tectonics chpt 2 Flashcards
1
Q
How do tectonic processes result in EQs ?
A
- EQs refer to shaking of ground due to sudden release of energy in earth’s lithosphere
- occurs when rocks on either side of fault pushed by tectonic forces
- friction causes rocks to get locked
- stress builds up, rocks cannot handle stress, either snap or move to a diff position
- sudden movement causes release of seismic waves
2
Q
Define focus and epicentre.
A
Focus - point in earth’s crust where seismic waves are released
Epicentre - point of earth’s surface directly above focus
3
Q
how are EQs measured ?
A
- richter scale
takes max seismic intensity
inaccurate in measuring EQs that last for long periods of time - moment magnitude scale
takes total energy released by EQ
more accurate in measuring EQs => 8mw
4
Q
Define both types of volcanic eruptions.
A
- high silica magma -> stratovolcanoes
- low silica magma -> shield volcanoes
5
Q
Define high silica magma.
A
- more viscous
- dissolved gases cannot easily escape
- more pressure builds up, escapes explosively
- violent, explosive eruptions
- strato
- ash and rocks settle on sides of volcanoes, more eruption -> alternating layers of ash rocks form tall volcano
- lava travels shorter distance before cooling and solidifying
- volcano has steep sides and narrow summit
6
Q
Define low silica magma.
A
- low viscosity magma
- gases able to escape easily -> less pressure buidup
- effusive, gentle eruptions
- lava travels longer distance before cooling and solidifying -> gently sloping sides with broad summit
7
Q
How are EQs distributed?
A
- EQs occur along all types of plate boundaries
- largest conc around pacific ring of fire
- plate pushed by tectonic forces, pressure build up, sudden release of energy -> EQs
8
Q
how are volcanoes distributed?
A
- located near convergent and divergent plate boundaries
- mantle melt form magma, rise to surface
- NOT found near transform and continental continental convergence
- hotspot volcanoes are found far away from plate boundaries (exceptions)
9
Q
name the EQ and volcanic hazards.
A
EQ
1. landslides
2. soil liquefaction
3. tsunamis (travel over long distance, not localised)
4. ground shaking
volcanoes
1. tephra (long distances, not localised)
2. pyroclastic flows
3. lava flows
3. volcanic gases and ash (travel over long distances, not localised)
4. lahars
5. volcanic landslides
10
Q
What impacts do tectonic hazards have on natural and human systems?
A
- destroys natural ecosystems
- destroys properties and infrastructure
- disrupts human services
- causes injuries and fatalities
11
Q
How does ground shaking affect natural and human systems?
A
- ecosystems
ruptures oil and chemical facilities polluting water and land - properties
weakens buildings, roads -> collapse - human services
snaps water and gas pipes, water shortages
breaks electricity and comm cables - affects call ins to rescue services - fatalities
people trapped under fallen buildings - loss of lives
12
Q
How does soil liquefaction affect natural and human systems?
A
- ecosystems
trees on liquefied soil sink and tip over - wildlife and biodiversity loss - properties
buildings and other infrastructure tip over - disrupts human services
roads and railways above liquefied soil may sink and get damaged - fatalities
trapped under collapsed buildings
13
Q
How does landslides affect the natural and human systems?
A
- ecosystem
fast moving debris can bury huge areas of forests and wetlands - infrastructure
debris buries villages and farms eg crops - disrupts human services
debris snaps electricity and comm cables - fatalities
debris can bury/hit people
14
Q
How do tsunami affect natural and human systems?
A
- ecosystems
seawater floods huge areas of coastal wetlands and forests -> damaging habitates - infrastructure
fast moving water carrying debris can sweep away buildings and infrastructure - disrupts human services
fast moving waters sweep away roads and railways -> makes it difficult for rescue teams to supply emergency aid - fatalities
sweeping waters can drown people
15
Q
How are tsunamis formed?
A
- undersea EQ causes seabed to be displaced
- large vol of water is lifted, forming waves of great wavelength and low height of less than 1m
- waves approach land at high speed around 800km/h
- greater friction of shallower seabeds slows down water
- waves get closer together and increase in height of up to 15m, travelling at slower speeds of 30-50 km/h
- before hitting, sea will recede from shore to fill in the void caused by displacement of seabed
16
Q
How does tephra affect natural and human systems ?
A
- ecosystems
ash carried for thousands of km by prevailing winds, polluting forests, rivers and habitates - infrastructure
ashfall accumulates on rooftops
ash is corrosive -> weakens building structures -> collapse - disrupts human services
ash particles damage plane engines - closure of air spaces - fatalities
ashfall causing respiratory tract infections
17
Q
How do volcanic gases affect natural and human systems ?
A
- ecosystems
sulfur dioxide in volcanic gases results in acid rain, kill wildlife and vegetation and soil - infrastructure
acid rain corrodes buildings and infrastructure - threatens public health
sulfur dioxide irritates skin, eyes, nose and throat
18
Q
How do lava flows affect natural and human systems ?
A
- ecosystems
hot, low silica lava travel over distances, destroying forests and ecosytems - infrastructure
lava burns through homes and buildings - disrupts human services
lava destroys electricity and comm cables plus water and gas pipes -> disrupting water and gas supplies
19
Q
how do pyroclastic flows affect the natural and human systems ?
A
- ecosystems
huge areas of forest are destroyed -> loss in biodiversity - infrastructure
hot flows destroys all homes, properties and infrastructure - disrupts human services
hot flows destroy electricity and comm cables, and gas pipes -> disrupts supply of gas services and comm - fatalities
extreme temperatures can burn, kills people in a fraction of a second
20
Q
how do lahars affect the natural and human systems ?
A
- ecosystems
lahars cover forests and other ecosystems with thick mud -> hardens like concrete, destroying habitats - infrastructure
lahars bury houses and buildings -> destroys them - disrupts human services
roads and railways blocked by debris -> difficult to rescue people or to supply emergency aid - fatalities
lahars bury houses and its residents -> loss of lives
21
Q
How do volcanic landslides affect natural and human system ?
A
- ecosystems
fast moving debris bury huge areas of forests and wetlands
debris pollutes rivers - infrastructure
debris buries villages and farms - disrupts human services
snap electricity and comm cables
destroy water and gas pipes - disrupting supply of these services - fatalities
debris bury people or hit them
blocks river -> floods -> drowning
22
Q
What are the benefits of volcanic eruptions and living near volcanoes ?
A
- Farming with fertile soil
- extracting precious minerals and fossil fuels
- harnessing geothermal energy
- tourism activities
23
Q
Define the benefits of farming with fertile soil.
A
- over thousands of years, volcanic rocks break up and undergo weathering to form fertile soils
- 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
24
Q
Define the benefits of extracting precious minerals and fossil fuels.
A
- magma cools and solidifies beneath volcano, turning into precious minerals eg copper, silver and gold
- locals living near volcanoes receive employment opportunities to mine these materials -> source of income
- gvmt sells materials for revenue which used to provide better social services eg education and healthcare
- volcanic materials eg ash and sand, may be mined and used as construction materials
25
Define the benefits of harnessing geothermal energy.
1. geothermal energy is derived from heat in earth’s crust
2. harnessed from tectonically active areas
3. beneath earth’s surface, hot rocks heat up groundwater flows into steam
4. steam harnessed can be used to generate electricity
5. cheaper electricity for locals
6. locals receive employment opportunities at geothermal power plants
26
Define the benefits of tourism activities.
1. tectonic envts are scenic and attractive to tourists
2. hiking and sightseeing activities for tourists
3. tourism offers employment opportunities to locals eg selling food and accommodation
4. tourism boosts economic dvlpment
