tsunami 4. Issue messages as appropriate
How will a Cascadia earthquake impact transportation in Portland? How will the transportation problems you described above impact rescue and recovery efforts after an earthquake?
1. Major bridges such as Hawthorne, Steel, and Interstate will likely collapse. So will ramps leading to just about all the bridges. 2. The city's roadways will crack and sink. 3. Highway 26's West Hills Tunnel will probably become impassable. 4. All of the city's road-clearing equipment will be inaccessible because it is stored beneath the certain-to-collapse Fremont Bridge ramps.
Describe three methods scientists use to monitor volcanoes for signs of activity. For each method, explain how the information is collected (what is measured, or what type of equipment is used), and what the information tells scientists about the volcano.
1. Monitoring earthquakes - seismographs, earthquakes indicate that magma is moving beneath the volcano. (more earthquake activity = volcano is more likely to erupt) 2. Satellite imagery 3. Gas emissions - Amnt of gas surrounding the volcano
1. Explain what caused the March 2011 earthquake in Japan and the December 2004 earthquake in Sumatra. 2. How were these two events similar? Your answer should include a brief description of what is happening to the tectonic plates in both regions.
1. The sudden movement of the Pacific tectonic plate under the North American plate caused the March 2011. The earthquake in Japan and the December 2004 earthquake in Sumatra was caused by the India Plate being subducted beneath the Burma micro-plate, part of the larger Sunda plate. 2. These two events were similar in the sense that they were both caused by shifting plates beneath the surface. In both cases one type of plate is being subducted beneath another.
Describe two ways that volcanic eruptions can cool the global climate. For each description, include what is erupted from the volcano and how it cools the climate.
1. Volcanoes emit ash into the atmosphere; ash particles block some of the sunlight that normally would have reached Earth, which cools the global climate. 2. Sulfur dioxide gas - Sulfur dioxide gas reacts with water in the atmosphere and forms a small particle of sulfur. These particles block some of the sunlight that normally would have reached Earth (much like ash or dust particles), which cools the global climate.
A large subduction zone earthquake in the Pacific Northwest will likely trigger a tsunami with waves ____ feet high and lasting up to ____ hours.
10-50 feet high, 8 hours
How many giant landslides have occurred in Hawaii during the past 4 million years? Could they occur again in the future?
15, yes
What is the minimum number of seismograph stations a scientist must have data from in order to locate the epicenter of an earthquake?
3
The last Cascadia earthquake occurred [number1] years ago.
317
What percentage of single-family homes in Portland were built before the first seismic codes, which means they are probably not bolted to their foundations and will be uninhabitable after a large Cascadia earthquake?
70%
A pyroclastic flow can best be described as:
A flow of hot GAS and ASH
What is a seismic shadow zone? Be sure you answer includes something about P-waves and S-waves, and the mediums through which each type of wave can travel.
A seismic shadow zone is the area of the earth from an earthquake that doesn't receive any direct P-waves. The S-waves are even refracted from the earth's liquid core. P-waves can travel through solid liquid and rock, and S-waves can only travel through rock.
How high were the tsunami waves created by ancient landslides in Hawaii?
About 1,000 feet (about 300 meters).
Which of the following describes what happens at divergent plate boundaries?
All of the above: - Two plates moving away from each other - New lithosphere is being created - Transform plate boundary
What is the definition of a volcano?
An opening in the crust of a planet, they can emit lava, rock fragments, gases, or just heat. These products may have been erupted in the past (extinct volcanoes are still considered volcanoes, even though they are unlikely to ever erupt again.)
The cold, rigid lithosphere is underlain by the hot, mobile ________________.
Asthenosphere
How does rock move during the passage of a P-wave through the rock? How does rock move during the passage of a S-wave through the rock?
Back and forth parallel to the direction of wave travel. Perpendicular to the direction of wave travel.
The crystallization of a mafic magma will generate the following rock type:
Basalt
What type of plate boundaries generate the most tsunamis?
Convergent plate boundaries - sunduction zones
By the late 1800s scientists had developed a simple model of Earth's interior. Name the 3 layers in this model, and the physical properties of each layer (as best they were understood at the time).
Crust (first layer) - made up of unknown thickness Substratum (second layer) - made up of elastic or plastic Core (nucleus) - could be solid or liquid
Which layers are classified by chemical composition?
Crust, mantle, core
Vesiculation in magma (or the formation of bubbles) can be promoted by __________.
Decompression (the magma rises toward the surface of the Earth). Crystallization (the magma starts to cool).
Mantle convection related to plate tectonics:
Divergent plate boundaries and hotspots are locations where hot material rises from mantle convection Subduction zones are locations where cool material sinks back to the mantle Tectonic plates on the surface of the Earth are dragged along by the lateral movement of convection cells in the mantle.
Which of the following is the correct sequence of events for the 1980 eruption of Mt. St. Helens?
Earthquake, landslide, lateral blast, vertical blast.
T/F: Mafic magma (e.g. basalt) is more viscous than felsic magma (e.g. rhyolite).
FALSE
T/F: One way that Oregon and Washington have mitigated against loss of life during large tsunamis is by building vertical evacuation structures in all coastal towns and cities.
FALSE
T/F: The interior of the Earth is completely molten.
FALSE
T/F: All volcanoes are tall cone-shaped mountains that erupt lava.
False
Which of the following best describes a volcanic vent where gas emissions occur, but no lava or ash is erupted?
Fumarole
The Hawaiian islands formed at a _______ boundary.
Hot-spots NOT: convergent, divergent or transform
Which of the following volcanic gases are hazardous to people, animals, agriculture, and property?
Hydrogen halides (HF, HCl, HBr) Hydrogen sulfide (H2S) Carbon dioxide (CO2) Sulfur dioxide (SO2)
If a S-wave travels from a solid to a liquid, what happens to its velocity? If a P-wave travels from a solid to a liquid, what happens to its velocity?
It slows down to zero. It slows down.
Sudden melting of glaciers on volcanoes can generate which of the following hazards?
Lahars
Which of the following is produced by the LEAST EXPLOSIVE types of volcanic eruptions?
Lava flows
Which layers are classified by physical properties?
Lithosphere, asthenosphere, mesosphere, outer core, inner core
HOT SPOTS
MOVEMENT: Not a type of plate boundary, but there is movement. The hot spot is stationary and the plate moves over the top of it. MAIN FEATURES THAT EXIST: Volcanoes DO VOLCANOES EXIST @ THIS BOUNDARY: Yes REAL WORLD EXAMPLE: The Hawaiian Islands
DIVERGENT PLATE BOUNDARY
MOVEMENT: When two tectonic plates move away from each other. Occur between oceanic plates and exist as mid-ocean ridges. MAIN FEATURES THAT EXIST: rift system DO VOLCANOES EXIST @ THIS BOUNDARY: Yes REAL WORLD EXAMPLE: The mid-atlantic ridge
CONVERGENT PLATE BOUNDARY
MOVEMENT: When two tectonic plates move towards each other MAIN FEATURES THAT EXIST: Subduction zones, oceanic trenches (+ volcanoes). Continental collisions - subduction doesn't occur here, instead plates are pushed up to form mountains. Earthquakes occur here but not volcanoes. DO VOLCANOES EXIST @ THIS BOUNDARY: Yes REAL WORLD EXAMPLE: Washington-Oregon coastline
TRANSFORM PLATE BOUNDARIES
MOVEMENT: when plates slide sideways past each other, or slide parallel to each other. MAIN FEATURES THAT EXIST: Faults DO VOLCANOES EXIST @ THIS BOUNDARY: No REAL WORLD EXAMPLE: Alpine Fault of New Zealand
Match the following tectonic settings with the best description of how magma is generated at each setting.
Mantle melts because of a.... Divergent PB = decrease in pressure Convergent PB - subduction zones = addition of water Convergent PB - continental collisions = Mantle does not melt at this location Hot spots = increase in temp Transform PB = Mantle does not melt at this location
Which of the following measures an earthquake's intensity based on the observed effects on people and structures? Which of the following measures an earthquake based on the amount of energy released?
Mercalli scale Moment magnitude scale
Body waves consist of:
P and S waves
To determine how far away from a seismograph station an earthquake occurred, scientists plot the difference in arrival times between:
P and S waves
In the Southern California ShakeOut website, what type of waves are most likely to be the first to pass through in each simulation map?
P-waves
Which type of seismic waves travel the fastest?
P-waves
Which of the following is not a stratovolcano?
Paricutin, Mexico
A magma's viscosity will increase with increasing ___________.
Polymerization, silica content
According to the Oregon Field Guide video Unprepared, what city in Oregon has been identified as the primary recovery site for the state after a Cascadia earthquake?
Redmond
Which type of faulting would be least likely to occur at divergent plate boundaries?
Reverse
Which type of faulting would be most likely to occur at convergent plate boundaries?
Reverse
This question is from the video, BBC-Supervolcano, but it is also a real scenario that happens worldwide when volcanic eruptions occur: Why are scientists cautious about what they say in the media about the potential for volcanic eruptions? In your answer to this question, you should explain the differences between what scientists want to convey to the public, and what the public wants to hear.
Scientist are cautious about what they say to the media because they often do not have specific details that the public wants to know. Scientists are working from good evidence that an eruption is likely to occur, but they cannot predict exactly when the eruption will happen, how big it will be, and what areas will be impacted. If they make predictions about these details and they end up being wrong, the public is often very angry because the scale of the eruption was either overestimated or underestimated. The public wants to know whether or not an eruption will occur, how big it will be, and what areas will be impacted. Scientists can give estimates about all of these things, but they cannot predict them with 100% accuracy. The public wants scientists to be absolutely certain - they do not want to be warned about an imminent eruption and go through the hassle of evacuating the area, only to have no eruption actually occur.
Compared to basalt, rhyolite has more _____________.
Silica (SiO2)
Types of volcanoes
Stratovolcano Shield volcano Cinder cone Tuff ring Caldera Volcanic fissure
Which type of faulting would be most likely to occur at transform plate boundaries?
Strike-slip
In all cases, tsunamis waves are caused by:
Sudden displacement of water
In general, the most destructive earthquake waves are __________.
Surface waves
Which waves cause the most damage?
Surface waves
T/F: Eruptions can be both explosive and effusive at the same time (if you are unsure, review the photos of eruptions in Lecture 3: Controls on Volcanic Eruptions - Gas Content).
TRUE
T/F: In general, subduction zone earthquakes in the Pacific Northwest are much larger than any recorded earthquake that has occurred in California.
TRUE
T/F: Soils that form in volcanic areas are very fertile.
TRUE
T/F: The viscosity of magma depends on the temperature, chemical composition, and gas content of the magma.
TRUE
T/F: Volcanic gases (especially carbon dioxide or CO2) can slowly seep out of the ground in volcanic areas, which poses a deadly threat even if no actual eruption occurs.
TRUE
Which of the following is the most widespread and frequent volcanic hazard?
Tephra (or volcanic ash)
Mantle Convection
The circulation of heat in the mantle. Hot material rises from the core, and cool material sinks from the surface of the Earth.
A caldera results from:
The emptying of a magma chamber, which causes the volcano to collapse in on itself.
Based on this week's reading materials, and this week's and last week's videos, how long could the shaking last during a large Cascadia earthquake?
Up to five minutes
According to the Southern California ShakeOut website, what portion of the San Andreas fault has been identified as the most likely source of a very large earthquake in California?
The southern section of the fault (from Los Angels south)
If a large asteroid landed in the Pacific Ocean between the Hawaiian Islands and the west coast of North America, what would be the impact of the tsunami waves?
They would wash out coastal cities on the west coasts of Canada, the U.S. and Mexico, and would cover most of the coastal areas of Hawaii.
Write out the equation that explains the relationship between velocity (or speed), frequency, and wavelength of a wave. Answer the following questions about this equation: 1. Based on this equation, if the frequency of a wave increases, what happens to the wavelength? 2. If the frequency of a wave decreases, what happens to the wavelength? 3. If the wave is traveling through a specific medium (for example water), does the velocity of the wave change if the frequency changes? Does the velocity change if the wavelength changes?
VELOCITY = FREQUENCY x WAVELENGTH 1. If the frequency of a wave increases, the wavelength becomes smaller. 2. If the frequency of a wave decreases, the wavelength becomes larger. 3. The velocity does not change if the frequency changes, and the velocity also doesn't change if the wavelength changes. The velocity is fixed.
_________ is defined as the ability of a substance to resist flow.
Viscosity
What is the most important control in determining the shape of a volcano?
Viscosity of lava
The magnitude of historical eruptions can be measured by the _____________.
Volcano Explosivity Index
Which of the following is the most common type of volcanic gas?
Water vapor (H2O)
Once tsunami waves wash inland in populated areas, what do they consist of?
Water, sediments, natural debris, and manmade debris (houses, cars, boats, etc).
Partial Melting
When rocks are heated they do not go from solid to liquid all at once. As rocks are heated, some of the minerals in the rock melt and others remain solid. This happens because each mineral has a different melting temperature. This is WHY partial melting occurs in rocks - if rocks were made of just one type of mineral they would melt all at once. Since they are made of different minerals, and since each mineral melts at a different temperature, part of the rock is molten while the rest of it is solid.
Cinder cones (or scoria cones) are composed of __________, whereas shield volcanoes are composed of _________.
basaltic tephra / basaltic lava flows
The gaseous cloud that killed people and livestock at Lake Nyos, Cameroon, was composed of _______.
carbon dioxide (CO2)
The most common cause of tsunamis is _________________.
earthquakes
What types of events cause tsunamis? Choose all that apply.
earthquakes, landslides, volcanic eruptions, meteor impacts
In deep water, tsunamis move at _____________. When they reach shallow water in coastal areas, the tsunami _____________ and ____________ in height.
fast speeds, slows down, increases
The most explosive eruptions are typically associated with magmas that have ________ viscosities and ________ dissolved gas contents.
high/high
The village of Armero, Colombia, was built directly on top of a(n) ____________ deposit that erupted from Nevado del Ruiz in 1845.
lahar
The amount of ground displacement in a earthquake is called the _________ .
offset
The root cause for the 1980 eruption of Mt. St. Helens was ________
subduction
The lava dome that formed after the 1902 eruption of Mt. Pelee, Martinique, was known as _________ because it was so tall.
the Tower of Pelee
Subduction
the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate
The eruption of Thera, Greece, in about 1600 B.C. devastated Minoan settlements in the Mediterranean and may have generated Greek myths about _______________.
the sinking of Atlantis.
Active volcanoes
volcanoes that are either actively erupting right now, or are showing signs of unrest (e.g. earthquakes, uplift, new gas emissions) that indicate future eruptions are likely.