Volcanoes 3

Question 1

name the four main types of volcanoes

Answer 1

• cinder cones (m, ex)
• shield volcanoes (m, non)
• stratovolcanoes (int-f, mixed)
• calderas / super volcanoes (f, ex)

Question 2

True or false: diff types of volcanoes can exist together

Answer 2

true
ex/ small cinder cones on side of large shield volcanoes

Question 3

which type of volcano can cause climate change?

Answer 3

calderas
(super volcanoes)

Question 4

eruption type and trends for cinder cones

Answer 4

• explosive
• erupt for a few years then never again

Question 5

size of cinder cones

Answer 5

height: < 0.5km
width: < 2km

Question 6

cinder cones material, behaviour, slope

Answer 6

• gas rich mafic (basalt)
• fire fountaining creates beds of pyroclastic ejecta
• angle of repose = 30-40˚ (not very steep)

Question 7

eruption type and trends for shield volcanoes

Answer 7

• effusive, not very explosive
• erupts often

Question 8

size of shield volcanoes

Answer 8

height: 4-10km
width: 100km

Question 9

shield volcanoes material, behaviour, slope

Answer 9

• mafic
• lava flows (pahoehoe then a’a)
• gentle slopes

Question 10

eruption type and trends for stratovolcanoes

Answer 10

• explosive
• can erupt many times and stay active for 100k yrs

Question 11

size of stratovolcanoes

Answer 11

height: < 5km
width: 10km

Question 12

stratovolcanoes material, behaviour, slope

Answer 12

• intermediate or felsic
• interbedded lava flows, pyroclastic flows, lahars
• steeper cuz viscous magma

Question 13

example of stratovolcano

Answer 13

mt st helens
mt baker
mt fuji

Question 14

example of shield volcano

Answer 14

Mauna Loa, hawaii

Question 15

example of cinder cones

Answer 15

opal cone, garibaldi park

Question 16

can we get felsic magma from the mantle?

Answer 16

no

Question 17

what causes stratovolcanoes? Where is it most common?

Answer 17

subduction
ring of fire

Question 18

how does plate subduction generate mafic/felsic magma?

Answer 18

plate subduction creates mafic magma
which melts crust to produce felsic magma

Question 19

eruption type and trends for calderas

Answer 19

• explosive
• not often

Question 20

size of calderas

Answer 20

huge!
up to 10’s km across

Question 21

calderas material

Answer 21

felsic pyroclastic

Question 22

how are calderas created

Answer 22

created from large, explosive felsic eruptions
when the roof of magma chamber collapses

Question 23

example of caldera

Answer 23

yellowstone

Question 24

what is a resurgent dome

Answer 24

when eruption causes a collapse (caldera), continued effusive eruption causes resurgent dome (usually in water)

Question 25

which type of volcano is the most explosive and most devastating?

Answer 25

calderas

Question 26

frequency of global eruptions for the four types of volcanoes (cinder cone, shield, strato, caldera)

Answer 26

1. cinder cones -> frequent 2. shield -> frequent/continuous, larger gaps btwn eruptions 3. stratovolcanoes -> frequent but discontinuous (active vs dormant) 4. calderas -> rare

Question 27

effusive eruption style

Answer 27

passive eruption of magma - gas plume + pyroclastic material, pummus deposits 1. laval flows (maf-int) 2. lava domes (fel-int) ex/ mt baker 3. gravitational collapse of flows/domes (block and ash flows)

Question 28

explosive eruption style

Answer 28

gas driven and violent - pyroclastic deposits - acid rain 1. buoyant eruption column of ash 2. pyroclastic airfall 3. pyroclastic flows (column collapse) 4. blocks & bombs (ballistics) proximal to vent

Question 29

volcano with sheets means ___ viscosity

Answer 29

low

Question 30

volcano with domes means ____ viscosity

Answer 30

high

Question 31

pyroclastic falls

Answer 31

1. eruption columns: 10s of kms 2. wide distribution of ash in downwind direction 3. ash blankets topography ex/ pinatubo

Question 32

pyroclastic flows

Answer 32

- gas-pyroclast mixtures - gravity driven, channel in valleys - super hot and fast - velocity 40 to >400km/h - temps 100-600˚C ex/ pinatubo

Question 33

primary volcanic processes

Answer 33

- lava flows, domes, graviational collapse - pyroclastic falls and flows - ballistics

Question 34

secondary processes

Answer 34

- reworking of primary deposits during eruption -> LAHARS

Question 35

what are lahars

Answer 35

volcanic mud flows of water and ash - super erosive and fast