Topic 1: Hazardous Earth

Global circulationThe atmosphere transfers heat around the Earth in a global circulation system. The way this circulation system creates areas of low pressure and high pressure explains why the Earth has areas with high rainfall (low pressure) and arid/dry (high pressure) areas. 1. Warm air rises at the equator. This is an area of low pressure2. Cool air falls. This is an area of high pressure.3. As the air falls, it warms again and flows back to complete

the cycle

Natural causes of climate changeThere are many natural causes of climate change throughout millions of years. These include: The Earth’s orbit changes a small amount once every 1,000,000 years. These are known as Milankovitch

cycles The amount of energy radiates from the Sun changes over an 11-year cycle Volcanic eruptions pump ash dust into the atmosphere causing a cooling effect Large asteroid collisions can cause cooling as material blocks out of the Sun. Asteroids hitting the Earth

can cause huge fires which release massive amounts of CO2 which subsequently has a warming effect Ocean current changes can cause cooling and warming. In the UK, we have a warm and wet climate

because of warm Atlantic currents. Sometimes the current shifts and we get a cooler climate for a short period of time.

Human causes of climate change Most scientists agree that the Earth’s climate is warming and that the warming is mostly due to human activity. Global warming is commonly due to rising atmospheric CO2. This is a power greenhouse gas and is released by many human activities, including: industry, transport, energy production, and farming.

The enhanced greenhouse effect: Heat (UV rays) from the Sun reaches the Earth’s atmosphere. Some is reflected back into space The land and oceans absorb the heat The land and oceans then radiate infrared heat back into the atmosphere Greenhouse gases in the atmosphere trap some of the heat (necessary for life on Earth) Human activity increases greenhouse gases in the atmosphere, leading to more warming

Evidence of climate change1. Global temperatures are rising – for example, in 2015 the average global temperature was 1oC above

the average global temperature in 1850-19002. Atmospheric CO2 levels are rising in parallel with global temperatures. This is mostly due to human

activity3. The oceans warmed by 0.11oC per decade between 1971 and 2010 4. Sea levels rose globally by about 14cm during the 20th century 5. Arctic sea ice covers 13% less of the sea each decade 6. Extreme weather events have become more frequent: heat extremes are 5 times more common now

than a century ago.

Consequences of global warming Biodiversity loss on land and in the oceans Coastal flooding from sea level rises More destruction from more frequent, stronger hurricanes

Spread of pests and diseases Changes in farming that could affect food supplies Loss of glaciers would mean water supply problems in some areas More flood from more frequent, heavier precipitation More droughts, lasting longer

Location of tropical cyclones Tropical cyclones are violent tropical storms. They have different names around the world – hurricanes,

cyclones, and typhoons. Tropical cyclones only form where seawater temperatures are above 26.5oC. This means they’re only

found around the tropics (starting between 5o and 30o latitude). They only occur in summer and late autumn when seawater gets the warmest.

Characteristics of tropical cyclonesThey have the following 3 key characteristics:1. Low pressure – very warm, moist air rises through the atmosphere, sucking more air up behind it2. Rotation – the Earth’s spin (Coriolis force) helps the rising air to spiral and drags in strong winds (there

isn’t much spin at the equator)3. Structure – tropical cyclones form a cylinder of rising, spiralling air surrounding an eye of descending,

high-pressure air. They are up to 640km wide and 10km high.

Formation of tropical cyclones1. Warm sea temperatures and high humidity – there needs to be a lot of moisture in the atmosphere 2. Rapid cooling – rising air must condense quickly to generate the huge amounts of energy powering a

tropical cyclone3. Low wind shear – if winds are blowing in different directions up through the atmosphere, the cyclone

won’t form 4. Coriolis force to give the cyclone spin – this isn’t usually strong enough within 5o latitude of the

equator

5. Pre-existing low-pressure disturbances – tropical cyclones usually form when smaller storms come together

Measuring tropical cyclone intensity The Saffir-Simpson scale classifies tropical cyclones into 5 categories

Category

Max. wind speed (km/hour)

Pressure (millibars)

Storm surge (metres) Damage

1 119-153 980 and over 1.0-1.7 Some damage – trees lose branches, power lines come down

2 154-177 979-965 1.8-2.6 Roofs and winds damaged, some trees blown over, coastal flooding

3 178-208 964-945 2.7-3.8 Structural damage to buildings. Flooding over 1m up to 10km inland

4 209-251 944-920 3.9-5.6 Major devastation – destroys buildings, floods up to 10km inland

5 252 or higher <920 >5.7 Catastrophic – destruction up to 5m above sea level. Mass evacuation needed

Physical hazards on people from tropical cyclones People may drown in the strong currents created by floodwater and storm surges Windspeeds in tropical cyclones can be strong enough to completely destroy buildings, which

means people are left homeless High winds and floodwater can carry large amounts of debris, which can kill or injure people Electricity supplies are cut off because cables are damaged or swept away by floodwater Flooding causes sewage overflows which contaminate water supplies The shortage of clean water and lack of proper sanitation makes it easier for diseases to spread In poorer countries, there’s often a shortage of food because crops are damaged and livestock

killed Unemployment increases because businesses are damaged or destroyed Damaged roads make it very difficult for aid and emergency vehicles to get through

Physical hazards on the environment from tropical cyclones Trees are uprooted by high winds which can damage or completely destroy wooded habitats Storm surges can erode beaches and damage coastal habitats, e.g coral reefs Flooding caused by storm surges can pollute freshwater environments with saltwater Landslides deposit sediment in rivers and lakes, which can kill fish and other wildlife Flooding can damage industrial buildings on the coast, e.g. oil or chemical factories. This causes

harmful chemicals to leak into the environment and cause pollution

Reasons why countries may be vulnerable to the impacts of tropical cyclonesPhysical vulnerability

1. Low-lying coastlines are vulnerable to storm surge flooding as well as large waves caused by the high winds

2. Areas in the path of tropical cyclones are hit more frequently 3. Steep hillsides may increase the risk of landslides

Economic vulnerability. Poorer countries are economically vulnerable because:1. Many people depend on agriculture which is often badly affected – this leads to a loss of livelihoods2. People may not have insurance to cover the costs of repairing damage caused by cyclones3. However, the economic impact is often greater in richer countries as the buildings and

infrastructure (roads, rail, bridges, etc) damaged are worth a lot more money.

Social vulnerability. Poorer countries are often more socially vulnerable because:1. Buildings are poorer quality so more easily damaged2. Healthcare isn’t as good so they struggle to treat all the casualties 3. There is little money for flood defences or training emergency teams4. It’s harder to rescue people because of poor infrastructure.

Strategies to prepare and respond to tropical cyclonesForecasting 1. When and where tropical cyclones will hit land can be predicted

2. Scientists can use weather forecasting and satellite technology to monitor cyclones. Computer models are then used to calculate a predicted path for the cyclone

3. The cyclone’s magnitude can be monitored by measuring its windspeed4. Predicting where and when a tropical cyclone is going to happy given people time

to evacuate and protect their homes and businesses, e.g. by boarding up windowsEvacuation 1. Warming strategies are used to alert people to a tropical cyclone. An alert will give

people enough time to leave their homes and get to a safe place2. Governments can plan evacuation routes to get people away from storms quickly3. Successful evacuations can reduce the number of deaths and injuries4. Emergency services can train and prepare for disasters, e.g. by practising rescuing

people from flooded areas with helicopters. This reduces the number of people killed

Defences 1. Defences (e.g. sea walls) can be built along the coast to prevent damage from storm surges. Buildings can also be designed to withstand a storm surge, e.g. they can be put on stilts so they’re safe from floodwaters.

2. This will reduce the number of buildings destroyed, so fewer people will be killed, injured, made homeless, and made unemployed.

Case studies on tropical cyclones

Developed country: USA Developing country: MyanmarBackground info

Name: Hurricane KatrinaMagnitude: Category 3 Place: South east USADate: 29th August 2005

Name: Cyclone NargisMagnitude: Category 4 Place: Irrawaddy delta, MyanmarDate: 2nd May 2008

Forecasting The USA has a sophisticated monitoring system to predict if and where a hurricane will hit

The National Hurricane Centre (NHC) in Florida tracks and predicts hurricanes using satellite images and planes that collect weather data on approaching storms

Myanmar doesn’t have a dedicated monitoring centre for tropical cyclones

Myanmar doesn’t have a radar network that can predict the height of storm surges and waves caused by clones

Warning & Evacuation

The NHC issued a hurricane warning on 26th August for Louisiana, Mississippi and Alabama. It continued to track the hurricane, updating the government on where and when it would hit

Mississippi and Louisiana declared states of emergency, and 70-80% of New Orleans residents were evacuated before the hurricane reached land. This reduced the

Indian weather agencies warned the government of Myanmar that Cyclone Nargis was likely to hit the country 48 hours before it did

Warnings were issued on the TV and radio, but they didn’t reach people in poor rural communities. This meant that people were killed because they didn’t know what to do or where to evacuate to

There were no emergency preparation plans, no evacuation plans and the country

number of people killed because lots of people had left the area where the hurricanes hit.

didn’t have any early warning system.

Defences The city of New Orleans was very badly damaged – flood defences (e.g. embankments) that were supposed to protect the city failed

This caused widespread flooding (over 80% of the city was underwater)

Mangrove forests protect the coast from flooding but loads had been chopped down in the decade before Nargis hit, reducing the natural protection

Impacts on environment

Coastal habits such as sea turtle breeding beaches were damaged

Some coastal conservation areas were destroyed, e.g. around half of Breton National Wildlife Refuge in Louisiana was washed away

Flooding damaged oil refineries in Louisiana, causing massive oil spills

The Irrawaddy delta in Myanmar was the hardest hit area – a large proportion of it is only just above sea level and 14,000km2 of land was flooded

38,000 hectares of mangrove forests were destroyed

The flooding caused erosion and salination (increased salt content) of the land

Impacts on people

More than 1800 people were killed 300,000 houses were destroyed

and hundreds of thousands of people were made homeless

3 million people were left without electricity

Roads were damaged and some bridges collapsed

230,000 jobs were lost from damaged businesses

More than 140,000 people were killed 450,000 houses were destroyed and

350,000 were damaged Around 65% of rice paddies in the

Irrawaddy delta were damaged, which led to a loss of livelihoods

A lot of people suffered from diseases caused by poor sanitary conditions and contaminated water

Layers of the Earth

1. At the centre of the Earth is the core: The core is a ball of solid (inner) and liquid

(outer) iron and nickel At the centre, it’s very dense. It becomes less

dense further out The temperature inside the core ranges from

4,400-6,000oC

2. Around the core is the mantle: The mantle is made up of silicon-

based rocks The part of the mantle nearest the

core is quite rigid The layer above this, called the asthenosphere, is semi-molten (it can flow) And the very, very top bit of the mantle is rigid The temperature of the mantle is between 1,000 and 3,700oC. It is hotter towards the core and

cooler towards the Earth’s surface

3. The solid outer layer of the Earth is called the crust: The crust is also made up of silicon-based rocks There are two types of crust – continental and oceanic

Continental crust is thicker and less dense Oceanic crust is thinner and more dense

4. The crust is divided into slabs called tectonic plates

Convection CurrentsTectonic plates move due to convection currents in the mantle

1. The tectonic plates float on the mantle2. Radioactive decay of some elements in

the mantle and core, e.g. uranium, generates a lot of heat

3. When lower parts of the asthenosphere heat up they become less dense and slowly rise

4. As they move towards the top of the asthenosphere they cool down, become dense, then slowly sink

5. These circular movements of semi-molten rock are called convection currents6. Convection currents in the asthenosphere create drag on the base of the tectonic plates (which are

solid and rigid) – and this causes them to move

Plate boundariesPlate boundary Description

Convergent boundaries Convergent boundaries are where two plates are moving towards each other, e.g. along the west coast of South America

Where an oceanic plate meets a continental plate, the dense oceanic plate is forced down into the mantle and destroyed

This often creates volcanoes and ocean trenches (very deep sections of the ocean floor where the oceanic plate goes down)

Where two continental plates meet, the plates collide, and the ground is folded and forced upwards to create mountain ranges

Divergent boundaries Divergent boundaries where two plates are moving away from each other, e.g. at the mid-Atlantic ridge.

Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust

Conservative boundaries Conservative boundaries are where two plates are moving sideways past each other, or are moving in the same direction but at different speeds, e.g. along the west coast of the USA

Crust isn’t created or destroyed

Volcano formation Volcanoes are found at convergent and divergent plate boundaries At convergent plate boundaries the oceanic plate goes under the continental plate because it’s more

dense. Here, the oceanic plate moves down into the mantle, where it’s melted and destroyed. A pool

of magma is then formed. The magma rises through cracks in to crust called vents. The magma then erupts into the surface (where it’s called lava) and formed a volcano.

At divergent plate boundaries the magma rises up into the gap created by the plates moving apart, forming a volcano

When a volcano erupts, it emits lava and gases. Some volcanoes emit lots of ash, which can cover land, block out the sun and form pyroclastic flows (super-heated currents of gas, ash, and rock).

Hot spotsSome volcanoes form in the middle of tectonic plates over hotspots: They occur where a plume of hot magma from the mantle moves towards the surface, causing an

unusually large flow of heat from the mantle to the crust Sometimes the magma can break through the crust and reach the surface. When this happens, there is

an eruption and a volcano forms Hotspots remain stationary over time, but the crust moves above them. This can create chains of

volcanic islands, e.g. Hawaii is a chain of volcanic islands in the middle of the Pacific plate

Types of volcanoesThere are two types of volcanoes: composite and shield.

Composite volcanoes Shield volcanoes

Occur at convergent plate boundaries Subducted oceanic crust contains lots of water. The

water reacts with magma and creates gases, which can cause the subducted crust to erupt

They have explosive eruptions that start with ashy explosions that deposit a layer of ash

They erupted andesitic lava that has a high silica content which makes it thick and sticky. The lava can’t flow far so forms a steep-sided cone

Example: Mount Fuji in Japan

Occur at hotspots or divergent plate boundaries

They are not very explosive and are made up of only lava

They erupt basaltic lava, which has low silica content and is runny. It flows quickly and spreads over a wide area, forming a low, gentle-sided volcano

Example: Mauna Loa on the Hawaiian islands

Earthquake formationEarthquakes occur at all three types of plate boundaries (convergent, divergent and conservative). 1. Earthquakes are caused by the tension that builds up at all three types of boundaries2. The plates eventually jerk past each other, sending

out shock waves (vibrations). These vibrations are the earthquake

3. Earthquakes are measured using the moment magnitude scale, which measures the energy released by the earthquake. You may still see some references to the Richter scale (which also measures the energy released) but it’s no longer used by scientists

Earthquake depths

The focus of an earthquake is the point in the Earth where the earthquake starts. This can be at the Earth’s surface or anywhere up to 700km below the surface

Shallow-focus earthquakes are caused by tectonic plates moving at or near the surface. They have a focus between 0km and 70km below the Earth’s surface

Deep-focus earthquakes are caused by crust that has previously been subducted into the mantle (e.g. at convergent plate boundaries) moving towards the centre of the Earth, heating up or decomposing. They have a focus between 70km and 700km below the Earth’s surface

In general, deeper earthquakes do less damage at the surface than shallower earthquakes. Shock waves from deeper earthquakes have to travel through more rock to reach the surface, which reduces their power (and the amount of shaking) when they reach the surface.

Tsunamis Earthquakes can cause tsunamis Tsunamis are a series of enormous waves caused when huge

amounts of water get displaced Underwater earthquakes cause the seabed to move, which

displaces water. Waves spread out from the epicentre of the earthquake (the point on the Earth’s surface that’s straight above the focus)

The depth of an earthquake affects the size of a tsunami – shallow-focus earthquakes displace more water because they’re closer to the Earth’s surface. This creases the size of a tsunami

The waves travel very fast in deep water so they can hit the shore without much warning. This means they can cause a high death toll.

Management of tectonic hazards

Earthquakes Earthquakes cannot be reliably predicted, but

scientists can still monitor certain signs that could indicate that an earthquake is likely

Lasers can be used to detect the movement of tectonic plates before an earthquake

Vibrations in the Earth’s crust can be monitored using seismometers. If vibrations increase, it could mean there’s going to be an earthquake

Scientists can measure gases (e.g. radon) that escape from cracks in the crust just before an earthquake

Rocks will crack and expand because of the increased pressure just before an earthquake

Volcanoes Volcanic eruptions can be predicted if the

volcano is well-monitored to look for the tell-tale signs that come before a volcanic eruption

Things such as tiny earthquakes and changes in the shape of the volcano (e.g. bulges in the land where magma has built up under it) all mean an eruption is likely

Thermal imaging cameras can be used to detect changes in temperature around the volcano. Temperatures increase before an eruption

Scientists can analyse the gases escaping from a volcano. Volcanoes emit lots of sulphurous gases before an eruption

Long-term planning to help countries prepare for tectonic hazardsWealthier, more developed countries can plan for tectonic hazards to help reduce the impacts: Emergency services can train and prepare for disasters, e.g. by practising rescuing people from

collapsed buildings or setting up shelters. This will reduce the number of people killed Buildings can be designed to withstand earthquakes, e.g. by using strong materials like reinforced

concrete or building special foundations that absorb an earthquake’s energy People can be educated so that they know what to do if an earthquake or eruption happens

Governments can plan evacuation routes to get people out of dangerous areas quickly and safely in case of an earthquake or volcanic eruption. This reduces the number of people killed or injured by things like fires, pyroclastic flows or mudflows

Emergency supplies like blankets, clean water and food can be stockpiled. If a natural hazard is predicted the stockpiles can be moved close to areas likely to be affected.

Short-term relief after a disasterShort-term relief deals with the immediate impacts of a tectonic hazard. Well-prepared countries are better able to: Provide food, drink and shelter to evacuated people Treat people who have been injured (e.g. from falling debris) to prevent more deaths Recover dead bodies to prevent the spread of disease Rescue people who have been trapped (e.g. in collapsed buildings) or cut off by damage to roads or

bridges Provide temporary supplies of gas, electricity, and communications systems if regular supplies have

been damaged

Earthquake case studiesDeveloped country: Japan Developing country: Pakistan

Background info

Where: North-east JapanWhen: 11th March 2011Magnitude: 9.0 on Richter scale

Where: Kashmir, PakistanWhen: 8th October 2005 Magnitude: 7.6 on Richter scale

Prediction The Japan Meteorological Agency (JMA) and local governments monitor seismic activity all over the country

If an earthquake is detected, people are warned immediately

Up until recently, there wasn’t extensive monitoring of seismic activity in Pakistan

This means earthquakes could strike without warning

Preparation Strict building laws help prevent major damage during an earthquake

Buildings are reinforced with steel frames to prevent them from collapsing

High-rise buildings have deep foundations with shock absorbers to reduce vibrations and shaking in the building

Japan has early warning systems to alert residents to earthquakes and tsunamis

High-speed ‘bullet’ trains automatically brake in the event of an earthquake to stop them from derailing

Automatic alarms stop mechanical equipment to alert workers and prevent injuries

As a developing country, Pakistan doesn’t have access to the same building materials or technologies as Japan

Many buildings are constructed using wood and cement which are easily destroyed during earthquakes

Up until recently, building laws didn’t include measures of protection against earthquake damage. Even now, they’re often ignored when constructing new buildings

Poor communication networks make it difficult to alert the population

Long-term planning

Japan’s population is educated on being prepared for earthquakes, e.g. Disaster Prevention Day is an annual nationwide drill to practice

There are lots of poor, remote settlements in Pakistan that have no education programme for teaching people what to do if there’s an earthquake

evacuations in the event of an earthquake

Schools carry out drills to teach children what to do if there’s an earthquake

People living in coastal communities practise getting to higher ground or emergency bunkers in the event of an tsunami

Planning evacuations is difficult because there are very few roads and poor communications

Primary impacts

Thousands of buildings were damaged

The earthquake caused severe liquefaction (where waterlogged soil behaves like a liquid). This caused many buildings to tilt and sink into the ground

The Pakistan earthquake causes around 80,000 deaths, mostly from collapsed buildings

Tens of thousands of people were injured Hundreds of thousands of buildings were

damaged or destroyed, including whole villages

Around 3 million people were made homeless

Water pipelines and electricity lines were broken, cutting off supply

Secondary impacts

The earthquake triggered a tsunami which killed thousands of people

Hundreds of thousands of buildings were completely destroyed. Over 230,000 people were made homeless

The tsunami cut off the power supplies to the Fukushima nuclear power plant, causing a meltdown

Road and rail networks suffered severe damage, e.g. 325km of railway tracks were washed away

Landslides buried buildings and people. They also blocked access roads and cut off telephone lines

Diarrhoea and other diseases spread due to the lack of clean water

Freezing winter conditions shortly after the earthquake caused more casualties and meant rescue and rebuilding operations were difficult

Short-term relief

International aid and search and rescue teams were brought in

Rescue workers and soldiers were sent to help deal with the aftermath

Transport and communications were restored a couple of weeks after the earthquake

Power supplies were restored in the weeks following the earthquake

The Pakistani army was initially slow to respond to the disaster

Help from India was refused because of political tensions between Pakistan and India

Help didn’t reach many areas for days or weeks, and many people had to be rescued by hand without any equipment or help emergency services

Tents, blankets and medical supplies were distributed, although it took up to a month for them to reach most areas

Long-term planning

The Japanese authorities gave an advance warning of the earthquake and the tsunami, which gave people time to evacuate and get to higher ground

Despite very strong shaking in Tokyo, not a single building collapsed thanks to buildings

Fault lines in the Himalayas were poorly monitored, which means that the Pakistan earthquake was unpredicted

The absence of building laws meant buildings weren’t reinforced and were extremely vulnerable to damage from earthquake shaking

Most buildings had been constructed using

designed to prevent earthquake damage

Nobody died on the bullet train network because of the automatic braking systems

poor quality materials, e.g. cement made from sand which crumbled during the earthquake