Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

yeah rocks > Volcanic processes and hazards > Flashcards

Volcanic processes and hazards Flashcards

1
Q

why are volcanoes both destructive and constructive?

A

the can destroy human infrastructure but also add material to the Earth’s surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

3 things effected by large volcanic eruptions

A
  1. atmosphere composition (addition of gases)
  2. bioshpere (kills plants, animals, humans)
  3. hydrosphere (tsunamis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

define VOLCANO

A

landform built by volcanic activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

define VOLCANISM

A

process in which magma rises through the Earth’s crust and erupts at the surface as lava flows and/or pyroclastic materials and gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is a VOLCANIC EDIFICE

A

part of the volcano above the ground

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

seamount

A

a volcano under the sea which doesn’t reach the surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

______ volcanoes form intra-plate, subduction volcanoes form at _______ margins, and rift volcanoes form at _______ margins.

A

hot-spot volcanoes form intra-plate, subduction volcanoes form at convergent margins, and rift volcanoes form at divergent margins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Active, dormant and inactive/extinct volcanoes?

A

active - erupted in historic time.
dormant - haven’t erupted in historic time, but they could.
Inactive - not expected to erupt again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Flood basalts form due to gigantic volcanic eruptions of ______ viscosity lava. They erupt due to __________ _______. A single eruption can cover 200,000km^2 and form large ________ ________. They have been cited as the cause of mass-extinction events.

A

Flood basalts form due to gigantic volcanic eruptions of very_low viscosity lava. They erupt due to continental rifting. A single eruption can cover 200,000km^2 and form large igneous provinces. They have been cited as the cause of mass-extinction events.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

shield volcanoes

A
  • form from low viscosity lava
  • gentle slopes
  • build up layers over time
  • eruption is effusive (not explosive) and can be continuous.
  • e.g. rangitoto
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

cinder cones

A
  • steep, scoria cone
  • formed from effusive eruptions of low viscosity lava
  • gases can vent long after the end of the eruption
  • e.g. mt eden, one tree hill
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is scoria and why is it red?

A

scoria forms from low viscosity, basaltic lava cooling rapidly as it flies through the air. It is red because it gets oxidised by steam.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

composite/ stratovolcanoes

A
  • tall, conical shaped volcanoes
  • explosive eruptions
  • form from higher viscosity (than mafic) felsic magma
  • no extensive lava flows
  • e.g. Mt Taranaki
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

rock types associated with felsic magma

A
  • rhyolite
  • dacite
  • andesite
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Volcanic domes

A
  • formed from lava too viscous to flow (high silica content)
  • lava accumulates around the vent
  • basaltic or rhyolitic
  • large pieces of rock (BRECCIA) break off as the dome grows
  • may erupt explosively, as gases get trapped and pressure builds up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the name given to a collapsed volcano? why do they collapse?

A

caldera. Volcanoes collapse when the magma chamber is emptied and the weight of the edifice is no longer supported.

17
Q

2 mechanisms by which a caldera can forms

A
  1. sudden emptying of the magma chamber in an explosive eruption, causing rapid collapse of the edifice through formation of a ring fault.
  2. Gradual emptying of the magma chamber associated with shield volcanoes (low viscosity), causing subsidence of the edifice
18
Q

4 types of volcanic eruption

A
  1. Hawaiian - mostly low viscosity lava, not much gas
  2. Plinian - large volume of gas, pumice and ash
  3. Strombolian - mixed gas/ pyroclastic material and lava
  4. hydrovolcanic - highly explosive, hot magma comes into contact with water in the ground and vaporises it.
19
Q

what is used to measure the size of a volcanic eruption?

A

Volcanic explosivity index.
Similar to the Richter scale.
Based on ammount of material, duration, and how high ejection is

20
Q

rhyolite, dacite, andesite and trachyte are all ____ viscosity lavas.

A

high

21
Q

igneous rock found with bubbles (vesicles), would’ve formed from …. why?

A

formed from high viscosity lava, because since the lava doesn’t really flow, the gases get trapped. (the opposite is the case with low viscosity lava)

22
Q

basalt and andesite are _____ viscosity lavas

A

low

23
Q

pyroclastic materials

A
  • form from explosive volcanism
  • classified as airfall deposits
  • range from ash to volcanic bombs (breccia)
24
Q

deposits from a pyroclastic flow are called?

A

Ignimbrite

25
Q

Ignimbrite composites comprise?

A
  • volcanic ash
  • pumice
  • lithics
  • they can be unconsilidated or welded by heat.
26
Q

do volcanic gases (SO2, HCl, HF, CO2) cause global warming?

A

no they form global cooling by reflecting sunlight back into space.

27
Q

lahar

A

fast flowing slurry of water, ash and rock. Occur if the eruption melts a lot of snow or ice or if there is heavy rain after an eruption.

28
Q

whats the most destructive volcanic hazard?

A

pyroclastic flow - mixture of hot (500 degrees c) gases and ash which travel at several hundred kph, destroying everything in their path

29
Q

5 main hazards of a volcano

A
  1. ash falls
  2. airborne ash
  3. lava flows
  4. pyroclastic flows
  5. lahar
30
Q

dangers of ash

A
  • abrasive (especially to aircraft)
  • corrosive
  • electrically conductive
  • suspend in the atmosphere for weeks
  • ash loading on buildings – increase the dead-load on the roof (even worse when wet) which may lead to collapse
  • impact water supplies (change composition, shortages during clean-up)
31
Q

does ash affect water quality?

A

yes, 55 soluble compounds (mineral acids). can change the pH of water and increase turbidity (addition of flocculants)

32
Q

Mitigation of the volcanic hazards at Mt Ruapehu.

Eastern Ruapehu Lahar Alarm and Early Warning System (ERLAWS)

A
  • installed after 1995 and successfully predicted 2007 lahar
  • array of geophones detect vibrations
  • buried tripwires detect dam collapse
  • water level sensors in crater lake detect sudden emptying
  • automatic barriers on SH1 if lahar detected
33
Q

other lahar mitigation techniques

A
  • bund preventing flow
  • overflow channel
  • sediment retention basin
  • channelisation of flow
34
Q

main things monitored on a volcano

A
  1. gas monitoring
  2. seismic activity (tiltmeters, extensometers and gps)
  3. deformation monitoring (large scale bulging)
35
Q

what is the most widespread hazard caused by a volcano?

A

ash fall

yeah rocks (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions