🗊 Volcanic Eruptions and Hazards

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Volcanic Eruptions and Hazards
Описание слайда:
Volcanic Eruptions and Hazards

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What is a volcano? A volcano is a vent or 'chimney' that connects molten rock (magma) from within the Earth’s crust to the Earth's surface. The volcano includes the surrounding cone of erupted material.
Описание слайда:
What is a volcano? A volcano is a vent or 'chimney' that connects molten rock (magma) from within the Earth’s crust to the Earth's surface. The volcano includes the surrounding cone of erupted material.

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How and why do volcanoes erupt? Hot, molten rock (magma) is buoyant (has a lower density than the surrounding rocks) and will rise up through the crust to erupt on the surface. Same principle as hot air rising, e.g. how a hot air balloon works When magma reaches the surface it depends on how easily it flows (viscosity) and the amount of gas (H2O, CO2, S) it has in it as to how it erupts. Large amounts of gas and a high viscosity (sticky) magma will form an explosive eruption! Think about shaking a carbonated drink and then releasing the cap. Small amounts of gas and (or) low viscosity (runny) magma will form an effusive eruption Where the magma just trickles out of the volcano (lava flow).
Описание слайда:
How and why do volcanoes erupt? Hot, molten rock (magma) is buoyant (has a lower density than the surrounding rocks) and will rise up through the crust to erupt on the surface. Same principle as hot air rising, e.g. how a hot air balloon works When magma reaches the surface it depends on how easily it flows (viscosity) and the amount of gas (H2O, CO2, S) it has in it as to how it erupts. Large amounts of gas and a high viscosity (sticky) magma will form an explosive eruption! Think about shaking a carbonated drink and then releasing the cap. Small amounts of gas and (or) low viscosity (runny) magma will form an effusive eruption Where the magma just trickles out of the volcano (lava flow).

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Explosive Eruptions Explosive volcanic eruptions can be catastrophic Erupt 10’s-1000’s km3 of magma Send ash clouds >25 km into the stratosphere Have severe environmental and climatic effects Hazardous!!!
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Explosive Eruptions Explosive volcanic eruptions can be catastrophic Erupt 10’s-1000’s km3 of magma Send ash clouds >25 km into the stratosphere Have severe environmental and climatic effects Hazardous!!!

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Explosive Eruptions Three products from an explosive eruption Ash fall Pyroclastic flow Pyroclastic surge
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Explosive Eruptions Three products from an explosive eruption Ash fall Pyroclastic flow Pyroclastic surge

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Volcanic Eruptions and Hazards , слайд №6
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Effusive Eruptions Effusive eruptions are characterised by outpourings of lava on to the ground.
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Effusive Eruptions Effusive eruptions are characterised by outpourings of lava on to the ground.

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Practical Exercise 1. What controls the violence of an eruption? How fast is magma ejected out of the volcano?
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Practical Exercise 1. What controls the violence of an eruption? How fast is magma ejected out of the volcano?

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Volcano Monitoring and Hazard Mitigation
Описание слайда:
Volcano Monitoring and Hazard Mitigation

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92,000 Tambora, Indonesia 1815 92,000 Tambora, Indonesia 1815 36,000 Krakatau, Indonesia 1883 29,000 Mt Pelee, Martinique 1902 15,000 Mt Unzen, Japan 1792
Описание слайда:
92,000 Tambora, Indonesia 1815 92,000 Tambora, Indonesia 1815 36,000 Krakatau, Indonesia 1883 29,000 Mt Pelee, Martinique 1902 15,000 Mt Unzen, Japan 1792

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Volcanic Hazards Pyroclastic flow Lahars/Mud flows Pyroclastic fall Lava flow Noxious Gas Earthquakes
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Volcanic Hazards Pyroclastic flow Lahars/Mud flows Pyroclastic fall Lava flow Noxious Gas Earthquakes

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Pyroclastic Flow For example, eruption of Vesuvius in 79 AD destroyed the city of Pompeii
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Pyroclastic Flow For example, eruption of Vesuvius in 79 AD destroyed the city of Pompeii

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Pompeii (79AD) On August 24, 79AD Mount Vesuvius literally blew its top, erupting tonnes of molten ash, pumice and sulfuric gas miles into the atmosphere. Pyroclastic flows flowed over the city of Pompeii and surrounding areas.
Описание слайда:
Pompeii (79AD) On August 24, 79AD Mount Vesuvius literally blew its top, erupting tonnes of molten ash, pumice and sulfuric gas miles into the atmosphere. Pyroclastic flows flowed over the city of Pompeii and surrounding areas.

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Pompeii (79AD) Pyroclastic flows of poisonous gas and hot volcanic debris engulfed the cities of Pompeii, Herculaneum and Stabiae suffocating the inhabitants and burying the buildings.
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Pompeii (79AD) Pyroclastic flows of poisonous gas and hot volcanic debris engulfed the cities of Pompeii, Herculaneum and Stabiae suffocating the inhabitants and burying the buildings.

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Pompeii (79AD) The cities remained buried and undiscovered for almost 1700 years until excavation began in 1748. These excavations continue today and provide insight into life during the Roman Empire.
Описание слайда:
Pompeii (79AD) The cities remained buried and undiscovered for almost 1700 years until excavation began in 1748. These excavations continue today and provide insight into life during the Roman Empire.

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Vesuvius today Vesuvius remains a hazardous volcano with heavily populated flanks: around 1.5 million people live in the city of Naples alone Naples is situated approx. 30 km from Vesuvius Pyroclastic flows can flow up to 100 km from source!
Описание слайда:
Vesuvius today Vesuvius remains a hazardous volcano with heavily populated flanks: around 1.5 million people live in the city of Naples alone Naples is situated approx. 30 km from Vesuvius Pyroclastic flows can flow up to 100 km from source!

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An eruption of Mt Peleé in 1902 produced a pyroclastic flow that destroyed the city of St. Pierre. An eruption of Mt Peleé in 1902 produced a pyroclastic flow that destroyed the city of St. Pierre.
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An eruption of Mt Peleé in 1902 produced a pyroclastic flow that destroyed the city of St. Pierre. An eruption of Mt Peleé in 1902 produced a pyroclastic flow that destroyed the city of St. Pierre.

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29,000 people died…. Only 2 survived! Why?
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29,000 people died…. Only 2 survived! Why?

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How do pyroclastic flows cause devastation?
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How do pyroclastic flows cause devastation?

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Pyroclastic Flow - direct impact
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Pyroclastic Flow - direct impact

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Pyroclastic Flow - burial
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Pyroclastic Flow - burial

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Pyroclastic Flow - burns
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Pyroclastic Flow - burns

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Pyroclastic Flow - lahars Hot volcanic activity can melt snow and ice Melt water picks up rock and debris Forms fast flowing, high energy torrents Destroys all in its path
Описание слайда:
Pyroclastic Flow - lahars Hot volcanic activity can melt snow and ice Melt water picks up rock and debris Forms fast flowing, high energy torrents Destroys all in its path

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Pyroclastic Fall
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Pyroclastic Fall

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Lava Flow It is not just explosive volcanic activity that can be hazardous. Effusive (lava) activity is also dangerous.
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Lava Flow It is not just explosive volcanic activity that can be hazardous. Effusive (lava) activity is also dangerous.

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Lava Flow - Heimaey, Iceland Iceland, January 23,1973. Large fissure eruption threatened the town of Vestmannaeyjar.
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Lava Flow - Heimaey, Iceland Iceland, January 23,1973. Large fissure eruption threatened the town of Vestmannaeyjar.

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Lava Flow - Heimaey, Iceland The lava flows caught the inhabitants by surprise Before the eruption was over, approximately one-third of the town of Vestmannaeyjer had been destroyed
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Lava Flow - Heimaey, Iceland The lava flows caught the inhabitants by surprise Before the eruption was over, approximately one-third of the town of Vestmannaeyjer had been destroyed

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Lava Flow - Heimaey, Iceland However, the potential damage was reduced by spraying seawater onto the advancing lava flows. This caused them to slow and/or stop, or diverted them away from the undamaged part of the town.
Описание слайда:
Lava Flow - Heimaey, Iceland However, the potential damage was reduced by spraying seawater onto the advancing lava flows. This caused them to slow and/or stop, or diverted them away from the undamaged part of the town.

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Practical Exercise 2. Assessing Volcanic Hazards
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Practical Exercise 2. Assessing Volcanic Hazards

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So…. So…. How do we minimize the risk of active volcanoes?
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So…. So…. How do we minimize the risk of active volcanoes?

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Volcano Monitoring
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Volcano Monitoring

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Volcano Monitoring Seismicity Deformation Gas Output (on volcano and remote sensing techniques)
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Volcano Monitoring Seismicity Deformation Gas Output (on volcano and remote sensing techniques)

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Seismic Activity Earthquake activity commonly precedes an eruption Result of magma pushing up towards the surface Increase volume of material in the volcano shatters the rock This causes earthquakes
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Seismic Activity Earthquake activity commonly precedes an eruption Result of magma pushing up towards the surface Increase volume of material in the volcano shatters the rock This causes earthquakes

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Seismic Activity
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Seismic Activity

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Deformation Monitoring “Tiltmeters” are used to measure the deformation of the volcano The tiltmeters measure changes in slope as small as one part per million. A slope change of one part per million is equivalent to raising the end of a board one kilometer long only one millimeter!
Описание слайда:
Deformation Monitoring “Tiltmeters” are used to measure the deformation of the volcano The tiltmeters measure changes in slope as small as one part per million. A slope change of one part per million is equivalent to raising the end of a board one kilometer long only one millimeter!

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Deformation Monitoring Tilltmeters can tell you when new material enters the magma chamber.
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Deformation Monitoring Tilltmeters can tell you when new material enters the magma chamber.

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Gas Monitoring Commonly gas output from a volcano increases or changes composition before an eruption. As magma rises to the surface it releases (exsolves) much of its gas content. This can be measured
Описание слайда:
Gas Monitoring Commonly gas output from a volcano increases or changes composition before an eruption. As magma rises to the surface it releases (exsolves) much of its gas content. This can be measured

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Gas Monitoring Gas samples are collected from fumaroles and active vents. Gas levels may also be monitored by remote sensing techniques
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Gas Monitoring Gas samples are collected from fumaroles and active vents. Gas levels may also be monitored by remote sensing techniques

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In Summary.. Volcanoes are extremely hazardous. However, the volcano can be studied, monitored and understood. Each volcano is different, and offers a unique set of dangers Plans may be emplaced to help control potential damage.
Описание слайда:
In Summary.. Volcanoes are extremely hazardous. However, the volcano can be studied, monitored and understood. Each volcano is different, and offers a unique set of dangers Plans may be emplaced to help control potential damage.

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Post-lecture Question: What should geologists do about volcanic eruptions in the future?
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Post-lecture Question: What should geologists do about volcanic eruptions in the future?

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Additional (Optional) Material
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Additional (Optional) Material

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Are there other volcano related hazards?
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Are there other volcano related hazards?

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Noxious Gas 1,700 people living in the valley below Lake Nyos in northwestern Cameroon mysteriously died on the evening of August 26, 1986.
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Noxious Gas 1,700 people living in the valley below Lake Nyos in northwestern Cameroon mysteriously died on the evening of August 26, 1986.

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Noxious Gas Lake Nyos is a crater lake inside a dormant volcano. The lake had become laden with carbon dioxide gas. This gas had suddenly bubbled out of the lake and asphyxiated nearly every living being in the surrounding valley.
Описание слайда:
Noxious Gas Lake Nyos is a crater lake inside a dormant volcano. The lake had become laden with carbon dioxide gas. This gas had suddenly bubbled out of the lake and asphyxiated nearly every living being in the surrounding valley.

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Noxious Gas A management plan has been developed to remove gas from the lake to prevent a further tragedy. An artificial vent to the lake surface was created with pipe. Water is pumped from the bottom of the lake to the surface through the pipe, where it can degas.
Описание слайда:
Noxious Gas A management plan has been developed to remove gas from the lake to prevent a further tragedy. An artificial vent to the lake surface was created with pipe. Water is pumped from the bottom of the lake to the surface through the pipe, where it can degas.

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Noxious Gas
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Noxious Gas

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Noxious Gas
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Noxious Gas

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Noxious Gas The Lake Nyos incident was not unique. Two years earlier, Lake Monoun, 60 miles to the southeast, released a heavy cloud of toxic gas, killing 37 people. A third lake, Lake Kivu, on the Congo-Rwanda border in Central Africa, is also known to act as a reservoir of carbon dioxide and methane, which is a valuable natural gas that is gathered from the lake and used locally.
Описание слайда:
Noxious Gas The Lake Nyos incident was not unique. Two years earlier, Lake Monoun, 60 miles to the southeast, released a heavy cloud of toxic gas, killing 37 people. A third lake, Lake Kivu, on the Congo-Rwanda border in Central Africa, is also known to act as a reservoir of carbon dioxide and methane, which is a valuable natural gas that is gathered from the lake and used locally.

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Earthquakes Large volumes of magma moving through the shallow crust can cause large earthquakes. This can lead to building collapse, slope failure and avalanches
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Earthquakes Large volumes of magma moving through the shallow crust can cause large earthquakes. This can lead to building collapse, slope failure and avalanches

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Earthquakes
Описание слайда:
Earthquakes

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