Volcanic hazards Flashcards
(25 cards)
On average how frequently do they occur?
168 in 45 years
What is the definition of an extinct volcano?
Has no chance of erupting again
What is the definition of a dormant volcano?
Has not erupted in the last 10,000 years but still have the potential to erupt
What is the definition of an active volcano?
Has erupted in the last 10,000 years and still have the potential to erupt
What is a primary hazard?
An impact directly linked to the volcanic activity in the given location
What are the primary hazards from a volcanic eruption?
Lava flows
Pyroclastic flow
Tephra and ballisitc flows
Gas emissions
Earthquakes
Debris avalanches
What is the temperature of a lava flow?
800-1200c
Below 800c- forms skin on surface
How do lava flows pose a threat to humans?
Low risk to human health due to slow moving nature
High risk of human displacement and disruption due to destructive nature
What is the definition of a pyroclastic flow?
A flow of hot gas and volcanic material, high density, travels close to the ground, following topographic lows (valleys)
What is the defiition of pyroclastic surge?
A turbulent, low density, high velocity part of a pyroclastic, not constrained by topography
What is the distance and speed range of pyroclastic flow?
Km to kms
Low to high speed
What are the related hazards to pyroclastic flows and surges?
Poor health (inhilation)
Destruction of infrastructure
Malfunction of machinery
Destruction by fire
Climatic effects
What gases are released during a volcanic eruption?
Sulfur dioxide- so2
Carbon dioxide- co2
Hydrogen fluoride- HF
Why is sulfur dioxide a hazardous gas?
Causes poor air pollution
Why is carbon dioxide a hazardous gas?
Lethal to people and animals (at concentrated levels)
Level of co2 emitted from anthropogenic activity higher than volcanic activity
Why is is hydrogen fluoride a hazardous gas?
Death and injury in livestock
How are earthquakes primary hazards?
Only when magnitide >5 on Richter scale
Triggers eruptions or landslides that results in eruptions
What is the definition of a secondary hazard?
An indirect hazard casued by volcanic activity in a given area
What are the secondary hazards from a volcanic eruption?
Lahars (mudflows)
Flooding/Tsunami
Fires
Air pollution
Diseases/Famine
Social effects
Climatic effects
How does a lahar form?
When pyroclastic flow meets water e.g. rain, glaciers, river water
The gas rich pyroclastic flow is converted to a fast moving heated mudflow
Why are lahars a secondary hazard of an eruption?
One of the most lethal and devestating hazards
Speed up to 200km/h
<100c
Can travel km to 10kms
How does a tsunami form?
Eruption triggeres pressure and gravity waves in the atmosphere and tsunami waves in the ocean
Why are tsunamis a secondary hazard of an eruption?
Huge economic damage
Damage to infrastructure and agriculture
Why are climatic effects a secondary hazard from an eruption?
Ash in the upper atmosphere reduces the amount of radiation reaching the ground
Can reduce temperature worldwide e.g. 0.5 for 10 years
