Ch. 5: Volcanoes

Question 1

Magma chamber

Answer 1

body of molten

material that feeds a volcano

Question 2

Flank

Answer 2

part of volcano that slopes
away from vent on top
crack on side

Question 3

Crater

Answer 3

area above vent where lava

has piled up

Question 4

Caldera

Answer 4

large depression formed when
volcano collapses into magma chamber
below it

Question 5

Fissure

Answer 5

flood basalt, plateau basalt, lava curtain
elongated fracture
horizontal crack

Question 6

Factors affecting viscosity:

Composition

Answer 6

silica content: higher silica content, higher viscosity

Question 7

Factors affecting viscosity: Temperature

Answer 7

Temperature: higher T, lower viscosity

Question 8

Factors affecting viscosity: Gas content

Answer 8

Gas content: higher gas content, lower viscosity

Question 9

Effusive

Answer 9

low viscosity, high T, volatile-rich lava flows; usually basaltic, shield volcano, gas escapes easily, lava flows

Question 10

Explosive

Answer 10

pyroclastic; usually andesitic & rhyolitic (int-high viscosity), strato

Question 11

Lava flows

Answer 11

different compositions depend on plate tectonic setting

Question 12

Pyroclastic flows

Answer 12

composed of tephra (ash, cinders, etc.) plus very hot gas

Question 13

Lahars

Answer 13

volcanic mudflows

Question 14

Volcanic gases

Answer 14

CO2, H2O, etc,—evidence in vesicles

Question 15

Mafic low

Answer 15

low SiO2—1200°C—low viscosity— effusive—basalt, shield, runny, high temp, high gas, low si

Question 16

Intermediate

Answer 16

andesite, pyroclastics, strata

Question 17

Felsic/sialic high

Answer 17

high SiO2—800°C—high viscosity—explosive—rhyolite, pyroclastics, cindercone, low t, low gas, high si

Question 18

Shield Volcanoe

Answer 18

broad with gentle slopes; basaltic; Hawaii

Question 19

Pahoehoe (shield)

Answer 19

ropey lava; low viscosity basalt rich in gas

Question 20

Columnar basalt (shield)

Answer 20

forms when lava flows cools & shrinks

Question 21

Pillow basalt (shield)

Answer 21

forms when basalt erupts into water

Question 22

Stratovolcanoes/Composite

Answer 22

steeper slope; andesitic; examples: Fuji, St. Helens, 
Vesuvius; Pliny the Younger’s letter
Eruption of Mt. St. Helens 1980:
earthquake-triggered landslide,
lateral blast, pyroclastic flows,
lahars, ash cloud
Subduction Zone

Question 23

Cinder cones

Answer 23

small conical piles of tephra

Question 24

tephra

Answer 24

blocks, bombs, ash

pyroclastic flow or nuée ardente

Question 25

Yellowstone

Answer 25

supervolcano; caldera; recurrence interval during past 2 million years

Question 26

where do you expect stratovolcanoes to

form?

Answer 26

Subduction zone, convergent plate boundary

Question 27

Active

Answer 27

Erupting, recently erupted or likely to erupt

Question 28

dormant

Answer 28

Hasn’t erupted in hundreds to thousands of years

Question 29

extinct

Answer 29

Not capable of erupting

Question 30

Effect of volcanic eruptions on climate

Answer 30

cooler T, contributed to extinction of dinosaurs, acid rain

Question 31

A’a lava

Answer 31

a’a forms when basalt loses gas, thickens, breaks

Question 32

Mt Pinatous

Answer 32

Philipines 1991
dormant 500 years
plinian eruption: enourmous explosion of volcanic material lots of materials into atmosphere decrease avg global temp

Question 33

Mt St. Helens

Answer 33

1980
convergent boundaries
magma. north flank (crack on side) bulged (stored magma), earthquake, landslide, release of presssure produced explosive lateral pyroclastic (explosive) eruption

Question 34

Krakatou

Answer 34

1883 Indonesia
exploded for several months, caldera, new volcano appears
cool weather
brilliant sunsets (the scream) long twilight due to acid rain

Question 35

Tambure

Answer 35

1815 Indonesia
Largest eruption of last 10,000 years
result is year without a summer
hit new england and europe with snow

Question 36

Vesivous

Answer 36

79 c.e. pompeii

pliny the younger letter