Geography Paper 1

Hazardous Earth

Climate

Tropical Cyclones

Tectonic Hazards

Climate

No case studies

Atmospheric Circulation

Air moves in a global pattern of circulation that transfers heat around the earth

Solar radiation

Drives our climate system. The suns rays heat earth, which in turn heats the air

Air pressure

The force or weight that the atmosphere exerts on earth

Low pressure

Where warm air is rising - creates unsettled weather and rainfall

High pressure

In areas of high atmospheric pressure air is sinking creating settled dry conditions

Wind

Is air moving from low to high pressure

Coriolis effect

The rotation of earth causes wind to follow a curved path

ITCZ

The intertropical convergence zone - is the band around the equator that receives the most concentrated solar radiation moves up and down throughout the year due to the tilt of the earth

Circulation cells

The polar, ferrel and hadley cells are the names of the main convection currents in the atmosphere

Hadley cell

Warm moist air rises at the ITCZ creating a band of low pressure rain and tropical rainforests at 30’ north or south the air cools and sinks creating a band of high pressure and arid deserts

Jet stream

Fast flowing rivers of air in the upper atmosphere that form between the polar and ferrel cells

Oceanic circulation

Convection currents also exist in the ocean e.g. the gulf stream impacting climates around the world

Climate change

The average climatic conditions of the planet vary over time earths climate has been through many cycles of natural cooling and warming in its 4.5 billion year history

Milankovitch cycles

Changes in the earths orbit affect the energy we receive from the sun e.g.

eccentricity - circular orbit = warmer earth , elliptical orbit = colder earth

axial tilt - when earth is more tilted, more extreme conditions

Other natural causes of climate change

Solar variation - changes in the amount of energy the sun produces

Volcanic eruptions - ash in atmosphere blocks out solar radiation

Asteroid collisions - also causes huge amounts of dust in the atmosphere

Evidence for natural climate change

Ice cores - analysing air bubbles trapped in ancient ice sheets in greenland allows us to see how atmospheric CO2 levels have changes

Tree rings - in warmer and wetter climates the space between rings widen

Historical sources - historical painting, diaries and records provide more evidence

The greenhouse effect

Natural processes that keep the earth warm enough to sustain life. greenhouse gases in the atmosphere (e.g. carbon dioxide, methane) trap some of the suns heat and stop it from being lost to space

The enhanced greenhouse effect

Human activity has greatly increased the amount of greenhouse gases in the atmosphere creating global warming as too much heat is trapped in

Evidence of human activities causing climate change

Global average temperature rise - measurements show an unusually rapid rise since the 1950s this correlates with rising CO2

Sea level rise - caused by melting ice, and thermal expansion (water expanding as it warms)

Declining arctic ice - each year more arctic ice melts in the summer

Human causes of climate change

Energy: burning fossil fuels (coal, oil, natural gas) releases CO2

Industry: rising incomes = more demand for manufactured goods

Transport: more people taking flights and driving cars burns more fuel

Agriculture: Intensive farming of cattle and rice creates methane

Consequences of climate change

Sea level rise could flood low lying islands, farmland and coastal settlements

Increased temperatures will melt sea ice and glaciers/increase droughts

Extreme weather - more tropical cyclones/heat waves/ flooding from intense rainfall

Predictions about climate change

Uncertainty around different variables (e.g. will human greenhouse gases continue rising) mean that projections of climate change impacts show a range of possible scenarios

Tropical Cyclones

2 case studies

Tropical cyclone

Large scale, rotating storms that form over the ocean in tropical areas - Southern hemisphere = spin clockwise , Northern hemisphere = spin anti clockwise

How do tropical cyclones form

1. Warm oceans heat the air above them, causing it to rise and creating extreme low pressure

2. Surrounding air rushes into the low pressure area, creating high winds

3. The warm rising air contains water vapour evaporated from the ocean this condenses into cumulonimbus (storm) clouds, bringing heavy rain

4. The Coriolis effect causes the wind and storm clouds to spin around a central point - the eye of the storm here cool air is sinking (high pressure) so it is cloudless and clear

Source regions

The area in which a tropical cyclone forms

What conditions are needed for cyclones to form

1. Warm seawater - water must be over 26.5℃ and 10-12km deep to provide the heat energy needed for tropical storms

2. Location - Tropical storms between 5-20° N and S of the equator (but not at the equator itself because there is not enough coriolis effect there)

3. Low wind shear - if winds at different heights are blowing at different speeds/directions they will pull the stoms apart

Cyclone seasons

Tropical cyclones form in late summer/autumn when oceans have warmed up

What hazards to tropical cyclones bring

1. Strong winds

2. Storm surges

3. Intense rainfall

4. Landslides

Strong winds

winds up to 160 miles an hour can take down power lines, trees and buildings, destroying settlements and killing/injuring people

Storm surges

Low pressure cyclones cause the ocean to expand as less air is pressing down on it this causes an extremely high tide that can flood coastlines

Intense rainfall

Tropical storms bring incredibly intense rainfall that can flood settlements and crops

Landslides

Land saturated by rainfall can give way, endangering property and lives.

Track

The pathway that a cyclone follows, driven by the patter of global wind circulation

Dissipation

When a cyclone moves over land or colder ocean it loses power as it no longer in contact with its heat source (warm seawater)

Saffir Simpson scale

Scale from 1-5 used to classify the power of a tropical cyclone, based on wind speed

Why are some countries more vulnerable to tropical storm?

1. Socio-economic factors

2. Physical factors

Socio-economic factors

• Housing and infrastructure in developing countries tends to be weaker and more easily damaged 

• Developing countries may have less funding for forecasting and early warning systems

• Populations with more very young or old people are more vulnerable as these age groups cannot evacuate as fast

Physical factors

Low-lying coastlines and islands are more vulnerable to flooding by storm surges

How can countries prepare for and respond to tropical cyclones?

1. Weather forecasting

2. Early warning systems

3. Evacuation strategies

4. Storm surge defences

Weather forecasting

Satellite technology can detect and monitor tropical storms. Computer models can combine data from satellites, weather stations, and aeroplanes to predict the path that a storm will take. 

Early warning systems

Vulnerable populations can be alerted to approaching storms via radio, text and TV and encouraged to prepare (e.g. reinforce buildings and prepare emergency kits)

Evacuation strategies

• Higher income countries with good roads and widespread car ownership can evacuate people quickly away from the coast.

• In developing countries people people can still be evacuated locally to storm shelters (raised, concrete buildings)

Storm surge defences

Coastal embankments and sea walls can be built to guard against flooding from storm surges

Case studies

1. Typhoon Haiyan, 2013

   The Philippines

   Developing country: HDI: 0.71

2. Hurricane Katrina, 2005

   USA

   Developed country: HDI 0.92

Haiyan power

• Category 5 tropical storm (one of the most powerful ever recorded)

• 195mph winds

• Originated in the NW Pacific Ocean

• Waves of up to 7m in height

Katrina power

• Category 5 tropical storm

• 175 mph winds

• Storm originated over the atlantic and made landfall over Louisiana and Florida

• Caused storm surges of over 6m

Haiyan impacts

• 7000 people killed

• Caused $5.8 billion of damage

• 1.9 million made homeless

• 90% of Tacloban (Philipines capital city) was flattened

• 71,000 hectares of farmland was affected.

Katrina impacts

• 1,800 people killed

• Caused $125 billion worth of damage (the costliest storm ever recorded)

• 80% of the city of New Orleans was flooded.

Haiyan planning + preparation

The Philippines is a fairly poor part of the world with fewer resources for prediction, planning and protection.

They had evacuation shelters but many were not built high enough to withstand the 7m storm surges.

PAGASA, the Philippines' meteorological agency saved many lives by broadcasting warnings 2 days before Typhoon Haiyan hit. This lead to the evacuation of approximately 750,000 residents.

Katrina planning + preparation

Although the state made an evacuation order, many of the poorest people remained in New Orleans because they either wanted to protect their property or could not afford to leave

More than half of New Orleans lies below sea level and is protected from the Mississippi river by levees. However these did not withstand the storm surges and water flooded the city.

Haiyan response

The Philippines formally declared 'A State of National Calamity' and asked for international help, one day after Typhoon Haiyan hit the country.

The Tacloban city government was devastated, with only 70 people at work immediately after the disaster. Many were killed, injured or simply too traumatised to work.

The United Nations launched an international aid appeal for £480 million to finance the humanitarian relief effort

Katrina response

The US Government was heavily criticised for its handling of the disaster. Despite many people being evacuated, it was a very slow process. The poorest and most vulnerable were left behind.

The Superdome stadium was set up as a centre for people who could not escape the storm. However there was a shortage of food & the conditions were unhygienic.

Looting occurred throughout the city. The National Guard was mobilised to restore law and order.

The government provided $50 billion in aid.

Tectonic hazards

2 case studies

Crust

The rocky surface of the earth (also known as the lithosphere)

Earth’s crust is cool and solid. It is split into tectonic plates that move at 2-5 cm per year

Continental crust

Forms the land. Made mostly of granite. (30-50km) thick.

Oceanic crust

Forms the seabed. Much thinner (6-8km) and denser. Made of basalt.

Astenosphere

Partially molten, uppermost layer of the mantle - upon which the lithosphere moves around.

Mantle

Mostly solid, made of peridotite rock.

Temperature is between 1000-4000℃

Outer core

Liquid because so hot

Composition: iron and nickel

Temperature: Outer core - 4000 -5000℃

Inner core

Solid because it is under so much pressure

Composition: iron and nickel

Temperature: Inner core reaches up to 5400 (as hot as the surface of the sun)

Radioactive decay

The reason that earth’s core is hot. Radioactive elements in earth’s core (e.g. uranium) decay and release huge amounts of heat.

Convection currents

The heat of the core causes earth’s mantle to move in circular movements, dragging tectonic plates along with it.

Conservative Boundary

When two continental plates move alongside each other - creating earthquakes. E.g. San Andreas fault, California

Convergent boundary

When oceanic + continental crust collides the denser oceanic crust is forced (subducted) under the continental plate. Huge pressure causes large volcanic eruptions & earthquakes.

E.g. Andres Mountains in Chile / Peru

Divergent boundary

Found under the ocean where two oceanic plates are moving apart. Underwater shield volcanoes create new oceanic crust

 e.g. mid-Atlantic Ridge

Earthquake causes

As plates slide past each other or collide, friction along the fault (crack) between them causes them to stick. Tension builds up until the plates slip, releasing energy as seismic waves.

Focus

The point underground, between two plates, where the earthquake takes place. The nearer to the earth’s surface this is, the more devastating the earthquake can be.

Epicentre

The point on earth’s surface, directly above the focus.

Magnitude

The power of an earthquake. 

Measured using the Richter scale, a logarithmic scale so each step up is 10 times more powerful than the last

Composite volcano

Explosive, violent volcanoes found on convergent boundaries. Lava is viscous (sticky) and doesn’t flow far before it solidifies, so the volcano builds into a cone shape

Shield volcano

Volcanoes with gently sloping sides. Lava is runny, so volcanoes are less explosive.

Found on divergent boundaries

Tsunami

Giant waves are usually caused by an underwater earthquake displacing water and creating a fast-moving wave that travels across the sea. When the wave reaches shallow water near the coast it is pushed up and becomes taller.

Primary impacts

Instant impacts, caused directly by the shaking of the ground

E.g. buildings collapsing, railway lines and roads buckling, deaths from falling rubble

Secondary impacts

Impacts that happen later, as a result of the secondary impacts

E.g. fires from fallen power lines, disease outbreaks, homlessness, tsunamis, looting

Prediction

Trying to foresee when a hazardous event might hit a country

Earthquake prediction methods

Methods of predicting earthquakes are still very limited and unreliable:

1/ Use a seismometer to monitor vibrations in the earth’s crust. Increasing vibrations could signal an impending earthquake

2/ Monitoring radon gas escaping from earth’s crust. An increase could indicate an earthquake

Volcano prediction methods

Volcanic eruptions are easier to predict by:

1/ Using thermal imaging to monitor increasing temperatures in the volcano

2/ Using a seismometer to monitor small earthquakes that occur as magma forces its way upwards through cracks

Planning and preparation

Taking action to reduce the impacts of any earthquakes that may hit
E.g. having trained & funded emergency services, running safety drills in schools and workplaces, building earthquake resistant buildings and tsunami shelters

Earthquake resistant buildings

In developed countries, ‘base isolation’ and steel cross bracing stops buildings from swaying

In poorer locations housing can still be made safer e.g. by using lightweight thatched roofs, and bamboo frames instead of brick / concrete

Seisometer

The instrument used to measure earthquakes and vibrations in the earth’s crust

Case studies

1. Haiti, 2010

   Developing country

   HDI: 0.49

2. Sendai bay, Japan, 2011

   Developed country

   HDI 0.91

Haiti causes

• Conservative plate boundary (North American + Caribbean plate sliding past each other)

• Magnitude 7 earthquake

• Focus 10km deep / epicentre 25 km from Haiti’s capital city, Port-au-Prince

Sendai bay causes

• Convergent plate boundary (Pacific plate is subducting under Eurasian plate)

• Magnitude 9 earthquake

• Focus was 30km deep /epicentre 70km from the coast

• Earthquake triggered a deadly tsunami

Haiti primary impacts

• Poorly built homes collapsed killing 316,000 

• Key infrastructure (e.g the port and  roads) totally destroyed

• Economic cost: $8 million

Senpai bay primary impacts

• Collapsing buildings killed 1,500 

• Damaged roads, rail, power, water

• Costliest disaster in history: $235 million of damage

Haiti secondary impacts

• Clean water cut off and cholera outbreak killed 8,000

• Loss of income - Haiti’s clothing factories which provide 60% of exports were damaged

• 1 million were made homeless

Senpai bay secondary impacts

• Created a 40m high tsunami that killed 15,500 thousand people

• Fukushima nuclear power was flooded and went into meltdown

Haiti prediction

There is no way of predicting earthquakes

Senpai bay prediction

No way of predicting earthquakes but the Pacific Tsunami warning centre gave people some time to evacuate from tsunami

Haiti planning and preparation

Not prepared at all:

• poor quality, densely packed buildings made of heavy concrete blocks - none were earthquake resistant

• did not have trained emergency services or infrastructure to cope.

Senpai bay planning and preparation

More prepared:

• 70% Earthquake resistant buildings in the area

• Well-trained emergency services

• Regular drills in public buildings in how to evacuate for tsunamis and protect oneself in a earthquake

Haiti short term response

Initially chaos and no one in charge - the port was destroyed so aid could not get in.

Senpai bay short term response

Rescue workers and military were mobilised immediately.

Haiti long term response

• Relied on international aid e.g. the US and UN

• Some buildings took 10 years to be replaced

Senpai bay long term response

Buildings were restored in 4 years

Development dynamics

1 case study

Level of development

How wealthy a country is, and how much progress it has made in health care, education, democracy etc