QUIZ #6
Core Geology 3.32
1. The Hawaiian Islands are composed of what type of volcanoes?
A) shield
B) stratovolcanoes
C) cinder cones
D) flood basalts
E) none of the above
2. The degree to which a substance resists flow is known as _______.
A) magma
B) composition
C) tephra
D) fumaroles
E) viscosity
3. The igneous rock in the figure below has what type of texture?
A)
B)
C)
D)
E)
glassy
aphanitic
phaneritic
porphyritic
none of the above
4. A _______ is a mixture of molten and solid rock.
A) tephra
B) pyroclastic flow
C) fractional melt
D) debris flow
E) complete melt
5. The figure below is an igneous rock with what type of texture?
A)
B)
C)
D)
E)
glassy
aphanitic
phaneritic
porphyritic
none of the above
6. The figure below has what type of texture?
A)
B)
C)
D)
E)
glassy
aphanitic
phaneritic
porphyritic
none of the above
7. Which of the following terms best describes the lava in the figure below?
A)
B)
C)
D)
E)
low viscosity
high viscosity
crystallized
fractionated
none of the above
8. The smallest type of tephra is known as _______.
A) lapili
B) volcanic ash
C) agglomerates
D) pyroclasts
E) calderas
9. Fine grained igneous rocks have a _______ texture.
A) aphanitic
B) phaneritic
C) porpyritic
D) glassy
E) vesicular
True/False
10. The presence of higher amounts of water usually results in the lower of the melting
temperature. TRUE
11. Hawaiian eruptions are extremely violent and produce large pyroclastic flows. FALSE
12. Igneous rocks high in feldspars and silicates are known as felsic rocks. TRUE
13. Vulcanian eruptions are not very explosive and only release ash 5km into the air. FALSE
Fill-In-The-Blank
14. The most violent volcanic eruptions in history are classified as _______ eruptions. Plinian
15. When magma is injected horizontally between layers and solidifies, a _______ forms. Sill
16. Igneous rocks with small crystals undergo _______ cooling. Fast
Short Essay
17. Other than lava flows, please list three hazards associated with volcanoes.
Primary hazard- shaking, explosion;
secondary – mudslides (lahars), tremors, tsunamis, floods; climate change – increase of acid
rains.
18. Contrast the igneous rock textures associated with those rocks formed internally and
externally.
Cooling rate determines the crystal size. If the cooling rate is slow – rock has bigger crystal size,
faster – rock has smaller grains size. We can classify igneous rocks into 2 types – volcanic
(same as extrusive) which has small grains or crystal size and plutonic (same as intrusive) which
has bigger grains or crystals. Igneous rocks textures - phaneritic (visible grains), porphyritic
(mixture of small crystals in a ground mass), and alphanitic (fine grained texture).
19. How does the presence of water affect the melting temperature of a rock?
More water in the rock – less temperature we need to melt it, it’s easier to melt the rock.
20. Discuss the difference between a sill and a dike.
A dike is an intrusive body of magma that intrudes vertically and a sill is an intrusive body of
magma that intrudes horizontally.
21. What is the correlation between volcanoes and plate boundaries?
Volcanic activity occurs along plate boundaries. The great majority of the world's active
volcanoes are located along plate boundaries. Volcanoes are generally found in convergent type
of boundaries (subduction zones). This generates a lot of geologic activities such as earthquakes,
mountain buildings, and volcanoes formation. Water released from the subducting plate lowers
the melting temperature of the overlying mantle wedge and creates magma. Usually this magma
is more viscous because it contains high amount of silica. This magma often does not reach the
surface and cools at depth. When it does reach the surface, a volcano is formed.