volcanoes

Question 1

how do we study volcanoes?

Answer 1

• study and monitor active systems
• forensic reconstruction

Question 2

magma definition

Answer 2

melted rock in the earth BELOW earth’s surface

Question 3

lava definition

Answer 3

melted rock in the earth ABOVE earth’s surface

Question 4

volcano definition

Answer 4

structure where magma is erupted at earth’s surface
includes erupted products

Question 5

dike

Answer 5

vertical intrusion of magma
formed by magma moving across earth’s crust

Question 6

sill

Answer 6

horizontal intrusion of magma
formed by magma moving across earth’s crust

Question 7

extrusive/volcanic rocks

Answer 7

igneous rocks cooled at the surface
small crystals
fast cooling

Question 8

intrusive/plutonic

Answer 8

igneous rocks cooled below the surface
large crystals
slow cooling

Question 9

felsic rocks

Answer 9

65 - 75% SiO2
light color
high viscosity
granie & rhyolite
high in K, Na, Al

Question 10

mafic rocks

Answer 10

45 - 55% SiO2
dark color
low viscosity
basalt & gabbro
high in Mg & Fe

Question 11

when does crystallization happen?

Answer 11

during cooling, increases the viscosity of the lava

Question 12

where do volcanoes occur?

Answer 12

plate boundaries & hotspots
convergent & divergent boundaries
ring of fire

Question 13

types of volcanoes

Answer 13

1. cinder cones
2. shield volcanoes
3. stratovolcanoes
4. calderas (supervolcanoes)

Question 14

cinder cones

Answer 14

• mafic
• explosive
• 30 - 40 degree angle of repose
• erupt for a few years and then never
  again, frequent eruptions
• beds of pyroclastic ejecta

Question 15

shield volcanoes

Answer 15

• lava erupts from fissure, runs down
  gentle slopes cooling
• erupts often, frequent-continuous
• mafic flows
• non-explosive

Question 16

stratovolcanoes

Answer 16

• lava flows & pyroclastic flows
• intermediate-felsic
• explosive
• frequent, will stay active for thousands
  of years

Question 17

calderas/supervolcanoes

Answer 17

• felsic
• explosive
• created when roof of magma chamber
  collapses
• rarely erupts

Question 18

styles of eruptions

Answer 18

• hawaiian
• strombolian
• vulcanian
• plinean
• phreatomagnetic

Question 19

hawaiian eruption

Answer 19

• low explosivity
• low viscosity
• basaltic magma

Question 20

strombolian eruption

Answer 20

• mildly explosive
• basaltic/andesitic magma
• bombs & lavas

Question 21

vulcanian eruption

Answer 21

• andesitic/rhyolitic magma
• very explosive
• ash explosions

Question 22

plinian eruption

Answer 22

• violently explosive
• large column of ash
• pyroclastic flows

Question 23

phreatomagnetic eruption

Answer 23

• occurs when there is contact between
  magma and water
• water flashes to steam
• violently explosive

Question 24

what determines VEI

Answer 24

1. volume of ash produced
2. height of eruption column
3. duration of eruption
   VEI is logarithmic

Question 25

volcanic hazards

Answer 25

lava flows
fire fountaining
pyroclastic falls & flows
lahars
sector collapses
volcanic gases

Question 26

lava flows

Answer 26

• slow
• not dangerous
• predictable flow path

Question 27

fire fountaining

Answer 27

• only happens with gas rich basaltic
  lava
• small explosive eruptions

Question 28

pyroclastic falls

Answer 28

• hot ash & gas ejected from volcano
  hazards: breathing in ash, collapsed roof, plane’s engines sucking in the ash and stop working

Question 29

pyroclastic flows

Answer 29

• very fast
• very hot
• stays in valley

Question 30

lahars (volcanic mud flows)

Answer 30

• flows of water & loose volcanic debris
• travels far
• can occur without an eruption

Question 31

sector collapse (debris avalanche)

Answer 31

collapse of part of the volcano may
occur, leading to a debris avalanche

Question 32

volcanic gases

Answer 32

highly acidic (ph 1) kills plants and animals
includes H2O, CO2, HCl, SO2, & HF