1.4 The impact of volcanic activity

Question 1

What scale do we use measure the magnitude of a volcano

Answer 1

Using the VEI scale (volcanic explosivity index), running on a scale from 8 to 0

It only measures explosivity and does not pass emissions or climatic impact

Question 2

How can we measure the frequency of a volcano

Answer 2

Interpret previous historic activity through…
1. Looking at deposits from around the volcano
2. Reading historical records

Question 3

How can we manage a hazard

Answer 3

Predict, Plan and Protect

Question 4

How can we predict a volcanic eruption

Answer 4

It is difficult to predict a volcanic eruption but some ways include…

1. Monitoring seismic activity
2. Monitoring changes in groundwater
3. Monitering land swelling
4. Being aware of the volcanoes frequency

Question 5

How can we protect from a volcanic eruption

Answer 5

Prior to event
1.Predict when the event will happen
2.Identify areas at great risk
3. Educate and Evacuation plans

During event
1. Foreign aid
2. Divert lava flows (dig trenches etc)

Question 6

What are the primary physical effects of a volcanic eruption

Answer 6

1. Tephra
2. Pyroclastic flows
3. Lava flows
4. Volcanic gases (Like CO2)

Question 7

What is Tephra

Answer 7

Solid material such as ash being ejected into the atmosphere

Question 8

What is pyroclastic flows

Answer 8

Extremely hot gas and tephra charged flows , which flow down the sides of volcanos up to 700kmh

Question 9

What are the secondary physical effects of a volcanic eruption

Answer 9

1. Lahars
2. Flooding (due to melted glaciers and ice caps)
3. Acid rain
4. Climate change
5. Aftershocks

Question 10

What is a Lahar

Answer 10

Melted snow mixed with ash, forming a mud flow moving at high speeds

Question 11

What are the 2 case studies

Answer 11

Montserrat
Mount Saint Helens (Washington)

Question 12

Give some context for the Montserrat eruption

Answer 12

It is a composite volcano , located above a destructive margin and erupted June 1997.

Earthquakes had happened 2 years prior to the event

Question 13

What were the primary and secondary physical effects of the Montserrat eruption

Answer 13

5 million cubic metres of material released
4km inundated by pyroclastic flows

Aftershocks

Question 14

What were the primary impacts of the Montserrat eruption

Answer 14

$1.2 billion in damages

2/3 of homes destroyed 2/3 population decline
19 deaths, 7 injuries

Farmland destroyed
Cities buried underneath ash

Question 15

What were the secondary impacts of the Montserrat eruption

Answer 15

Destroyed infrastructure and natural beauty meant that tourism was severely effected

Question 16

What were the primary responses of the Montserrat eruption (Before and straight after)

Answer 16

Observatory was set up in 1995 and correctly predicted eruption

Exclusion zones identified and evacuated

NGO’s like the Red Cross set up schools and gave out food

Question 17

What were the secondary responses of the Montserrat eruption (long after)

Answer 17

UK funded a 3 year redevelopment scheme of £420 million

UK offered whole population with residency in 1998 and citizenship 4 years after

Tourism managed to redeem itself

Question 18

What were the criticism for how Montserrat handles the eruption

Answer 18

Infrastructure had been prior built in known areas of risk

There was no disaster management plan and therefore slow responses

Question 19

Give some context for the Mount saint Helens eruption

Answer 19

It is a composite volcano located on a destructive plate margin and erupted in May 1980

Mini earthquakes and a large bulge appeared 2 months before the eruption

Question 20

What were the primary and secondary physical effects of the Mount Saint Helens eruption

Answer 20

5.1 magnitude earthquake
540 million tonnes of ash
8km inundated by pyroclastic flows

Flooding

Question 21

What were the primary impacts of the Mount Saint Helens eruption

Answer 21

$1.1 billion in damages

200 homes destroyed
57 deaths

240km of forest ruined
Water level raised 60m by sediment
Thousands of animals dead

Question 22

What were the secondary impacts of the Mount Saint Helens eruption

Answer 22

Loss of infrastructure made it difficult to redevelop

The sediment polluted water and caused flooding

Question 23

What were the primary responses of the Mount Saint Helens eruption

Answer 23

When earthquakes happened 2 months before, USGS monitored it around the clock and warned the most hazardous zones, evacuating 2,000 people

FEMA set up emergency centres and face masks

Question 24

What were the secondary responses of the Mount Saint Helens eruption

Answer 24

900,000 tonnes of ash cleaned
18.4 million trees replanted
Water supplies monitored

Question 25

What made the handling of Saint Helens better than the handling of Montserrat

Answer 25

They had better management.

While both eruptions accurately predicted and evacuated , Mount Saint helens better handled dealing with the aftermath themselves, whereas Montserrat relied on foreign aid