Chapter 6: Natural Hazards

Question 1

Structure of earth

Answer 1

Crust - oceanic and continental tectonic plates
Mantle - convection currents move plates
Core - highest pressure to move iron in convection current for magnetic field

Question 2

Distribution of earthquakes and volcanoes

Answer 2

convention currents in mantle cause tectonic plates to move and collide with each other’s plate boundaries

Question 3

Types of plate boundaries

Answer 3

constructive (divergent) - plates move apart to form new crust as magma rises (rift valleys)

destructive (convergent) - oceanic and continental come together, oceanic pushed down as more dense into subduction zone, melts so magma rises (volcanoes, ocean trenches)

collision- two continental collide and pushed upwards since same density (fold mountains)

conservative - plates run alongside causing friction (earthquakes)

Question 4

Formation of earthquakes

Answer 4

tectonic plates locked together due to friction
pressure builds up
strain released
shock waves of energy travel outward from focus underground towards epicentre surface

Question 5

Factors of amount of damage of earthquakes

Answer 5

depth of focus
geology of area (sedimentary rocks vibrate)
magnitude
vulnerability of population

Question 6

Impact of earthquake

Answer 6

loss of life
destroyed infrastructure
water bourne diseases (cholera)
landslides
tsunamis
financial losses

Question 7

Types of volcanoes

Answer 7

Fissure - lava erupts from long thin vent
Shield - runny lava, wider
Dome - thicker, steep convex slope
Strato - viscous lava + ash

Question 8

Structure of volcano

Answer 8

magma chamber
lava flows (surface of volcano)
volcanic bombs
crater
layers of lava and ash (inside)
ash and gas
side vent (from magma flowing upwards)

Question 9

Impact of volcanoes

Answer 9

lava flows
gas clouds (co2 and n2o)
volcanic bombs (giant rocks)
pyroclastic flows (fast clouds of ash and gas)
lahars (violent mudflows of ice or snow melt)
loss of life
ash fall
destroyed habitats

Question 10

Managing impacts before an earthquake

Answer 10

before -
monitor fault lines
satellite technology
earthquake proof designed buildings
retrofit old buildings
education
earthquake drills

Question 11

Managing impacts during an earthquake

Answer 11

seismometers send signals to rescue stations
emergency supply kits
technology for fast warnings

Question 12

Managing impacts after an earthquake

Answer 12

search rescue (sniffer dogs/ lifting equipment)
emergency hospitals
emergency aid/ foreign aid
repair and clear up
reconstruct and rebuild

Question 13

Managing impacts before an volcanic eruption

Answer 13

evacuation plans based on historic ash records
monitored from space or tiltmeters
seismometers detect movement in magma
volcano shelters
education
evacuation

Question 14

Managing impacts after an volcanic eruption

Answer 14

search and rescue
rebuild buildings
ash fall cleared
settlements abandoned

Question 15

Distribution of tropical cyclones

Answer 15

between 5 and 20 degrees north and south of the equator
warm tropical water 27 degrees celsius
ocean depth of 60m

Question 16

Life cycle of tropical cyclone

Answer 16

Disturbance - warm moist air causes thunderstorms to form, pushed by winds

Depression - storms combine and spin

Storm - spiralling winds churn up sea, moisture picked up, grows in strength and speed

Cyclone - rotation around central eye, low pressure in centre creates suction causing storm surges

Question 17

Impact of tropical cyclones

Answer 17

loss of lives
fishing industry
damage to infrastructure
waterborne diseases
saltwater floods destroy crops
uprooted trees

Question 18

Managing impacts before a tropical cyclone

Answer 18

track using satellites
predictions and forecasting path of storm
warnings
evacuation plans
emergency training drills
cyclone shelters
education
buildings raised from ground and resistant to winds

Question 19

Managing impacts after a tropical cyclone

Answer 19

food water shelter
search and rescue of trapped under debris
social networking to reunite families
reconstruct infrastructure

Question 20

Causes of flooding

Answer 20

heavy rainfall
prolonged rainfall
snow melt
land relief
saturated soil, compact soil
deforestation
cultivation
urbanisation
story surges
tsunamis
rise in sea level

Question 21

Impacts of floods

Answer 21

loss of life
loss of livestock
loss of crops and rise of food prices
damaged infrastructure
contaminated water stores
waterbourne diseases due to contamination and sewage
financial losses - collapse in tourism agriculture and mining industry

Question 22

Managing impacts before a flood

Answer 22

storm hydrograph - recurrence interval, rise in sea levels, groundwater flow
flood risk map - geology, slope angle, vegetation cover, land use
build dams
plant trees
flood insurance
risk assessment

Question 23

Managing impacts after a flood

Answer 23

damaged infrastructure
loss of lives
pumping of water
damage assessment
flood insurance
flood management plans

Question 24

Human causes of drought

Answer 24

Human -
poor farming practices (overcultivation, cash crops leads to groundwater depletion)
over-abstraction (removing groundwater from wells and aquifers)
deforestation (surface run off and soil erosion)
conflict (migration to drought areas)

Question 25

Natural causes of drought

Answer 25

climate change
ENSO
distance from sea
altitude
level of moisture

Question 26

Impact of droughts

Answer 26

death of organisms
water sources dry up
decline in crop yield
starvation
increased soil erosion
desertification (overgrazing overcultivation)
decreased air quality
increased risk of wildfires

Question 27

Managing impacts before a drought

Answer 27

desalination
exploit aquifers
reduce water consumption
forecast and monitoring
drought risk analysis

Question 28

Managing impacts after a drought

Answer 28

develop water supplies
drought resistant crops
education on water conservation

Question 29

Advantages of volcanoes

Answer 29

fertile soil due to ash for crops
tourism boosts economy
mineral for mining are sold
geothermal power

Question 30

Advantages of floods

Answer 30

alluvium (deposited sediment) increases soil fertility (sand silt clay organic matter gravel)
generates income