Name________________________________________________________
ISNS 4359 EARTHQUAKES AND VOLCANOES Spring 2005 TEST2 (100 points) Select the best alternative(s) by
filling in the blank or circling the T or F for true or false.
T F 1. Basalt magma at 1200C has a lower viscosity (that is, more ‘fluid-like’) than rhyolite magma at 800 C.
T F 2. The 1783 Laki (Iceland) and 1991 Pinatubo (Philippines) eruptions caused global temperatures to drop ~0.5 C for a year.
T F 3. Stratovolcanoes commonly occur in volcanic arcs associated with subduction zones.
T F 4. Strombolian eruptions have been observed to inject ash as high as 10 to >30 km into the atmosphere (the stratosphere).
T F 5. Most deaths resulting from the 1883 eruption of Krakatau, Indonesia were caused by tsunami.
T F 6. Yellowstone & the Hawaiian islands are examples of volcanic complexes caused by hot spots or mantle plumes.
T F 7. Ash flow tuff caldera-forming eruptions are the largest eruptions on Earth.
T F 8. Mauna Loa, Hawaii is the largest volcano on Earth in terms of volume and height above its base on the seafloor.
T F 9. Eruptions of hot spot shield volcanoes such as Mauna Loa generally produce carbonatite lavas.
T F 10. Plinian eruptions were named after the eruption of Mt. Pelee in the Lesser Antilles.
T F 11. Volcanoes can be either deep depressions or tall mountain-like positive features on the Earth’s surface landscape.
T F 12. Magmas formed at seafloor spreading centers (divergent plate boundaries) are mainly rhyolite in composition.
T F 13. When magma nears the surface from below, gases come out of solution and help cause explosive volcanic eruptions.
T F 14. Most magma formed in the Earth’s upper mantle is generated by decreasing the pressure of hot (T>1200C),
solid rock, peridotite, in a process called ‘decompression melting.’
T F 15. The most dangerous volcanoes tend to be in the same general plate tectonic settings as the largest earthquakes in
the world (subduction zones).
16. Oldoinyo Legai volcano in Tanzania on the East African Rift is unique on Earth for its lavas composed of
___________________________which hold the record for being the lowest________________________of all lavas.
17. What type volcano has steep (>20-30) slopes and is composed of interbedded lava flows and pyroclastic deposits?
___________________________
18. What is the source of expanding gases, explaining the main difference between phreatic and magmatic explosions?
Phreatic:_________________________________ Magmatic: ______________________________________
19. What is the main mechanism involved with development of a caldera?
________________________________________________________________________________________
20. The 1902 eruption of Mt.____________________resulted in ~29,000 deaths due to pyroclastic flows (nuée ardente).
_____21. Most magma on Earth is formed within (A) continent-continent collision zones, (B) subduction zones,
(C) mid-ocean ridge spreading centers, (D) continental rifts, or E) hotspots/mantle plumes.
_____22. What type of rock results from the partial melting of mantle peridotite and is the most abundant volcanic rock on Earth?
(A). pumice
(B). rhyolite
(C).
basalt
(D). andesite
(E). dacite
_____23. Solid Mantle Rock (peridotite) may partially melt by: (A) decreasing its pressure, (B) decreasing its temperature
(C) decreasing its water content, (D) all of these, (E) only B and C, (F) none of these are correct.
_____24. Some of Earth’s most beautiful mountains are what type of volcano, including Mount Fuji (Japan),
Mt. Kilimanjaro (Tanzania), Mt. Shasta (CA), and Mt. Rainier (WA)?
(A) Calderas, (B) Cinder cones, (C) Shield volcanoes, (D) Stratovolcanoes, or (E) Flood Basalt Fields
_____25. Basaltic lava commonly has a smooth, ropey surface texture called:
(A) aa, (B) baba, (C) caca, (D) pahoehoe, (E) None of these are correct.
_____26. If basaltic lava reaches the sea or a lake, it cools rapidly into: (A) bed lava, (B) sheet lava, (C) blanket lava,
(D) pillow lava, or (E) sofa lava.
_____27. Which of these Cascade chain volcanoes has been the most active over the past 4000 years?
(A) Mt. Shasta, (B) Mt. Baker, (C) Mt. Rainier, (D) Mt. Lassen, (E) Mt. St. Helens, or (F) Mt. Juan de Fuca
_____28. Active volcanoes of the Cascade chain in Washington state, Oregon, & N CA result from: (A) heat generated by
friction along the San Andreas Fault, (B) subduction of the Juan de Fuca plate beneath the North American plate, (C)
subduction of the Pacific plate beneath the North American plate, (D) seafloor spreading along the Juan de Fuca ridge, (E)
the Hawaiian mantle plume, or (F) none of these.
_____29. The eruption of Mt. Pinatubo (Philippines) in 1991 endangered people, animals, and property mainly because of:
(A) massive lava flows, (B) lahars and pyroclastic flows, (C) acid rain, (D) famine, or (E) poisonous gases
____30. VEI (Volcanic Explosivity Index) is exponentially related to the volume of erupted material (or its mass) and
ranges from: (A) 1 to 10, (B) 2 to 9, (C) 0 to 100, (D) 0 to 8, or (E) I to XII.
_____31. Pyroclastic deposits are classified on the basis of transport process into three types. Which one does not belong on
the list? (A) pyroclastic surge, (B) pyroclastic flow, (C) pyroclastic fall, or (D) pyroclastic lava.
____32. Which magmatic eruption style is the least explosive, and observed in eruptions with the lowest VEI?
(A) Hawaiian, (B) Vulcanian, (C) Plinian, or (D) Strombolian.
____33. Which magmatic eruption style is the most explosive, and observed in eruptions with the highest VEI?
(A) Hawaiian, (B) Vulcanian, (C) Plinian, or (D) Strombolian.
____34. Which one of the five following caldera types generally forms the smallest depressions?
(A) Debris-avalanche, (B) Stratovolcano collapse, (C) volcanic field, (D) basaltic shield, or (E) Ash-flow tuff.
_____35. The 1991 eruption of Mt. Unzen (Japan) occurred in what plate tectonic environment? (A) hotspot/mantle plume,
(B) subduction zone, (C) continental rift, (D), continent-continent collision zone or E) mid-ocean ridge spreading center.
_____&____36. The 1783 eruption of Laki (Iceland) occurred in what two plate tectonic environments? (A) continental rift,
(B) subduction zone, (C) hotspot/mantle plume, (D), continent-continent collision zone or E) mid-ocean ridge spreading center
_____37. The 1883 eruption of Krakatau (Indonesia) occurred in what plate tectonic environment? (A) continental rift, (B)
subduction zone, (C) hotspot/mantle plume, (D), continent-continent collision zone or E) mid-ocean ridge spreading center
38. What is a lahar?___________________________________________________________________________________
39. What happens when lava erupts beneath a glacier?________________________________________
____________________________________________________________________________________________________
40. Describe what occurs in Black Smoker Vents and where they are found:______________________________________
__________________________________________________________________________________________________________________
41. Give 2 examples of the works of literature or paintings that owe their origin to major eruptions of the 19 th century (list
the volcano, date and title of each).________________________________________________________________________
_______________________________________________________________________
_____42. Which of the following has the highest silica (SiO2) contents? (A). rhyolite (B). dacite (C) andesite (D).. basalt
_____43. Which of the following has the lowest silica (SiO2) contents? (A). rhyolite (B). dacite (C) andesite (D).. basalt
_____44. What type of magma generally possesses the highest viscosity (least fluid-like) at its typical eruption temperature?
(A). andesite, (B). rhyolite, (C). basalt, (D). dacite, (E) carbonatite
T F 45..The 1883 eruption of Krakatau, Indonesia was caused by the rifting between the Eurasian & Indo-Australian Plates.
T F 46. The 1980 eruption of Mt. St. Helens resulted from a <2 km depth M5 earthquake that triggered a debris avalanche.
T F 47. Calderas are smaller diameter depressions than craters located at the summits of stratovolcanoes.
T F 48. The eruption of Vesuvius in 79 CE is thought to have been the source of Plato’s legendary Island of Atlantis.
T F 49. The 1815 eruption of Tambora, Indonesia was volumetrically the largest eruption of the last two centuries.
T F 50. Many thousands of pyroclastic flows were observed at Kilauea in Hawaii from 1991-1993.
Extra Credit (max 5 pts): In what country would you expect a major stratovolcano eruption (the size of Pinatubo 1991) to occur in the next 100
years? Describe the plate tectonic setting of this country.