HAZARDS - volcanoes Flashcards Preview

GEOGRAPHY physical > HAZARDS - volcanoes > Flashcards

Flashcards in HAZARDS - volcanoes Deck (28)
Loading flashcards...
1
Q

pyroclastic flow

A

mixture of hot rock, lava, ash and gasses which erupt from a volcano and move rapidly along the ground

2
Q

tephra

A

rock fragments ejected during the volcanic eruption

3
Q

nuée ardente

A

dense rapid moving cloud of ash, hot gasses and lava fragments - type of pyroclastic flow

4
Q

primary hazards of a volcano

A

pyroclastic flow, lava flow, tephra, nuée ardente

5
Q

secondary hazards of a volcano

A

acid rain, lahars, tsunamis

6
Q

lahars

A

destructive mudflow - ash and other volcanic materials mixed with water.

7
Q

spatial distribution of earthquakes

A

95% of plate boundaries are associated with constructive and destructive plate boundaries. 5% are intraplate.

8
Q

what are the three factors that increase the viscosity of magma?

A

low temperature
high silica content
low volume of dissolved gas

9
Q

what are the characteristics of high viscosity magma?

A

thick, cooler magma = violent eruptions as it blocks vents

10
Q

what are the characterisitics of low wiscosity magma

A

hot, runny magma
less pressure so gasses can escape and vents are not blocked.
less violent eruptions

11
Q

basaltic magma

A

-high temperature, low silica content = LOW viscosity =
-non-violent eruptions
-found at constructive plate boundaries
(balsamic vinagar is runny)

12
Q

rhyolitic

A

-low temperature, high silica content =thick HIGH viscosity magma
-violent eruptions
-found at destructive margins
(Ryan is chilled out and slow)

13
Q

andesitic

A
low temp, high silica = HIGH viscosity
- VERY explosive - affects large areas
- basaltic and continental crust at subduction zone
- destructive margin
(Andrea is even slower than Ryan)
14
Q

how is the magnitude of volcanoes measured?

A

VEI volcano explosivity index 0-8 = based on the amount of material ejected and how high it is blasted.

15
Q

frequency

A

depends on the volcano

  • constructive - basaltic lava = frequent with smaller mag.
  • destructive - rhyolitic lava = every 100,000 yrs with larger mag
16
Q

predictability

A

volcanologists look at eruption history and current data

BUT impossible to predict magnitude, nature and timing.

17
Q

seismometer and seismograph

A

measure seismic activity due to rising magma causing fracturing and cracking of overlying rock

18
Q

tiltmeter, laser based electronic distance measurements

A

show ground deformation

19
Q

magnetometer

A

measures upward movement of iron rich magma.

changing magnetism =rising magma

20
Q

hydrolic instruments

A

measure increased water temp/ gas content

rising magma heats ground water and contaminates with gasses

21
Q

remote sensing equipment

A

measures warning signs such as landslides, gas emission, small eruptions.
uses solar powered digital camera surveillance and thermal imaging in and around the main crater.

22
Q

primary impact

A

occurs directly following the eruption

23
Q

examples of primary impacts

A

lava and pyroclastic flow - destroy crops, infrastructure
ash fallout- damages crops, contaminates water
increased co2 and sulphur
deaths, injuries

24
Q

secondary impacts

A

occur as a result of primary impacts - occur in days and weeks following the eruption

25
Q

examples of secondary impacts

A
fertile soil
economic loss from crop failure
unemployment due to business failure
shortages of resources - no transport
lahars
flooding
acid rain 
phycological issues due to trauma and loss
26
Q

short term response eg’s

A

evacuation, emergency services, try to block lava flow, shelters and evacuation camps

27
Q

long term responses 4 categories

A

preparedness, mitigation, prevention and adaption

28
Q

examples of long term responses

A
  • investment in prediction and warning systems
  • hazard map evacuation strategies
  • stores of emergency food and water supplies.