2.4 plate tectonics Flashcards
what are the hazards associated with earthquakes?
- ground shaking
- soil liquefaction
- landslides
- tsunamis
how does ground shaking affect the natural systems?
natural systems:
- destroys ecosystem
->ruptures oil and chemical factories, polluting land and water
-> fractures and uproot trees, causing widespread trees injuries and deaths and damaging wildlife habitats
example: 2010 christchurch New Zealand earthquakes
- many trees were damaged and more than 300 had to be removed, reducing availability of habitats for terrestrial species
how does ground shaking affect human systems?
human systems:
- destroys properties and infrastructure
-> weakens buildings, bridges, roads&railways, causing them to collapse, making it difficult to rescue people or supply emergency aid
- disrupt services
-> snaps water and gas pipes, resulting in water shortages and disruptions to gas supply
-> electricity and communication cables break, affecting important communication services such as tsunami warnings and television broadcast - causes injuries and fatalities
-> people may get trapped under collapsed buildings and infrastructure, resulting in loss of lives and injuries
example: 2010 Christchurch New Zealand earthquakes
- many trees were damaged and more than 300 had to be removed, reducing availability of habitats for terrestrial species
how does soil liquefaction affect the natural systems?
definition: liquefaction occurs when the violent ground shaking causes saturated loose soil to its soil structure and transforms into a thick fluid
- destroys ecosystem
-> trees on liquefied soil sink and tip over, damaging wildlife habitats, causes forest and biodiversity loss
-> liquefied soil may enter rivers and suffocate aquatic plants, causing them to die
-> sewage pipes may be broken and untreated waste materials may pollute rivers, killing aquatic species
example: 2010-2011 Christchurch New Zealand earthquakes
-> triggered sever liquefaction, as the city lies on a forest swamp area where soils are loose and saturated
-> more than 60 000 residential buildings and infrastructure were damaged
-> liquefied soil entered rivers, and untreated sewage from broken pipes polluted rivers
-> resulted in reduction of some species such as the caddisflies
how do landslides affect the natural systems?
definition: landslides occur as violent vibrations form cracks on steep slopes, loosening the rocks and soil. it triggers the loose rocks and soil to move downslope
- destroys ecosystem
-> fast-moving debris can bury huge areas of forest & wetlands
-> rivers can be polluted with debris, killing aquatic life
-> rivers can be blocked, causing floods that can damage nearby ecosystem and properties
example: 2018 Papua New Guinea earthquake (Mw 7.5) - triggered landslides that caused huge amounts of debris to enter the rivers
- caused flooding, destroyed forests and polluted waters & killed fish
how do landslides affect human systems?
- destroys properties and infrastructure
-> debris can bury villages & farms, destroying properties and infrastructure - disrupts services
-> debris can snap electricity & communication cables, and water and gas pipes
-> roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid. - causes injuries and fatalities
-> debris can bury people or hit them, causing injuries and loss of lives
-> debris can block rivers, resulting in floods, which can drown people
example: 2008 Great Sichuan China Earthquake (Mw 7.9) - triggered more than 15000 landslides
- destroyed many buildings and infrastructure
- caused nearly 20 000 deaths
what are tsunamis? how do they occur
tsunamis are a series of ocean waves which can be caused by undersea earthquakes. they occur when:
- an undersea earthquake causes 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 800 km/h
- on approaching the coast, greater friction with shallower seabed slows wave down
- the waves get closer together and increase in height and hit the coast
how do tsunamis affect natural systems?
- destroys ecosystem
-> the seawater can flood huge areas of coastal wetlands & forests, damaging habitats
-> large amounts of debris carried in by the waves can pollute these areas, damaging ecosystems and killing wildlife
example: 2004 Indian Ocean Tsunami - triggered by 9.1 Mw undersea earthquake near Sumatra, Indonesia
- tsunami waves slammed into the coasts of 11 indian ocean countries
- more than 230 000 were killed
- entire coastlines and habitats were destroyed
how does tephra affect her natural systems?
-destroys ecosystems
-> 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
example: 1991 Mount Pinatubo eruption in Philippines
- emitted huge amounts of ash
- buried more than 180 km^2 of forests in ash of about 25 cm
- destroyed 800 km^2 of rice fields, affecting the livelihoods of many farmers
- 7 airports had to be closed, many fights cancelled which disrupted transport
- some planes were also damaged
how does tephra affect human systems?
- destroys properties and infrastructure
-> volcanic bomb, ranging from a few centimetres 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, causing building’s roof to collapse
-> thick blanket of ash can damage farm land, suffocating crops and destroying livelihoods - disrupt services
-> ash particles can damage plan engines, leading to closure of air spaces and disrupting air transportation services - causes injuries and fatalities
-> volcanic bombs can hit people, causing injuries and loss of lives
-> ashfall can cause respiratory problems, eye irritation and suffocate people
example: 1991 Mount Pinatubo eruption in Philippines
- emitted huge amounts of ash
- buried more than 180 km^2 of forests in ash of about 25 cm
- destroyed 800 km^2 of rice fields, affecting the livelihoods of many farmers
- 7 airports had to be closed, many fights cancelled which disrupted transport
- some planes were also damaged
what is tephra?
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what is volcanic gases affect the natural system?
- destroys ecosystem
-> sulphur dioxide which produces acid rain when it reacts with water in the air, can damage vegetation and soil, kills wildlife
-> cold carbon dioxide which is heavier than air, becomes concentrated in low-lying volcanic areas such as river valleys
-> large amounts of carbon dioxide in air which kills wildlife & destroy vegetation
how do volcanic gases affect human systems?
- destroys properties & infrastructure
-> sulphur dioxide results in acid rain which corrodes buildings and infrastructure - threatens public health and cause injuries and fatalities
-> sulphur dioxides irritates skin, eyes, nose & throat
-> air containing over 3% carbon dioxide can cause headaches & breathing difficulties
-> air containing over 15% carbon dioxide may cause death
example: Dieing volcano eruption in indonesia in 1979 - released deadly amounts of carbon dioxide&killed about 150 people
what are lava flows?
lava flows are extremely hot and travel overcome distances within geographic region of the volcano
how does lava flows affect natural systems?
- destroys ecosystem
-> hot , low silica lava can travel over some distances, destroying forests, other habitats and ecosystems in them
example: 2018 Kilauea eruption in Hawaii
- far reaching lava flows destroyed more than 600 homes
- destroyed huge areas of forests and ecosystems
- telephones and power lines damaged, causing widespread communication outages
how does lava flows affect human systems?
- destroys properties & infrastructure
-> lava can burn through homes, properties & infrastructure - disrupts services
-> lava can destroy electricity and communication cables, and water and gas pipes
example: 2018 Kilauea eruption in Hawaii
- far reaching lava flows destroyed more than 600 homes
- destroyed huge areas of forests and ecosystems
- telephones and power lines damaged, causing widespread communication outages
what are pyroclastic flows?
a pyroclastic flow is a hot cloud of gas, ash and rocks travelling down the slopes of a volcano at great speeds.
how does pyroclastic flows affect natural systems?
- destroys ecosystem
-> huge areas of forests my be destroyed, resulting in biodiversity loss
-> thick layers of ash cover the path of flows, polluting huge areas of forests
how does pyroclastic flows affect the human system?
- destroys properties and infrastructure
-> the hot flows can burn through all homes, properties and infrastructure in their path - disrupts services
-> the hot flows can destroy electricity and communication cables and gas pipes, destroying supply of these services - threatens public health and cause injuries and fatalities
-> the extreme temperatures can burn, and kill people in a fraction of a second
example: 2010 Merapi eruption in Indonesia - blasted a series of pyroclastic flows down the slopes of volcano which were inhabited by many villagers
- about 350 people killed, mostly due to burns and blast injuries
- huge areas of forest were burnt
what are lahars?
lahars are mudflows comprising water and volcanic ash.
occurs when pyroclastic flows melt snow and ice, mix with water on volcanic cone as they travel down, intense rainfall washes down the ash
how does lahars affect the natural systems?
- destroys ecosystems
-> lahars can cover forests and other ecosystems, with thick mud which hardens like concrete, destroying them
-> lahars can pollute rivers, killing aquatic life
how does lahars affect human systems?
- destroys properties and infrastructure
-> lahars can bury houses and buildings, destroying them
-> lahars can cover farms with thick mud, which hardens like concrete, damaging them - disrupts services
-> roads and railway can be blocked by debris, making it difficult to rescue people or supply emergency aid
-> lahars can damage communication cables, water and gas pipes, disrupting service supply - threatens public health and cause injuries and fatalities
-> buries houses and its residents, resulting in loss of lives
example: 1985 Nevado Del Ruiz eruption in colombia - released huge amounts of ash and volcanic ash rocks which melted snow and ice
- melted water mixed with ash and rocks to form lahars
- fast-moving lahars buried more than 20 000 people in nearby town of Armero within seconds
- rivers were highly muddied by lahars, killing many fishes
what are volcanic landslides?
blast from explosive eruption which triggers downward movement of loose volcanic material causes landslides
how does volcanic landslides affect natural systems?
- destroys ecosystem
-> fast moving debris can bury huge ares of forests and wetland - debris from polluted rivers and kill aquatic life
- debris blocks rivers, causing floods that can damage nearby ecosystems and properties
