Lesson 9-What are hazards associated with volcanic activity?

Question 1

Lava flows

Answer 1

• Aa-metres thick,uneven shapes,sharp edged ash and cinder blocks
• Pahoehoe-fluid rather than viscuous but doesnt move quick as surface layer is hard and beneath is fluid

Question 2

Pyroclastic and ash fallout

Answer 2

• Coulds of hot volcanic gases
  -caused by collaping eruption collum

Question 3

Tephra

Answer 3

• Fragments of rock that are produced when magma/ rock is explosively ejected

Question 4

Lahars

Answer 4

• Hot ot cold mixture of ash and water
  -snow melts from high alttitude or excess rain

Question 5

Gases/Acid

Answer 5

• Magma contains dissolved gases which provides extra forces in eruptions
  -gases are emitted-CO2, Sulfur and Hydrogen Sulphate

Question 6

Lava Flows example

Answer 6

• Eldfell, Iceland
• Pumped 7.3 million cubic metres of seawater
• Flow of lava towards harbour was stopped

Question 7

Pyroclastic and ash fallout example

Answer 7

• Mt St Helens
• Maximum speed of pyroclastic flows
  -250moh
• 200houses burned, 27 bridges destroyed, 190 miles of road destroyed

Question 8

Tephra (volcanic ash) example

Answer 8

• E15, Iceland 2010
• 4000 flitghts cancelled
• Airlines lost a total combined 130 million pound per day

Question 9

Lahars example

Answer 9

• Nevado Del Ruiz, 1985
• 3181 m
• 25 km squared of snow and ice
• 50 k/
• Over 23k died

Question 10

Gases/acid rain example

Answer 10

• Lake Nyos, Cameroon
• 1200 people dead
• 100,000-300,000 tons of C02
• Released in a cloud reaching 10km

Question 11

Sieismometer/earthquakes to predict volcanic eruptions

Answer 11

• Seismic data from networks is processed to understand processes happening beneath the ground surface.
• Effective as it tracks live data automatically

Question 12

Tiltmeters to predict volcanic eruptions

Answer 12

• Measuring ground deformation-GPS>satellites
• Rising magma will increase tilt, decreasing tilt less likely to erupt
• Someone has to install it, potential harm

Question 13

Ground deformation to predict volcanic eruptions

Answer 13

• Inflates like a balloon/bulges
• Bulge measured by GPS system
  Defomation may be small, not good as its only recognised by sinsitive instrments

Question 14

Volcanic gases to predict volcanic eruptions

Answer 14

• Increase in sulfur dioxide
• Often done by plane which cant pick up suface level gases

Question 15

Preparedness and planning

Answer 15

• Devlop emergency plans so people know what to do
• Hzard perception may ruin this

Question 16

Volcanic history/ time since last eruption to predict volcanic eruption

Answer 16

• Understanding the fequency of volcanos in the past may help us predict the future
• May not follow the predicted patterns

Question 17

Hydrology for predicting volcanic eruptions

Answer 17

• Directly before an eruption the depth of the water table decreases as water rises due to higher temp
• May lead to evaporation of water in the water table