GCSE Geography Paper 1
Section A: The Challenge of Natural Hazards
Natural Hazards
Natural Hazard
- lives at risk
- naturally occurring event, pose major threat to people & property around the world
- eg. tectonic events, weather events, climate change
Hazard Risk
- chance / probability being affected by natural events
Factors Affecting Hazard Risks
- Urbanisation- increase 50% of the world’s population living in cities
- densely populated urban areas are at great risk from natural events
- Poverty- poorer parts of world poverty may force people to live in areas at risk
- shortage of housing led to people building on unstable slopes
- cause floodings and landslides
- Climate change- warmer world, more energy in the atmosphere
- more intense storms and hurricanes
- some parts of the world become wetter, increase risk of flooding
- some parts of the world become hotter, increase risk of droughts
- some places have increased risk of famine
- Framing- flooding, deposits fertile silt
- increase the risk of floodplains
Types of Natural Hazards
- Atmospheric Hazards, weather related eg. hurricanes, storms, droughts & wildfire
- Tectonic Hazards eg. earthquakes, volcanoes & tsunamis
- Geomorphological, happens on the ground eg. rock falls, mudslides & avalanches
Tectonic Hazards
Lithosphere
- upper most part of the mantle & crust, 100m thick, solid
- floats on moving part of the mantle
Continental Oceanic Crust
Crust
Earth’s 40% 60%
surface
Age Oldest Youngest
Thickness Thickest (up to Thinnest (up
75km) to 5-10km)
Denseness Less dense Most dense
Rock type Granite Basalt
,Types of Plate Boundaries
Destructive boundary
- also known as convergent, 2 plates pushed together
- heavier oceanic gets subducted beneath
- oceanic plate sticks & locks as it tries slide under
- heat from friction & mantle melts subducted plate
- eg. Coast of South America, West Chile
Constructive boundary
- also known as convergent, 2 plates moving apart
- molten magma rises to fill the gap
- solidifies and create new rocks on the seabed
- over time layers of new rock build up
- then break through ocean surface
- eg. The Himalayas
Conservative boundary
- also known as transform
- 2 plates sliding in the same direction, different speed
- plates slide past each other, they snag
- pressure and tension builds up as plates lock
- plates break, causes a sudden surge forward
- eg. San Andrea’s Fault, North America
Global Distribution of Volcanoes & Earthquakes
Pacific ring of fire
- along the pacific ocean with active volcanoes and frequent earthquakes
- volcanoes can only occur at constructive and destructive plate margins
- earthquakes can occur at all types of plate margins
Features of an Earthquake
Focus
- point underground where quakes occur
- stored energy suddenly released
- pressure built up by pushing plates
- closer focus to surface, bigger the impact
Epicentre
- location on the surface directly above focus
- quake & damage, most severe there
Seismic waves
- fast waves of energy released by a quake
- travel through rock to surface
- shaking recorded on seismograph
,Aftershock
- series of smaller tremors in the days after the main quake
- slow down the rescues efforts, causes extra damage
Measuring the Scale of Earthquakes
Richter scale
- used to measure the magnitude of a quake, the amount of energy released
- ranges from 0-10
- increase of 1, quake ten times more powerful
- 30 times more energy than the previous level
- before Richter scale, Mercalli scale used
Primary & Secondary Effects of Earthquakes
Primary effect
- happens as ground is shaking, during and immediately after the main earthquake
- eg. immediate deaths, buildings/bridges collapsing, loss of homes and property
- eg. gas & water pipes bursting, destruction of power plants, broken infrastructure
Secondary effect
- results of the primary effects (ground shaking), occur after the earthquake
- their length depend on a number of factors such as the development of the country
- eg. tsunamis, landslides, dust clouds, fires from ruptured gas mains, hunger and thirst
- lack of food and water, rubble and rubbish left in street, risk of disease spreading
The Effect of Hazards on Places with Different Levels of Development
LICs can take much longer to recover than HICs
- Communication systems may be underdeveloped
- population may not be well educated on what to do in event of earthquake / eruption
- Construction standards tend to be poor
- homes and other buildings may suffer serious damage when disaster occurs
- Buildings collapsing can cause high death tolls
- Evacuation & other emergency plans can be difficult to put into action
- due to limited funds & resources
- Clearing up can be difficult as may not be enough money to rebuild homes quickly & safely
- many people could be forced to live in emergency housing or refugee camps
Tectonic Hazard Case Studies
Chile earthquake
- Chile is part of pacific ring of fire, destructive plate, happened on 27/02/2010
- 8.8 Richter scale, 500 deaths, 12000 injured, 53 ports destroyed, 1500km roads damaged
- power and water restored to 90% homes in 10 days
- government launched housing reconstruction plan after a month
, Nepal earthquake
- Himalayas mountain range, collision plate
- 25/04/2015, 7.9 Richter scale, 9000 deaths, 20000 injured
- 3 million people left homeless / landslides and avalanches triggered
- financial aid pledged from many countries, lakes cleared to avoid flooding
Volcanoes
Formation of volcano
- rupture on the ground where magma emerges, cools into lava
- layers and layers of ash and lava build volcanoes
Volcanoes
- opening, rupture in planet’s surface of crust
- allows hot magma, volcanic ash & gases to escape from the magma chamber
- magma chamber below surface
- usually found at constructive & destructive plate boundaries
Pyroclastic flow
- highly destructive, fast-moving clouds of dust, hot ash, rocks, gases & steam
- moving at up to 320km/h (200mph)
Ash cloud
- blocks out the sun, causes suffocation, leads to many health problems
Lahar
- 95km/h (60mph) mudslide made of melted snow and volcanic ash
Shield volcano
- covers a large area with very gently sloping sides
- normally found along constructive plate boundaries
- also found at hot spots, runny lava
Composite/ Strato volcano
- tall, conical volcano composed of many layers
- normally found along destructive plate boundaries, thicker lava
Active volcano- liable to erupt
Dormant (sleeping) volcano- not erupted for many years (most dangerous)
Extinct volcano- not erupted for many thousands or millions of years
Hotspot volcanoes
- area in the mantle from which heat rises, thermal plume from deep in the Earth
- high heat & lower pressure at the base of lithosphere, facilitates melting of the rock
- melt called magma, rises through cracks and erupts from volcano
- as tectonic plate moves over the stationary hotspot
- volcanoes rafted away, new ones form in their place
- results in chains of volcanoes eg. Hawaiian islands
