Tectonics - Topic 2 Flashcards
Earthquakes & Volcanoes (100 cards)
1
Q
What is lava?
A
Molten rocks that have erupted onto Earth’s surface; it is called magma when found below the Earth’s surface
2
Q
How are earthquakes measured?
A
Earthquakes are measured using seismometers
The greater the seismic energy released during an earthquake, the greater the magnitude
Scientists use the following scales to rate the magnitudes of earthquakes
1. Richter Scale (ML)
2. Moment Magnitude Scale (Mw)
3
Q
What’s a seismometer?
A
- Seismometers are sensitive instruments that detect ground vibrations and determine the magnitude of an earthquake
3
Q
What is the Richter Scale (ML) ?
A
- The Richter Scale caluclates earthquake magnitude using the height of the largest wave recorded on seismometers
- Thus, earthquake magnitude is measured based on the maximum seismic intensity reached, rather than the total seismic energy released throughout the earthquake
- The scale is numbered from 1 to 10, with 10 being the greatest magnitude
- Scale is logarithmic – an earthquake of magnitude 6 releases about 32 times more energy than a magnitude 5 earthquake
4
Q
What is the limitation of the Richter Scale (ML) ?
A
The Richter Scale would rate an earthquake with a single drastic spike in wave energy as having a higher magnitude than a long earthquake with many large, intense waves:
- This underestimates longer earthquakes which release more overall energy by rating them as having lower magnitudes even though they are likely to do more damage
- Hence, the Richter Scale is no longer commonly used, except for small, local earthquakes
5
Q
What is the Moment Magnitude Scale (Mw)?
A
- The Mw scale rates earthquake magnitude based on the total energy released during the earthquake
- It estimates the total energy released during an earthquake instead of just the largest wave like the Richter Scale.
- Hence, it is generally more accurate, especially in measuring earthquakes of magnitude 8 and above.
- Scientists have adjusted the magnitudes of past earthquakes which were intially measured using the Richter Scale
- Like the Richter Scale, the Mw is also logarthmic - an earthquake of magnitude 6 releases about 32 times more energy than a magnitude 5 earthquake.
6
Q
Give me an example of an earthquakes’ magnitudes adjusted from the Richter Scale to the Moment Magnitude Scale
A
The Prince William Sound Earthquake in Alaska, USA, in 1964. was intially rated 8.6 on the Richter Scale, but was later adjustred to 9.2 based on the Mw scale.
7
Q
How do tectonic processes result in volcanic eruptions?
A
- A volcano is a landform created when lava erupts onto the Earth’s surface.
- It may form a cone-shaped mountain as more lava erupts and accumulates over time
8
Q
Where do volcanic eruptions occur at?
A
- Divergent plate boundaries
- Convergent plate boundaries
9
Q
What is a crater?
A
- Bowl-shaped depression at the top of the volcano
9
Q
Explain how volcanic eruptions happen at divergent plate boundaries
A
- Plates move apart, the crust stretches and fractures develop
- The decreas in overlying pressure casuses parts of the underlying mantle to melt, forming magma
- Magma contains dissolved gases and is less dense than the surrounding materials
- Therefore, magma rises through weak areas in the crust to the Earth’s surface to erupt as lava, causing a volcanic eruption
- The lava cools, solidifies and accumulates over time, forming a volcano
10
Q
Explain how volcanic eruptions happen at convergent plate boundaries
A
- Plates move towards each other and the denser plate subducts under the other
- As the subducting plate sinks into the mantle, the high pressure forces water out of it s oceanic crust. Water lowers the melting point of the overlying mantle, causing it to melt, forming magma
- Magma contains dissolved gases and is less dense than the surrounding materials
- Therefore, magma rises through weak areas in the crust to the Earth’s surface to erupt as lava, causing a volcanic eruption.
- The lava cools, solidifies and accumulates over time, forming a volcano
11
Q
What are the characteristics of high silica magma?
A
- More viscous magma
- As magma rises towards the Earth’s surface, the dissolved gases in the magma cannot escape easily
- More pressure builds up until gases escape explosively
- Resulting in violent, explosive eruptions
- Generally associated with stratovolcanoes
12
Q
What are the characteristics of low silica magma?
A
- As magma rises towards the Earth’s surface, the dissolved gases in the magma can escape easily
- Less pressure builds up
- Resulting in gentle, effusive eruptions
- Generally associated with shield volcanoes
13
Q
Give an example of where viscous magma does not result in explosive eruption, and explain why
A
- When Mount Merapi is a stratovolcano, its eruption in 2006 was not explosive as the viscous magma rose in a way that allowed dissolved gases to escape easily
14
Q
How do stratovolcanoes form, and give an example of one
A
Stratovolcanoes form when:
* High visocisty magma rises through weak areas in the rust to the Earth’s surface and erupts explosively as lava, ash and rocks.
* The ash and rocks settle on the sides of the volcano, and are later covered by the lava
* Over successiuve eruptions, a tall volcano consisting of alternating layers of ash and lava develops
* As the highly viscous lava travels a shorter distance before cooling and solidifying, the volcano has steep sides and a narrow summit
Example:
* Mount Mayan in the Phillipines
15
Q
How do shield volcanoes form, and give an example of one
A
Shield volcanoes form when:
* Low viscosity magma rises through weak areas in the crust to the Earth’s surface and erupts effusively
* Over succesive eruptions, a volcano consisting of layers of lava develops
* As the less viscous lava travels a longer distance before cooling and solidifying, the volcano has gently sloping sides with a broad summit
Example:
* Kilauea in Hawaii, USA
16
Q
How are volcanic eruptions measured?
A
The Volcanic Explosivity Index (VEI) measures the magnitude of different volcanic eruptions based on explosivuty using the following criteria:
* Volume of ejected material
* Hei ght of the eruptiuon cloud
* Duration of eruption
It is measured on a scale of 0 to 8
* Effusive eruptions are generally given a value of 0 or 1, as they are non-explosive with less than 0.0001km3 of material ejected
–> Example: The ongoing effusive eruption of Kilauea, Hawaii, which is non-explosive
- A value of 8, represents a mega-colossal explosive eruption that can eject more than 1,000km3 of tephra, with an eruption cloud colum height of over 25km
–> Example: Toba Volcano, in Northern Sumatra, Indonesia, 74000 years ago. – The volcanpo erupted apporximately 2800km3 of material, which covered India and parts of Southeast Asia in over 15cm3 in ash.
- VEI scale is logarthmic - an increase of ‘1’ on the VEI scale indicates an eurption 10 times more powerful than the number before it.
17
Q
What is an active vent?
A
- An opening on the Earth’s surface through which lava erupts. It is situated at the bottom of the crater
18
Q
What is a conduit?
A
- A central passageway in the volcanp through which magma travels. It conntects the magma chamber to the vent
19
Q
What is a volcanic cone?
A
- The traingle-shaped hill or mountain formed as lava accumulates around the vent
20
Q
What is a magma chamber?
A
- Location in the Earth’s crust where magma is located
21
Q
What does it mean when magma is “viscous”?
A
Viscous: Thick, sticky consistency
22
Q
What does it mean when an eruption is “effusive”?
A
Effusive: A relatively gentle eruption that is mainly dominated by the outpouring of lava onto the ground (as opposed to explosive eruption which involve violkent ejection of tephra)
23
What is tephra?
* Any type or size of rock fragment that is forcibly ejected from the volcano and travels an airobone parth during an eruption (inlcuding ash and volcanic bonds)
24
What is "distribution" (geographically)?
Distribution: The way something is spread out or arranged over a geographic area
25
What is the Pacific Ring of Fire?
A broad belt around the Pacific Ocean where most earthaukes and active volcanoes occur
25
What are hot spot volcanoes?
Volcanoes that dvelip over extra hot regions in the mantle. These volcanoes may develop in locations away from plate boundaries
26
What is soil liquefaction?
A phenomena wherby saturated, loose soil loses its soil structure and transforms into a thick fluid due to ground shaking
27
What are Pyroclastic flows?
Hot clouds of gas, ash, and rocks travelling down the slopes of a volcano
27
What are Lahars?
* Mudflows comprising volcanic ash and water
* A series of ocean waves which can be caused by undersea earthquakes, volcanic eruptions and landslides
28
What is a Tsunami?
* A series of ocean waves which can be caused by undersea earthquakes, volcanic eruptuons and landslides
* Tsunamis can travel iver thousands of kilometeres and devastate huge areas of coastline
28
List down the earthquake hazards
* Ground shaking
* Soil liquefaction
* Landslide
* Tsunamis
29
List down the volcanic eruption hazards
* Tephra
* Volcanic gases
* Lava flows
* Pyroclastic flows
* Lahars
* Volcanic landslides
30
How are tectonic hazards distributed?
* Earthquake hazards such as ground shaking, soil liquefaction and landslides are often localised
* They are generally located within the same geographic region as the earthquake
* As earthqukakes are found along plate boundaries, their hazards are also found near plate boundaries
* Similairly, volcanic hazards such as volcanic gases, lava flows, pyroclastic flows, lahars and volcanic landslides are often found around the volcanoes.
* Since volcanoes are found along convergent plate boundaries, these hazards are also generally found along these plate boundaries
31
Explain how not all tectonic hazards are localised (include examples in your explanation)
* Other hazards such as tsunamis and volcanic ash may spread beyond the geographic regions where earthquakes and volcanoes are located
* Tsunami waves and volcanic ash may travel thousands of kilometres from where they orignated
* Tsunami waves can travel long distances without great loss of energy
**Example:**
* The 2004 Indian Ocean tsunami travelled almost 5000km to Africa with sufficient energy to cause deaths and destruction
* Ashfall can travel far from the geographic region where the volcanic eruption occurs
**Example:**
* During the eruption of Mount Pinatubo in 1991, ash spread across Southeast Asia
* However, whether the dispersal of ash is localised or spreads far beyond the geographic region of the volcano is dependent on wind conditions as well as the volume of ash erupted and the height the ash is thrown into the atmosphere.
32
List down the impacts on how ground shaking affect the natural and human systems
* Destroys ecosystems (natural systems)
* Destroys properties and infrastructure (human systems)
* Disrupts services (human systems)
* Causes injuries and fatalities (human systems)
33
Explain how ground shaking results in the destruction of ecosystems (natural systems)
* Ruptures oil and chemical factories, polluting land and water
* Fractures and uproot trees, causing widespread tree iinjury and death and damaging wildlife habitats
34
Explain how ground shaking results in the destruction of properties and infrastructure (human systems)
* Weakens buildings, bridges, roads and railways, causing them to collpaose, making it difficult to rescue people or supply emergency aid
34
Explain how ground shaking results in the disruption of services (human systems)
* Snaps water and gas pipes, resulting in water shortages and disruptions to gas supply
* Electricity and communicarion cables break, affecting important communication services such as tsunami warnings and television broadcasts
35
Give examples of how ground shaking impacts natural and human systems
2010 Haiti earthquake (Mw 7.0):
* Surrounding area around factories were polluted
* Debris polluted rivers
* More than 250,000 houses collapsed due to violent vibrations
* About 220,000 people were killed
* Water pipes ruptured, causing water shortages
2010 Christchurch, New Zealand earthquakes:
* Many trees were damaged and more than 300 had to be removed reducing availability of habitats for terrestrial species
35
Explain how ground shaking results in the casuation of injuries and fatalities (human systems)
* People may get trapped under collapsed buildings and infrastructure, resulkting in loss of lives and injuries
35
Explain how soil liquefaction results in the destruction of ecosystems (natural ecosystems)
* Trees on liquefied soil sink in and tip over, damaging wildlife habitats, causing forest and biodiversity loss
* Liquefied soil may enter rivers and smother aquatic plants, causing them to die
* Sewage piped may be broken and untreated waste amterials may pollute rivers, killing aquatic species
36
Explain how soil liquefaction results in the destruction of properties and infrastructure (human systems)
* Buildings and other infrastructure can sink in and t.ip over, and the damage makes it difficult to rescue people or supply emergency aid
36
Explain how soil liquefaction results in the disruption of services (human systems)
* Electricity and communication cables, and water and gas pipes can sink in and snap, disrupting supply of these services
* Roads and railways above liquefied soil can sink in and get damaged making it difficult to resuce people or supply emergency aid
37
Explain how soil liquefaction results in the causation of injuried and fatalities (human systems)
* People can get trapped under collapsed buildingd and infrastructure, reuslting in injuries and loss of life
38
Explain how landslides results in the destruction of ecosystems
* Fast-moving debris can bury huge areas of forest and wetlands
* Rivers can be polluted with debris, killing aquatic life
* Rivers can be blocked causing floods that can damage nearby ecosystems and properties
39
Give an example whereby landslides affected the natural systems
2018 Papua New Guinea earthquake:
* Triggered landslides that caused huge amounts of debris to enter the rivers
* Caused flooding
* Destroyed forests
* Polluted water and killed fish
40
Give an example whereby soil liquefaction affected the natural and human systems
2010-2011 Christchurch, New Zealand earthquakes:
* Triggered severe liquefaction, as the city lies on a former swamp area where soils are loose and saturated.
* More than 60,000 residential buildings and infrastructure covering about one-third of the city area were damaged.
* Liquefied soil entered rivers, and untreated sewage from broken pipes polluted rivers. This resulted in the reduction of some species such as the caddisflies.
41
How does landslides occur?
Landslides occur as the violent vibrations:
1. Form cracks on steep slopes, loosening the rocks and soil
2. Trigger the loose rocks and soil to move downslop
41
Explain how landslides results in the destruction properties and infrastructure (human systems)
* Debris can bury villages and farms, destroying properties and infrastructure
42
Explain how landslides results in the disruption of services (human systems)
* Debris can snap electricity and communication cables, and water and gas pipes, disrupting supply of these services
* Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid
43
Explain how landslides results in the causation of injuries and fatalities (human systems)
* Debris can bury people or hit them, causing injuries and loss of lives
* Debris can block rivers resulting in floods, which can drown people
44
Give an example whereby landslides affected the human systems
2008 Great Sichuan China Earthquake (Mw 7.9):
* Triggered more than 15,000 landslides
* Destroyed many buildings and infrastructure
* Caused nearly 20,000 earthquakes
45
When do tsunamis occur?
Tsunamis occur when:
* An undersea earthquake causes the seabed to be displaced
* A large volume of water is lifted forming waves of great wavelength and low height of less than 1 metre
* The waves travel towards land at high speeds around 800km/h
* On approaching the coast, greater friction with the shallower seabed slows the waves down
* The waves get loser together and increase in height. Waves can reach up to a height of 15m or more, travel at a speed of 30-50 km/h and devestate shorelines the waves hit
* Before a tsunami occurs, the sea may reced from the shore because the sea water fills in the void caused by displacement of the seabed
46
Explain how tsunamis results in the destruction of ecosystems (natural systems)
* The seawater can flood huge areas of coastal wetlands and forests damagaing habitats
* Large amounts of debris carried in by the waves can plollute these areas, damaging ecosystems and killing wildlife
47
Explain how tsunamis results in the destruction of properties and infrastructure (human systems)
* Fast moving waters and the large amounts of debris carried in by the waves can sweep away buildings and infrastructure destroying them
48
Explain how tsunamis results in the disruption of services (human systems)
* Fast moving waters and the lathe amount of debris carried in by the waves can snap electricity and communication cables , disrupting supply of these services
* Fast moving water can sweep away roads and railways, making it difficult to resuce people or supply emergency aid
48
Explain how tsunamis results in the causation of injuries and fatalities (human systems)
* Sweeping waters can drown people
* Large amounts of debris carried in by the waves can hit people
48
Give examples whereby tsunamis affected the natural and human systems
2004 Indian Ocean Tsunami:
* Triggered by a 9.1 M undersea earthquake near Sumatra, Indonesia.
* Tsunami waves slammed into the coasts of 11 Indian Ocean countries. from Indonesia to Somalia in Africa.
* More than 230,000 people were killed and entire coastlines and habitats were destroyed.
2011 Tohoku, Japan earthquake (Mw 9.0):
* Triggered a tsunami up to 40m in height.
* Waves destroyed homes and infrastructure.
* Tsunami waves carried debris inland, flooding and polluting large areas of land.
* Coastal city of Sendai suffered extensive damage and half its population was killed.
* In Iwate, 70,000 pine trees were knocked down, resulting in forest and biodiversity loss.
* The tsunami hit the Pacific islands, devastating the ecosystems.
* `Entire bird nesting sites were lost, and more than 100,000 Layson Albatross Chicks were killed, and thousands of fish were washed ashore where they suffocated.
48
Explain how tephra results in the destruction of ecosystems (natural systems)
* Ash can be carried thousands of kilometres by prevailing winds, polluting huge areas of forests, rivers and .other habitats, and destroying ecosystems
* Ash can suffocate and kill wildlife
* Ash can cause blindness to birds, with their eyelids getting gummed together
48
Explain how tephra results in the destruction of properties and infrastructure (human systems)
* Volcanic bombs, ranging from a few centimeters to the size of vehicles, can hit. properties, damaging them
* Ashfall can accumulate on roofs of buildings
* When saturated with water, the weight of ash can double, casuing building roofs to collapse
* Being corrosive, ash weakens building structures making them more likely to collapse.
* Thick blankets of ash can damage farmland suffocating crops and destroyong livelihoods
49
Explain how tephra results in the disruption of services (human services)
* Ash particles can damage plane engines, leading to closure of airspaces, and disrupting air transporation services
49
Explain how tephra results in the causation of injuries and fatalities (human systems)
* Volcanic bombs can hit people, causing injuries and loss of lives
* Ashfall can cause respiratory problmes, eye irriation and suffocate people
49
Give an example whereby tephra affected the natural and human systems
1991 Mount Pinatubo eruption in the Philippines:
* Emitted huge amounts of ash.
* Buried more than 180km² of forests in ash of about 25cm.
* Destroyed 800km² of rice fields, affecting the livelihoods of many farmers.
* Seven airports in the Philippines had to be closed and many flights were cancelled, disrupting transport.
* Some planes were also damaged.
50
Explain how volcanic gases results in the destruction of ecosystems (physical systems)
* Sulfur dioxide results in acid rain when it reacts with water in the air, which can damage vegetation, in the soil and kill wildlife
* Cold carbon dioxide is heavier than air, so it can become concentrated in low-lying volcanic areas such as river valleys
* Large amounts of carbon dioxide in the air can kill widlife, and in the spoil, can destroy vegetation
51
Explain how volcanic gases results in the destructions of properties and infrastructure (human systems)
* Sulfur dioxide results in acid rain, which can corrode buildings and infrastructure
52
Explain how volcanic gases results in the threatening of public health and the causation of injuries and fatalities
* Sulfur dioxide irritates skin, eyes, nose and throat
* Air containing over 3% carbon dioxide can cause headaches and breathing difficulties, and when it exceeds 15%, may cause death
53
Give an example whereby volcanic gases affected the natural and human systems
Dieng volcano eruption in Indonesia in 1979:
* Released deadly amounts of carbon dioxide and killed about 150 people
54
Describe the characteristics of lava flows
* Lava flows are extermely hot and can travel over some distances within the geographic region of the volcano
* However, deaths caused directly by lava flows are uncommon as people can easily move out of their way
55
Explain how lava flows results in the destruction of ecosystems (physical systems)
* Hot, low-silica magam can travel over some distances, destroying forests, other habitats and ecosystems in them
56
Explain how lava flows results in the destruction of properties and infrastructure (human systems)
* Lava can burn through homes, properties and infrastructure
57
Explain how lava flows results in the disruption of services (human systems)
* Lava can destroy electricity and communication cables, andwater and gas pipes, disrupting supply of these services
58
Give an example whereby lava flows affected the natural and human systems
2018 Kilauea eruption in Hawaii:
* Far-reaching lava flowsd destroyed more than 600 homes
* Destroyed huge areas of forests and ecosystems.
* Telephone and power lines were damaged causing widespread communication outages
59
Describe the characteristics of pyroclastic flows
* A pyroclastic flow is a hot cloud of a gas, ash and rocks travelling down the slopes of a volcano at great speds (more than 200km/hour)
60
Explain how pyroclastic flows results in the destruction of properties and infrastructure (human systems)
* The hot flows can burn through all homes, properties and infrastructure in their path
61
Explain how pyroclastic flows results in the disruption of services (human services)
* The hot flows can destroy electricity and communicatiom cables and gas pipes, disrupting supply of these services
62
Explain how pyroclastic flows results in the threatening of public health and the causation of injuries and fatalities
* The extreme temperatures can burn, and kill people in a fraction of a second
63
Explain how pyroclastic flows results in the destruction of ecosystems (natural systems)
* Huge areas of forests may be destroyed, resulting in biodiversity loss
* Thick layers of ash cover the path of the flows polluting huge areas of forests
63
Give an example whereby pyroclastic flows affected the natural and human systems
2010 Merapi eruption in Indonesia:
* Blasted a series of pyroclastic flows down the slipes of the volcano, which were inhabited by many villagers
* About 350 people were killed, mostly due to burns and blast injuries
* Huge areas of forest were burnt
64
Explain how lahars results in the destruction of ecosystems (natural systems)
* Lahars can cover forests and other ecosystems with thick mud which hardens like concrete, destorying them
* Lahars can pollute rivers, killing aquatic life
65
Describe the characteristics of lahars
* Lahars are mudflows comprising water and volcanic ash
* Formed when huge amounts of ash and rocks ejected during an eruption mix with water
* Lahars can occur when pyroclastic flows melt snow and ice, and mix with the water on the volcanic cone as they travel done
* They can also occur when intense rainfall washed down the ash
* Lahars are capable of flowing at high speeds (up to 200k/h), and over considerable distances within the geographic region of the volcano
66
Explain how lahars results in the destruction of properties and infrastructure (human systems)
* Lahars can bury houses and building, destroying them
* Lahars can cover farms with thick mud, which hardens like concrete, damaging them
67
Explain how lahars results in the disruption of services (human systems)
* Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid
* Lahars can damage communication cables, and water and gas pipes, disrupting supply of these services
68
Explain how volcanic gases results in the threatening of public health and the causation of injuries and fatalities
* Lahars can bury house and its residents, resulting in loss of lives
69
Give an example whereby lahars affected the natural and human systems
1985 Nevado Del Ruiz eruption in Columbia:
* Released huge amounts of ash and volcanic rocks which melted snow and ice
* The meltwater mixed with ash and rocks to form lahars
* Fast-moving lahars more than 20,000 people in the nearby town of Armero within seconds
* Rivers were highly muddled by the lahars, killing many fish
70
Describe the characteristics of volcanic landslides
* Volcanic eruptions are common on tall and steep volcanic cones which comprise thousands of solidifies lava layers and loose tephra
* The blast from an explosive erutpion can trigger the downward movement of loose volcanic material, causing a landslide
* The high velocity and great momentum of landslides allow them to travel considerable dsitances within the geographic region of the volcano
71
Explain how lava flows results in the destruction of ecosystems (natural systems)
* Fast-miving debris can bury huge areas of forest and wetlands
* Debris from landslides pollutes rivers, killing aquatic life.
* Debris blocks rivers, causing floods that can damage nearby ecosystems and properties
72
Explain how lava flows results in the causation of injuries and fatalities (human systems)
* Debris can bury people or hit them, casuing injuries and loss of lives
* Debris blocks rivers, resulting in floods, which can drown people
73
Explain how lava flows results in the destruction of properties and infrastructure (human systems)
* Debris buries villages and farms, destroying properties and infrastructure
74
Give an example whereby lava flows affected the natural and human systems
1980 Mt St Helens eruption in USA:
* North face of the volcanic cone collapsed
* Caused volcanic landslides that traveled as far as 30km from the volcano
* Destroyed huge areas of land and kiled many wildlife
75
What are the benefits of volcanic eruptions and living near volcanoes
The benefits that attract people to live near volcanoes include:
* Farming with fertile soil
* Extracting precious materials and fossil fuels
* Harnessing geothermal energy
* Tourism activities
76
Elaborate, with an example, on how farming with fertile soil attracts people to live near volcanoes on how farming with fertile soil attracts people to live near volcanoes
* Over thousands of years, volcanic rocks break down and undergo weathering to form fertile soils
* They are suitable for agriculture as they can produce higher crop yields
* Locals benefit from growing a variety of crops or earning more from higher crop yields
76
Elaborate, with examples, on how harnessing geothermal energy attracts people to live near volcanoes
* Geothermal energy is derived from heat in the Earth's crust
* It can be harnessed in tectonically active areas
* Beneath Earth's surface, hot rocks heat up groundwater
* Steam that is formed is harnessed to generate electricity
* Locals benefit from cheaper electricity produced locally
* Locals can also can be employed to work in the geothermal power plants
77
Elaborate, with an example, on how extrcting precious minerals and fossil fuels attracts people to live near volcanoes
* Some magma may cool and solidify beneath volcanoes, farming precious minerals such as copper, silver and gold
* Locals living near volcanoes can be employed to mine these minerals, which provides them with a source of income
* Governments may sell these precious minerals to generate revenue which can in turn be used to provide social services to locals such as education and healthcare
* Volcanic materials, such as ash and sand, may also be mined and used as construction materials
78
Give an example on how farming with fertile soil attracts people to live near volcanoes
**Example:**
The best rice-growing regions in Indonesia are near volcanoes, such as in Bali, which has several volcanoes such as Mount Agung.
* Despite their continous use, soils in Bali are more fertile than most non-volanic areas of Indonesia
79
Give an example on how extracting precious minerals and fossil fuels attracts people to live near volcanoes
**Example:**
* Thousands of locals living on Mount Merapi are employed to mine volcanic snad as it is suitable for constructing buildings
79
Give examples on how harnessing geothermal energy attracts people to live near volcanoes
**Examples:**
* Most of Iceland's electricity is generated from geothermal power because of the large number of volcanoes in the country
* In Northern California, the Geysers geothermal field produced enough electricity to meet the power demands of San Francisco
80
Give an example on how tourism activities attracts people to live near volcanoes
**Example:**
The Hawaiian islands are popular tourist locations for its scenic volcanic landscapes
* Tourism generates an annual income of about US$88 million and provides locals with thousands of jobs
81
Elaborate on how tourism activities attracts people to live near volcanoes
* Tectonic environments can be attractive to tourists
* Different volcanic features like the crater appeal to tourists
* Tourists can engage in various activities, such as hiking and sightseeing
* Tourism provides locals with employment opportunities, such as tour guides, providing tourist accomodation and selling food and souvenirs
* Tourism thus boosts local economic development
