Deck 7: Volcanoes: Hazards and Mitigation

Question 1

If an ash flow approaches you from the opposite side of a large hill,are you likely to be safe?

A) Safe. You are fine being behind a hill; ash flows go down valleys.
B) Safe. The ash flow would stop at the hill or go around the sides of it.
C) Safe. You can duck, and it will go over the top of you.
D) Not safe. If you are close to the volcano, fast-moving ash flows can go over nearby hills.
E) Not safe. Even well away from the volcano, when the ash flow reaches the top of a hill, it picks up speed going down the far side, and that takes it to the top of the next hill, and so on.

Answer 1

D

Question 2

Which of the following is "the largest,highest,and most spectacular volcano in the main line of the High Cascades"?

A) Mount St. Helens
B) Mount Hood
C) Mount Shasta
D) Mount Rainier
E) Mount Mazama

Answer 2

D

Question 3

What are harmonic tremors?

A) a variation of a surge
B) volcanic eruptions
C) a type of lava flow
D) a rare mountain building event
E) a low-frequency rolling ground movement

Answer 3

E

Question 4

Where were the first tiltmeters installed in the 1920s?

A) Mount Vesuvius, Italy
B) Mount St. Helens
C) Yellowstone, Wyoming
D) Kilauea, Hawaii
E) Santorini, Greece

Question 5

A big bulge sometimes slowly grows on the flank of an active Cascades volcano.Why?

A) Thick lava flows pile up around the vent.
B) A huge gas bubble released from the magma inflates it.
C) The magma reacts with snow on the volcano, causing magma inflation.
D) The hot magma melts older ash, causing it to expand.
E) Rising magma is pushing it up.

Question 6

What is the term describing the process of gases coming out of solution,when the pressure drops and magma rises?

A) expire
B) vog
C) lahar
D) exsolve
E) absorption

Question 7

Three Sisters are located just west of which city?

A) Redding, California
B) Portland, Oregon
C) Bend, Oregon
D) Cascade, Oregon
E) Weed, California

Question 8

What is tuff?

A) ash after deposition forms a rock
B) ash hardened from ash flow
C) broken and hardened magma
D) frothy rock light enough to float
E) pillow shaped lava fragments

Question 9

Which of these is NOT a Cascade volcano of western North America?

A) Mount St. Helens
B) Mount Rainier
C) Mount Vesuvius
D) Mount Hood
E) Three Sisters

Question 10

Which volcanoes are thought to have been about the same size prior to major eruptions?

A) Three Sisters
B) Mount Mazama and Mount Shasta
C) Mount Mazama and Mount Lassen
D) Mount Mazama and Mount Hood
E) Mount Shasta and Mount St. Helens

Question 11

Following the May 1980 eruption of Mount St.Helens,Washington,thousands of trees lay on the ground,all parallel to one another.Why?

A) A lateral blast at the beginning of the eruption blew them all down.
B) A big earthquake at the beginning of the eruption shook them down.
C) Huge mudflows racing downslope flattened them.
D) A giant landslide from the volcano toppled them.
E) Thermal winds during the eruption toppled them.

Question 12

According to the text,which of the following is "one of the most hazardous volcanic areas in the world"?

A) Campi Flegrei
B) Mount Vesuvius
C) Mount St. Helens
D) Mount Hood
E) Mount Mazama

Question 13

If an ash flow approaches you from across a kilometer-wide lake,are you likely to be safe or not? Explain why.

A) Safe. Hot ash flows would chill and stop as soon as they hit cold water.
B) Safe. Ash flows move along the ground; they would continue harmlessly underwater.
C) Safe. Hot ash flows would boil the water, and that would stop them.
D) Not safe. A fast-moving ash flow would cause a deadly tsunami wave.
E) Not safe. Ash flows can cross much wider bodies of water.

Question 14

What is the best way to avoid a mudflow?

A) Run away from it as fast as you can.
B) Climb up the valley wall.
C) Crawl up into a ball.
D) Jump over it.
E) Climb a tree.

Question 15

Volcanic mudflows are caused when which of the following combine?

A) rocks and lava
B) water and dirt
C) ash and water
D) ash and lava
E) lava and dirt

Question 16

In contrast to an old ash-flow deposit,an old ash-fall tuff does NOT include which of the following?

A) thin layers
B) layers that become coarser-grained toward the base
C) ash that evenly coats hills and valleys
D) ash that is never welded to black obsidian
E) differences in thickness based on valleys and hills

Question 17

What is a surge?

A) a tremendous earthquake
B) a type of volcano
C) a high speed, violent ash-rich shock wave
D) an underground magma flow
E) a mixture of hot volcanic ash and steam that rushes down the volcano's slope

Question 18

The first tiltmeters were simple levels made with water tubes __________ long.

A) 25 feet
B) 25 yards
C) 5 meters
D) 50 meters
E) 25 meters

Question 19

What evidence is NOT used by scientists to decide whether a stratovolcano may be getting ready to erupt?

A) whether there are changes in the temperatures of volcanoes and erupted steam
B) whether numerous microearthquakes are occurring
C) whether a large bulge is growing on the flank of the volcano
D) whether there is an increase in sulfur oxide gas emissions from the volcano
E) whether red-hot molten magma is visible when looking down the crater

Question 20

What is the smallest amount of volcanic ash on a roof that would commonly cause it to collapse?

A) no amount of ash would cause collapse; it is too light to be a problem
B) more than about 3 cm
C) more than about 20 cm
D) more than 2 meters
E) more than 20 meters

Question 21

What is Wizard Island in Crater Lake?

Question 22

Why is Mount Shasta considered a major hazard as it currently stands?

Question 23

What is paleovolcanology?

Question 24

How can you approximate the travel distance and which hills a pyroclastic flow might cross?

Question 25

What characteristics of an old ash-fall tuff will permit you to distinguish it from an old ash-flow tuff?

Question 26

What two factors,according to the text,encourage people to settle close to active volcanoes?

Question 27

Why,in some cases,are the gases of an eruption more dangerous than lava flows,debris flows,or ash flows?

Question 28

Harmonic tremors recorded on seismographs near volcanoes are generally interpreted as __________.

Question 29

What signs suggest that a volcano may be getting ready to erupt?

Question 30

Describe the process that created Crater Lake and how this differs from what geologists originally thought occurred.What evidence supports this conclusion?

Question 31

What evidence do scientists use to decide whether a volcano may be getting ready to erupt?

Question 32

Why would a volcanic eruption at Mount Vesuvius pose a huge hazard?

Question 33

Why is paleovolcanology important in predicting future volcanic eruptions?

Question 34

You work at an international airport in the Aleutian Islands of Alaska.Your airport has just canceled all flights for the next 3 days and shut down all flight operations.Explain to angry customers why their flights have been canceled.

Question 35

What are some strategies used to mitigate damage from volcanoes?