Volcanoes study guide

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 will 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 the FINAL EXAM is highlighted in red. There will also be comprehensive questions on the final.

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 continental 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 tectonics?
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 measured?

Earth Materials: Minerals and Rocks

What is a mineral?
What is the basic structural unit of silicate minerals?
Name the six 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 basaltic 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.

Terrestrial Volcanism

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 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?
What is the difference between a block and a bomb?
How is the dispersal of air-fall pyroclastic material controlled by the wind?
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?

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 magma affect the way in which it erupts?
What are the characteristics of a Hawaiian eruption? Of a Strombolian eruption? Of a Vulcanian 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 and the Historical Record

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?

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: epicenter, hypocenter, focus, fault plane, rupture surface, hanging 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 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 seismograph?
Why are amplification and filtering necessary in a seismograph system?
Where and why would a strong motion seismograph be used?
What are the Z, N, and E components in a basic seismograph system?
What are some different types of seismogram (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 geology affect the intensity of an earthquake?
What is the name of the most commonly used scale used to characterize earthquake magnitude, 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?
How does total energy release relate to magnitude?
What is 'seismicity'?
What is a Gutenberg-Richter plot? What is the typical relationship between earthquake magnitude 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?

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 thickness of the oceanic lithosphere 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 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) associated 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 subduction 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 (Chris Newhall talk)

What were the first signs of 'unrest' at St. Helens in 1980?
What triggered the major eruption of St. Helens?
What type of volcanic products did the 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 has been happening at Mt. St. Helens since late 2004?

Eruptions of the 1980s

Which eruption in the 1980s injected a large amount of SO₂ into the stratosphere?
Which eruption in the 1980s nearly caused air disasters due to jumbo jets flying into the ash plume from the eruption?
Which eruption in the 1980s produced lahars which killed some 22,000 people?

Mt. Pinatubo Eruption

Where is Mt. Pinatubo?
When was the large eruption of 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 Pinatubo eruption produce?
How large was the Pinatubo eruption?
What was the aftermath of the eruption?
Was there any long-term (years) effect on global climate from the 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?
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 earthquakes?
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 subducted 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?
What are some important characteristics of major subduction zone earthquakes: 1700 Washington-Oregon; 1755 Lisbon, Portugal; 1964 Anchorage, Alaska; 1976 Tangshan, China; 1985 Mexico City; 1995 Kobe, Japan, 2004 Sumatra, 2005 Pakistan.

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 (such as the Big Bend of the San Andreas fault) in transform faults?
How has the San Andreas transform evolved over the last few tens of millions of years?

The San Andreas Fault System

What is the difference between the terms "San Andreas Fault System" and "San Andreas Fault"?
Name some other faults that are part of this plate boundary.
From Simon Winchester's talk, know the significant points about the 1906 quake and the response to it.
Know the details of the other major California earthquakes listed in the notes.
Was the Loma Prieta earthquake forecast/predicted? If so, how?
Be familiar with some of the more important facts about the Loma Prieta earthquake: Location, size, nature and magnitude of fault slip, surface rupture, damage and its relationship to local geology, etc.
What lessons can be learned from this earthquake? How does it figure into planning for an even larger earthquake in this region?

Hotspot Volcanic Activity

What is the relationship of hotspots 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 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?

Kilauea Eruption

When did the continuing Kilauea eruption start? How many episodes have there been in the eruption so far? How has the eruption varied over time?
What is "vog"? What has been the effect of vog in this eruption?
What is the cause of earthquakes on the Big Island of Hawaii?
What is the significance of the slump and avalanche deposits on the sea-floor around the Big Island?

Continental Hotspots and Rifts

About how long has the Yellowstone hotspot 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 an eruption at Yellowstone?
What is the compositional range of the lavas erupted in association with continental hotspots and rifting, and what are the sources of the lava?
Where is the location of a region of active continental rifting and incipient continental break-up?
Why did Pangaea break-up?

Intraplate Earthquakes

The largest historic earthquakes in the contiguous US 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 is the difference between the felt area for earthquakes of the same magnitude in the central US and in California? Why?
Why are there intraplate earthquakes?

Oklahoma Earthquakes

About how many recorded earthquakes per year in Oklahoma? About how many felt earthquakes per year in Oklahoma?
The largest historic Oklahoma earthquake occurred where and when? What intensity and magnitude?
Are earthquakes distributed uniformly across Oklahoma? If not, in what areas are earthquakes concentrated?
The only fault scarp east of the Rocky Mountains is where?
When and about how big was the earthquake that formed this fault scarp?

Natural Disasters

What is the trend of human population on Earth and what implications does this have for natural disasters?
Since 1950, what has been the trend in the economic impact of natural disasters?
Since 1900, how significant (fatalities and damage) have earthquake and eruption disasters been in the US 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?
Since 1900, what is the magnitude of the largest earthquakes that have occurred? What is the size (VEI) of the largest eruptions that have occurred?
How are natural hazards and exposure to those hazards used to determine the risk associated with natural phenomena?
In the US, how do the odds of dying in an earthquake compare to those of dying in an auto accident? In a plane crash? In a tornado?
What are the insurance implications of major natural disasters, and what is Catastrophe Bond?

Volcano Monitoring and Eruption Prediction and Mitigation

What is the difference between "forecast" and "prediction"?
How is volcanic risk assessed? How well monitored are "very high" and "high" risk volcanoes in the US?
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 does monitoring of Mauna Loa volcano say about how close the volcano is to its next eruption?
A volcanic eruption that is an example of an unsuccessful prediction. Of a successful prediction.
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 Prediction and Mitigation

Why is earthquake prediction a desirable goal?
What distinguishes science from pseudoscience? On what basis have pseudoscience-based predictions of earthquakes been made, and with what results/consequences? Science-based predictions?
The only official earthquake "prediction" in the US was issued for where? What happened?
What are the main physical precursors that can be used to predict earthquakes?
At the present time, is earthquake forecasting useful? Is earthquake prediction useful?
For what type of construction are buildings most prone to collapse in an earthquake? Least prone to collapse?
What are the main ways in which the effects of earthquakes can be mitigated? What is the cost of mitigation (e.g., building structures to be earthquake resistant; seismic retrofit of buildings and bridges; etc.).
What are seismic risk/hazard maps and how are they used?
What "experiment" originally suggested that earthquakes can be induced? What are the potential problems with inducing earthquakes?

Volcanoes and Climate

What is the main greenhouse gas in the atmosphere? What are its main sources?
What happens to the SO₂ injected into the stratosphere by explosive eruptions?
What is the effect of SO₂ in the stratosphere?
How can we assess the historic and prehistoric effect of volcanic eruptions on climate?
Which eruption may have come close to resulting in the extinction of Homo sapiens?
About 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 countries) 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?