1.4 The impact of volcanic activity Flashcards
What scale do we use measure the magnitude of a volcano
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
How can we measure the frequency of a volcano
Interpret previous historic activity through…
1. Looking at deposits from around the volcano
2. Reading historical records
How can we manage a hazard
Predict, Plan and Protect
How can we predict a volcanic eruption
It is difficult to predict a volcanic eruption but some ways include…
- Monitoring seismic activity
- Monitoring changes in groundwater
- Monitering land swelling
- Being aware of the volcanoes frequency
How can we protect from a volcanic eruption
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)
What are the primary physical effects of a volcanic eruption
- Tephra
- Pyroclastic flows
- Lava flows
- Volcanic gases (Like CO2)
What is Tephra
Solid material such as ash being ejected into the atmosphere
What is pyroclastic flows
Extremely hot gas and tephra charged flows , which flow down the sides of volcanos up to 700kmh
What are the secondary physical effects of a volcanic eruption
- Lahars
- Flooding (due to melted glaciers and ice caps)
- Acid rain
- Climate change
- Aftershocks
What is a Lahar
Melted snow mixed with ash, forming a mud flow moving at high speeds
What are the 2 case studies
Montserrat
Mount Saint Helens (Washington)
Give some context for the Montserrat eruption
It is a composite volcano , located above a destructive margin and erupted June 1997.
Earthquakes had happened 2 years prior to the event
What were the primary and secondary physical effects of the Montserrat eruption
5 million cubic metres of material released
4km inundated by pyroclastic flows
Aftershocks
What were the primary impacts of the Montserrat eruption
$1.2 billion in damages
2/3 of homes destroyed 2/3 population decline
19 deaths, 7 injuries
Farmland destroyed
Cities buried underneath ash
What were the secondary impacts of the Montserrat eruption
Destroyed infrastructure and natural beauty meant that tourism was severely effected
What were the primary responses of the Montserrat eruption (Before and straight after)
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
What were the secondary responses of the Montserrat eruption (long after)
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
What were the criticism for how Montserrat handles the eruption
Infrastructure had been prior built in known areas of risk
There was no disaster management plan and therefore slow responses
Give some context for the Mount saint Helens eruption
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
What were the primary and secondary physical effects of the Mount Saint Helens eruption
5.1 magnitude earthquake
540 million tonnes of ash
8km inundated by pyroclastic flows
Flooding
What were the primary impacts of the Mount Saint Helens eruption
$1.1 billion in damages
200 homes destroyed
57 deaths
240km of forest ruined
Water level raised 60m by sediment
Thousands of animals dead
What were the secondary impacts of the Mount Saint Helens eruption
Loss of infrastructure made it difficult to redevelop
The sediment polluted water and caused flooding
What were the primary responses of the Mount Saint Helens eruption
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
What were the secondary responses of the Mount Saint Helens eruption
900,000 tonnes of ash cleaned
18.4 million trees replanted
Water supplies monitored
What made the handling of Saint Helens better than the handling of Montserrat
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
