A Level geography Revision lesson

Learning objective: To review our learning so far

and identify gaps in our knowledge

Revision session based on lesson so far (Nov

2016)

Revision session based on lesson so far (Nov

2016)

1. Concepts of Hazards

2. Plate tectonics 3. Storm Hazards

4. Volcanic Hazards

1. Nature, forms and potential impacts of natural hazards (geophysical, atmospheric and hydrological).

2. Hazard perception and its economic and cultural determinants.

3. Characteristic human responses – fatalism, prediction, adjustment/adaptation, mitigation, management, risk sharing – and their relationship to hazard incidence, intensity, magnitude, distribution and level of development.

4. The Park model of human response to hazards. 5. The Hazard Management Cycle.

When does a hazard become a hazard?

Natural Event Population

No hazard

Natural Event Population

If there is an interaction= hazard!

Nature of the hazard

Complete the mind map below; what factors

change the impacts of a hazard?

Factors that affect the nature

of the hazard

Scale of the disaster e.g. size of earthquake or volcano.

A hazard is a threat which has the potential to cause injury, loss of life, damage to property, socio-economic disruption or environmental

degradation.

What is a Hazard?

Socio-economic disruption: disruption to social lifestyle or economic aspects.

Environmental degradation: the deterioration of the natural environment.

Think back over the last couple of lessons..

There are a number of ways we can classify hazards.

Look at the list below and think of the categories that you could sort them into.

How can we classify hazards?

CATEGORIES

Nature of the hazard (e.g. geomorphological, biological, tectonic)

Natural or man made

Magnitude

Frequency

Impact

Think.. Are these categories suitable? Is there overlap? Can you

see any issues with using them?

Characteristics

Natural Hazard Characteristics

Clear origins and distinctive effects

Scale and impact requires emergency response

Little or no warning Involuntary exposure to risk

Damage and loss of life occur shorty after

hazard, with long term impacts

Effects Primary Secondary Short Term Long Term

Death

Economic Loss

Loss of wildlife

Storm Surge

Poverty

Climate Change

Flood

Infrastructure Damage

Disease

Homelessness

Injury

Food Scarcity

Emotional Stress

Evacuation

Tsunami

Fires

Shaking

Pyroclastic Flow

Effects

Task: Identify using a tick which of the categories each of the effects can be grouped in. Can you think of two more effects and repeat the process.

Adaptation: Implementing strategies to

prevent the event becoming a hazard. Earthquake proof

buildings.

Fatalistic: An optimistic approach

Some believe that hazards are God’s will.

Losses are inevitable People stay where they are.

Prediction: Using technology available to them to

predict and prepare for the event. E.g. weather forecasts and seismic

monitoring.

Risk Sharing: Insurance to ensure that the cost of a hazard is spread between a

number of parties.

Quick questions: Which of these is more suited to an LIC? Which of these is more suited to a HIC?

Why?

Managing Natural Hazards

Community Preparedness/Risk

Sharing

Integrated Risk Management

Mitigation

Monitoring Prediction

Prevention

Protection

Reconstruction

Rehabilitation

Relief Resilience

Responses

There are 3 different types of responses that people can have to hazards: 1. Fatalism (acceptance) 2. Adaptation 3. Fear

For each of the 7 influences identify which responses are likely to occur. E.G. High level of education will likely have the response of adaptation. 1. Socio-economic status 2. Level of education 3. Occupation/ employment status 4. Religion, cultural/ethnic

background 5. Family and material status 6. Past experience 7. Values, personality and

expectations.

Fatalism (Acceptance) = Such hazards are natural events that are part of living in an area. Some communities would go as far as to say that they are ‘God’s will’. Action is therefore usually direct and concerned with safety. Losses area accepted as inevitable and people remain where they are. Adaptation = People see that they can prepare for, and therefore survive the event(s) by prediction, prevention and technological circumstances of the area in question. Fear = The perception of the hazard is such that people feel so vulnerable to an event that they are no longer able to face living in the area and move away to regions perceived to be unaffected by the hazard.

The park model for responding to a hazard

Look at the model in front of you. What do you think the model is trying to show?

Things you need to know;

The model refers to the strategies and approaches taken to being

‘back to normal’ after a disaster.

These methods span from immediate ‘relief’ to providing

temporary housing to reconstructing after the damage.

Each of these is more easily

achieved in countries with higher incomes.

The Risk Management cycle.

Both before and after a disaster, whether that be hydrological,

atmospheric or geophysical strategies can be used to reduce the damage of the current and

future hazards.

The Risk Management cycle outlines the appropriate strategies

that can be taken.

Construct your own cycle and try to come up with an example for each

stage.

1. Earth structure and internal energy sources. 2. Plate tectonic theory of crustal evolution: tectonic plates;

plate movement; gravitational sliding; ridge push, slab pull; convection currents and sea-floor spreading.

3. Destructive, constructive and conservative plate margins. 4. Characteristic processes: seismicity and vulcanicity. 5. Associated landforms: young fold mountains, rift valleys,

ocean ridges, deep sea trenches and island arcs, volcanoes.

6. Magma plumes and their relationship to plate movement

Layers of the Earth

Characteristics Continental Crust Oceanic Crust

Thickness 6-10 km 30-70 km

Age Less than 200 million years

Over 1.500 million years

Density 2.6 (lighter) 3.0 (heavier)

Composition Mainly granite; silicon, aluminium, oxygen (SIAL)

Mainly basalt; silicon, magnesium, oxygen (SIMA)

Crust Characteristics

Plate Tectonics

• This picture shows the plates of the world and the way they are moving.

Plate Movement

Convection currents, basal drag and slab suction The higher temperatures of the earth’s core generate zones of hotter, more fluid magma

which upwells, with cooler and denser material sinking downward, creating a continuous

circulatory motion (mantle convection currents).

These pull the crust apart by basal drag (friction) at spreading ridges and rift zones, and pull

oceanic crust down in to the mantle (slab suction) at subduction zones.

Slab pull Plate motion is also driven by the weight of cold, dense plates sinking into the mantle at

trenches.

Gravitational sliding (slab push) As oceanic lithosphere is formed at spreading ridges from hot mantle material, it gradually

cools and thickens with age (and thus distance from the ridge). Cool oceanic lithosphere is

significantly denser than the hot mantle material from which it is derived and so with

increasing thickness it gradually subsides into the mantle, resulting in a slight lateral incline

with distance from the ridge.

Plume tectonics This is an alternative theory which suggests that mantle plumes are the major driving force of

the earth’s plates.

Evidence for Plate Tectonics

Explanation

Continental fit Jigsaw fit of continental shelves proved that they were once joined together

Fossils Fossils of similar species are found in South America and South Africa

Climate Zones Certain places experienced ice ages when their location would deem that impossible

Geology Rocks of similar composition found in different places. Identical rocks found in opposite locations which means they once formed side by side.

Plate Boundaries and hotspots (or hot plumes)

https://www.youtube.com/watch?v=AhSaE0omw9o

https://www.youtube.com/watch?v=bYv6V5EJAKc

What is a hotspot?

Hotspots

Hotspots are volcanic regions fed by underlying mantle that is

anomalously hot compared to the mantle.

The two theories (hot spots)

• Tuzo Wilson: Theory in 1963. That a static radioactive element in the mantle which creates plumes of magma. Satellite imagery shows bulges in the earth’s crust which shows that there are large plumes of magma near the surface.

• ALTERNATIVE

• Foulger: 2003 faults in the crust are responsible for allowing the plume of magma through the crust. Weaknesses in tectonic plates responsible for the formation of hotspots.

Landforms created by tectonic processes

Ocean Trenches are deep water areas that run along a coastline which has a destructive plate margin. They are created by subduction, and mark the point where the Oceanic crust is being pushed under the Oceanic crust. There is often quite a large section of continental crust between this margin and the ocean's edge, and sometimes a volcanic island arc such as Japan or the Aleutian Islands can be found in between the trench and the continental shelf. These are not to be confused with mid ocean ridges, which are long ridges of mountains created by 2 plates moving apart at a constructive plate margin. Where these mountains rise above the level of the sea Islands such as Iceland are formed. http://www.coolgeography.co.uk/A-

level/AQA/Year%2013/Plate%20Tectonics/

Plate%20tectonics/Margins%20and%20lan

dforms.htm

Landforms created by tectonic processes

Fold mountains are large mountain ranges where the layers of rock within them have been crumpled as they have been forced together. They can be formed at destructive or collisional plate boundaries, where tectonic plates are moving together forcing layers of rock to be crumpled upwards. The layers of rock can form 2 basic features, if the folding is up over the feature if known as an anticline, or down over into a syncline. If the folded rocks in an anticline go over the top of themselves we get a feature known as an overfold.

What are mantle plumes? •Stationary, long-lived areas of heat flow within the mantle •They have a long thin tail and a bulbous head that spreads out at the base of the lithosphere. •A HOTSPOT exists above a magma plume. •The magma is mafic and produces a shield volcano.

Ocean Trenches

1. The nature of vulcanicity and its relation to plate tectonics:

2. Forms of volcanic hazard: nuées ardentes, lava flows,

mudflows, pyroclastic and ash fallout, gases/acid rain, tephra.

3. Spatial distribution, magnitude, frequency, regularity and

predictability of hazard events.

4. Impacts: primary/secondary, environmental, social, economic,

political.

5. Short and long-term responses: risk management designed

to reduce the impacts of the hazard through preparedness,

mitigation, prevention and adaptation.

6. Impacts and human responses as evidenced by a recent

volcanic event.

Describe the distribution of volcanoes

Introduction.

• Volcanoes are vents (openings) in the Earth’s crust through which lava, tephra (ash, dust and fragments of material produced in a volcanic eruption) and gases erupt.

• Molten rock beneath the surface is called magma, but when it is ejected at the surface it is called lava.

• Magma, in addition to molten rock, may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in magma chambers that may feed a volcano or turn into a pluton.

• Underground, the enormous pressures exerted by overlying rocks keeps hot rocks in a semi-solid state.

• Fissures and fractures in the crust create areas of lower pressure that allow some of the rocks to become molten and rise.

• If these molten rocks reach the surface they are said to be extrusive.

• If they are injected in to the crust without reaching the surface they are called intrusive.

Volcanoes are classed as:

Active: have erupted in living memory

Dormant: have erupted within historical record

Extinct: will not erupt again

Types of Lava

• At different plate boundaries volcanoes have different characteristics..

• This is because the elements in the magma change.

• Magma is classified by the amount of silica present..

Basaltic/Basic lava (45-52%silica) Andesitic/Acid Lava (52-66% silica)

Hot (12000C) & runny, low viscosity Viscous, cooler (8000C) flows more slowly for

shorter distances

Low silica content Higher silica content

Flows as rivers of molten rock as takes longer to

cool

Flows very short distances as soon cools and

solidifies

Keeps its gas content so is more mobile Loses gas quickly so becomes more viscous

Produces extensive, gently sloping landforms Steep-sided, localised features

Relatively gentle but frequent eruptions Less frequent eruptions but are violent because of

gas build up

Lava and steam erupted Pyroclastics- ash, rock, gases & steam and lava

ejected

Found at constructive plate margins

e.g. fissures along Mid-Atlantic Ridge

e.g. over hot spots –Mauna Loa, Hawaii

Found at destructive margins where oceanic crust

is destroyed, melts & rises

e.g. subduction zones Mt. St.Helens

e.g. as island arcs Mt. Pelee, Martinque

Volcanoes at different plate boundaries The tectonic setting of volcanic activity- CONSTRUCTIVE

Oceanic Rift Volcanism

Ocean ridges occur due to the ocean lithosphere being stretched and thinned by tectonic forces. This thinning allows mantle material to rise which causes widespread melting and volcanism.

This volcanism mainly takes the form of fissure eruptions along spreading Mid-Oceanic Ridges such as the Mid Atlantic ridge. Such volcanoes tend to produce basic or basaltic lavas. These lavas have a relatively low viscosity and are mobile, forming gently sloping lava domes, called shield volcanoes.

Continental Rift Volcanism

Where the lithosphere is thinning, the mantle is able to rise. This occurs within vast rift valleys.

The acidic, viscous magmas erupt explosively when gas bubbles escape, forming composite and dome volcanoes.

The most notable example of this form of volcanism is along the East African Rift Valley, which extends for over 4000 km.

Subduction Zone Volcanism

When cold oceanic lithosphere is subducted into the mantle, at depths of approximately 125 km this basaltic material begins to melt and yields a magma.

Magmas derived from the melting of the basaltic ocean floor are less dense than the mantle; they rise through fissures and melt their way through the overlying rock until they form volcanoes on the surface.

At sites of oceanic and continental plate convergence, the magma incorporates elements of the continental crust as it rises, becoming more silica-rich, producing viscous, acidic andesitic lava which creates explosive composite volcanoes.

Hot spots It has been suggested that mantle plumes originating deep within the mantle are

responsible for volcanic activity away from constructive and destructive plate margins,

e.g. the Hawaiian Islands.

As basaltic shield volcanoes erupt through the drifting oceanic crust, volcanic islands

form. As the plate moves, the volcanoes gradually move away from the heat source and

become less active or extinct. Shield volcanoes are known for their frequent but gentle

eruptions.

New volcanoes erupt over the fixed hot spot and a chain of volcanic islands are formed.

Some islands will become eroded by waves and form flat-topped sea mounts called

guyots.

Effect of volcanoes

• nuées ardentes,

• lava flows,

• mudflows,

• pyroclastic and ash fallout,

• gases/acid rain,

• tephra

_________________________ _____________________ ______________________

_____________________ _____________________

Effects of Volcanoes

Primary Effects Secondary Effects

Tephra Pyroclastic flows/Nuees

Ardentes Lava Flows Volcanic

Gases

Lahars

Flooding

Volcanic landslides

Tsunamis

Acid Rain

Climate change

Tephra

Pyroclastic flows

Lava flows

Volcanic gases

Lahars

Flooding

Volcanic Landslides

Tsunamis

Acid Rain

Climate Change

1. The nature of tropical storms and their underlying causes.

2. Forms of storm hazard: high winds, storm surges, coastal

flooding, river flooding and landslides.

3. Spatial distribution, magnitude, frequency, regularity,

predictability of hazard events.

4. Impacts: primary/secondary, environmental, social, economic,

political.

5. Short and long-term responses: risk management designed

to reduce the impacts of the hazard through preparedness,

mitigation, prevention and adaptation.

6. Impacts and human responses as evidenced by two recent

tropical storms in contrasting areas of the world.

Nature, Distribution and Magnitude

The “hurricane season” is just a name for the time period when we expect to see tropical systems develop. The hurricane season for the Atlantic runs from June 1st – November 30th. Peak season is the middle part of

September…why do you think this is?

What Exactly Is a Hurricane?

A hurricane can best be described as a huge tropical storm (up to 600 miles in diameter)!

Winds can be up to 200 mph!

Storm usually doesn’t last for more than 7-10 days.

It moves across the ocean at around 10-20 mph…not too fast really!

The winds are the strongest around the eye wall. The eye of the storm is usually about 20 miles in diameter. Within the eye, winds are

calm and the weather is great. Strongest winds are on the right side, heaviest rain is usually on

the left side.

Arrows indicate “feeder bands”

or “rain bands”

Where are these “Atlantic Basin” Hurricanes forming?

Storms of the Atlantic basin will begin forming in one of three places:

• Off the coast of Africa

• In the Caribbean Sea

• In the Gulf of Mexico

What is the ITCZ?

Intertropical Convergence Zone

The ITCZ is an area of low pressure located roughly 5 degrees North and South of the Equator. It is a place where air converges, rises, and condenses (forming clouds). It is the rainiest place on Earth!

What Does a Hurricane Need in Order to Develop?

A hurricane needs: • Warm water (>27°C, time to grow, winds are too strong, they will blow the

hurricane apart – we ca • Favorable upper level winds in the troposphere. If the ll that wind shear! • Ocean depth >70m, this moisture provides latent heat to drive the system. • Location 5°N or 5°S of the equator.

Saffir-Simpson Scale of Hurricane Intensity

What kind of damage are we talking about here?

The vulnerability of people to storm events depends upon a range of factors, both Physical and human: • The intensity of the storm • Speed of movement, the length of time over a

specific area. • Distance from the sea • Physical geography of the coastal area – width of

the coastal plain or size of delta • Preparations made by a community. • Warnings and community response.

Heavy Rainfall

Floods: Flooding occurs when water rises. More people are killed by floods during a hurricane than by any other hazard. Tidal surges push ocean water in hurricanes and can cause deadly flash flooding. Landslides and mudslides can cause devastation.

Winds

They can often exceed 150mph, this can cause structural damage to buildings, roads and bridges. They can bring down electricity transmission lines and devastate agricultural areas. Debris that is throw about causes serious threat to people’s lives.

What is a storm surge? Storm surge: Storm surge is a massive dome of water, that sweeps across the coast near the area where the eye of the hurricane makes landfall. The stronger the hurricane, the higher the storm surge. For those living along the coast, storm surge is one of the most dangerous parts of a hurricane. Here are examples of a storm surge flooding a coastal town.

Prevention Cloud seeding over the oceans to increase precipitation has been investigated, however the long term effects have not been validated.

Prediction Using weather satellites, hurricanes can be plotted with computer models to predict their path. This gives correct warnings and allow for accurate evacuation. In the USA, it costs $1m to evacuate 1 km of coastline. Often there is only 12-18hours warning, not enough time for a proper evacuation.

Protection Evacuation being a priority to reduce deaths. This leaves property open to looting. There are ways to strengthen homes and hurricane drills are practised. Seawalls, breakwaters and flood barriers can be out in place to reduce coastal flooding.

Preparedness This included mitigation plans, e.g. North Carolina Outer Banks have a plan to save lives, reduce costly damage improve the speed of recovery and have post disaster funding.

Reducing the impacts

Behavioural or structural.

Preparedness – increasing awareness of the hazard and through their actions minimise the likely impact of the hazard.

Mitigation – actions aimed at reducing the severity of the an event, which can involve direct intervention or post event support in the form of aid and insurance.

Prevention – actions aimed at preventing large scale events occurring e.g. wildfires.

Adaptation – accepting that natural events are inevitable and adapting our behaviour accordingly.

Preparedness • Education and public awareness

• Minor structural alteration on buildings

• Planning evacuations

• Insuring property

• Cyclone shelters

• Use satellites to track and monitor

• Computer models to issue ‘Hurricane Watch’ if winds are predicted within 36 hrs.

• ‘Hurricane Warning’ if landfall in 24hrs.

• NOAA uses SLOSH (sea, lake and overland surges from hurricanes)

Mitigation Structural mitigation

• Soft engineering – planting trees and building up beaches.

• Hard engineering – sea walls,

• Coral reefs reduce storm surge intensity, work to protect coral reefs.

• North Carolina offers grants to maintain homes to be storm safe. This leads to less insurance claims and lower premiums.

Disaster Aid

• Immediate humanitarian aid – search rescue, food, water, medicines and shelter.

• Longer term reconstructural aid to support recovery and reconstruction.

• After a disaster most nations seek help from neighbouring countries. EU, world bank, NGO’s or UN.

Hurricane Matthew October 2016 • Category 4 Hurricane • Made landfall at Haiti on

Monday 3rd October • High levels of rainfall • Moving at 7mph, meaning

some places will have more than 24 hours of prolonged rainfall.

• Central winds around 40mph but gusts up to 145mph.

Matthew: How do Florida and Haiti compare?

Florida

Haiti

How were they prepared?

In Florida, there have been mass evacuations of the coastal areas. Millions of people were urged to leave their homes in the southern US states. In some areas traffic was rerouted to allow people to escape. Residents stocked up on food, water and petrol, causing long queues at fuel stations. Many residents also shored up their homes with shutters and plywood boards.

n Haiti, preparedness was difficult as the country is fragile and vulnerable to disasters. But evacuations were ordered for some high-risk areas, including in outlying islands where people were brought to safety by boat. Since the earthquake in 2010, the country has also been hit by Hurricane Sandy in 2012. It also suffered a drought. Infrastructure is poor in rural areas, making it difficult for the local population to prepare for such a large-scale disaster.

What is the infrastructure like?

In Florida, Governor Rick Scott said 600,000 people were without power. But Florida Power and Light, the largest energy provider in the state, said they already had 15,000 people in place to respond to the power cuts. The state opened 147 shelters for more than 22,300 people during the storm.

In Haiti, emergency rescue teams have struggled to reach the hardest hit areas. In the city of Jeremie, 80% of buildings were levelled and 30,000 homes destroyed in Sud province. Care International says the city of Jacmel is also badly affected. The number of people in shelters increased from 2,700 to 4,000 in one day.

What is the damage like?

n Florida, the extent of the damage is still unclear, but hundreds of thousands, if not millions are expected to lose power. Homes may also be destroyed.

In Haiti, hundreds of people have been killed as a result of the storm and aid agencies are warning of a possible cholera epidemic. Care International's country director in Haiti says three people have already been infected. People also face an immediate food crisis as the storm wiped out many Haitians' food reserves and crops.

What's the government's response like?

In Florida, Governor Rick Scott has strongly advised residents to evacuate and take shelter. President Barack Obama has declared a state of emergency in Florida and has released federal funds.

In Haiti, the government has been slow to respond, leaving many affected residents to fend for themselves. Many Haitians have been angered and frustrated. Some international NGOs are already on the ground in Haiti working to provide food, shelter, and water to local residents. US military personnel are expected to deliver food and water to the worst affected areas in several helicopters.

http://www.bbc.co.uk/news/world-us-canada-37584632

Hurricane Katrina Overview

Between the dates of August 23rd and August 31st, a category 4 hurricane hit the south eastern coast of America, causing billions of dollars’ worth of damage – mainly to the city of New Orleans. Hurricane Katrina was the eleventh named storm and fifth hurricane of the 2005 Atlantic hurricane season.

It was the costliest natural disaster (just over $108 Billion US Dollars), as well as one of the five deadliest hurricanes on record. It is also ranked as the 3rd most intense hurricane in the history of the United States. As the hurricane moved itself of the water and onto land, it struck New Orleans as a category 4, but out at sea the hurricane was rated a category 5. Winds of up to 140mph were recorded in and around New Orleans.

Causes

Deep water, Hurricane Katrina formed over the Atlantic Ocean consisting of deep waters. This is well known around this area as ‘Hurricane Alley’. It has been assigned its’ name because of numerous hurricanes being formed here.

Warm water, most hurricanes need at least 27 C, but Katrina had an average surface temperature of 32 C.

Equatorial trade winds – winds that follow the line of the equator around the globe. As the air cools the trade winds lose the track of the equator and travel in different directions away from the equator.

The rotation of the Earth. Needed for almost every hurricane and is a natural process.

Hurricane Katrina Effects • After the hurricane passed, a spokesman said “New Orleans suffered from a large

number of casualties, a lack of drinkable water, severe property damage, electrical outages and many more difficulties as a result of Hurricane Katrina.”. By August the 31st 2005, almost 80% of New Orleans was flooded. The flooding was mainly caused because of the city being below sea level. Levees (flood walls) surrounded the city but because of the 6m high storm surges the city went underwater.

• Category 4 storm

• The most severe parts of the hurricane lasted from 25th to 30th of August.

• 1,500 people killed

• $108 Billion US Dollars

• 80% of New Orleans Flooded

• Storm surges over 6m in height

• People sought refuge in the Superdome stadium. Conditions were unhygienic, and there was a shortage of food and water. Looting was commonplace throughout the city.

• Tension was high and many felt vulnerable and unsafe.

• One million people were made homeless.

• Oil facilities were damaged and as a result petrol prices rose in the UK and USA.

Hurricane Katrina Responses On 31st August, president Bush calls for a whole evacuation of the city and advises everyone to leave if possible. He sent $50 million US Dollars of aid to the city within a matter of days. The majority of people refused to leave and stayed in their homes or the super dome. Among the aftermath was criticism towards the authorities for being slow in their response towards the disaster. Although many people were evacuated I was a slow process. The poorest and weakest would usually be left behind. The police, national guard and other authorities seemed to care more about restoring justice and law to the streets instead of rescuing people from their homes that were underwater. The super dome became a violent and unhygienic place, even though this was what saved many people’s lives during the hurricane. Eventually, the super dome was also evacuated meaning nearly all of the cities inhabitants were forced to leave.