Volcano hazards

Question 1

What is a lahar?

Answer 1

-mixture of hot and cold water with rock fragments

Question 2

How do lahars form?

Answer 2

-when erupted volcanic material gets saturated

Question 3

Where are lahars most common?

Answer 3

-on stratovolcanoes
(Due to their greater gradients)

Question 4

What makes lahars so dangerous?

Answer 4

-they are capable of setting like concrete
-they grow as the travel
-they will destroy anything in their path
-have been known to move car-sized objects

Question 5

What is ashfallout?

Answer 5

-term for aash and tephra that falls to the earths surface

Question 6

What can happen to ash and tephra during eruptions?

Answer 6

-it can be sent up to incredible heights
-can travel many kilometres

Question 7

What problems can ash fallout cause?

Answer 7

-health problems
-disrupt air travel
-damage machinery
-contaminate water supplies
-collapse structures

Question 8

What is a mudflow?

Answer 8

-form of mass movement involving fast-moving flow of debris

Question 9

What speeds can a mudflow reach?

Answer 9

-ranges from 3 metres/minute to 5 metres/second

Question 10

How can mudflows travel so far?

Answer 10

-they contain significant amounts of clay
-are a secondary effect of a volcanic eruption

Question 11

What triggers a mudflow?

Answer 11

-heavy rainfall
-snowmelt
-groundwater flowing through cracked bedrock
-form after an eruption

Question 12

Why are mudflows so dangerous?

Answer 12

-can carry large boulders and trees
-damage water supplies
-damage gas pipes
-damage electrical infrastructure
-can cause secondary effects such as disease

Question 13

What are volcanic gases?

Answer 13

-gases that are released during volcanic activity or an eruption

Question 14

What are some examples of volcanic gases?

Answer 14

-sulphur dioxide
-carbon dioxide
-hydrogen chloride
-hydrogen fluoride
-hydrogen sulphide

Question 15

Why are volcanic gases so dangerous?

Answer 15

-they are hazardous to human health
-cause respiratory problems
-can lead to death
-air quality alerts
-health warnings

Question 16

What makes volcanic gases difficult to be aware of?

Answer 16

-they are invisible
-they are denser than air so tend to pool in depressions surrounding the volcano

Question 17

What is an example of gases being deadly?

Answer 17

-lake Nyos in Cameroon
-killed 1700 people
-massive amounts of carbon dioxide released in lake Nyos

Question 18

What are pyroclastic flows?

Answer 18

-dense, fast moving flow of solidified lava pieces, hot ash and hot gases expelled from a volcano during an eruption

Question 19

How does a pyroclastic flow form?

Answer 19

-mainly happens with explosive eruptions

Question 20

How are pyroclastic flows so dangerous?

Answer 20

-move at speeds of up to 200m/s
(Impossible to escape from)
-cover the ground in solidified lava and ash
-water levels are made to rise
-causes secondary flooding

Question 21

What is an example of a pyroclastic flow?

Answer 21

-Pompeii and Herculaneum when Vesuvius erupted in 79AD

Question 22

What is acid rain?

Answer 22

-precipitation that has elevated levels of hydrogen ions

Question 23

What does acid rain effect?

Answer 23

-trees
-freshwater sources
-soil
-insects and aquatic life forms
-corrosion of metal bridges and structures
-impacts human health

Question 24

How is acid rain created?

Answer 24

-sulfur dioxide gas can lead to acid rain and air pollution downwind of a volcano

Question 25

What is tephra?

Answer 25

-rock fragments and participles ejected by a volcanic eruption
(Also referred to as pyroclasts)

Question 26

What happens to tephra once it hits the ground?

Answer 26

-remains as tephra unless its hot enough to fuse into pyroclastic rock or tuff

Question 27

What dangers does tephra pose?

Answer 27

-can trigger fires if falling on ignitable material
-reduces visibility
-causes complete blackout
-hazards for driving
-contaminates water

Question 28

what are lava flows?

Answer 28

-a stream of molten rock that pours out of a volcano during an eruption

Question 29

Which eruption motivated the first systematic epidemiological and toxicological research?

Answer 29

-Mount St Helens in 1980

Question 30

What happens to lava once it’s out of the volcano?

Answer 30

-it remains molten and flows across the ground until it cools and hardens into rock
(Because it’s so hot = over 1,100 degrees C)

Question 31

Are lava flows a major threat?

Answer 31

-no
-they can be very destructive but are rarely a threat to humans directly
-they move very slowly so people can outrun it

Question 32

What is an example of a lava flow?

Answer 32

-lava flows at Etna volcano in Italy
-destroyed up to 12 villages and part of the city Catania

Question 33

What does ‘nuees ardente’ mean?

Answer 33

-glowing cloud

Question 34

What is a nuees ardente?

Answer 34

-turbulent, fast-moving cloud of hot gas and ash erupted from a volcano

Question 35

What is an example of a nuees ardente?

Answer 35

-1902 eruption of Mount Pelee
-killed 29,000 people
-destroyed the city of St.Pierre

Question 36

How do nuees ardentes form?

Answer 36

-during explosive eruptions as columns of material collapse
-or when volcanic rock collapses in non-explosive eruptions

Question 37

Why are nuees ardentes so dangerous?

Answer 37

-flow into valleys at speeds up to 50mph
-range from 204-704 degrees C
-accompanied by large boulders