3.1.5.3 Volcanic Hazards

Question 1

What area has a high density of volcanoes

Answer 1

Pacific ring of fire (Japan,phillipines,New Zealand)

Question 2

Where are volcanoes mostly in belts (destructive + constructive)

Answer 2

Along plate boundaries

Question 3

Example of some volcanoes that are intraplate

Answer 3

Hawaiian hot spot

Question 4

What margins have no volcanic activity

Answer 4

Conservative

Question 5

3 types of volcanoes (activity)

Answer 5

Active
Dormant
Extinct

Question 6

2 types of volcanoes that have regular eruptions

Answer 6

Icelandic

Hawaiian

Question 7

What volcanoes are more explosive

Answer 7

Krakatoan

Question 8

What are Hawaiian eruptions like

Answer 8

Not explosive/destructive

Produce low-viscosity, low-gas content lava that produces shield volcanoes + lava plateaus

Question 9

What do Strombolian eruptions do

Answer 9

Put small amounts of lava into the air 15-90m
Lava has high viscosity
Small eruptions with booming sounds
Small amounts of ash

Question 10

What eruptions are highly explosive e.g Pompei

Answer 10

Plinian eruptions

Question 11

What are plinian eruptions like

Answer 11

Highly viscous magma -> high gas content
Pyroclastic material into atmosphere
Last for days - tall eruption plume

Question 12

2 types of magma

Answer 12

More basic Basaltic/fluid lava

More acidic lavas e.g Andesite + Rhyolite

Question 13

How is volcanic eruptions magnitude measured

Answer 13

0-8 on a logarithmic scale called the Volcanic Explosivity Index (VEI)

Question 14

How is frequency of volcanic eruptions determined

Answer 14

By its previous history of activity

Question 15

2 types of equipment that can monitor volcanoes

Answer 15

Seisometers

Seismographs

Question 16

What can be produced to identify areas most at risk

Answer 16

Hazard maps

Question 17

Explain why volcanic activity is found along oceanic ridges

Answer 17

Plates are moving apart and magma is forcing its way to the surface, cooling and forming new crust
(Sea-floor spreading)

Question 18

Explain why volcanic activity is found on/near subduction zones

E.g

Answer 18

E.g Pacific ring of fire

Deeper oceanic plate descends, hotter surroundings get
This and friction melts plate to magma
It rises in plutons of magma and these reach the surface forming volcanoes

Question 19

What are lava flows

Answer 19

Molten rock (magma) flowing onto surface

Question 20

What lava solidifies very quickly

Answer 20

Acid lava

Question 21

What lava flows some distance before solidifying

Answer 21

Basic lava (basaltic)

Question 22

What are mudflows called in Indonesia

Answer 22

Lahars

Question 23

2 causes of Lahars

Answer 23

• Eruptions ejecting water from crater
• rapid melting of ice/snow on volcano
• heavy rainfall
• pyroclastic flows entering streams

Question 24

4 primary effects of volcanoes

Answer 24

Tephra
Pyroclastic flows (nuées Ardennes)
Lava flows
Volcanic gases

Question 25

6 secondary effects of volcanoes

Answer 25

Lahars
Flooding
Volcanic landslides
Tsunamis
Acid rain
Climatic change

Question 26

What’s tephra

Answer 26

Solid material of varying grain size ranging from volcanic bombs -> ash, all ejected into the atmosphere

Question 27

What are pyroclastic flows (nuées Ardentes)

Answer 27

Very hot (over 800*c), gas charged, high velocity flows made up of a mixture of gas + tephra
Usually hug the ground + flow down sides of volcano up to 700km/hour

Question 28

3 examples of volcanic gases

Answer 28

CO2
CO
Hydrogen sulphide
Sulphur dioxide
Chlorine

Question 29

What are Lahars

Answer 29

Melted snow + ice due to an eruption, combined with volcanic ash forms mud flows that can move down course of river valleys at high speeds

Question 30

When can flooding occur from a volcanic eruption

Answer 30

When an eruption melts glaciers/ice caps

Question 31

What are tsunamis

Answer 31

Sea waves generated by volcanic eruptions

Question 32

3 famous volcanic eruptions where pyroclastic flows occurred

Answer 32

Mount Pinatubo, 1991 - phillipines
Krakatoa 1883 - Indonesia
Nevado Del Ruiz - Colombia
Mount St Helens - Washington state

Question 33

3 famous volcanic eruptions where ash clouds occurred

Answer 33

Mount Pinatubo - Phillipines
Vesuvius - Italy
Krakatoa - Indonesia
Nyiragongo - great Rift Valley 
Eyjafallajokul - iceland

Question 34

3 famous volcanic eruptions where earthquakes occurred

Answer 34

Mount Pinatubo - Philippines
Eyjafallajokull - Iceland
Nevado del Ruiz - Colombia
Mount St. Helens - Washington state

Question 35

What can minimise damage of volcanic eruptions

What’s most important aspect of this

Answer 35

Management

Prediction is most important part

Question 36

Who monitor volcano warning signs

Answer 36

Volcanologists

Question 37

What equipment is a safe, accurate way of measuring volcanoes

Answer 37

Remote sensing e.g thermal imaging

Question 38

What measures seismic activity

Answer 38

Seismometers

Question 39

What measures bulging of ground caused by rising magma

Answer 39

Tiltmeters

Question 40

What does rising gas release that can be monitored to predict eruptions

Answer 40

Gases

Question 41

What country has an alert system

Answer 41

New Zealand

Question 42

How do they raise awareness

Answer 42

Education

Question 43

reasons monitoring volcanoes is useful

Answer 43

• allow evacuation time
• can decide how much protection is needed
• things can be put in place to divert lava