The Violent Earth Questions
True or False?
Modern geologic knowledge is the product of curious individuals, who 1) questioned our knowledge of scientific fact, 2) investigated natural processes, and 3) honestly reported the facts.
So far we’ve focused on the differences between volcanic calderas and a volcanic craters… which both form at volcano peaks.
True or false?
Calderas and craters are similar because they are both landforms that show a collapse in the land surface above an area of volcanic activity.
What criteria do geologists use to designate a supervolcano?
a. If it has a caldera
b. If it erupts more than a specific volume of material
c. If it is a shield volcano
d. If it formed over a hot spot
What evidence do geologists study to understand the relative magnitude or frequency in time of past volcanic eruptions?
Hint: Please consider the data shown on our geologic map of past lahars around Mt Rainier. 🙂 These mapped lahars enable us to estimate the risk of building in a particular area.
a. The relative extent of volcanic deposits
b. The relative age of volcanic deposits
c. The relative thickness of volcanic deposits
d. All of these
Consider the age of the various Hawaiian Islands given below in millions of years. Remember, the formation of the Hawaiian Islands reflects: 1) the movement of the Pacific plate, and 2) stationary volcanic hotspot activity over time.
Which direction is the Pacific plate currently moving?
Maps are plan or bird’s eye views of the earth’s surface. Here, the top of the figure is north, and the bottom of the figure is south. The left side of the figure is west, and the right side is east.
Prior to 45 million years ago, the Pacific plate was moving in a different direction. Remember, the number on the map above are volcano ages, in millions of years.
Using the same plot, answer this next question.
Prior to 45 million years ago, in which direction was the Pacific plate moving?
Prior to the 2018 eruption, Kilauea volcano was:
Hint: You can learn the answer by viewing the public lecture or searching the internet. Your text gives definitions of the terms below.
a. An extinct volcano
b. A dormant volcano
c. An active volcano
Last year’s eruptions emerged from fissures in the East Rift Zone (ERZ) on the big island of Hawaii. This zone is not located at the peak of Kilauea, but instead, near the base.
Choose the statement that most accurately describes the tectonic setting of the East Rift Zone (ERZ) on the big island of Hawaii.
Hint: To remind yourself the details of the tectonic setting, refer to your Hazard Explorations… Also, it is recommended that you consult a plate tectonic map of the earth (in your text!) to identify the plate tectonic setting at each of the following locations.
The figure of Hawaii below shows the shape of the East Rift Zone, which consists of fissures, and the locations of craters that formed along it.
a. The ERZ is most similar to fissures in the Snake River plain of Idaho, which erupted basaltic lava.
b. The ERZ is most similar to the East African rift zone, where fissures surrounding Mt. Nyiragongo erupt basaltic lava.
c. The ERZ is most similar to mid oceanic rifts on Iceland, which erupt curtains of basaltic lava.
d. The ERZ is most similar to the Mid Atlantic Ridge which erupts basaltic lava from fissures.
e. The ERZ is most similar to fissures along the mid oceanic East Pacific Rise which erupt basaltic lava.
The primary hazards to residents during the 2018 eruption of Kilauea were the following:
Hint: The answer is found by listening to the story in the Kilauea talk! 🙂
a. Pyroclasts and airfall
b. Lava and volcanic gases
c. Volcanic bombs and lapilli
d. East Rift Zone lahars
Kyle shows a diagram in his talk at 11 minutes and 43 seconds.
The diagram is best described as a(n):
a. Oblique view
b. Profile or cross section view
c. Bird’s eye view
d. Map view
What process is the source of thermal heat that emerges as a hotspot?
Hint: This is a review of HE#1 & HE#2 material… Please consider the definition of a hotspot. It is widely believed that hotspots form where the inner core makes contact with the mantle or lowermost asthenosphere.
a. Radiation from the sun
b. Convection in the asthenosphere
c. Conduction in the lithosphere
d. Radioactivity in the core
Geologists rely on new technology more and more. Some new technology allows us to model the earth’s surface, like the model you see in the Google Earth tool, and some describe the area below the earth’s surface!
Which method of investigation allows geophysicists to best “visualize” or model a buried magma chamber beneath a caldera or crater formed on the earth’s surface?
Hint: These methods are discussed in both talks and answer is mentioned in the Kīlauea talk!
b. Seismic tomography
Deformation of the earth’s crust happens above a buried magma chamber.
Volcanos, fissures, craters, and calderas are all types of surface deformation.
As the magma chamber fills up, it expands like a balloon and pushes up on the ground surface. In response, the ground over the magma chamber stretches (again just like the rubber of a balloon!) and develops cracks.
Imagine two people are standing facing one another, and then a wide, broad crack in the earth’s surface grows between them. Imagine that crack is just like the crack shown by Kyle at 15 minutes in the video on Kilauea.
Do the two people on either side of this crack move closer together or further apart?
Hint: draw a picture to help you visualize this situation!
a. Closer together, so the deformation is due to compression of the crust.
b. Further apart, so the deformation is due to extension of the crust.
c. Neither, so the amount of crustal deformation is negligible
In Hazard Exploration #7, we discussed volcano monitoring methods, such as global positioning system (GPS) receivers.
Often geologists use global positioning system (GPS) receivers fixed to earth’s surface to measure deformation. Unlike your smartphone, these particular GPS receivers are literally bolted to the ground.
Because the receiver is fixed to the ground, if one moves—then the ground itself moved! This change could indicate a few things, including tectonic plate motion, landsliding, or the bulging of a magma chamber!
Geologists can also pound 2 stakes into the ground, and then monitor their location during surveys.
It is useful to place 2 stakes or GPS receivers on either side of a volcano or an earthquake fault to monitor any crustal motion that occurs.
Which of the following events resulted in stretching of the crust such that the GPS receivers or markers move further apart?
Hint: draw a sketch for each scenario and listen to Kyle’s story!
a. A quiet period of inactivity for the Mt. Waialeale caldera on the island of Kauai.
b. Emptying and deflation of the magma chamber below Pu’u O’o Crater on the island of Hawaii.
c. Any quiet period of inactivity between 2 earthquakes on the San Andreas fault.
d. Filling and swelling of the magma chamber below Pu’u O’o Crater on the island of Hawaii.
A number of studies indicate periods of deformation on the floor of Yellowstone caldera and outside of the caldera. The total stretching or bulging over the past couple decades amounts to about 70 centimeters of swelling!
What process does this deformation most likely reflect?
Hint: The answer is mentioned in the Yellowstone talk!
a. Magma leaving the chamber buried below the floor of the caldera.
b. Earth tides in northwestern Wyoming
c. Magma filling the chamber buried below the floor of the caldera.
d. Temperature changes due to solar radiation.
What was unique about the 2018 eruption of Kilauea, when compared with the 1924 eruption?
Hint: Many similarities are discussed, and the difference is also highlighted, if you listen to the Kīlauea talk until the ending.
a. The viscosity of the lava
b. The fissure eruption
c. Drop of the lava lake level in the summit crater of Kilauea
d. The phreatic eruption
Collapse of the flank of the big Hawaiian island happened toward the south and dropped the land into the sea! In some ways, this event is similar to the collapse of a large bulge on the side of Mt. St. Helens.
In your homework, we described the chain of events leading to the eruption of Mt. St. Helens. Now we focus on a similar story for Kilauea via Kyle’s talk.
Which of the following events did NOT occur during BOTH the Mt. St. Helens and Kilauea eruptions?
a. A large magnitude earthquake
b. A large landslide-type collapse
c. A lateral volcanic blast
d. Emptying of magma from a buried magma chamber
True or False?
The volcanic gases emitted during the 2018 eruption will have a long term impact on climate.
Hint: The answer is mentioned in the Kīlauea talk! Be sure to watch the question and answer period at the end of the talk, too.
How much carbon dioxide (CO2) does a volcanic eruption of Kilauea typically emit?
Hint: The answer is mentioned in the Yellowstone and Kīlauea talk!
a. 45,000 tons per day (equal to one large coal-fired power plant)
b. 450,000 tons per day (equal to ten large coal-fired power plants)
c. 4,500,000 tons per day (equal to 100 large coal-fired power plants)
d. 45,000,000 tons per day (equal to 1000 large coal-fired power plants)
What new tool did geologists use to estimate the flow rates of lava travelling from Kilauea to the sea over the duration of this eruption?
Hint: The answer is mentioned by Kyle in the Kīlauea talk!
a. GPS receivers on rubber duckies
b. Radio transmitters on rubber duckies
c. Thermal sensors on rubber duckies
d. Models of the landscape from drones
Match the lava viscosity with the type of basaltic rock that it forms.
Watch A’A form here:
Watch Pahoehoe form here:
Watch the thin skin of rock on a lava lake form here:
Hint: This is mentioned by Kyle in the Kilauea talk!
High viscosity —— ______________
Medium Viscosity —— ______________
Low Viscosity —— ______________
True or False?
This 2018 eruption of Kilauea was the first historical caldera collapse ever witnessed by modern cultures.
Hint: the answer is in the Kilauea story told by Kyle.
When calderas like the one at the top of Kilauea collapse, they form cracks like faults around the region.
Here’s a lovely drone video showing some examples:
Kyle Anderson talks about Kilauea caldera sinking or subsidence. He mentioned that the cracks are normal faults inside the caldera. He shows a video of one growing. In this class, we’ve discussed normal faults.
Choose the principle force in effect that causes normal faults:
Hint: this is the same as for tectonic faults!
d. All of these
Kyle shows a histogram that directly correlates earthquakes that happened with deformation at Kilauea.
What did the mid June swarms of earthquakes at Kilauea record specifically?
a. Subsidence of rock over a dropping magma reservoir
b. Periodic inflation of the magma reservoir and related ground tilt
Based on the record of individual earthquakes throughout this eruption, which process is associated with more earthquakes?
Hint: The answer is shown in the Kīlauea talk!
a. Magma inflation or bulging of the caldera surface
b. Caldera collapse or subsidence
How many people died in the 2018 eruption of Kilauea?
Which very young geographic feature will look like Kilauea in the most distant future, a few million years from now?
c. Mauna Loa
e. Mauna Kea
The map view of Idaho and Wyoming below shows the relative ages in millions of years of volcanic centers (including Yellowstone and the older Snake River Plain).
Based on these relative ages, in which direction has the North American tectonic plate been moving over the hotspot during the past 14 million years?
Hint: the top of the map is north, the bottom is south, the left side is west, and the right side is east. The active Yellowstone caldera in Wyoming is labeled the Yellowstone Plateau VF.
Why do researchers of Yellowstone caldera think a super eruption (1000 cubic kilometers or more of material) is very unlikely? (A smaller eruption is still possible and more likely, because the volcano is active!)
Hint: The answer is mentioned in the Yellowstone talk!
a. There is relatively little magma in the chamber (10-15%)
b. Observed earthquakes are relatively small (< M 4.5)
c. Emissions of volcanic gases are relatively low
d. There are little to no steam explosions associated with seismicity
e. All of these