Volcanoes and Earthquakes - Geology 1003

Study Guide for Exams

The exams will mostly comprise multiple choice and true/false answer questions. The following questions indicate the sorts of topics which likely will be covered in the exams. If you can answer these questions, coping with the multiple choice questions on the exams should be no problem! However, I do reserve the right to ask questions about additional material from the web pages for the course.

The material to be tested in each exam is indicated.

Exam 1

Units and the Scientific Method

Be familiar with metric units, particularly those for length and density.
Be familiar with the scientific method, particularly the distinction between hypothesis and theory, and how both are developed.

Continental Drift

Who was the 'father' of continental drift? About when did he live?
List and explain the main lines of evidence he presented for continental drift (pre-1950s).
What was the name of the supercontinent, existing 200 million years ago, comprised of all the present-day continents?
What mechanisms were proposed for driving continental drift? Were they generally accepted?
What counter-arguments were suggested to refute continental drift?
What argument(s) did earthquake seismologists like Sir Harold Jeffreys use against contin-ental drift?

Plate Tectonics

How did paleomagnetism support continental drift?
How does the direction of the Earth's magnetic field vary with latitude?
How did paleomagnetism support sea-floor spreading?
How does the age of the sea-floor vary with distance from the Mid-Atlantic Ridge?
How are Silly Putty and glaciers like the Earth's asthenosphere?
As a unifying theory, plate tectonics is analogous to what theory in the life sciences?
Besides volcanoes and earthquakes, what else is at least partially explained by plate tect-onics?
The distribution of what clearly reveals the plate boundaries?
How many plates comprise the surface of the Earth? What are their names?
What are the three different types of plate boundary?
Why can't continents be subducted?
What is a hotspot?
What are the typical rates of motion of the plates? How are the rates of plate motion meas-ured?

Earth Materials: Minerals and Rocks

What is a mineral? A rock?
What is the basic structural unit of silicate minerals?
Name the five important silicate minerals that comprise igneous rocks.
What are the three different types of rock called? What are their origins?
How are igneous rocks classified?
What are the differences between basalt and gabbro? The similarities?
How would a coarse-grained igneous rock have formed? A fine-grained igneous rock?

The Mineral and Rock Composition of the Earth

Where does basalt magma originate from?
What is the rock that makes up the mantle?
What is the overall chemical composition of the oceanic crust? Of the continental crust?
Define what is meant by crust, mantle, lithosphere, and asthenosphere.

Volcanoes and Eruptions

The Properties of Magma

What determines the viscosity of magma? Why are viscosity and gas content important in determining the eruptive style of a volcano?
What important role do magma chambers play in controlling the composition of the magma erupted from volcanoes?

Volcanic Products

What are the most common chemical components in volcanic gas?
What is the difference between a pahoehoe and an aa lava flow? Can a single lava flow be of both of these types? If so, why?
What is a lava dome?
How are pyroclastic rocks formed?
What is the classification of air-fall pyroclastic material?
How is the dispersal of air-fall pyroclastic material controlled by the wind?
What is the difference between a block and a bomb?
What is a pyroclastic flow? How can a pyroclastic be generated?
What is a phreatic eruption? What is a phreatomagmatic eruption?
What is a lahar? How can a lahar be generated?
What is a tsunami? How can tsunami be generated?
What are the hazards associated with the various volcanic products?

Exam 2

Volcanoes and Eruptions continued

Volcano Types

What are the characteristics of a shield volcano? Of a stratovolcano? Of a scoria cone?
What is a caldera and how does it form?

Eruption Styles

How does the chemical composition of a magma affect the way in which it erupts?
What are the characteristics of a Hawaiian eruption? Of a Strombolian eruption? Of a Vulcan-ian eruption? Of a Plinian eruption? Of a Peleean eruption?

Characterizing Volcanoes

What is the average duration for volcanic eruptions? What are the extremes (shortest running eruptions, longest running eruption)?
How is a volcano defined as being active, dormant, or extinct?
What is the repose time of a volcano?
Approximately how many active volcanoes are there worldwide? Approximately how many volcanoes erupt in any one year? Approximately how many volcanoes are erupting at any one time?
Has there been a real change in the number of erupting volcanoes during the last few hundred years?

Eruption Size

What is the criterion for assigning a size to a volcanic eruption on the Volcanic Explosivity Index (VEI)?
What are the similarities and differences between the VEI scale and the Richter magnitude scale for earthquakes?
Which are more common, low VEI eruptions or high VEI eruptions?
What is the relationship between VEI and repose time for volcanoes?
What potential climate effect can large VEI eruptions have?
What is the mass magnitude of an eruption and how does the mass magnitude scale differ (advantages; disadvantages) from the VEI scale? What is the largest mass magnitude eruption known?
Which type of volcanic product is most fatal to humans? Least fatal? Why?

Earthquakes

Types of Earthquake

What is an earthquake?
What are the four types of earthquake?
What are examples of each type?

Faults

What is a fault?
In describing faults, what is: epicentre, hypocentre, focus, fault plane, rupture surface, hang-ing wall, foot wall, fault trace?
What are the three main types of faults? Be able to identify them from sketches or photos, including left-lateral vs. right-lateral strike-slip.
What kinds of stresses are responsible for each fault type?
What is the predominant fault type at each of the three types of plate boundary?
How does the strength of rock vary between extension, compression, and shearing? What implications does this have for the maximum size of earthquakes anticipated at the different plate boundaries?

Elastic Rebound and Recurrence

Who observed what and where to arrive at the idea of elastic rebound?
Where does rock behave as an elastic-brittle material? Where does rock behave as an elastic-plastic material?
What is the elastic rebound theory?
How does the elastic rebound theory, taken together with plate tectonics, predict recurring earthquakes at a plate boundary?

Earthquake Waves

What are body and surface waves? What are the types of body and surface waves?
How do P- and S-waves behave when they encounter a boundary between two layers with different chemical and/or physical properties?
What are the relative velocities, particle motions, and symbols for P, S, Love, and Rayleigh waves?
Which type of wave can be used to estimate the direction to an earthquake?
Which correspond to P and which to S waves: compressional/shear; slower/faster; can/cannot travel through fluid, particle motion parallel/perpendicular to wave travel.

Recording Earthquakes

On what physical principle does a seismograph work?
What is the earliest know example of a simple seismograph?
What simple mechanical system is a vertical seismograph based on? A horizontal seismo-graph?
Why are amplification and filtering necessary in a seismograph system? What is 'cultural' noise?
Where and why would a strong motion seismograph be used?
What are the E, N, and Z components in a basic seismograph system?
What are some different types of seismograms (the physical record)?
What are the important things to "read" on a seismogram?

Locating Earthquakes

Why do we need specialized techniques for locating earthquakes?
How do we locate earthquakes?
How can we use P and S arrival times to find the distance to and origin time of an earthquake?
How can we use Rayleigh waves to roughly find the azimuth of an earthquake?
What is the near real time procedure used by the NEIC to rapidly locate earthquakes?
How is the focal mechanism for an earthquake derived?
What is the focal mechanism ("beach-ball diagram") for a normal fault? For a reverse fault? For a strike-slip fault?
What is the inherent ambiguity in a focal mechanism and how can it be resolved?

Earthquake Intensity, Magnitude, Frequency

What is the difference between an intensity scale and a magnitude scale?
What is the name of the scale used to characterize earthquake intensity, and what are the significant features of the scale?
How does the local surface geology affect the intensity of an earthquake?
What is the name of the most commonly used scale used to characterize earthquake mag-nitude, and what are the significant features of the scale?
How does the amplitude of ground motion relate to magnitude?
What is the magnitude of the smallest recordable earthquakes? Of earthquakes for them to be 'felt'? Of the largest recorded earthquake?
What is the practical upper limit for earthquake magnitude, if there is one?
What is the currently used magnitude scale that more accurately measures the size of large earthquakes?
For an earthquake to do significant damage, what is the minimum intensity of ground shak-ing?
For an earthquake to do significant damage, what is the minimum magnitude of the quake?
Location, location, location is important in determining the impact of an earthquake. What are examples of the location effects?
How does total seismic energy release relate to earthquake magnitude?
What is 'seismicity'?
What is a Gutenberg-Richter plot? What is the typical relationship between earthquake mag-nitude and number on a Gutenberg-Richter plot?
In the global earthquake energy budget, which magnitude range accounts for most of the energy release?
What is the focal depth range for shallow earthquakes? For intermediate earthquakes? For deep earthquakes?
What are the focal depths observed for mid-ocean ridge earthquakes? For subduction zone Earthquakes? For transform fault earthquakes?

Exam 3

Mid-Ocean Ridge Volcanic Activity

How is the ocean crust sampled?
What is the composition and structure of the oceanic crust?
How does the thickness of the oceanic crust vary with distance away from a mid-ocean ridge spreading centre?
How does the melting point of mantle peridotite vary with pressure?
Why is magma produced under mid-ocean ridge spreading centres?
What is the composition of the lava erupted at mid-ocean ridges?
What are the important consequences of the circulation of seawater through young oceanic crust?

Mid-Ocean Ridge Earthquakes

What is the typical size range, location, focal mechanism (i.e., the overall seismicity) assoc-iated with mid-ocean ridge earthquakes?
What are OBSs and why are they necessary/useful?
Why are MOR earthquakes small and shallow?

Subduction Zone Volcanic Activity

What are the most common and least common magma compositions erupted from oceanic arc volcanoes? From continental arc volcanoes?
At what depth is magma produced in subduction zones? How is magma produced in sub-duction zones?
Why are higher silica magmas volumetrically more significant in continental volcanic arcs than in oceanic volcanic arcs?
What factor(s) cause eruptions from subduction related volcanoes to mostly be violent and explosive?

Classic Eruptions

Which historic eruption gave rise to the legend of Atlantis?
Which historic eruption destroyed the city of Pompeii?
Which historic eruption produced the "year without summer" in Europe and North America in the year following the eruption?
Which historic eruption produced huge tsunami which killed some 36,000 people?
Which historic eruption produced a pyroclastic flow which killed some 30,000 people?

Mt. St. Helens Eruption

What were the first signs of 'unrest' at St. Helens in 1980?
What triggered the major eruption of St. Helens in 1980?
What type of volcanic products did the 1980 St. Helens eruption produce?
How large was the 1980 St. Helens eruption?
How long did eruptive activity continue at St. Helens after the major 1980 eruption? What was this eruptive activity?
What happened at Mt. St. Helens in late 2004?

Mt. Pinatubo Eruption

Where is Mt. Pinatubo?
Approximately how long is the repose time of Pinatubo?
What were the first signs of 'unrest' at Pinatubo in 1991? How was the volcano monitored in the build-up to the eruption?
What type of volcanic products did the 1991 Pinatubo eruption produce?
How large was the 1991 Pinatubo eruption?
What was the aftermath of the 1991 eruption?
Was there any long-term (years) effect on global climate from the 1991 eruption? If so, what was the effect?

Montserrat Eruption

Where is Montserrat?
When did the continuing eruption on Montserrat start?
What type of volcanic products has the eruption produced? What has been the effect of the eruption on the island?
What are the criteria for determining that the eruption has ended? Currently, does the eruption continue or has it ended??
There are some major differences between the Montserrat eruption and the eruptions of Mt. St. Helens and Mt. Pinatubo. What are they?

Subduction Zone Earthquakes

What is the significance of subduction zones in terms of the global energy budget of earth-quakes?
Subduction zone earthquakes occur over what depth range? Why?
How can the location of a subducting plate be "mapped out" in the mantle? Where does sub-ducted plate end up?
What are the various important geological consequences of continental collision, particularly in terms of earthquakes?
Where in a subduction zone do the largest earthquakes occur? Why?
What are the characteristic focal mechanisms for subduction zone earthquakes?

Subduction Zone Earthquake Case Studies

What are the important characteristics and impacts of these subduction zone earthquakes: 1700 Cascadia; 1976 Tangshan, China; 1995 Kobe, Japan; 2004 Sumatra; 2011 Japan; 2017 Mexico.

Transform Fault Earthquakes

In what plate tectonic setting are transform faults most common?
In this setting, what is the difference, if any, between the apparent offset and the actual sense of motion across a transform fault?
What is a fracture zone and what relationship do fracture zones have to transform faults?
What are the typical magnitudes and focal depths of earthquakes associated with oceanic transform faults?
What are the typical magnitudes and focal depths of earthquakes associated with continental transform faults?
What is significant about kinks/bends (e.g., the Big Bend of the San Andreas Fault) in trans-form faults?
How has the San Andreas transform evolved over the last few tens of millions of years?

The San Andreas Fault System

What's the difference between the terms "San Andreas Fault" and "San Andreas Fault System"?
Name some other significant faults that are part of this plate boundary.
Know the details of the major California earthquakes listed in the notes.
Was the 1989 Loma Prieta earthquake anticipated (forecast or predicted)? If so, how?
Be familiar with the more important facts about the 1989 Loma Prieta and 1994 Northridge earthquakes: Location, size, nature and magnitude of fault slip, surface rupture, damage and its relationship to local geology, etc.
What lessons were learned from these earthquakes in the context of planning for an even larger earthquake in this region?

Transform Fault Earthquake Case Studies

What are the important characteristics and impacts of these transform earthquakes: 2010 and 2021 Haiti; 2012 Sumatra; 2019 Ridgecrest.

Final Exam

Hotspot Volcanic Activity

What is the relationship of hotspot volcanism to present-day plate tectonics?
From where within the Earth do mantle plumes originate?
What is the deep mantle source for plumes?
What is the relationship between mantle plumes and flood basalt eruptions?
For at least how long has the Hawaiian hotspot been active?
What is the present direction of motion of the Pacific Plate relative to the Hawaiian hotspot? Has this direction been constant over time? Has the rate of motion been constant over time?
What is the typical composition of the magma erupted from oceanic hotspot volcanoes? Is this volcanism typically passive or explosive? Why?

Hawaii and Kilauea Case Study

For how long did the 1983 Kilauea eruption run? How many episodes were there in the eruption? What were the significant impacts of the eruption?
What, if anything, has happened at Kilauea in 2020 and 2021? What's the current USGS Alert Level for Kilauea?
What is 'vog'? What has been the effect of vog in the 1983 Kilauea eruption?
What is the cause of earthquakes on the Big Island of Hawaii?

Iceland Case Study

What's the plate tectonic setting of Iceland?
What's the source of the lava erupted on Iceland?
What was the significant impact of the 2010 Iceland eruption?
What implications, if any, does the 2020 eruption have for the impact of future eruptions on Iceland?

Continental Hotspots and Rifts

What is the compositional range of the lavas erupted in association with continental hotspots and rifting? What are the sources of the lavas?
About how long has the Yellowstone mantle plume been active under the North American plate and what sort of hotspot track has it produced?
When did the three most recent caldera-forming mega-eruptions occur at Yellowstone and how large (VEI) were they?
It what ways is Yellowstone a "restless" caldera?
How realistic is the docudrama Supervolcano in the portrayal of a present-day very large explosive Yellowstone eruption and its impacts?
Where is the location of a region of active continental rifting and incipient continental break-up?
Why did the supercontinent Pangaea break-up?

Intraplate Earthquakes

The largest historic earthquakes in the midcontinent U.S. occurred where?
When did these earthquakes occur, what was their estimated magnitude, and what were their effects?
What is the recurrence interval for great earthquakes in this region?
What would be the impact now in this region of a recurrence of a large quake?
What is the difference between the felt area for earthquakes of the same magnitude in the midcontinent U.S. and in California? Why?
Why are there intraplate earthquakes?

Oklahoma Earthquakes

The only fault scarp east of the Rocky Mountains is where?
When, and about how big, was the earthquake that formed this fault scarp?
Prior to 2009, were earthquakes distributed uniformly across Oklahoma? If not, in what areas were earthquakes concentrated?
Prior to 2009, about how many felt (M≥3.0) earthquakes per year were there in Oklahoma?
The largest pre-2009 historic Oklahoma earthquake was where and when? Maximum MMI and magnitude?
In 2009 the number of earthquakes in Oklahoma started to escalate; when (year) was the peak number of quakes?
When (year) was it officially (by the Oklahoma Geological Survey and the State) recognised that the escalation in seismicity was induced rather than natural?
The induced earthquakes were being caused by what human activity?
What actions (by the State) were taken to mitigate the induced seismicity?
How effective has that action been?
In 2021, how many M≥3.0 quakes per month occurred in Oklahoma?
How long is it likely to be before there is a return to the natural, background tectonic level of quakes in Oklahoma?

Natural Disasters

Since 1900, how significant (fatalities and damage) have earthquake and eruption disasters been in the U.S. compared to other types of natural disaster?
Since 1900, how do the ten worst global earthquake disasters compare, in terms of fatalities, to the ten worst eruption disasters?
Since 1900, approximately how many lives have been lost and damage caused worldwide as a result of earthquake disasters? As a result of eruption disasters?
Meteorological vs. geological natural disasters since 1980: Which are most deadly? Which are most costly?
Which is the most costly natural disaster ever?
In the U.S., how do the odds of dying in an earthquake compare to those of dying in an auto accident? In a cataclysmic storm? In a volcanic eruption?
Which megacity has the highest natural hazard risk index? Why?
What is a catastrophe bond and why have they become increasingly popular?

Volcano Monitoring and Eruption Prediction and Mitigation

How is volcanic threat assessed? How well monitored are "very high" and "high" risk volcan-oes in the U.S.?
What are the three most useful parameters that are monitored in order to predict the eruption of a volcano?
How is the deformation (inflation and deflation) of a volcano monitored?
What are the significant characteristics of volcano-tectonic earthquakes? Of long-period earthquakes? Of harmonic tremor?
Which are most useful in making a short-term (days or hours) eruption prediction, volcano-tectonic or long-period earthquakes?
In monitoring volcanoes, which is the most useful gas to monitor - H₂O, CO₂, or SO₂?
What's the current USGS Alert Level for Mauna Loa volcano, HI?
An example of an unsuccessful eruption prediction? A successful eruption prediction?
Which volcano presents the ultimate prediction dilemma?
Why are volcanic hazard maps useful in eruption mitigation?
Have lava flows ever been successfully stopped or re-directed by human intervention? If so, where, when, and how?

Earthquake Forecasting, Prediction, and Mitigation

What's the difference between a forecast and a prediction?
Why is earthquake prediction a desirable goal?
What distinguishes science from pseudoscience? On what basis have pseudoscience-based forecasts/predictions of earthquakes been made, and with what results/consequences? Science-based forecasts/predictions?
The only official earthquake "prediction" in the U.S. was issued for where? What happened?
What are the main physical precursors that can potentially be used to predict earthquakes?
At the present time, is long-range earthquake forecasting useful? Is short-range earthquake prediction useful?
Was the 2011 Japan earthquake forecast or predicted?
Which fault in the Bay Area has the highest probability of producing a large earthquake before 2043?
What actions should you take during an earthquake?
What's the worst worse-case scenario for losses (life; economic) in an earthquake?
How does an earthquake early warning (EEW) system work?
What are the important ways in which the effects of earthquakes can be mitigated?
In terms of collapse during an earthquake, what is the most dangerous style of building construction globally? In the U.S.?
In the long-term, what's the most cost-effective for residential earthquake mitigation, earth-quake insurance or seismic retrofit?
What are seismic hazard maps and how are they used?
What "experiment" originally suggested that earthquakes can be induced? What are the pot-ential problems with inducing earthquakes?

Volcanoes and Climate

What is the major greenhouse gas in the atmosphere? What are its main sources?
What happens to volcanic ash and SO₂ injected into the stratosphere?
What is the effect of volcanic ash and SO₂ in the stratosphere?
What was the climate impact of the 1991 Pinatubo eruption? Of the 1883 Krakatau eruption? Of the 1815 Tambora eruption?
How can we assess the climate impact of historic and prehistoric volcanic eruptions?
How globally extensive was the atmospheric impact of the 1257 CE Samalas, 1783 CE Laki, and 1815 CE Tambora eruptions?
Which eruption may have come close to resulting in the extinction of Homo sapiens?
At the present day, what would the global climate impact be from a low latitude Yellowstone-type mega-eruption?
When did the dinosaurs become extinct? Why did they become extinct?
What is the association between volcanic eruptions and mass extinction events in the fossil record?

Benefits of Volcanoes

What are the benefits of volcanoes in terms of building materials and mineral deposits?
Why are volcanic regions good for geothermal energy production? Where (country or count-ries) has geothermal energy been well utilized?
Are volcanic regions poor or good for agriculture? Why?
What role has volcanic activity played in the evolution of Earth's atmosphere?