Question 1

Viscosity is the measure of a fluid's resistance to a flow. Which of the following factors affect the viscosity of magmas? A) temperature and SiO₂ content B) density and temperature C) elevation and density D) density and water content E) water and SiO₂ content

Accepted Answer

The temperature and SiO2 content are the two main factors that affect the viscosity of magmas. As temperature decreases and SiO2 content increases, the viscosity of the magma increases. This is because the SiO2 molecules link together, forming long chains that impede the flow of the magma.

Question 2

Which of the following tectonic settings is the most likely to generate an explosive volcanic eruption?&#10;A) subduction zone&#10;B) mid-ocean ridge&#10;C) oceanic hot-spot&#10;D) rift valley&#10;E) fold mountain belt

Accepted Answer

Subduction zones occur when an oceanic plate is forced beneath a continental plate, creating a destabilizing environment that can lead to explosive volcanic eruptions. The subducting plate melts and rises through the overlying plate, forming a magma chamber beneath the surface. As the pressure builds, explosive eruptions can occur, often with little warning. Mid-ocean ridges and oceanic hot-spots tend to produce more gentle, effusive eruptions, while rift valleys and fold mountain belts are not typically associated with volcanic activity.

Question 3

What best describes a pyroclastic flow?&#10;A) dry avalanche of hot material&#10;B) lava flow that has caught on fire&#10;C) hot mudflow&#10;D) dense ash fall&#10;E) volcanic tsunami that makes landfall

Accepted Answer

A pyroclastic flow is a dense, fast-moving avalanche of hot ash, rocks, and gas that flows down the slopes of a volcano during an explosive eruption. It is often likened to a hot, dry avalanche in its destructive power.

Question 4

Volcanic tsunamis can form around volcanic islands during large explosive events or massive landslides.

Accepted Answer

Volcanic tsunamis, also known as "mega-tsunamis," can form around volcanic islands during large explosive events or massive landslides. The energy of the explosion or landslide can displace massive amounts of water, creating a tsunami that can travel great distances and cause significant damage. Examples of volcanic tsunamis include the 1883 eruption of Krakatoa and the 1958 landslide of Lituya Bay in Alaska.

Question 5

Volcanic ash forms when rock particles and lava droplets are ejected skyward.

Accepted Answer

Volcanic ash is composed of rock particles and lava droplets that are ejected into the atmosphere during a volcanic eruption. These small particles can travel long distances and have the potential to cause harm to humans and the environment.

Question 6

What best describes the relatively small volcanoes that form when fragments of erupted lava cool and accumulate around a vent?&#10;A) cinder cone&#10;B) shield volcano&#10;C) composite cone&#10;D) lava dome&#10;E) fissure dome

Accepted Answer

Cinder cones are small volcanoes that form when fragments of erupted lava cool and accumulate around a vent.

Question 7

There are two basic types of volcanoes, shield and composite cone. Which of the following best describes composite cone volcanoes?&#10;A) relatively small, erupt andesitic magma, and are highly explosive&#10;B) relatively small, erupt basaltic magma, and are highly explosive&#10;C) relatively large, erupt andesitic magma, and are non-explosive&#10;D) relatively large, erupt basaltic magma, and are highly explosive&#10;E) relatively large, erupt basaltic magma, and are non-explosive

Accepted Answer

Composite cone volcanoes, also known as stratovolcanoes, are relatively large, erupt andesitic magma, and are known for their highly explosive eruptions. This description matches option A, except for the size aspect which is incorrectly stated as "relatively small" in the option, but correctly aligns with the explosive nature and magma type of composite cone volcanoes. However, given the options, A is the closest match due to the emphasis on andesitic magma and explosiveness, which are key characteristics of composite cone volcanoes. The correct description should note that they are relatively large, not small.

Question 8

Which of the following hazards is LEAST likely to be associated with explosive volcanic eruptions?&#10;A) lava flows&#10;B) pyroclastic flows&#10;C) tsunamis&#10;D) ash fall&#10;E) mudflows

Accepted Answer

Lava flows are more characteristic of effusive volcanic eruptions rather than explosive ones. Explosive eruptions are more likely to produce pyroclastic flows, ash fall, and mudflows, and can sometimes trigger tsunamis through the displacement of water by volcanic material.

Question 9

Attempts at predicting volcanic eruptions have largely been unsuccessful.

Accepted Answer

While predicting the exact timing and size of volcanic eruptions remains challenging, significant advancements in monitoring techniques, such as seismic activity, gas emissions, and ground deformation, have improved the ability to forecast volcanic activity and issue warnings, leading to successful evacuations and risk mitigation in many cases.

Question 10

Which of the following is NOT a tool that scientists use to predict volcanic eruptions?&#10;A) deep drilling and magma sampling&#10;B) volcanic gas sampling&#10;C) monitoring topographic changes&#10;D) seismic monitoring&#10;E) monitoring geophysical and groundwater changes

Accepted Answer

Deep drilling and magma sampling are tools that scientists use to understand the characteristics of magma and the volcano's internal structure, but they do not directly help in predicting volcanic eruptions.

Question 11

The nature of volcanic eruptions is closely related to plate tectonics and magma type. Which of the following best describes basaltic magma? A) relatively SiO₂ poor and hot B) relatively SiO₂ poor and cool C) relatively SiO₂ rich and hot D) relatively SiO₂ rich and cool

Accepted Answer

The answer of The nature of volcanic eruptions is closely...

Question 12

Which of the following factors determine whether a volcanic eruption will be explosive or non-explosive?&#10;A) magma viscosity and gas content&#10;B) depth of magma and elevation&#10;C) magma viscosity and elevation&#10;D) depth of magma and rock fractures&#10;E) gas content and rock fractures

Accepted Answer

The answer of Which of the following factors determine whether...

Question 13

Water vapor is often the most abundant dissolved gas within magma. What best describes the source of water in gas-rich magmas?&#10;A) water-rich sediment in subduction zones&#10;B) seepage of seawater into oceanic crustal rocks&#10;C) heavy rainfall in tropical areas&#10;D) shallow groundwater circulating through continental crustal rocks&#10;E) all of the answers listed here

Accepted Answer

The answer of Water vapor is often the most abundant...

Question 14

Which of the following is NOT a common a problem associated with volcanic ash-fall?&#10;A) forest fires&#10;B) destruction of crops&#10;C) building collapse&#10;D) disruption of air travel&#10;E) filling of stream channels

Accepted Answer

The answer of Which of the following is NOT a...

Question 15

Which of the following volcanoes in the U.S. is most notably for having a history of massive mudflows, which today threatens large numbers of people?&#10;A) Mt. Rainier, Washington&#10;B) Mt. St. Helens, Washington&#10;C) Mt. Shasta, California&#10;D) Mt. Spur, Alaska&#10;E) Mauna Loa, Hawaii

Accepted Answer

The answer of Which of the following volcanoes in the...

Question 16

Which of the following is an example of a hot-spot, or intraplate volcano?&#10;A) Hawaiian Islands&#10;B) Mt. St. Helens&#10;C) the Ring of Fire&#10;D) Mt. Fuji&#10;E) Mt. Rainier

Accepted Answer

The answer of Which of the following is an example...

Question 17

Which of the following would most likely result in a lava flow that is hazardous to humans?&#10;A) low viscosity basaltic magma&#10;B) high viscosity rhyolitic magma&#10;C) high viscosity andesitic magma&#10;D) low viscosity andesitic magma&#10;E) high viscosity basaltic magma

Accepted Answer

The answer of Which of the following would most likely...

Question 18

Which of the following terms is used to describe a large circular depression that forms after an eruption when a magma chamber becomes empty and collapses in on itself?&#10;A) caldera&#10;B) crater&#10;C) lava pit&#10;D) tuff-cone&#10;E) sinkhole

Accepted Answer

The answer of Which of the following terms is used...

Question 19

What best explains why volcanic mudflows are so dangerous to humans?&#10;A) they move down stream valleys where people tend to live&#10;B) the high temperature of the mud&#10;C) they trigger other types of landslides&#10;D) all of the answers listed here&#10;E) they are more fluid and move more rapidly than a normal flood

Accepted Answer

The answer of What best explains why volcanic mudflows are...

Question 20

Which of the following best explains why some volcanoes erupt so violently?&#10;A) rapid decompression of dissolved gases&#10;B) rapid temperature drop as magma reaches the surface environment&#10;C) cooling effect of seawater beneath island arc volcanoes&#10;D) combustion as nitrogen gas compounds react with atmospheric oxygen&#10;E) all of the answers listed here

Accepted Answer

The answer of Which of the following best explains why...

Deck 6: Volcanoes and Related Hazards