Geography P1 ~ Natural Hazards

Natural Hazard

A natural event such as an earthquake, volcanic eruption, tropical storm or flood.

• It is caused by 'natural' processes, so would occur even if humans were not on the planet.

3 types of natural hazard

1. Geomorphological hazards E.g. Earthquakes & volcanoes
2. Atmospheric hazards E.g. tropical storms & drought
3. Flooding hazards E.g. floods

Earths layers

The Earth's internal structure is divided into layers: the core, mantle and the crust (continental & oceanic):

Core

At the centre of the Earth is the core, which is extremely hot (5000oC) and under a lot of pressure.

• The inner core is solid and has a density of 12.5 g/cm3
• The outer core is made up of liquid iron and nickel.

Mantle

The mantle that surrounds the core is made of molten material that can flow very slowly via convection currents.

• The upper portion of the mantle is a weak layer called the asthenosphere, which can deform like a plastic.
• The mantle is 2,900km thick

Crust

The outermost layer of the earth is the crust, which is very thin compared to the mantle and the core.

• Oceanic crust is young, thin, dense and constantly being destroyed.
• Continental crust is older, thicker, less dense and thus more buoyant

Where are earthquakes & volcanoes located?

• 90% of earthquakes & volcanoes occur on or near plate margins
• Earthquakes are found at all 3 plate margins whereas volcanoes are only found at 2 plates margins (constructive & destructive)
• The large band of volcanoes & earthquakes which circles the Pacific Ocean is known as the 'Ring of Fire'.
• Some also occur in the middle of plates. These are known as 'hot spots', where the Earth's crust is thought to be particularly thin

CONSTRUCTIVE (aka 'divergent') plate margins

• At constructive margins, the upper part of the mantle melts and the hot molten magma rises.
• As the tectonic plates are moved away from each other by slab pull and ridge push, the molten magma rises in between and cools down to form newly constructed solid rock - this forms part of the oceanic plate.
• The new solid plate sometimes fractures as it is moved, causing quakes.
• Much of the magma never reaches the surface but is buoyant enough to push up the crust to form an ocean ridge or a rift valley forms on land.
• Over many gentle eruptions, wide-bottom & concave-sloping shield volcanoes form e.g. Skjaldbreiður in Iceland - it means "broad shield

DESTRUCTIVE (aka 'convergent') plate margins

• Destructive plate margins occur when tectonic plates move towards each other.
• If an oceanic plate and a continental plate move towards each other, the denser oceanic plate is subducted and sinks under the continental plate and into the earth's mantle, where it is recycled.
• The pressure and strain of an oceanic and continental plate moving towards each other can cause the Earth's crust to crumple and form fold mountains e.g. the Andes Mountains in South America.
• As the plates converge, pressure builds up. The rocks fracture causing an earthquake, which can be very destructive.
• The magma here is very sticky (viscous), often producing composite volcanoes e.g. Mt St Helens.

CONSERVATIVE plate margins

• A conservative plate margin occurs when tectonic plates are moving parallel to each other.
• The two plates can move side by side, either in the same direction but at slower speeds, or simply in different directions
• As the plates move past each other, friction causes them to become stuck.
• Pressure builds up until eventually the rock fractures and seismic energy is released. This is felt at the surface as an earthquake.
• However, volcanoes are not formed at conservative margins as there is no gap created and therefore no space for magma to rise. •
• The San Andreas Fault stretches 800km through California in the USA. In 20 million years time, Los Angeles may be as far north as San Francisco

Primary & secondary effects of a hazard

PRIMARY effects :

• Property, buildings & homes destroyed
• People injured & killed
• Ports, bridges, road & railways damaged
• Water & gas pipes & electric cables broken

Primary & secondary effects of a hazard

SECONDARY effects :

• Business crippled & money spent repairing damage, so economy slow downs
• Blocked transport infrastructure hinders emergency services => further casualties
• Broken gas pipes & fallen electricity cables start fires => more destruction & deaths
• Burst water pipes leads to a lack of clean water & sanitation => diseases spread

Immediate & long-term responses to a hazard

IMMEDIATE responses :

• Issue warning for volcanic eruptions
• Rescue teams search for survivors
• Treatment given to those injured
• Provide shelter, food & water
• Recovering bodies
• Extinguish fires

Immediate & long-term responses to a hazard

LONG-TERM responses :

• Repair & rebuild properties & transport infrastructure
• Improve building regulations
• Restore utilities: water, gas & electricity
• Resettle locals elsewhere
• Develop opportunities for recovery of the economy
• Install increased monitoring technology

CASE STUDY: Haiti earthquake 2010 vs. Christchurch earthquake (2011) - effects

PRIMARY effects :

Haiti 2010 ~

• 230,000 deaths + 300,000 injuries
• 100,000 homes destroyed
• 1.5 million homeless
• 4 bridges collapsed
• 8 hospitals damaged

Christchurch 2011 ~

• 185 deaths + 2,000 injuries
• 200,000 homes destroyed
• 0 hospitals damaged

CASE STUDY: Haiti earthquake 2010 vs. Christchurch earthquake (2011) - effects

SECONDARY effects :

Haiti 2010 ~

• 2 million people without food + water
• Damage to port = no aid could get in
• 70,000 people in tent 3 years after
• $8.7 billion of damage (109% of GDP)

Christchurch 2011 ~

• Liquefaction = 400,000 tonnes of silt
• Christchurch airport unaffected
• Over ½ of deaths in 6-storey CTV
• $15 billion of damage (8.2% of GDP)

CASE STUDY: Haiti earthquake 2010 vs. Christchurch earthquake (2011) - responses

IMMEDIATE responses :

Haiti 2010 ~

• Damaged port = aid slow to arrive
• USA sent 10,000 troops inc. water
• UK government donated £20 million

Christchurch 2011 ~

• Full emergency plan within 2 hours
• Australian government = NZ$6.7m
• 60 water supplies restored in 1 week

CASE STUDY: Haiti earthquake 2010 vs. Christchurch earthquake (2011) - responses

LONG-TERM responses :

Haiti 2010 ~

• World Bank waived 5 years of debt
• 6 months after, 98% rubble remained
• $1.1bn raised, but only 2% released

Christchurch 2011 ~

• Liquefaction silt cleared by August
• 80% of roads repaired by August
• $900m in building insurance claims

CASE STUDY: Comparing the effects & responses of the Haiti 2010 & Christchurch 2011 earthquakes

Haiti (LIC) ~

Income level
• Low

GDP
• $8 billion

GNI per capita
• $1790

Time of day
• 4.53pm

Deaths
• 230,000

Homeless
• 1.5 million

Hospitals damaged
• 8

Sites of special interest damaged
• 70% of public service
buildings destroyed

Cost of damage
• $8.7 billion (= 109% of GDP)

Amount of aid
• $15 billion

CASE STUDY: Comparing the effects & responses of the Haiti 2010 & Christchurch 2011 earthquakes

New Zealand (HIC)

Income level
• High

GDP
• $181 billion

GNI per capita
• $44,342

Time of day
• 12.51pm

Deaths
• 185

Homeless
• 200,000 homes destroyed

Hospitals damaged
• 0

Sites of special interest damaged
• CTV building collapsed, spire fell off Christchurch cathedral

Cost of damage
• $15 billion (= 8.2% of GDP)

Amount of aid
• n/a

Why were the EFFECTS so different?

• The Haiti earthquake measured 7.0 on the Richter Scale, whereas Christchurch was 6.3, hence the stronger the earthquake the greater the impact.
• Population density Port-au-Prince is 10,000 people per km2, whereas Christchurch was 250, hence the more people the more potential injuries & deaths.
• The Haiti earthquake lasted for 35 seconds, whereas Christchurch was 12 seconds, hence buildings were shaken for a longer period of time

Why were the RESPONSES so different?

• 8 hospitals were damaged in the Haiti earthquake but no hospitals were damaged in Christchurch, thus medical facilities were able to respond better.
• Even though $15bn pledged in aid to Haiti, 70,000 people still living in tents 5 years on, hinting at the possibility of corruption in diverting aid & supplies.
• Haiti only had 1 seismometer in the island whereas New Zealand had 600, meaning more resources available to monitor earthquakes to reduce risks.

Why do people live at risk from tectonic hazards?

• Approximately 8% of the 7.5 billion people who live in the world live near volcanoes.

• 50% of the 320 million people in the USA live at risk of earthquakes.

Geothermal power plant ~ Krafla volcano, Iceland

• Hot water from Earth's crust provides heating + water for 90% of all buildings
• Volcanic rock used for construction
• Tourism
• Natural hot water is used to heat greenhouses and swimming pools
• Geothermal energy used to generate 25% of all the countries electricity

Topic: How monitoring can reduce the risks from a tectonic hazard

MONITORING :

Fact ~

• Prior to the 2010 quake, Haiti had 1 seismometer, NZ had 600 in 2011.

• Used to predict + measure tremors and foreshocks before the main earthquake.

Topic: How prediction can reduce the risks from a tectonic hazard

PREDICTION -

Fact ~

• Even though NZ had 600 seismometers, it still failed to predict the time + date of the quake.

• Possible to predict where / what location it will hit, but hard to know what time or date.

Topic: How protection can reduce the risks from a tectonic hazard

PROTECTION -

Fact ~

• The Christchurch Women's hospital is fitted with 41 led rubber bearings - absorb the impact

• Provide protection

Topic: How planning can reduce the risks from a tectonic hazard

PLANNING -

• Planning and preparing can help people to know what to do, calmly and safely. Reduces the risk of injury

What is the influence of latitude?

• The most important influence on worldwide variations in climate is latitude.
• Because of the curved surface of the Earth, the Equator receives much higher insolation (sun's rays) than polar latitudes.
• As a result, air at the Equator is heated strongly. It becomes less dense and rises to a high altitude (height).
• This creates a global climate zone of low pressure, known as the Equatorial (tropical) zone.
• Meanwhile, the low insolation received at Polar latitudes results in colder, dense air and high pressure
• As the air sinks towards ground level, it spreads out and flows towards the Equator.

How does global atmospheric circulation work?

• At the Equator - where the two Hadley Cells meet - air is heated intensely so it rises in low pressure conditions.
• The air flows towards the North & South Poles. As warm air rises it cools and condenses.
• Low pressure = cloudy skies & rain.
  The sinks at 30 degrees north & south of the Equator under high pressure.
• This is where the Hadley & Ferrel Cells meet. High pressure = clear skies & dry.
• Air at the polar latitudes is colder & denser so the air sinks towards the ground surface under high pressure conditions.
• The air flows towards the Equator. The air warms as it reaches about 60 degrees and again rises under low pressure.
• This is located between the Hadley & Ferrel cells.

Wind

Winds on the surface of the Earth are experienced as air moves from high to low pressure areas in the convection cells.

What are tropical storms?

• Tropical storms are natural hazards that occur when tropical warm air rises to create an area of intense low pressure.
• The sea temperatures must be above 27oC, to a depth of 60-70 metres.
• This provides the heat & moisture that causes the warm air to rise rapidly in this low-pressure region.
• Latent heat is then released which powers the tropical storm.
• There is usually a low wind shear = wind remains constant and doesn't vary with height.
• Tropical storms do not develop along the Equator, because the Coriolis effect is not strong enough for storms to spin.

Topic: Causes of tropical storms and the sequence of their formation and development

1. Air is heated above the surface of warm tropical oceans.

2. Warm air rises rapidly under low-pressure conditions.

3. Strong winds form as rising air draws up more air & moisture.

4. The rising air spins around a calm central eye of the storm due to the Coriolis effect.

5. The rising air cools, condenses => cumulonimbus clouds and torrential rainfall

6. Heat is given off as it cools, powering the tropical storm. 7. Cold air sinks in the eye so it is clear, dry and calmer.

7. The tropical storm travels across the ocean with the prevailing wind.

8. On meeting land, it loses its source of heat and moisture so loses power. Storms track north in the northern hemisphere and south in the southern hemisphere

How might climate change affect tropical storms?

• As the temperature increases, sea levels will rise due to thermal expansion => rising sea levels => storm surges will become higher.

• Warmer atmosphere => air can hold more moisture => heavy rainfall is expected to increase => flooding expected to be more destructive

Topic: How climate change might affect the distribution of tropical storms

Distribution

The location of tropical storms is not expected to change significantly, but there may be more in areas such as the South Atlantic and parts of the subtropics as sea surface temperatures increase

Topic: How climate change might affect the frequency of tropical storms

Frequency

The overall frequency of tropical storms is expected to stay the same or decrease. However, the frequency of powerful category 4 and 5 storms is expected to increase, while weaker category 1-3 storms will decrease.

Topic: How climate change might affect the intensity of tropical storms

Intensity

Since the 1970s the number of the most severe category 4 or 5 tropical storms has increase. Every 1oC increase in sea surface temperature will mean a 3-5% increase in wind speed

CASE STUDY: The effects of Typhoon Haiyan (2013)

PRIMARY effects :

Social

• 50% of houses destroyed.
• 4.1 million made homeless. - 6,190 people died.

Economic

• US$12 billion of damage.
• Damage to rice crops costs US$53 million.
• 75% of farmers & fishermen lost their income.

Environmental

• Oil barge ran aground = 800,000 litre oil leak.
• 400 millimetres of rainfall caused flooding.
• 1.1 million tonnes of crops were destroyed.

CASE STUDY: The effects of Typhoon Haiyan (2013)

SECONDARY effects

Social

• Diseases spread due to contaminated water.
• Power supplies were cut off for a month.
• Many schools destroyed = education affected.

Economic

• Airport badly damaged + roads blocked by trees.
• Looting was rife due to a lack of food & supplies.
• By 2014, rice prices had risen by nearly 12%

Environmental

• 10 hectares of mangroves were contaminated by the oil barge leak.
• Flooding caused landslides.

CASE STUDY: Responses to Typhoon Haiyan (2013)

IMMEDIATE responses

• Authorities evacuated 800,000 people.

• Philippine government ensured vital supplies were sent out, but in one regional centre medical supplies were washed away.

• Emergency aid supplies arrive 3 days later by plane. Within 2 weeks, 1 million food packs + 250,000 litre of water given out.

• The government imposed a curfew 2 days after the typhoon to reduce looting.

CASE STUDY: Responses to Typhoon Haiyan (2013)

LONG-TERM responses

• 33 countries and aid agencies pledged help. More than US$1.5 billion was pledged in foreign aid.

• In July 2014, government established "Build Back Better" idea. Buildings were upgraded to protect against future disasters.

• A 'no-build zone' was established in the Eastern Visayas. Homes were rebuilt away from flood-risk area.

• President promised to rebuild 205,000 homes in coastal areas, but 3 years after, only 25,000 built, with only 2,500 occupied.

Topic: How monitoring can reduce the effects of tropical storms

MONITORING

Fact ~

• NASA used 2 aircrafts - global hawk drones - to monitor weather across the Atlantic

• Allows predictions to be made

Topic: How prediction can reduce the effects of tropical storms

PREDICITON

Fact ~

• National Hurricane Centre predicts storms path + intensity in advance

• Are able to give warnings + show accurate locations

Topic: How protection can reduce the effects of tropical storms

PROTECTION

Fact ~

• Bangladesh has 2,500 cyclone shelters along 710km of coastline

• To reduce damage

• Elevated to reduce flooding risk

Topic: How planning can reduce the effects of tropical storms

PLANNING

Fact - National Hurricane Preparedness Week

• Know what to do in the case of a Hurricane

What is extreme weather?

• Extreme weather includes unexpected, severe or unseasonal weather, which is clearly different to the usual weather pattern.
• Extreme weather is defined as being in the most unusual 10%.

What CAUSED the 'Beast from the East'?

• Under normal circumstances, winters in the UK are mild due to a polar vortex - a large mass of cold air - in the upper atmosphere. This vortex is what causes air to usually move from west to east.
• However, there was a huge rise in air temperature of around 50oC in an area around 18 miles above the Earth in the North Pole.
• Sudden stratospheric warming caused a weakening of the jet stream. This led to a change in direction of the winds approaching the UK from west to east to east to west, allowing a cold air mass (polar continental air mass) from Russia to cover the UK

What were the IMPACTS of the 'Beast from the East'?

• SOCIAL - 10 people died during the extreme weather event.

• ECONOMIC - £1.2bn in lost revenue due to disrupted businesses.

• ENVIRONMENTAL - Rural areas had temperature lows of -12°C.

How did MANAGEMENT STRATEGIES help to reduce the risk?

• Flood warnings were issued by the Environment Agency for parts of Cornwall's south coast. Residents told to expect tides to be 400mm.
• High on the Pennines on the M62, the military was called in to help rescue vehicles stranded in 50cms of snow.
• Rail passengers were warned to avoid travelling to/from Scotland.

Is the UK's weather getting more extreme?

• Extreme weather is not new to the UK. There are many examples of extreme weather in the past.
However, the frequency of extreme weather in the UK is increasing.

• Since the 1980s, UK temperatures have increased by about 1°C and winter rainfall has increased.

What are the predictions for future UK weather?

• Precipitation is expected to become even more seasonal. But the annual UK total will stay the same.
• Some rivers are expected to flood more frequently in winter.
• Evaporation will increase (higher air temperatures) => drought.

Is climate change responsible?

• Climate change cannot be responsible for individual extreme weather events.
Yet scientists suggest that the increasing frequency of extreme events can be blamed on climate change.

• Evidence suggests that climate change is warming the planet. The Atlantic Ocean is increasing in temperature, which can help explain the UK's changing rainfall pattern.

• Yet there are long-term cyclical changes also taking place e.g. the Atlantic was relatively warm between 1931 & 1960, before cooling.

What is the Quaternary Period?

• The Earth is believed to be 4.6 billion years old and so geologists have divided time into: era, periods & epochs.

• The periods of time that stretches from 2.6 million years ago to the present day is called the Quaternary Period and is split into two epochs: the Pleistocene & Holocene.

What is the evidence for climate change?

• An increase in air temperatures by 1oC over 100 years.

• The warmest ocean temperatures since 1850.

• A 19 centimetre rise in sea levels since 1900.

Evidence from ICE CORES and OCEAN SEDIMENTS

• Antarctic ice cores act like time capsules, holding information about climate change as different layers of snow build up. Records go back about 800,000 years ago.

• The ratio of 18O and 16O oxygen isotopes are measured to work out what climate was like.

• The billions of tonnes of sediment deposited at the bottom of the sea also act as a timeline for providing evidence of climate change.

Organisms & plankton in ocean sediments reveal water temperatures, oxygen levels & nutrients

CASE STUDY: Possible natural causes of climate change
SOLAR OUTPUT

SOLAR OUTPUT

• The solar output of the Sun is measured by observing sunspots on the Sun's surface. Sunspots are causes by magnetic activity.

• The output of the Sun increased slightly from 1900 to 1940.

• However, satellite data shows that solar output from the Sun has barely changed in the last 50 years. In fact, it has decreased slightly, so solar output cannot be responsible for recent changes.

CASE STUDY: Possible natural causes of climate change
ORBITAL CHANGES

ORBITAL CHANGES

• The Earth's orbit around the Sun is an ellipse, and every 100,000 years it changes shape => alters distance => alters Earth's climate.

• The Earth's axis is tilted on an angle. The angle of tilt moves back & forth every 41,000 years => exaggerates climate change.

• The Earth is not a perfect sphere, so as the Earth spins, it wobbles on its axis in a 20,000-year cycle.

CASE STUDY: Possible natural causes of climate change
VOLCANIC ACTIVITY

VOLCANIC ACTIVITY

• Volcanic eruptions can temporarily cause climate change. In June 1991, Mount Pinatubo in the Philippines erupted, with ash thrown vertically 40km into the stratosphere.

• Approximately 20 million tonnes of sulphur dioxide was released by Mount Pinatubo, reflecting sunlight away. Following the Mount Pinatubo eruption, global temperatures dropped by 0.5oC.

CASE STUDY: Possible human causes of climate change
FOSSIL FUELS

FOSSIL FUELS

• Burning fossil fuels accounts for over 50% of greenhouse gas emissions. Burning these releases CO2 into the atmosphere.

• Fossil fuels are used in transportation, building, heating homes, manufacturing & burnt in power stations to generate electricity.

• As the world's population increases, people are demanding more & more energy, which increases the levels of fossil fuels and CO2.

CASE STUDY: Possible human causes of climate change
AGRICULTURE

AGRICULTURE

• Agriculture contributes about 20% of the global greenhouse gas emissions & large quantities of methane from cattle digestion.

• As the world's population increases, more food is required, especially in Asia where rice is the staple diet.

• When countries increase their standard of living, there is almost always an increasing demand for meat => more CO2 and CH4.

CASE STUDY: Possible human causes of climate change
DEFORESTATION

DEFORESTATION

• Deforestation is the clearing of forests on a huge scale. If this continues at the current rate = no forest in 100 years.

• The main reasons why forests are cut down include clearing land for agriculture (see above), logging, building roads & settlements.

• The process of deforestation leaves fewer trees to absorb CO2, whereas burning felled trees releases all the captured CO2.

CASE STUDY: Managing climate change: mitigation (action taken to reduce greenhouse gases)
RENEWABLE ENERGY

RENEWABLE ENERGY

Fact ~

• 2019, renewable energy made up 40% of the UK's energy mix, more than gas at only 39%

Alternative energy production - such as wind, solar, geothermal, wave & tidal - reduced greenhouses gases compared to burning fossil fuels (coal, oil & gas). They will last longer. Still expensive, but becoming cheaper.

CASE STUDY: Managing climate change: mitigation (action taken to reduce greenhouse gases)
CARBON CAPTURE