1
Q
Main Topics
A
- Internal Structure of the Earth
- Continental Drift Theory
- Theory of Plate Tectonics & Types of Plate Movement - Convergent, Divergent, Transform
- Volcanoes - Formation, Types, Impacts, Mitigation
2
Q
Internal Structure of the Earth
Layers of the Earth
4
A
Layer
Est. Temperature
Depth / Thickness
Material
Crust
* Temperature dependent on weather & climate of the atmosphere above it
* About 70km thick
* Solid rocks & soil forming landforms
Mantle
* 800 - 3000 °C
* About 2900km thick
* Semi-molten rock called Magma
Outer Core
* 5000 °C
* About 2200km thick
* Liquid Iron
* Nickel
Inner Core
* 6000 °C
* About 1250km thick
* Solid Iron Sphere
* Radioactive Materials (e.g. Uranium)
3
Q
Internal Structure of the Earth
Layers of the Earth
Crust
Est. Temperature
Depth / Thickness
Material
A
Crust
* Temperature dependent on weather & climate of the atmosphere above it
* About 70km thick
* Solid rocks & soil forming landforms
4
Q
Internal Structure of the Earth
Layers of the Earth
Mantle
Est. Temperature
Depth / Thickness
Material
A
Mantle
* 800 - 3000 °C
* About 2900km thick
* Semi-molten rock called Magma
5
Q
Internal Structure of the Earth
Layers of the Earth
Outer Core
Est. Temperature
Depth / Thickness
Material
A
Outer Core
* 5000 °C
* About 2200km thick
* Liquid Iron
* Nickel
6
Q
Internal Structure of the Earth
Layers of the Earth
Inner Core
Est. Temperature
Depth / Thickness
Material
A
Inner Core
* 6000 °C
* About 1250km thick
* Solid Iron Sphere
* Radioactive Materials (e.g. Uranium)
7
Q
The Earth’s crust & Lithosphere (5-7pts)
A
- The crust, which is the most outermost layer of the earth, is broken into tectonic plates that move in relation to one another.
- These tectonic plates are part of the Lithosphere, which includes the crust and the uppermost mantle.
- Tectonic plates can be made up of either oceanic crust, continental crust or a combination of both.
- Oceanic crust is found beneath deep oceans and are denser than continental crust, which are located beneath the earth’s continental land masses and under the shallow seas close to continents.
- Oceanic crusts are denser than continental crust as they consist mainly of basalt, a heavy and dense rock formed from magma which has cooled quickly.
- Continental crust consists of lighter rocks, including granite, which age range widely from very recently formed to nearly 4 billion years old.
- The asthenosphere is the denser, weaker layer beneath the lithospheric mantle.
8
Q
Plate Tectonics Theory
2pt
A
Plate Tectonics Theory
* The Plate Tectonics theory states that the Earth is in constant motion.
* Convection currents in the mantle drives the movement of plates.
* Plate movements creates major landscape and landforms such as volcanoes, fold mountains and many more.
* Plate movements also cause earthquakes.
9
Q
Movement of Tectonic Plates
2pt
A
- The movement of the earth’s crustal plates is believed to be due to convection currents which occur in the mantle.
- Convection currents are created by heat from the earth’s core - much of which is generated by radioactive decay in the core.
10
Q
Movement of Tectonic Plates
How & Why Plates Move:
8 steps
A
- When radioactive materials break down in the core, heat is released.
- Convection currents are movements of heat within the mantle. Material in the mantle is heated by the core, causing the mantle material to expand, rise and spread out beneath the plates.
- This causes the plates to be dragged along and to move away from each other.
- Then, the hot mantle material cools slightly and sinks, pulling the plates along.
- The sinking mantle material heats up again as it nears the core - the whole process repeats.
- Slab-pull force occurs when a denser oceanic plate is forced beneath a less dense continental plate or oceanic plate in a process called subduction. This is thought to be the main driving mechanism for plate movement.
- As the plate subducts, it pulls the rest of the plate along. The subducting or sinking plate drives the downward moving portion of convection currents.
- The mantle material which is found away from where the plates subduct drives the rising portion of convection currents.
11
Q
Movement of Tectonic Plates
What is slab-pull force?
A
- Slab-pull force is a geophysical mechanism whereby the cooling and subsequent densifying of a subducting tectonic plate produces a downward force along the rest of the plate. The denser plate sinks back into the mantle and pulls the rest of the plate along.
12
Q
Distribution of Volcanoes, oceanic trenches and earthquakes (read through ig)
A
- Volcanoes (red) are found along the plate boundaries.
- Some volcanoes can be located in the middle of the plate, away from the boundaries (e.g. Hawaiian Islands)
- Oceanic trenches (yellow) are also found along the plate boundaries and near the volcanoes.
- They are also found in the Pacific Ring of Fire, along the boundary of the Pacific Plate, Indo-Australian Plate, the Philippine Plate and the Nazca Plate.
- Ocean trenches are long, narrow depressions on the seafloor. These chasms are the deepest parts of the ocean—and some of the deepest natural spots on Earth.
- Volcanoes, oceanic trenches and earthquakes are found along plate boundaries, such as at the Pacific Ring of Fire.
- Volcanoes and earthquakes can occur at locations in the middle of the plate (but not oceanic trenches).
- Plate movements that take place along these boundaries cause the formation of volcanoes and oceanic trenches, and the occurrence of earthquakes.
- There are different types of plate movements responsible for the formation of the different features.
13
Q
Types of Plate Movement
3 types, 3 1 1
A
Types of Plate Movement
1. Convergent Plate Movement (Destructive Plate Boundary)
i. Continental – Continental Convergence (C-C Convergence)
ii. Oceanic – Oceanic Convergence (O-O Convergence)
iii. Oceanic-Continental Convergence (O-C Convergence)
- Divergent Plate Movement (Constructive Plate Boundary)
i. Oceanic - Oceanic Divergence (O-O Divergence) - Transform Plate Movement (Conservative Plate Boundary)
i. 2 plates sliding past each other
14
Q
- Convergent Plate Movement
how many?
A
- Convergent Plate Movement
* Convergent Plate Movement (Destructive Plate Boundary) - Continental – Continental Convergence (C-C Convergence)
- Oceanic – Oceanic Convergence (O-O Convergence)
- Oceanic-Continental Convergence (O-C Convergence)
- Continental = form fold mountains, Oceanic = form volcanoes
15
Q
Continental-Continental Convergence (C-C Convergence) (6pt)
A
- Continental-continental convergent boundaries pit large slabs of crust against each other.
- Due to lower density, both of the continental crustal plates are too light and buoyant to be subducted.
- In most cases, neither plate subducts.
- Instead, the continental crust at these convergent boundaries gets folded, faulted, and thickened, forming great mountain chains of uplifted rock. (fold mountains)
- Little volcanic activity occurs because rocks from the crust do not sink deep into the mantle.
- Earthquakes, faulting & folding are common.
- The Himalayas and the Tibetan Plateau, the result of 50 million years of collision between the Indian and Eurasian plates, are the most spectacular manifestation of this type of boundary.
16
Q
Oceanic-Oceanic Convergence (O-O Convergence) (4pt)
A
Oceanic-Oceanic Convergence (O-O Convergence)
* Tip of the subducting oceanic plate melts due to friction with the overriding oceanic plate, and heat at great depth, producing silica-rich magma (silicon dioxide)
* Magma moves up any breaks or fractures on the overriding oceanic plate to form a magma chamber, as it is less dense than the asthenosphere and as gases in the magma expands.
* The built-up of pressure in the magma chamber forces magma to escape through the vents on the oceanic crust as lava. Lava cools and solidifies around the vent. Overtime, through repeated eruptions, it accumulates/builds up to form a submarine volcano at or near the subduction zone.
* When the volcano builds up and rise above sea level, it forms a volcanic island or a chain of volcanoes known as a volcanic island arc.
17
Q
Oceanic-Continental Convergence (O-c Convergence) (7pt)
A
- When a thinner and denser oceanic plate converges with a thicker and lighter continental plate, the oceanic plate descends beneath the latter due to ‘slab-pull’ force into the asthenosphere.
- A long, narrow and deep oceanic trench is formed where the oceanic plate dips into the asthenosphere.
- The movement of the subducting plate is not smooth, producing vibrations called earthquakes along the subduction zone.
- Tip of the subducting oceanic plate melts due to friction with the overriding continental plate, and heat at great depth, producing silica-rich magma.
- Magma moves up any breaks or fractures on the overriding continental plate to form a magma chamber, as it is less dense than the asthenosphere and as gases in the magma expands.
- The built-up of pressure in the magma chamber forces magma to escape through the vent on the land surface as lava. Lava cools and solidifies around the vent. Overtime, through repeated eruptions, it accumulates/builds up to form a volcano.
- Edges of continental plate, and sediments near the edges of continental shelf and on the seafloor are contorted and folded to form fold mountains.
18
Q
- Divergent Plate Movement
how many?
A
- Divergent Plate Movement
* Divergent Plate Movement (Constructive Plate Boundary) - Oceanic - Oceanic Divergence (O-O Divergence)
19
Q
Oceanic-Oceanic Divergence (O-O Divergence) (5pt 2 subpt)
A
- When two oceanic plates move away from each other, the rising convection current below lifts the lithosphere producing a mid-ocean ridge, rows of submarine mountains.
- The ridge is a high area compared to the surrounding seafloor because of the lift from the convection current below.
- Tensional forces stretch the lithosphere and produce a deep fissure forming the spreading centre.
- A fissure is a long, narrow crack opening along the surface of Earth.
- When the fissure opens, pressure is reduced on the super-heated mantle material below. It responds by melting and the new basaltic magma flows into the fissure. The magma then cools and solidifies to form new seafloor. This process is called seafloor spreading.
- Being less dense than the surrounding older rocks, the new sea floor rises in elevation, resulting in gravitational sliding that pushes the older rocks away from the spreading center. This is known as the ‘ridge push’ force.
- Shallow earthquakes are often associated with this crustal stretching. Basaltic magma from the asthenosphere wells up along any crustal fractures to form submarine/undersea volcanoes. Some of these volcanoes rise above sea level to form volcanic islands.
20
Q
- Transform Plate Movement
how many?
A
- Transform Plate Movement
* Transform Plate Movement (Conservative Plate Boundary) - 2 plates sliding past each other
21
Q
- Transform Plate Movement (Conservative Plate Boundary)
1. 2 plates sliding past each other
A
2 plates sliding past one another at conservative plate boundary
* They occur when 2 plates slide past each other.
* Great amount of stress built up in these areas, but there is little volcanic activity & little crustal material is destroyed
- Eg : the San Andreas Fault in California, USA
* Plates slide past each other along transform faults (could be opposite directions / same direction but one moving faster than the other)
* Causes fault line & earthquakes
22
Q
Volcanoes (3pt)
A
- A volcanic cone is a triangle-shaped hill formed as material from volcanic eruptions piles up around the volcanic vent, or opening in Earth’s crust.
- A landform produced by magma merging via an opening in the crust is lava flow
- Lava cools and solidifies to form a layer of volcanic material
- With each eruption, layer upon layer of cooled rock built up to form a volcano.
23
Q
Craters & Calderas (5pt)
A
- Craters are formed by the outward explosion of rocks and other materials from a volcano.
- Calderas are formed by the inward collapse of a volcano.
- Craters are usually more circular than calderas. (Calderas may have parts of their sides missing because land collapses unevenly.)
- Craters are also usually much smaller than calderas, only extending to a maximum of one kilometer (less than a mile) in diameter
- Crater or caldera eventually filled with water → crater lake
24
Q
Diff. b/w craters and calderas? (2)
A
- Craters are usually more circular than calderas. (Calderas may have parts of their sides missing because land collapses unevenly.)
- Craters are also usually much smaller than calderas, only extending to a maximum of one kilometer (less than a mile) in diameter
25
how is a crater formed
Craters are formed by the outward explosion of rocks and other materials from a volcano.
26
how is a caldera formed
* Calderas are formed by the inward collapse of a volcano.
27
Structure of a Volcano
Part
Definition
Magma Chamber
Reservoir of molten rock within or beneath the Earth’s crust
Pipe / Conduit
Passage in a volcano through which magma and volcanic gases rise towards the surface
Secondary Cone
Smaller cones that build up on the sides of a volcano
Vent
Any opening at the Earth’s surface through which magma erupts or volcanic gases are emitted
Crater
Bowl-shaped depression produced by impact of volcanic activity on summit of volcano
28
Structure of a Volcano
Magma Chamber
Magma Chamber
Reservoir of molten rock within or beneath the Earth’s crust
29
Structure of a Volcano
Pipe/Conduit
Pipe / Conduit
Passage in a volcano through which magma and volcanic gases rise towards the surface
30
Structure of a Volcano
Secondary Cone
Secondary Cone
Smaller cones that build up on the sides of a volcano
31
Structure of a Volcano
Vent
Vent
Any opening at the Earth’s surface through which magma erupts or volcanic gases are emitted
32
Structure of a Volcano
Crater
Crater
Bowl-shaped depression produced by impact of volcanic activity on summit of volcano
33
Formation of a Volcano
Step
Description
1
Millions of years ago, magma forced its way between two plate tectonic boundaries
2
The lava cooled and turned into rock. Many years later magma forced its way up again
3
The process repeated over and over again. The cooled lava formed layers of rock.
4
In between, the volcano spewed out ash and steam. The ash settled on the volcano and cemented into rock.
5
Over millions of years, the layers built up to form a volcano.
34
Classification of Volcanoes (3)
* Active: erupts frequently and in recent times
* Dormant: not erupted for quite some time but is not considered extinct
* Extinct: has not erupted in historic times; solidification sealed off vent and volcanic shape may disappear
35
Types of Volcanoes (5PT)
* Viscosity - resistance to flow. Magma with lower viscosity flows easily. Explosive eruptions typical of magmas which have high viscosities.
* Pyroclastic flow – hot mixture of rock fragments, gas, ash that travels rapidly. Dense fast-moving flow of solidified lava pieces, volcanic ash & hot gas
* Acid lava is high in silica which prevents gases escaping; is very explosive; found at convergent (destructive) plate margins (O-O or O-C convergent)
* Basic lava is low in silica; lava flows freely; found at divergent (constructive) plate margins. Gentle lava eruptions. (O-O Divergent)
* There are 3 types of volcanoes: Acid lava volcanoes (enrichment), Stratovolcanoes/Composite volcanoes and Shield volcanoes
36
What is viscosity?
* Viscosity - resistance to flow. Magma with lower viscosity flows easily. Explosive eruptions typical of magmas which have high viscosities.
37
What is pyroclastic flow?
* Pyroclastic flow – hot mixture of rock fragments, gas, ash that travels rapidly. Dense fast-moving flow of solidified lava pieces, volcanic ash & hot gas
- A pyroclastic flow is a fast-moving current of hot gas and volcanic matter (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph). The gases can reach temperatures of about 1,000 C (1,830 F).
38
Stratovolcanoes / Composite Volcano
Characteristics of Volcano
* concave (steep towards top, gentler at base)
* cone-shaped
* alternate layers of acid lava and ash & cinder
39
Stratovolcanoes / Composite Volcano
Characteristics of Lava
* viscous
* acidic
* flows slowly
* presence of ash & cinder
40
Stratovolcanoes / Composite Volcano
Characteristics of Eruptions
* violent
* lava may escape through secondary cones
41
Shield Volcano
Characteristics of Volcano
* broad-based
* cone-shaped
* gentle slopes
42
Shield Volcano
Characteristics of Lava
* frequent but quiet & gentle eruptions
* explosions are less powerful due to easier release of gases from basic lava
43
Shield Volcano
Characteristics of Eruptions
* fluid
* basic
* flows faster than acid lava
* cools & solidifies slowly
44
Shield Volcanoes & Stratovolcanoes - how are they similar (shape, formation and location - 3pt)
In terms of shape, they are both cone-shaped.
In terms of formation, they are both formed when magma rises and erupts as lava on the surface of the earth’s crust, cools and solidifies.
In terms of location, they are formed along plate boundaries.
45
Shield Volcanoes & Stratovolcanoes
diff b/w Type of Lava
Shield Volcanoes
* Basic Lava
- Low silica content
- Fluid/Less viscous, can travel long distance
- Cools slowly
- Usually Higher temperature
Stratovolcanoes
* Acidic Lava
- High silica content
- Viscous, flows more slowly
- Cools faster, solidifies quickly
- Usually Lower temperature
46
Shield Volcanoes & Stratovolcanoes
diff b/w Type of Eruption
Shield Volcanoes
* Quiet eruptions
- Gas and steam escape more easily, does not trap gas
Stratovolcanoes
* Violent eruptions
- Gas and steam are trapped and do not escape easily, resulting in explosive eruptions
47
Shield Volcanoes & Stratovolcanoes
diff b/w shape
Shield Volcanoes
* Broad summit
* Broad-based
* Gently sloping sides
Stratovolcanoes
* High/Tall volcano
* Concave profile (steep towards top, gentler at base)
* Steeply sloping sides
48
Shield Volcanoes & Stratovolcanoes
diff b/w composition
Shield Volcanoes
* Built almost entirely of fluid lava flows
Stratovolcanoes
* Alternate layers of lava, ash and other volcanic material
49
Shield Volcanoes & Stratovolcanoes
diff b/w location
Shield Volcanoes
* Common near Divergent plate boundaries and at hotspots
Stratovolcanoes
* Common near Convergent plate boundaries (when subduction takes place)
50
Impacts of Volcanic Eruptions
What is vulcanicity?
* Vulcanicity is the process through which molten rocks (magma) are intruded within the Earth’s crust or extruded onto the Earth’s surface.
* A volcanic event can have a range of impacts, affecting the area immediately around the volcano or the entire planet. Effects can be categorized into primary and secondary.
51
Impacts of Volcanic Eruptions
Primary Effects (4)
1. Tephra
- Solid material of varying grain size, from volcanic bombs to ash particles, ejected into the atmosphere
2. Pyroclastic flows
- A pyroclastic flow is a fast-moving current of hot gas and volcanic matter (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph). The gases can reach temperatures of about 1,000 C (1,830 F).
- Very hot (800 °C) , gas-charged, high-velocity flows made up of a mixture of gases and tephra
3. Lava flows
4. Volcanic gases
- Including carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine
52
Impacts of Volcanic Eruptions
Secondary Effects (5)
* Secondary effects consist of:
1. Lahars
- Volcanic mud flows
2. Flooding
- Melting of glaciers and ice caps
3. Tsunamis
- Giant sea waves generated after violent caldera-forming events
4. Volcanic landslides
5. Climate change
- The ejection of vast amounts of volcanic debris into the atmosphere can reduce global temperatures and is believed to have been an agent in past climatic change
53
Benefits of Vulcanicity (4)
* formation of soil
* precious stones and minerals
* tourism
* geothermal energy
54
Why do people still live near volcanoes?
Economic Reasons
Fertile Soil for Agriculture
* The lava that has weathered down to form soils and ash that has settled on the ground are rich in nutrients to aid plant growth.
* People have a livelihood by earning an income through the sale of crops
* As food is grown, this provides access to food and food security
Mining for Resources
* Working as sulphur miners is employment for people to earn income
* Sulphur is sold for revenue. Some industrial uses of sulphur include making fertilisers, disinfectant and black gun powder (for fireworks).
Tourism Revenue
* The tourism industry makes use of the scenic beauty and attractions provided by the volcanic landscape, such as the volcano itself and its hot springs.
* People can be employed as hotel employees and tour guides, or earn a livelihood by running businesses such as cafes near these attractions.
* Hot springs or onsens in Japanese, are tourist attractions, where people visit to have a bath. Hot spring operators earn revenue from providing this service. Hotels are booked based on the quality of their hot springs.
* Taking a hike, a hot spring bath and watching the scenery of the volcanic region are recreational activities that people enjoy doing.
Geothermal Energy
* Geothermal energy is heat within the earth. Geothermal energy is a renewable energy source because heat is continuously produced inside the earth. People use geothermal heat for bathing, to heat buildings, and to generate electricity.
* This generation of electricity is necessary for industrial and commercial development, as electricity is needed to drive machinery and equipment; as well as the use of electrical appliances, for heating in winter and cooling in summer in homes for domestic consumption.
Unwillingness to Relocate (Poverty – no means to relocate)
* Key factors explaining why people live in these dangerous situations are attachment to place and the protection of their livelihoods as well as a capacity to adapt to natural hazards and the reduced perception of risk that involves.
* One of the reasons is that some people simply do not have the financial resources to move.
Cultural Rootedness
Sense of Belonging
* Cultural/Spiritual Attachment/Rootedness
* E.g. Mount Merapi eruption
55
Why do people still live near volcanoes?
Economic Reasons
Fertile Soil for Agriculture
Fertile Soil for Agriculture
* The lava that has weathered down to form soils and ash that has settled on the ground are rich in nutrients to aid plant growth.
* People have a livelihood by earning an income through the sale of crops
* As food is grown, this provides access to food and food security
56
Why do people still live near volcanoes?
Economic Reasons
Mining for Resources
Mining for Resources
* Working as sulphur miners is employment for people to earn income
* Sulphur is sold for revenue. Some industrial uses of sulphur include making fertilisers, disinfectant and black gun powder (for fireworks).
57
Why do people still live near volcanoes?
Economic Reasons
Tourism Revenue
Tourism Revenue
* The tourism industry makes use of the scenic beauty and attractions provided by the volcanic landscape, such as the volcano itself and its hot springs.
* People can be employed as hotel employees and tour guides, or earn a livelihood by running businesses such as cafes near these attractions.
* Hot springs or onsens in Japanese, are tourist attractions, where people visit to have a bath. Hot spring operators earn revenue from providing this service. Hotels are booked based on the quality of their hot springs.
* Taking a hike, a hot spring bath and watching the scenery of the volcanic region are recreational activities that people enjoy doing.
58
Why do people still live near volcanoes?
Economic Reasons
Geothermal Energy
Geothermal Energy
* Geothermal energy is heat within the earth. Geothermal energy is a renewable energy source because heat is continuously produced inside the earth. People use geothermal heat for bathing, to heat buildings, and to generate electricity.
* This generation of electricity is necessary for industrial and commercial development, as electricity is needed to drive machinery and equipment; as well as the use of electrical appliances, for heating in winter and cooling in summer in homes for domestic consumption.
59
Why do people still live near volcanoes?
Economic Reasons
Unwillingness to Relocate (Poverty – no means to relocate)
Cultural Rootedness
Sense of Belonging
Unwillingness to Relocate (Poverty – no means to relocate)
* Key factors explaining why people live in these dangerous situations are attachment to place and the protection of their livelihoods as well as a capacity to adapt to natural hazards and the reduced perception of risk that involves.
* One of the reasons is that some people simply do not have the financial resources to move.
Cultural Rootedness
Sense of Belonging
* Cultural/Spiritual Attachment/Rootedness
* E.g. Mount Merapi eruption
60
Reducing Volcanic Threats: Predict, Prevent, Prepare
Prediction
* While volcanic eruptions are unpredictable, scientists can monitor volcanoes to try and estimate when they are likely to erupt. Additionally, most volcanoes provide warnings before an eruption.
* Magmatic eruptions involve the rise of magma toward the surface, which normally generates detectable earthquakes. It can also deform the ground surface and cause anomalous heat flow or changes in the temperature and chemistry of the groundwater and spring waters.
* Scientists can use a variety of techniques to monitor and predict. If threat is imminent, they can issue timely warnings of an impending blow, through use of sirens and media broadcasts, to evacuate people from dangerous places around the volcano.
* But even then, like weather forecasting, experts can only offer probabilities that an event will occur, they can never be sure how severe a predicted eruption will be or, whether it will even erupt at all.
* seismometers - used to measure earthquakes occurring near an eruption tiltmeters and global positioning systems (GPS) satellites - these devices monitor any changes in landscape, eg volcanoes tend to swell near an eruption
* thermal imaging - this allows a camera to monitor heat sources within the crust or volcano, it may help predict the onset of an eruption
* infrared camera imagery - these images can potentially show the magma chamber and any build-up of hot gases, steam or lava
* monitoring gases escaping from a volcano using robots called spiders - often there is an increased release of sulphur dioxide near an eruption as the magma gets closer to the surface
* measuring temperature - volcanoes become hotter when magma starts to rise through the main vent
* looking at previous eruptions - scientists can identify patterns of activity
* observations of noticeable precursors to an eruption - increase in the frequency and intensity of felt earthquakes, Subtle swelling of the ground surface
* Precursors can continue for weeks, months, or even years before eruptive activity begins, or they can subside at any time and not be followed by an eruption.
61
Reducing Volcanic Threats: Predict, Prevent, Prepare
Prediction
what are some ways to predict volcanic eruptions? (8)
* seismometers - used to measure earthquakes occurring near an eruption tiltmeters and global positioning systems (GPS) satellites - these devices monitor any changes in landscape, eg volcanoes tend to swell near an eruption
* thermal imaging - this allows a camera to monitor heat sources within the crust or volcano, it may help predict the onset of an eruption
* infrared camera imagery - these images can potentially show the magma chamber and any build-up of hot gases, steam or lava
* monitoring gases escaping from a volcano using robots called spiders - often there is an increased release of sulphur dioxide near an eruption as the magma gets closer to the surface
* measuring temperature - volcanoes become hotter when magma starts to rise through the main vent
* looking at previous eruptions - scientists can identify patterns of activity
* observations of noticeable precursors to an eruption - increase in the frequency and intensity of felt earthquakes, Subtle swelling of the ground surface
62
Reducing Volcanic Threats: Predict, Prevent, Prepare
Prevention
3pt
Prevention
* Removing the people most at risk from tectonic hazards is vital in reducing vulnerability.
* Hazard mapping allows local areas to limit access to the danger zones and prevent buildings near to potential hazards from being built.
* Exclusion zones can also be created, where no-one is allowed in them before, during or after an event. In essence, hazard mapping can be used to restrict development and make people aware of the risks in living in certain areas. People can understand the danger zones and safe areas in the event of an eruption.
63
Reducing Volcanic Threats: Predict, Prevent, Prepare
Preparedness
* Governments and organisations can help reduce the vulnerability by actively trying to enhance people's preparedness, and capacity to cope with the volcanic hazards. It is crucial for them to reduce inequality and poverty in countries, thereby tackling the root cause of vulnerability. Everyone, regardless of wealth, should have the same status and right to protection.
64
Reducing Volcanic Threats: Predict, Prevent, Prepare
Preparedness
Building codes stipulating appropriate roof construction
3pt
* The effects of ash loads on buildings vary greatly depending of their design and construction, including roof slope, construction materials, roof span and support system, and age and maintenance of the building. In general, flat roofs are more susceptible to damage and collapse than steeply pitched roofs, and roofs made of smooth materials like sheet metal and glass are more likely to shed volcanic ash than roofs made of rough materials like thatch and asphalt or wood shingles.
* Buildings designed to withstand a heavy load of winter snow will clearly support thicker accumulations of ash than buildings not engineered for any type of load or shear stress.
* Avoid obstructions on roofs such as chimneys, parapets, roof tanks or solar panels. These may lead to a greater accumulation of ash next to these features if the ash is drifting with the wind.
65
Reducing Volcanic Threats: Predict, Prevent, Prepare
Preparedness
Education
4pt
Education
* Educating people about what to do, and having regular drills, are helpful in building capacity to cope. This reduces levels of panic and irrational behaviour during an event.
* Conducting drills in all public buildings so that people know what to do, so as to reduce the impact and increases people's chance of survival.
* Educate on evacuation route and the different types of volcanic hazards
* Packing an emergency kit in each household: keep goggles and a mask in an emergency kit, along with a flashlight and a working, battery-operated radio. Advisable not to wear contacts.
66
Reducing Volcanic Threats: Predict, Prevent, Prepare
Preparedness
Redistribution of losses
3pt
Redistribution of losses
* to make losses tolerable by spreading losses over a wider group of stakeholders & tax payers (e.g. public relief, subsidized insurance schemes)
* subsidized insurance for poor farmers, and poor communities living in remote areas of close proximity to an active or dormant volcano
67
Reducing Volcanic Threats: Predict, Prevent, Prepare
Preparedness
Responses
2pt
Responses are how countries react to a natural hazard. They are categorised as follows:
* Short-term or immediate response - in the hours, days and weeks immediately after a disaster, it mainly involves search and rescue efforts and helping the injured. Planned for evacuation routes, provision of emergency shelters and necessary aids
* Long-term response - continues for months and years after a disaster and can involve rebuilding damaged or destroyed houses, schools, hospitals, etc. Kick-starting the local economy is also considered a long-term response.
geography
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