How Volcanoes Work

Lithograph of 1822 Vesuvius eruption (from V. Day & Sons)


No. of Questions= 10
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1.  Basaltic eruptions can produce teardrop shaped lapilli called ___________.
a) reticulite  
b) Pele's tears  
c) spatter  
d) scoria  
e) bombs  
2.  The basaltic rock below has the lowest density of any rock on earth, with vesicles comprising 98% of the total rock volume.
a) pumice  
b) scoria  
c) spatter  
d) reticulite  
e) spongite  
3.  Which of the following is best described as a fluidized mixture of solid to semi-solid fragments and hot, expanding gases that flows down the flanks of a volcano at hurricane-force speeds.
a) pyroclastic flow  
b) lahar  
c) inflated pahoehoe sheetflow  
d) obsidian flow  
e) pyroclastic arifall  
4.  As a general rule, a pyroclastic flow that forms from the collapse of a lava dome is called a(n)__________, whereas one that forms from the collapse of an eruption column is called a(n) ___________.
a) nuee ardente / lahar  
b) lahar / pumice flow  
c) nuee ardente / pumice flow  
d) pumice flow / nuee ardente  
e) ash flow / block flow  
5.  The following term is used to describe an accumulation of relatively dense pyroclastic material deposited by a nuee ardente.
a) block-and-ash deposit  
b) ignimbrite  
c) lahar  
d) pumice flow  
e) plinian fall deposit  
6.  The following term is used to describe an accumulation of relatively low-density pyroclastic material deposited by a pumice flow.
a) block-and-ash deposit  
b) plinian airfall deposit  
c) ignimbrite  
d) lahar  
e) agglomerate  
7.  Although most lahars are generated by intense rainfall during an eruption, many are generated directly by an eruptive process. Historically, the major eruptive process responsible for lahar generation is:
a) basalt melting of glaciers by lava flows  
b) surficial melting of snow and ice by lava flows  
c) disruption of crater lakes  
d) melting of snow and ice by pyroclastic flows  
e) steam eruptions mixing with tephra  
8.  The ________ lahar erupted from ________ about 5700 years ago.
a) Tacoma / Mt. Rainier  
b) Spirit Lake / Mt. St. Helens  
c) Armero / Nevado del Ruiz  
d) Osceola / Mt. Rainier  
e) Coldwater Ridge / Mt. St. Helens  
9.  Which gas constitutes 70-90% of the gases dissolved in magma.
a) water vapor  
b) CO2  
c) SO2  
d) H2S  
e) H  
10.  Global climate conditions were abnormally cold for years after the __________ eruption.
a) Laki (1783)  
b) Tambora (1815)  
c) Krakatau (1883)  
d) Mt. Pinatubo / Mt. Hudson (1991)  
e) all the above  

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