HAZARDS - volcanoes

Question 1

pyroclastic flow

Answer 1

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

Question 2

tephra

Answer 2

rock fragments ejected during the volcanic eruption

Question 3

nuée ardente

Answer 3

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

Question 4

primary hazards of a volcano

Answer 4

pyroclastic flow, lava flow, tephra, nuée ardente

Question 5

secondary hazards of a volcano

Answer 5

acid rain, lahars, tsunamis

Question 6

lahars

Answer 6

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

Question 7

spatial distribution of earthquakes

Answer 7

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

Question 8

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

Answer 8

low temperature
high silica content
low volume of dissolved gas

Question 9

what are the characteristics of high viscosity magma?

Answer 9

thick, cooler magma = violent eruptions as it blocks vents

Question 10

what are the characterisitics of low wiscosity magma

Answer 10

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

Question 11

basaltic magma

Answer 11

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

Question 12

rhyolitic

Answer 12

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

Question 13

andesitic

Answer 13

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)

Question 14

how is the magnitude of volcanoes measured?

Answer 14

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

Question 15

frequency

Answer 15

depends on the volcano

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

Question 16

predictability

Answer 16

volcanologists look at eruption history and current data

BUT impossible to predict magnitude, nature and timing.

Question 17

seismometer and seismograph

Answer 17

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

Question 18

tiltmeter, laser based electronic distance measurements

Answer 18

show ground deformation

Question 19

magnetometer

Answer 19

measures upward movement of iron rich magma.

changing magnetism =rising magma

Question 20

hydrolic instruments

Answer 20

measure increased water temp/ gas content

rising magma heats ground water and contaminates with gasses

Question 21

remote sensing equipment

Answer 21

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.

Question 22

primary impact

Answer 22

occurs directly following the eruption

Question 23

examples of primary impacts

Answer 23

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

Question 24

secondary impacts

Answer 24

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

Question 25

examples of secondary impacts

Answer 25

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

Question 26

short term response eg’s

Answer 26

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

Question 27

long term responses 4 categories

Answer 27

preparedness, mitigation, prevention and adaption

Question 28

examples of long term responses

Answer 28

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