natural hazards

Question 1

constructive plate boundaries

Answer 1

1) pressure release of plates moving apart causing the crust to melt
2) magma rises through the gap, forming a ridge
3) the ridge builds up as more magma rises through the gap, and is pushed down by gravity, pushing the plates further apart
4) over time, ridges can rise above sea level and form shield volcanoes

Question 2

destructive plate boundaries

Answer 2

1) denser oceanic plate subducts under continental plate
2) friction between rough edges and the mantel builds up, which when released causes earthquakes
3)water from the crust and heat from the mantel causes the crust to melt, creating magma
4) magma rises and erupts out of the crust, and cools many times, eventually forming composite volcanoes

Question 3

conservative plate boundaries

Answer 3

1) as plates move past each other, friction builds up, causing them to become stuck and building up pressure
2) eventually a crack forms and releases pressure in the form of an earthquake
3) there is no gap in between them, so magma cannot rise and form volcanoes

Question 4

composite volcanoes features

Answer 4

• alternate layers of lava and ash
• tall, steep sided cone
• narrower base (lava doesn’t travel as far)
• andesitic lava - more viscous
• explosive eruptions

Question 5

shield volcanoes features

Answer 5

• made from magma
• low, gentle sloping relief and wide base
• basaltic lava - more runny and travels further
• effusive eruptions (more gentle and frequent)

Question 6

hotspots features

Answer 6

• formed by a plume of superheated rock rising through the mantel
• not formed at plate boundaries
• causes base of the lithosphere to melt, forming magma that rises through cracks in the crust
• ocean hotspots have basaltic lava, continental hotpots have andesitic lava
• mantle plumes fixed in place, so as plate moves, hotspot location moves away from volcano

Question 7

pyroclastic flows

Answer 7

• mixture of hot steam, rock, ash and dust
• faster than a car, usually up to 20m
• death and severe injuries

Question 8

lahars

Answer 8

• water + ash =mudflow
• high speeds and travels far
• often happens consecutively and with little warning

Question 9

tephra

Answer 9

• ash and volcanic bombs
• tiny sharp fragments and big boulders (both cause injuries)
• from volcanin vents

Question 9

volcanic gases

Answer 9

• particulates = cancer and global dimming
• sulphur dioxide = poisonous and acid rain
• carbon dioxide = global warming

Question 10

earthquakes

Answer 10

• focus = where earthquake is released
• epicenter = point on the curst directly above the focus
• focal depth = distance between focus and epicenter
• seismic waves = released from focus, causing earthquakes

Question 11

primary effects of volcanic eruptions

Answer 11

• homes/buildings damaged
• gas and electricity lines and sewage systems damaged
• deaths and injuries
• acid rain

Question 12

secondary effects of volcanic eruptions

Answer 12

• farmer go bankrupt
• water supply will be contaminated by sewage, which means the spread of diseases
• homeless people
• insurance costs go up
• economy/trade suffers
• psychological trauma from deaths

Question 13

management of volcanic eruptions

Answer 13

• monitoring and prediction = signs of eruptions (tremors, gases, changes in temperature, etc.)
• planning = evacuation strategies, education (drills, first aid), emergency shelters
• protection = evacuation, lava diversion channels, artificial lahar barriers

Question 14

primary effects of earthquakes

Answer 14

• ground shaking
• damage to infrastructure
• deaths and injuries
• possible landslides

Question 15

secondary effects of earthquakes

Answer 15

• economy suffers
• job losses
• homeless people

Question 16

management of earthquakes

Answer 16

• monitoring and prediction = difficult to predict anything other than location - seismometers used to measure tremors, past earthquakes mapped to spot patterns
• planning = furniture, etc fastened down, emergency supplies, education and drills
• protection = stronger infrastructure, shock absorbers, etc.

Question 17

why do people live in areas of risk?

Answer 17

• geothermal energy - steam heated from magma
• farming - weathering of lava leaves behind mineral rich, fertile soil
• mining - valuable minerals, although dangerous
• family and friends, sentimental value, hometown, etc. - maybe in denial of risk

Question 18

global atmospheric pressure

Answer 18

• due to earth’s curvature, sunlight is directly overhead at the equator, so it is concentrated over a smaller area
• at the poles, it hits at an angle, so is spread over a larger area
• hot air rises (low pressure and wet conditions) and cool air sinks, creating pressure cells (Hadley, Ferrel and Polar)
• air circulating between these cells transfers heat between them
• trade winds blow from either direction towards the equator (30 N or 30S)
• westerlies blow from those point towards the poles

Question 19

formation of a tropical storm

Answer 19

1) at more than 26.5 degrees, warm air rises, and winds converge at the warmed ocean surface, causing more air to rise
2) the winds begin to spin due to the rotation of the earth (Coriolis effect)
3) more surface winds accelerate inwards and upwards, replacing rising air
4) condensation releases heat, powering storm further, and means large cumulonimbus clouds overhead - they form the eyewall
5) cold air sinks at the centre, creating the eye, to get reheated and accelerate upwards again
6) dissipates once it reaches land, as it has lost its fuel source

Question 20

characteristics of a tropical storm

Answer 20

• only forms in the Hadley cell south of the equator
• lasts 7 - 14 days
• 100 - 1000 km, 15km tall
• strongest and most destructive winds in the eyewall

Question 21

impacts of a tropical storm

Answer 21

• high winds (250km/hour) which could cause the uprootal of trees and debris flying around could injure people
• intense rainfall from cumulonimbus clouds, could lead to flooding
• storm surges, where sea levels rise and throw water at the coast, which could also cause flooding and the erosion of beaches
• landslides - intense rainfall causes heavy saturated soil, leading to mass movement
• coastal flooding from intense rain and storm surges

Question 22

management of tropical storms

Answer 22

• monitoring and prediction = satellites and atmospheric readings, super programs and modelling programs can help predictions
• planning - hurricane drills and using the internet and social media to educate people, emergency shelters, etc.
• protection = coastal defenses against storm surges, evacuation orders, durable infrastructure