Chapter 2

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Shyhwee

Cards (40)

How is earthquakes formed:
Earthquakes are the shaking of the ground due to sudden release of energy
Occurs when rocks around fault is pushed and get locked, building up stress
Rock snaps and move to a new place, releasing energy resulting in ground shaking
Richter Scale (ML):
Based on height of the largest wave recorded on the seismometer
Based on maximum seismic intensity reached rather than total energy released
Scale is from 1 to 10 with a logarithmic increase in value
Will underestimate longer earthquakes that release more energy overall
Not commonly used except for small local earthquakes
Moment Magnitude scale:
Based on total energy released during the earthquake
Estimates total energy released during an earthquake instead of the largest way
Generally more accurate especially for earthquakes with magnitudes 8 and above
Logarithmic based form of measurement
Tectonic process resulting in formation of volcano:
A volcano is formed when lava erupts to Earth’s surface
It may form a cone shaped mountain as more lava erupts and accumulates over-time
Divergent plate boundaries:
Plates move apart, the crust stretches and fractures develop.
The decrease in overlying pressure causes 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
Convergent plate boundary:
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 its 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.
High silica magma:
More viscous
Dissolved gases cannot escape easily
More pressure builds up until gases escapes explosively
Results in violent and explosive eruptions
Generally associated with Stratovolcanoes
Low silica magma:
Less viscous magma
Dissolved gases can escape more easily
Less pressure builds up resulting in more gentle and effusive eruption
Generally associated with shield volcanoes
Stratovolcanoes form when:
High viscosity magma rises through weak areas in the crust 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 successive 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.
Shield volcanoes form when:
Low viscosity magma rises through weak areas in the crust to the Earth's surface and erupts effusively.
Over successive 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.
Volcanic explosive index:
Measures magnitude of different volcanic eruptions based on volume of ejected material, height of eruption cloud and duration of eruption
Measure on a logarithmic scale from 0 to 8
Distribution of earthquakes:
Earthquakes occur along all types of plate boundaries.
The largest concentration of earthquakes is at the Pacific Ring of Fire.
At plate boundaries, plates are pushed by tectonic forces, stress builds up and energy is eventually released.
Earthquakes occur more commonly along convergent plate boundaries at subduction zones as more stress is built up during subduction.
Some earthquakes may occur away from plate boundaries, such as within the Eurasian plate.
Pacific ring of fire:
Broad belt around the Pacific Ocean where most earthquakes and active volcanoes occur.
Comprise all three types of plate boundaries.
Convergent: Pacific plate moving towards the Philippine plate.
Divergent: Pacific plate moving away from the Cocos plate.
Transform: Pacific plate sliding past the North American plate at the San Andreas Fault.
Distribution of volcanoes:
Volcanoes are generally located near convergent and divergent plate boundaries.
Convergent plate boundaries: A belt of volcanoes along subduction zones in the Pacific Ring of Fire.
Divergent plate boundaries: A belt of volcanoes along divergent plate boundaries between the North American and Eurasian plates.
Unlike earthquakes, volcanoes are not found near transform plate boundaries.
At these boundaries, magma does not rise to the Earth's surface to form volcanoes.
Hot spot volcanoes are exceptions that can be found away from plate boundaries.
Distribution of tectonic hazards:
Most earthquake hazards and volcanic hazards are localised and within the same areas as the disaster
Some hazards like tsunamis and ashfall can reach beyond the geographic region
Ground shaking effects on natural and human system:
Ruptures oil and chemical factories, polluting land and water
Fractures and uproot trees, causing widespread tree injury and death and damaging wildlife habitats.
Weakens buildings, bridges, roads and railways, causing them to collapse, making transportation of goods difficult
Can snap water and gas pipes disrupting the supply
Break electricity and communication cables affecting communications
People might be trapped under collapsed buildings, resulting in loss of life and infrastructure
Ground shaking example: Haiti earthquake 2010
Areas around factories are polluted due to bursting of pipes
Debris polluted rivers
250 000 houses collapsed
200 000 people killed
Water pipes were ruptured causing water shortages
Soil liquefaction on natural and human system:
Sewage pipes may be broken and untreated waste materials may pollute rivers, killing aquatic species.
Buildings and other infrastructure can sink in and tip over, and the damage makes it difficult to rescue people or supply emergency aid.
Electricity and communication cables, and water and gas pipes can sink in and snap, disrupting supply of these services.
People can get trapped under collapsed buildings and infrastructure, resulting in injuries and loss of lives.
Affects of landslides on human and nature:
Fast-moving debris can bury huge areas of forest and wetlands.
Rivers can be polluted with debris, killing aquatic life and causing floods that can drown people
Debris can bury villages and farms, destroying properties and infrastructure.
Debris can snap electricity and communicationcables, 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.
Debris can bury people or hit them, causing injuries and loss of lives.
Example for soil liquefaction: 2010-2011 Christchurch, New Zealand earthquake
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
Liquefied soil entered river with untreated sewage, polluting the river, reducing species like the caddisflies
Example for landslide: 2018 Papua New Guinea earthquake, 7.5
Landslides caused huge amounts of debris to enter rivers
Debris also destroyed forest, polluted water and killed fish
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 closer together and increase in height. Waves can reach up to a height of 15m or more, travel at a speed of 30 - 50km/h and devastate shorelines the waves hit.
Tsunami impact on human and nature system:
The seawater can flood huge areas of coastal wetlands and forests. damaging habitats.
Debris carried by waves can pollute ecosystems and kill wildlife
Waves can sweep away buildings and infrastructure, destroying them
Waves can damage electricity and communication lines, as well as sweep away roads and railways
Waves of tsunami can drown people and debris can hit and kill people
Example of impacts of tsunami: 2011 Tohoku Japan earthquake
Tsunami 40 metres in height destroyed homes and brought large amounts of debris inland, polluting the environment
70 000 pine trees were knocked down and 100 000 Albatross were killed, reducing biodiversity
Tephra affecting nature and human system:
Ash can be carried thousands of kilometres by prevailing winds, polluting huge areas of forests, rivers and other habitats, and destroying ecosystems
Volcanic bombs, ranging from a few centimetres to the size of vehicles, can hit properties,
Thick blankets of ash can damage farmland, suffocating crops and destroying livelihoods.
Ash particles can damage plane engines, leading to disruption of air transportation services.
Volcanic bombs can hit people, causing injuries and loss of lives.
Example of tephra causing damage: 1991 Mount Pinatubo
Ash emitted buried 180km^2 of forest and destroyed 800km^2 of rice fields
Several airports have to be closed and flights were cancelled
Volcanic gases and its effect on humans and nature:
Sulfur dioxide results in acid rain when it reacts with water in the air, which can damage vegetation, soil and kill wildlife.
Large amounts of carbon dioxide in the air can kill wildlife, and in the soil, can destroy vegetation.
Acid rain from the formation of Sulfur dioxide corrodes buildings and damages them
Sulfur dioxide is an irritant that causes skin and eye irritation
Carbon dioxide can cause breathing difficulties and even death if in high enough concentration
Example of impacts of volcanic gases: Dieng eruption in Indonesia 1979
Released deadly amounts of carbon dioxide that killed 150 people
Impacts of lava flow:
Hot, low-silica lava can travel over some distances, destroying forests, other habitats and ecosystems in them.
Lava can burn through homes, properties and infrastructure.
Lava can destroy electricity and communication cables, and water and gas pipes, disrupting supply of these services.
Examples of impact of lava: 2018 Kilauea eruption in Hawaii
Lava destroyed more than 600 homes
Destroyed huge areas of forest and ecosystems
Telephone lines and power lines were damaged causing widespread communication outages
Impacts of pyroclastic flow:
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.
The hot flows can burn through all homes, properties and infrastructure in their path.
The hot flows can destroy electricity and communication cables, and gas pipes, disrupting supply of these services.
The extreme temperatures can burn, and kill people in a fraction of a second.
Example of pyroclastic flow: 2010 Merapi eruption in Indonesia
350 people killed from pyroclastic flow due to burns and injuries
Huge areas forest were burnt
Impacts of Lahars:
Lahars can cover forests and other ecosystems with thick mud which hardens like concrete, destroying them.
Lahars can pollute rivers, killing aquatic life.
Lahars can bury houses and buildings, destroying them.
Lahars can cover farms with thick mud, destroying the harvest for farmers
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.
Lahars can bury houses and its residents, resulting in loss of lives.
Example for damages by Lahars: 1985 Nevado Del Ruiz eruption in Colombia
Fast moving lahars buried 20 000 people in a town nearby in seconds
Rivers were polluted, killing many fish
Impacts of volcanic landslides:
Fast-moving 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.
Debris buries villages and farms, destroying properties and infrastructure.
Debris can snap electricity and communication cables, and water and gas pipes, disrupting supply of these services.
Debris blocks roads and railways, making it difficult to rescue people or supply emergency aid.
Debris can bury people or hit them, causing loss of life
Example of impact of volcanic landslides: 1980 Mount St Helens eruption in USA
Caused landslide that travelled 23km from the volcano
Destroyed huge amounts off land and killed many wildlife
Farming with fertile soil:
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 earn more from higher crop yield
The best rice-growing regions in Indonesia are near volcanoes, such as in Bali, which has several volcanoes such as Mount Agung.
Despite their continuous use, soils in Bali are more fertile than most non-volcanic areas of Indonesia.
Extracting precious minerals and fossil fuels
Some magma may cool and solidify beneath volcanoes, forming 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.
Ash and sand, may also be mined and used as construction materials.
Example:Thousands of locals living on Mount Merapi are employed to mine volcanic sand as it is suitable for constructing buildings.
Harnessing geothermal energy
Geothermal energy is derived from heat in the Earth's crust.
It can be harnessed in tectonically active areas.
Locals benefit from cheaper electricity And can be employed to work in the geothermal power plants.
Example:
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 produces enough electricity to meet the power demands of San Francisco.
Tourism activities
Tectonic environments can be attractive to tourist
Tourists can engage in various activities, such as hiking and sightseeing.
Tourism provides locals with employment opportunities, such as four guides, providing tourist accommodation and selling food and souvenirs thus boosts local economic development.
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.