volcanic hazards

Question 1

what is vulcanicity

Answer 1

refers to all volcanic activities related to magma being forced into the crust

Question 2

what are volcanoes

Answer 2

are openings in the Earth’s crust through which lava, ash and gases erupt

Question 3

what is the difference between magma and lava

Answer 3

Molten rock beneath the surface is referred to as magma,
but once it is ejected at the surface it is called lava

Question 4

how man active volcanoes are there

Answer 4

1500

Question 5

how many volcanic eruptions are associated with plate margins

Answer 5

95%

Question 6

how many volcanic eruptions are associated with intraplate

Answer 6

5%

Question 7

what plate margins are volcanoes found at

Answer 7

• constructive (ocean crust)
• constructive (continental crust)
• destructive
• intraplate over hot posts

Question 8

how does magma differ between constructive and destructive plate margins

Answer 8

constructive = basaltic
destructive = acidic (andesitic and rhyolite)

Question 9

how does lava differ between constructive and destructive plate margins

Answer 9

constructive = runny, less viscous and low silica
destructive = slow moving, viscous and high silica

Question 10

how does the type of eruption differ between constructive and destructive plate margins

Answer 10

constructive = little violence, effusive, gases escape
destructive = potentially explosive

Question 11

how does the frequency of volcanic eruptions differ between constructive and destructive plate margins

Answer 11

constructive = regular and may be continuous
destructive = from time to time, long dormant periods

Question 12

what is the spatial distribution of volcanoes

Answer 12

most occur in linear belts along plate boundaries e.g pacific ring of fire

Question 13

what is magnitude in relation to volcanoes

Answer 13

refers to its explosive power

Question 14

what scale measures volcanoes

Answer 14

since 1982 magnitude has been measured by a logarithmic scale known as the volcanic exclusivity index

Question 15

what is the scale of the vei

Answer 15

1-8

Question 16

how can we accurately predict an eruption

Answer 16

• vulcanologists need to know a volcanos eruption history
• and be currently monitoring it

Question 17

what are the warning signs volcanologist monitor

Answer 17

• local seismic activity using seismometers, tremors indicate rising magma
• ground deformation measured by tilts meters
• changes in concentration of gasses e.g carbon dioxide and sulphur dioxide
• rising temp of ground water
• physical changes around the crater

Question 18

what is a primary impact

Answer 18

occur immediately afterwards and are a
direct result of the material ejected from the volcano

Question 19

what are examples of primary impacts from a volcanic eruption

Answer 19

• lava and pyroclastic flows destroy roads and cause buildings to collapse
• ash fall out may contaminate crops and water supplies
• tephras may kill or injure people

Question 20

what are secondary impacts

Answer 20

occur in the days or weeks that follow and are indirectly related to the eruption itself, can be social, economic or environmental

Question 21

examples of secondary impacts from volcanic eruptions

Answer 21

• Lahars can kill or injure people and can cause additional damage to roads and bridges, making it difficult for emergency services to reach people in need
• People who have lost loved ones or their home or job in the eruption can experience psychological problems
• Environmental impacts could include fires caused by lava flows and pyroclastic flows or damage to vegetation and fresh water habitats by acid rain

Question 22

what risk management can be taken to reduce impacts of volcanoes

Answer 22

prediction and protection including preparedness, mitigation and adaption

Question 23

what does prediction involve

Answer 23

• accurate hazard mapping
• analysing seismic shockwave patterns
• sampling gas and lava emissions

Question 24

what is an example where prediction of volcanoes worked

Answer 24

2000 Mexico eruption of Popocatepetl, volcano erupted 48 hours after local population evacuation

Question 25

what does protection involve

Answer 25

reducing risk of damage by preparing - warnings are issued - instructions given on how to react before, during and after - hazard mapping and land use planning to avoid development in at risk areas - in at risk areas, alert systems, shelters and evacuation maps, emergency food and water supplies

Question 26

how can we adapt to volcanic eruptions

Answer 26

design solutions such as - windows facing the volcano - shutters for windows to make them air tight - triple roof support for extra strength to prevent collapse - steep slope roof and smooth roof material so ash is less likely to accumulate - concrete rather than timber frames for additional strength

Question 27

what is a lava flow

Answer 27

Molten rock flowing over the surface. Basaltic (basic) lavas have higher temperatures and a low silica content (less than 52%), which means that they tend to flow some distance before solidifying (e.g. on the Hawaiian Islands). Acid lavas (either andesitic or rhyolitic) are more viscous; flow more slowly and often solidifies in the vent of the volcano, resulting in unpredictable and explosive eruptions

Question 28

what is a pyroclastic flow

Answer 28

A mixture of hot rock, lava, ash and gases rising from a volcanic eruption that moves at a rapid speed (up to 200m/s) along the ground. The most dangerous are those that erupt sideways due to a blocked summit crater. Temperatures are between 350- 1000oC. Pyroclastic flows are more common in eruptions of acidic lava at subduction zones

Question 29

what is a tephra

Answer 29

Solid rock fragments ejected during volcanic eruptions. The largest fragments can be over 1m in diameter and fall close to the volcano (potentially causing injury or death to people); the smallest fragments (ash less than 2mm) are carried by wind and travel great distances (vertically and laterally)

Question 30

what is a Nuees ardente

Answer 30

Means ‘glowing cloud’ and is a dense, rapidly moving cloud of hot gases, ashes and lava fragments from a volcanic eruption. It is a type of pyroclastic flow that contains more dense material and so doesn’t travel as far

Question 31

What is ash fallout

Answer 31

Ash can be ejected high into the atmosphere and, depending on prevailing winds, can cover a large area. Ash is highly abrasive and can cause breathing problems, disrupt machinery and clog filters. It can also obstruct sunlight, reducing visibility and temperatures

Question 32

What are volcanic gases

Answer 32

These are dominated by steam – often superheated – but also include carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine. These gases are highly dangerous

Question 33

what are mudflows/lahars

Answer 33

Lahars are destructive mudflows formed when ash and other volcanic material are mixed with water. They flow at speeds of up to 60km/h and are highly erosive

Question 34

what is acid rain

Answer 34

Volcanoes emit sulphurous gases, which can result in acidic rainwater when combined with atmospheric moisture

Question 35

example of a pyroclastic flow

Answer 35

AD 79 from Mount Vesuvius overwhelmed the Roman city of Pempeii

Question 36

what is an example of a lava flow

Answer 36

during 2014-15 eruption of Fogo Volcano in Cape Verde engulfed 75% of buildings within three villages

Question 37

what is an example of a tephra

Answer 37

2010 eruption of Eyjajallajokull led to the cancellation of 100,000 flights

Question 38

what is an example of a nuees ardente

Answer 38

1902 French Caribbean island of Martinique swept down the slopes of Mount Pelee killing all but 29,000 residents

Question 39

what is an example of ash fallout

Answer 39

2010 eruption of Eyjafjallajokull

Question 40

example of volcanic gasses

Answer 40

1986 - At least 1,200 people were killed and 300 hospitalized when an underwater volcanic explosion unleashed deadly gases at Lake Nios in a remote area of northern Cameroon

Question 41

example of a mudflow/lahar

Answer 41

November 13, 1985 small eruption produced enormous lahar that buried the town of Armero in Tolima causing an estimated 25,000 deaths - deadliest lahar in recorded history

Question 42

what is an example of acid rain

Answer 42

Tonga 2022 - Since the initial eruption, the volcano has been releasing sulfur dioxide and nitrogen oxide — two gases that create acid rain when they interact with water and oxygen in the atmosphere