Lecture 3 - Volcano hazards

Question 1

What kind of hazard is a volcano?

Answer 1

Geological
- Earthquake
- Volcano
- Mass movement
- Rockfall, landslide, avalanche, subsidence

Question 2

How many Holocene volcanoes are listed in the VOTW database, and where are they concentrated?

Answer 2

1,500 volcanoes are listed in the VOTW database, with most eruptions concentrated along the Pacific Ring of Fire, Indonesia, Japan, Iceland, and Central America.

Question 3

Which tectonic settings are most associated with Holocene eruptions?

Answer 3

Most Holocene eruptions occur at convergent plate boundaries, especially subduction zones, as well as along mid-ocean ridges like the Mid-Atlantic Ridge

Question 4

What are some notable regions and statistics for Holocene eruptions?

Answer 4

75% of eruptions occur along the Pacific Ring of Fire, with Indonesia having the most Holocene volcanoes. Additionally, 70% of volcanic activity happens underwater, but only a small fraction is documented

Question 5

How many people globally live within 100 km of an active volcano?

Answer 5

Over 800 million people live within 100 km of an active volcano, placing them at potential risk from volcanic hazards.

Question 6

Which regions have the highest populations living near volcanoes?

Answer 6

The highest populations are concentrated in Southeast Asia (Indonesia, Philippines), Japan, Central America, and parts of the Mediterranean.

Question 7

Why are so many people living near volcanoes?

Answer 7

Many people live near volcanoes due to the fertile soils that are suitable for agriculture, economic opportunities, and historical settlement patterns despite the volcanic risks.

Question 8

What is a divergent boundary?

Answer 8

A divergent boundary is where tectonic plates move away from each other, creating new crust. Examples include mid-ocean ridges like the Mid-Atlantic Ridge and continental rifts like the East African Rift.

Question 9

What is a convergent boundary?

Answer 9

A convergent boundary is where tectonic plates move toward each other, often causing subduction. Examples include the Andes Mountains (oceanic-continental) and the Himalayas (continental-continental).

Question 10

What is a transform boundary?

Answer 10

A transform boundary is where tectonic plates slide horizontally past each other. Examples include the San Andreas Fault in California and the Alpine Fault in New Zealand.

Question 11

How does basaltic magma composition affect volcanic hazards?

Answer 11

Basaltic magma is low in silica, making it low-viscosity and allowing lava to flow easily. This creates hazards like lava flows and fire fountains, which are less explosive but can cover large areas (e.g., Hawaiian eruptions).

Question 12

How does andesitic magma composition influence volcanic hazards?

Answer 12

Andesitic magma has moderate silica content, leading to higher viscosity and more explosive eruptions. Hazards include pyroclastic flows, ashfall, and lava domes, commonly seen in stratovolcanoes (e.g., Mount St. Helens).

Question 13

What hazards are associated with rhyolitic magma?

Answer 13

Rhyolitic magma is high in silica, making it very viscous and prone to violent explosions. It can generate dangerous hazards such as large pyroclastic flows, volcanic ash clouds, and caldera formation (e.g., Yellowstone).

Question 14

What are the characteristics and hazards of a composite volcano (stratovolcano)?

Answer 14

Composite volcanoes are large, steep-sided cones formed from layers of lava and ash. They are associated with explosive eruptions due to viscous magma (often andesitic or rhyolitic). Hazards include pyroclastic flows, ashfall, lava domes, and lahars (e.g., Mount Vesuvius)

Question 15

What are the characteristics and hazards of a shield volcano?

Answer 15

Shield volcanoes have broad, gently sloping sides, formed from low-viscosity basaltic lava that flows easily. Hazards include extensive lava flows that can cover vast areas, though eruptions are typically non-explosive (e.g., Mauna Loa, Hawaii).

Question 16

What are the characteristics and hazards of a cinder cone volcano?

Answer 16

Cinder cones are small, steep-sided volcanoes made from volcanic fragments like ash and cinders. Eruptions are usually short-lived, producing lava fountains, ash, and lapilli. While smaller in size, their eruptions can still pose hazards to nearby areas (e.g., Parícutin, Mexico)

Question 17

What are the characteristics and hazards of a fissure volcano?

Answer 17

Fissure volcanoes form along cracks in the Earth’s crust, from which basaltic lava flows out. They produce extensive lava flows, covering large areas, but lack a central cone. Hazards include widespread lava inundation (e.g., the Laki fissure in Iceland).

Question 18

What are the characteristics and hazards of a lava dome volcano?

Answer 18

Lava domes are formed by the slow extrusion of viscous lava (often rhyolitic or andesitic), creating steep-sided mounds. Hazards include dome collapse, leading to pyroclastic flows, and explosive eruptions if gas pressure builds (e.g., Mount St. Helens lava dome).

Question 19

What are the characteristics and hazards of a caldera volcano?

Answer 19

Calderas form when a volcano’s summit collapses following a large explosive eruption. Hazards include massive pyroclastic flows, ashfall, and long-term hazards from residual volcanic activity. Calderas can be enormous, with eruptions causing widespread devastation (e.g., Yellowstone Caldera).

Question 20

What is the Hawaiian eruption style?

Answer 20

The Hawaiian eruption style is characterized by non-explosive, relatively gentle eruptions where basaltic lava flows easily from vents or fissures, creating broad, shield-shaped volcanoes (e.g., Mauna Loa, Kīlauea).

Question 20

What are the main volcanic hazards associated with Hawaiian eruptions?

Answer 20

The main hazards include lava flows, which can cover large areas, destroy infrastructure, and ignite fires, and lava fountains, which shoot molten lava into the air, though they pose less risk to life compared to explosive eruptions.

Question 21

How does magma composition affect Hawaiian eruptions?

Answer 21

Hawaiian eruptions involve basaltic magma, which has low silica content, making it low-viscosity and allowing lava to flow easily, resulting in slow-moving lava flows rather than explosive eruptions

Question 22

What are Strombolian eruptions characterized by?

Answer 22

Strombolian eruptions are characterized by intermittent bursts of lava and explosive activity, producing lava fountains and small pyroclastic flows.

Question 23

What type of magma is associated with Strombolian eruptions, and what are the hazards?

Answer 23

Strombolian eruptions typically involve basaltic or andesitic magma, leading to hazards like lava fountains, pyroclastic flows, ashfall, and ballistic projectiles.

Question 24

Where are Strombolian eruptions commonly found, and how do they differ from Hawaiian eruptions?

Answer 24

Commonly found in subduction zones, such as Stromboli Island in Italy, they differ from Hawaiian eruptions by having more episodic and explosive activity rather than continuous lava flow.

Question 25

What are Vulcanian eruptions characterized by?

Answer 25

Vulcanian eruptions are characterized by short, violent explosions of thick, viscous magma that result in ash clouds, pyroclastic flows, and the ejection of volcanic rock fragments.

Question 26

What type of magma is associated with Vulcanian eruptions, and what are the typical hazards?

Answer 26

Vulcanian eruptions are associated with andesitic or rhyolitic magma, leading to hazards such as ashfall, pyroclastic flows, and ballistic projectiles, which can pose serious risks to nearby populations.

Question 27

Where are Vulcanian eruptions commonly found?

Answer 27

Commonly found in stratovolcanoes (e.g., Vulcano in Italy)

Question 28

What are Sub-Plinian eruptions characterized by, and what is an example?

Answer 28

Sub-Plinian eruptions involve paroxysmal ejection and wide dispersal of tephra (including pumice), sometimes associated with pyroclastic surges. An example is the Vesuvius eruption in Italy, 1631.

Question 29

What defines Plinian eruptions, and what is a notable historical example?

Answer 29

Plinian eruptions are marked by paroxysmal ejection and wide dispersal of tephra (including pumice), often linked to caldera collapse. A notable example is the Vesuvius eruption in AD 79.

Question 30

What characterizes Ultra-Plinian eruptions, and can you provide an example?

Answer 30

Ultra-Plinian eruptions feature paroxysmal ejection and wide dispersal of tephra (including pumice), often resulting in caldera collapse and formation of ash plumes. An example is the Tambora eruption in Indonesia, 1815.

Question 31

What is magnitude in the context of volcanic eruptions, and how is it calculated?

Answer 31

Magnitude measures the size of an eruption based on a logarithmic index of erupted mass, defined as: Magnitude = log10 (erupted mass in kg) - 7.

Question 32

How is intensity defined in relation to volcanic eruptions?

Answer 32

Intensity measures the eruption rate and is calculated as: Intensity = log10 (mass eruption rate in kg/s) + 3.

Question 33

What is the Volcanic Explosivity Index (VEI)?

Answer 33

The Volcanic Explosivity Index (VEI) is a scale that categorizes eruptions based on their magnitude and intensity, allowing for a comparison of eruption sizes and impacts.

Question 34

What are the two main types of volcanic hazards?

Answer 34

The two main types are direct hazards (events produced during or shortly after an eruption) and indirect hazards (destructive processes incidental to eruptions).

Question 35

What are examples of direct hazards associated with volcanic eruptions?

Answer 35

- Ballistics (ejected lava/rock fragments) - Ash and tephra fall (airborne volcanic material) - Lava flows (molten rock flow) - Pyroclastic falls, flows, and surges (hot volcanic materials) - Gases (volatile compounds released)

Question 36

What are ballistics in the context of volcanic eruptions?

Answer 36

Ballistics are fragments of lava (bombs) or rock (blocks) ejected during explosive eruptions. They can range from a few centimetres to tens of meters in diameter and can travel up to ~10 km from the vent

Question 37

How do ash and tephra fall occur during volcanic eruptions?

Answer 37

Tephra consists of fragments of rock and lava of any size that become airborne during an eruption. Volcanic ash is specifically tephra <2 mm in diameter, carried downwind and falling out of suspension.

Question 38

What are the characteristics of lava flows?

Answer 38

Lava flows are the most common hazard from non-explosive eruptions, typically moving slowly (a few meters to several kilometers per hour). The distance they travel depends on their viscosity, effusion rate, and the surrounding topography.

Question 39

What are pyroclastic flows and how do they differ from pyroclastic surges?

Answer 39

Pyroclastic flows: High particle concentration density currents of hot rock and lava. Pyroclastic surges: Lower particle concentration, moving rapidly with more turbulent flow.

Question 40

What are the dangers associated with lateral blasts during an eruption?

Answer 40

Lateral blasts share characteristics with pyroclastic flows but have an initial low-angle component of explosive energy. They can fan out up to 180°, travel hundreds of kilometers per hour, and are not dependent on topography.

Question 41

What types of gases are released during volcanic eruptions?

Answer 41

Water vapor (H₂O) Sulfur dioxide (SO₂) Hydrogen sulfide (H₂S) Fluoride compounds (HF) Carbon monoxide (CO) and carbon dioxide (CO₂) Metals (e.g., mercury)

Question 42

How do volcanic gases impact the environment and human health?

Answer 42

The effects depend on the amount and type of gas emitted, the height at which they are released, local topography, and meteorological conditions. For example, the 1986 Lake Nyos incident in Cameroon was caused by a sudden release of carbon dioxide from the lake.

Question 43

What are examples of indirect hazards related to volcanic activity?

Answer 43

Lahars and floods (volcanic mudflows) Debris avalanches and landslides Tsunamis (triggered by volcanic eruptions) Earthquakes and ground movement

Question 44

What are debris avalanches, and how do they form?

Answer 44

Debris avalanches are large, mobile flows of rock debris formed during the collapse of volcanic edifices. They can be associated with volcanic eruptions or magmatic intrusions and can cross topographic barriers over 100 m high if they have sufficient momentum.

Question 45

How are volcanogenic tsunamis generated?

Answer 45

Sudden ground deformation Explosions Collapse or subsidence of volcanic edifices Debris avalanches or pyroclastic flows entering water bodies Atmospheric shock waves coupling with the sea

Question 46

What are the four types of volcanic earthquakes?

Answer 46

High-frequency earthquakes Low-frequency earthquakes Explosion earthquakes Volcanic tremors

Question 47

What are some other indirect hazards associated with volcanic eruptions?

Answer 47

Famine: Crop failure and long-term agricultural productivity loss. Epidemic disease: Contamination of water supplies. Drowning: From volcanic tsunamis or floods. Transport accidents: Due to visibility issues and structural damage. Shock and exposure: Leading to cardiac arrests. Breakdown of law and order: Following a disaster.

Question 48

How do volcanogenic tsunamis differ from earthquake-generated tsunamis?

Answer 48

Volcanogenic tsunamis typically have shorter wave periods than earthquake-generated tsunamis and exhibit more rapid dispersion during propagation.

Question 49

What impact can famine have as an indirect hazard from volcanic eruptions?

Answer 49

Famine can result from crop failures and livestock losses, leading to long-term loss of agricultural productivity in affected areas.

Question 50

How can transport accidents occur as an indirect hazard of volcanic eruptions?

Answer 50

Transport accidents can occur due to obscured road markings, traction and visibility problems, signal failures, and structural damage to infrastructure caused by volcanic activity.

Question 51

What is the timeframe for the recorded global historical volcanic fatalities?

Answer 51

Fatalities from volcanic eruptions have been recorded from 1600 to 2010 using data from sources like the Smithsonian Institution and Munich RE.

Question 52

Why is a volcano-by-volcano investigation important for volcanic crisis management?

Answer 52

Each volcano produces multiple hazards that must be recognized and accounted for individually, as there is no 'one size fits all' approach to mitigate their impacts effectively.

Question 53

What is general prediction in volcanic hazard management?

Answer 53

General prediction, also known as hazard mapping and assessment, involves studying a volcano's past behavior to determine the frequency, magnitude, and style of eruptions, as well as to identify high-risk areas.

Question 54

What does specific prediction entail in the context of volcanic eruptions?

Answer 54

Specific prediction involves the surveillance of a volcano and monitoring changes (like seismic activity and ground deformation) to forecast the time, place, and magnitude of an impending eruption.

Question 55

What are the two broad categories of hazard maps?

Answer 55

Background hazard maps: Long-term maps used to communicate potential hazards during periods of volcanic repose. Crisis hazard maps: Temporary maps utilized during specific eruption crises.

Question 56

Why is reliable hazard assessment essential in volcanic crisis management?

Answer 56

Reliable hazard assessment is crucial because it allows for informed decision-making and effective mitigation strategies tailored to the unique risks posed by each volcano.

Question 57

What is the role of monitoring in volcanic prediction?

Answer 57

Monitoring involves tracking changes in seismic activity, ground deformation, thermal characteristics, and gas geochemistry to provide data for predicting volcanic eruptions accurately.

Question 58

How does understanding past volcanic behavior contribute to eruption prediction?

Answer 58

Studying past volcanic behavior helps determine the frequency, magnitude, and damage types of previous eruptions, aiding in the assessment of potential future risks.

Question 59

What are the five predominant types of volcanic hazard maps?

Answer 59

Lava flow hazard maps Ashfall hazard maps Pyroclastic flow hazard maps Lahar hazard maps Volcanic gas hazard maps

Question 60

What are some less common hazard map types not typically included in the main categories?

Answer 60

Nested maps Rapid response maps Scenario maps

Question 61

Who are the primary users of volcanic hazard maps?

Answer 61

Hazard maps are typically produced by scientists and disseminated by local and national emergency managers to various audiences, including the general public, policymakers, and disaster response teams.

Question 62

What is the primary purpose of hazard maps?

Answer 62

The primary purpose of hazard maps is to answer the many questions different users have about volcanic hazards, helping inform decision-making and risk management.

Question 63

How do scientists contribute to the creation of hazard maps?

Answer 63

Scientists conduct research and analysis to assess volcanic hazards, which informs the development of hazard maps that visually represent risks associated with specific volcanic activities.

Question 64

What is the EXPLORIS project, and what does it aim to address?

Answer 64

The EXPLORIS project (Explosive Eruption Risk and Decision Support for EU Populations Threatened by Volcanoes) is an EU-funded research initiative that develops a multi-hazard, multi-vulnerability impact model for European volcanoes.

Question 65

What key components does the EXPLORIS model incorporate?

Answer 65

Hazard scenarios Human and building vulnerabilities Buildings and population exposure

Question 66

How does the EXPLORIS project influence mitigation policies?

Answer 66

The data and insights from the EXPLORIS model feed directly into mitigation policies, helping inform decision-making for volcanic risk management.

Question 67

What limitation does the EXPLORIS model face regarding hazard and vulnerability assessment?

Answer 67

Some aspects of hazards, particularly vulnerabilities, cannot be geo-referenced, posing challenges for comprehensive risk assessment.

Question 68

Why is monitoring environmental changes crucial for volcanic prediction?

Answer 68

Monitoring environmental changes is essential because most eruptions are preceded by these changes, which helps construct reliable forecasting and warning systems.

Question 69

What types of instrumental monitoring are used to assess volcanic activity?

Answer 69

Tracking earthquake activity under a volcano Measuring ground surface deformation Sampling and analyzing emitted gases and water Observing volcanic activity using webcams and thermal imagery Measuring geophysical properties (electrical conductivity, magnetism, or gravity)

Question 70

How can GIS maps be utilized in volcanic risk management during an eruption?

Answer 70

GIS maps developed for hazard assessment can be modified in real-time once an eruption begins, allowing for updated risk communication and decision-making.

Question 71

Why is forecasting important in volcanic activity?

Answer 71

Forecasting is crucial for the effective operation of early warning systems, allowing authorities to predict the onset of an eruption and track its course once it starts.

Question 72

What is a major challenge in volcanic forecasting?

Answer 72

A key challenge is determining whether an episode of unrest will culminate in an eruption, which can be difficult to predict.

Question 73

What are Volcano Observatories (VO)?

Answer 73

Volcano Observatories are institutions or groups that monitor active volcanoes and provide early warnings about future activities to authorities and the public.

Question 74

How many Volcano Observatories are there globally, and how many volcanoes do they monitor?

Answer 74

There are over 100 Volcano Observatories monitoring approximately 1551 active or potentially active volcanoes worldwide.

Question 75

What is the role of the World Organization of Volcano Observatories (WOVO)?

Answer 75

Most Volcano Observatories are members of WOVO, which facilitates cooperation and information sharing among observatories globally.

Question 76

What is one critical role of all Volcano Observatories?

Answer 76

A critical role of all Volcano Observatories is to provide information to Volcanic Ash Advisory Centres (VAACs) to manage the impacts of volcanic ash on aviation and public safety.

Question 77

What methodological challenge do specific predictions face?

Answer 77

A major methodological issue is that if predictions indicate an event (like an earthquake) is likely to occur but do not lead to a clear outcome, it challenges the validity of the predictive methods used.

Question 78

What implication does the uncertainty in predictions have on volcanic forecasting?

Answer 78

If a firm prediction is made and the event does not occur, it suggests the method used for prediction may be invalid, while if it occurs, it does not necessarily confirm the prediction method's accuracy.

Question 79

What is the purpose of hazard and risk mapping in volcanic preparedness?

Answer 79

Hazard and risk mapping involves reconnaissance mapping of hazards and risks at previously unmapped volcanoes to better understand potential threats.

Question 80

Why is volcano surveillance important?

Answer 80

Volcano surveillance, including baseline monitoring and minimum surveillance at dangerous volcanoes, helps ensure affordable procedures and local involvement to enhance safety.

Question 81

What role does public education play in volcanic hazard preparedness?

Answer 81

Improved public education about volcanic hazards is crucial for increasing awareness and preparedness in communities at risk

Question 82

How should scientists engage with public officials regarding volcanic risks?

Answer 82

Scientists should engage in discussions with public officials about emergencies and land-use planning to facilitate informed decision-making and risk management.

Question 83

What was the purpose of the Decade Volcano demonstration projects initiated by the IAVCEI?

Answer 83

The Decade Volcano projects aimed to select about 10 volcanoes for integrated, multinational, and multidisciplinary studies to demonstrate effective mitigation activities.

Question 84

What is IAVNET and how does it support volcanic crisis management?

Answer 84

IAVNET is an electronic mail system that facilitates cooperation and advice among scientists before and during a volcanic eruption

Question 85

Why is the development of reference materials important in volcanic preparedness?

Answer 85

Developing archives on dangerous volcanoes provides valuable resources for research, training, and preparedness efforts.

Question 86

What is the goal of training in volcanic crisis management?

Answer 86

Training aims to equip both new and experienced scientists, civil defense officials, and planners with the knowledge and skills needed for effective disaster response.

Question 87

What is the focus of low-cost equipment development for volcanic monitoring?

Answer 87

The focus is on creating affordable, reliable, and easy-to-repair equipment to support monitoring efforts in developing countries.

Question 88

How does satellite monitoring contribute to volcanic crisis management?

Answer 88

Satellite monitoring collects images of geological features, SO2 plumes, and secures communications during eruptions, enhancing data collection and response coordination.

Question 89

What are some key aspects of crisis assistance during volcanic emergencies?

Answer 89

Key aspects include supplementing local personnel, building local expertise, preparing local scientists for eruptions, and helping national scientists become self-sufficient.

Question 90

How does seed money facilitate local initiatives in volcanic crisis management?

Answer 90

Seed money encourages local initiatives and helps generate finance for community-based preparedness and response efforts

Question 91

Why are publications important in the context of volcanic eruptions?

Answer 91

Publications and the wide dissemination of lessons learned from eruptions help inform future preparedness and response strategies

Question 92

Why is communication crucial in volcanic risk reduction?

Answer 92

Communication is essential for effective volcanic risk reduction, but it is complex due to uncertainties in eruption predictions and the different roles of scientists, emergency managers, regulators, media, authorities, and the public.

Question 93

How can records of past eruptions improve future preparedness?

Answer 93

Historical observations of volcanic activity enhance understanding of eruptions, inform response planning, and help identify hazards and community vulnerabilities.

Question 94

What types of vulnerabilities can affect community resilience to volcanic hazards?

Answer 94

Vulnerabilities include physical, economic, social, behavioral, and environmental factors that influence how communities and assets respond to volcanic risks.

Question 95

What are some potential economic benefits of volcanism?

Answer 95

Benefits include fertile lands, valuable rocks and minerals, harnessed thermal energy for hot water and electricity, chronological markers from past eruptions (tephra layers), and geotourism.

Question 96

Why are volcanic lands sometimes considered fertile?

Answer 96

Volcanic soils are often rich in nutrients, making them highly fertile for agriculture.

Question 97

What role do tephra layers play in understanding volcanic eruptions?

Answer 97

Tephra layers serve as chronological markers in sediments, helping to date past eruptions and understand their frequency and impacts.