Unit 2 Revision PowerPoint

TROPICAL STORMS

What are tropical storms?

There are four types of tropical storms:• Hurricanes• Willy willies• Typhoons • Cyclones These are the different terms used, butthey all mean the same!!

What is a tropical storm?• Tropical storms are large areas of low pressure or extreme depressions• Depressions bring very wet and windy conditions. Depressions occur all throughout the year, but

are most common around Autumn into Winter. Depressions also bring lots of clouds with them (try to remember a Depression as a depressingly wet and windy day!!!)

• The opposite to a Depression is an Anti-Cyclone. Anti-cyclones bring calm weather with clear skies. You can also experience an anti-cyclone all throughout the year. During the summer months, anti-cyclones bring very hot weather with very little cloud and no rain, during the winter you usually get clear skies at night which makes it very cold. Usually in winter you will get lots of frost and fog in the morning as the night brought clear skies. Brrrrrrrr!!! Anti-Cyclones are also referred to as areas of High Pressure.

• On satellite images they are shown up as, swirling masses of cloud, with the eye clearly visible at the centre

• The eye of the storm is where you will find the calm and clear area at the centre of the tropical storm.

• THINK: Why do you think that the eye of the storm may be considered as being dangerous to people?

What is a hurricane?

The formation of a tropical storm could appear in two types of question; one involving diagrams and the other asking for a more detailed written response. Make sure that you can tackle both tasks effectively.

EXAM TIP

Where can we find tropical storms?

Task: Name down four countries that experience tropical storms.

Images of Haiti, an between the Caribbean Sea and the Atlantic Ocean

The island of Haiti was greatly affected by Hurricane Hanna

Task: 1. Describe what these images show you 2. Using the photos, can you identify the primary and secondary effects?

What is a Storm Surge?

http://www.nhc.noaa.gov/HAW2/english/storm_surge.shtml

Storm surges: Abnormal rise of the sea along a shore as the result of a storm; sometimes called a tidal surge

Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm.

This advancing surge combines with the normal tides to create the hurricane storm tide.

This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides.

The level of surge in a particular area is also determined by the slope of the continental shelf. A shallow slope off the coast (right, top picture) will allow a greater surge to inundate coastal communities.

Communities with a steeper continental shelf (right, bottom picture) will not see as much surge inundation, although large breaking waves can still present major problems. Storm tides, waves, and currents in confined harbours severely damage ships, marinas, and pleasure boats.

A storm surge is...

Reducing the damage from tropical storms

In order to reduce the damage from tropical storms, people are advised to follow these three steps:

Forecast Prepare Act

Forecasting and Preparing for Tropical Storms

Did you know?!?! Forecasters analyse large amounts of weather data and use complexcomputer modelling, but still only have a 20-25% chance of knowing exactly where atropical storm will strike 48 hours in advance.

Two large agencies monitor the movement of tropical storms, one is the ‘National Hurricane Centre’ (Atlantic) and the other is the ‘Joint Typhoon Warning Centre’ (Pacific).

Warnings are issued to places where a tropical storm is likely to strike, but it is difficultto predict their movement with complete accuracy. WHY?

Tropical Cyclone Aila

What happened?

Tropical Cyclone Aila hits Bangladesh and India on Monday 25th May 2009 (LEDCs)

The tropical cyclone formed in the North Indian Ocean basin which includes the Bay of Bengal and the Arabian Sea

For a tropical storm to form it needs the sea surface temperature to exceed 27 degree centigrade and this is common throughout the year in some regions of the Bay of Bengal

Tropical Cyclone Season:The first tropical cyclone season peaks in April and May and the second in late October-early November and are caused by areas of low pressure

Effects of the Aila Tropical Cyclone

Tropical cyclone Storms are the more dangerous and harmful in Bangladesh, They kill many people and livestock and destroy houses and crops as they push inland with force. The effects of the storm surge are greatest when the storm hits at the time of high tide.

Aila has left 27 dead and over 400,000 affected in West Bengal so far.

NGO schemes in Bangladesh

Most people in less developed countries, such as Bangladesh, are unable to afford the same protection as those in richer countries like the USA.

With the help of Non-Government Organisations (NGOs), simple yet effective measures are being put in place to protect people from the cyclones that strike the country.

Wildfires Warm

Up

What & Where are they?• Wildfires are a major hazard.• Can spread quickly & burn for a long time!• Dead plants mean that the fires will spread

quickly.• Santa Ana Winds – drive the Californian wildfires.• Physical geography (shape) also affects the

spread.• South facing slopes mean that the sun dries

vegetation. • Steep slopes encourage the fire.

CASESTUDY : California – Mainly physical Causes

CASESTUDY: Greece – Mainly Human Causes

CAUSES

Natural• Lightning – Biggest single cause of

wildfires.• Need the right conditions to

develop as smaller strikes die out quicker.

• Spontaneous Heating - is the warming up of material until it catches fire without a spark being present.

• Need large amounts of dead dry plant.

• Volcanic eruptions - with red hot lava and ash.

• Hot & Dry conditions.

Human• Accidents – to blame for

starting many wildfires.• Matches, Campfires, Cigarettes.• Broken bottles magnify the

sunlight.• Slash & burn, can get out of

control.• Arson is when people set fires

deliberately.• Others include sparks from

train wheels or machinery, military, BBQs & Chimneys.

EFFECTS

Primary• Loss of Life• Injury• Destruction of Property &

Possessions• Burning of Vegetation &

Crops• Water & Air Pollution• Health Problems• Breathing Difficulties

Secondary• Loss of Jobs & Income• Farm Workers & Businesses• Homelessness• Rebuilding of Properties takes a

long time• Insurance increase• Damage to Economy• Tourism disrupted• Restricted access to recreational

areas• Increase risk of soil erosion &

landslides • Increased surface run-off• Loss of habitats

Responses• Fire-Fighting teams spray them with water & foam.• Aeroplanes & Helicopters can access the area• AIR DROPS • Water & Fire-Retardant chemicals• Large Buckets attached to planes• Fire lines/fire breaks, act as a barrier• Dig trenches or clear areas of ground• Remove dry grasses, bushes, leaves, twigs, which act as fuel for

the fire• Pulaski – cross between a hoe & an axe• Backfire – controlled burning in the path of the fire.

Preventing & Preparing

• Volunteer groups – remove leaves• Controlled burning• EDUCATION! Enhances public awareness• The Smokey Bear campaign• Advice on burning debris- Reducing the risk of sparks- Posters, leaflets, advertisements, - DVD’s sent to schools• Evacuation plans• GIS technologies

Prediction (more to come)• Changes to wildfire intensity (severity of burning)• Increase in areas experiencing them• Increase in wildfire season• High amount of wildfires coincide with above-average temperature

and early snowmelt• Some scientists believe that climate change, due to global

warming, mean that wildfires will continue to increase• They also believe that areas that don’t currently experience

wildfires will do soon• In areas where they are common they will burn for longer, and be

more intense• These will release stored CO2 into the atmosphere, further

contributing to global warming.

Other Beliefs

• Some believe that periods of increased wildfires are part of a natural cycle

• Higher temperatures & lower rainfall• Detailed studies of wildfires across the globe

to see if changes are permanent

• Cost of damage is increasing• Especially in MEDCs

INSIDE THE EARTH• There are four main layers of

Earth• The inner core is a solid. It is five

times more dense than surface rocks.

• The outer core is a liquid. • The mantle is a semi liquid,

containing low-density material, and is about 2,900 km thick.

• The crust is a solid and is divided into two main types: oceanic crust and continental crust. The crust• The depth of the crust varies

between 6 km and 64 km. • Continental crust is mostly formed

of granite. • Continental crust is less dense than

the oceanic crust. • Because it is denser the oceanic

crust plunges beneath the continental one when they come together.

The crust is solid and varies in size between about 6 to 64km (4 to 40 miles) thick

The mantle is semi liquid at the top solid near the bottom. And is 2,900km (1,800 miles) thick

The outer core is a liquid, 2,000 km (1,240 miles) thick

The inner core is a solid, 2,740km (1,700 miles) thick

Task: Draw an annotated diagram of a cross section through the earth.

As early as 1620 Francis Bacon noted the jigsaw-like ‘fit’ of the continents

In 1912 Wegener put forward the theory of continental drift

He proposed that a ‘super continent’ called Pangea split into Gondwanaland and Laurasia, separated by the Tethys Sea

What was his evidence?

Geology – Geological correspondence between continents, e.g. the Appalachian Mountains of the USA and the mountains of NW Europe

Climatology - Evidence of glaciation in Brazil and India. Coal, sandstone and limestone would not have formed in Britain’s present climate

Biology - Evidence of same fossils from each side of Atlantic Ocean, e.g. Mesosaurus fossils found only in Brazil and South Africa

Source; USGS

Continental Drift

Plate movement

What makes plates move?Powerful convection currents generated from the heat of the Earth’s centre, move the plates above

Rule Explanation

The Earth isn’t shrinking or expanding

Plates aren’t always made up of one type of crust

Most significant activity and landforms occur at boundariesPlates cannot overlap, and neither are there gaps

Oceanic crust is heavier and is being destroyed in some places (subduction). In others it is being formed (e.g. Mid-Atlantic Ridge)

The Eurasian plate is a mixture of both types

This is where plate movement causes earthquakes and / or volcanoes and landforms associated with the particular type of boundaryThey’re either pushed up, subducted or new crust forms between them

What is continental drift?

THE WORLD’S MAIN PLATE BOUNDARIES

14 1

2

3

18

18

17

5

7

3

10

5 5

3

2

2

3

5

5

2

7

2

Earthquake foci

Destructive zones

Constructive margin

Movement of plates

Collision zone

Uncertain plate boundary

key Plates

A AdriaticB AegeanC Turkish

D Juan de FucaE Cocos

6 Rate of movement(cm per year)

Complete worksheet and stick in your books.

TYPES OF PLATE BOUNDARY

Task: Using these slides and page 64 and page 65 of the text book draw annotated diagrams of each plate

boundary.1 Constructive margins(spreading or divergent plates)

Processes• Two plates move apart from each

other.• New oceanic crust is formed,

creating mid ocean ridges.• Volcanic activity is common. • Mid Atlantic Ridge (Europe is

moving away from North America).

2 Destructive margin (subduction zone)

Processes• The oceanic crust moves

towards the continental crust and sinks beneath it due to its greater density.

• Deep sea trenches and island arcs are formed.

• Volcanic activity is common.• Example: Nazca sinks under the

South American plate.

Plate 1 Plate 2

Lithosphere

Asthenosphere

Oceanic crustMid-ocean ridgeRift valley

Divergent marginPlate 1 Plate 2

Oceanic trench Continental crust

Asthenosphere

Oceanic crust

Lithosphere

Convergent margin (subduction)

Iceland lies on the plate boundary between the North American and the Eurasian plates. The Island has been created by the divergent plate movement. The photo shows Thingvellir – to the right is the Eurasian plate, and to the left is the North American plate

Iceland

Plates pulling apart

TYPES OF PLATE BOUNDARY (CONTINUED)

3 Collision zones Processes

• Two continental crusts collide. • As neither can sink they are

folded up into fold mountains.

• Example: The Indian plate collided with the Eurasian plate to form the Himalayas.

4 Conservative margins (passive

margins or transform plates)

Processes• Two plates move sideways past

each other but land is neither destroyed nor created.

• Example: San Andreas fault in California.

Lithosphere

Plate 1 Plate 2

Continental crust

Asthenosphere

Convergent margin (collision)Plate 1 Plate 2

Transform fault

Lithosphere

Asthenosphere

Continental crust

Transform fault margin

The San Andreas FaultRuns 1300km through CaliforniaThe last great earthquake to hit San Francisco was in 1906….

Tectonic hazards: earthquakes

An earthquake is the shaking of the ground due to a sudden release of energy. What causes this to happen?

The focus is the place where the fracture or break in actually happens inside the crust

The epicentre is the place on the surface, directly above the focus, where the earthquake waves are first felt

Seismic waves spread out from the focusThe further the waves travel the more energy they lose and the less damage they are likely to do

It occurs because there is a fracture (break) or sudden movement in the Earth’s crust. This usually happens because the plates that make up the Earth’s crust are moving.

Why does the damage from an earthquake vary substantiallyfrom one location to another?

The extent of earthquake damage is influenced by: • Magnitude• The time of the day it strikes• The structural materials of the buildings• The duration of the earthquake• The depth of the focus and distance from epicentre• The nature of the underlying material (rock or unconsolidated sediment)• The population (total and density) of the area• The level of economic development / disaster response• The vulnerability of the population• Secondary hazards such as fires, landslides and tsunami. • The occurrence of aftershocks• Other factors may hinder rescue and response efforts, e.g. conflicts, terrain,

weather• Human alterations to the natural environment

Varying impacts

IMPACTS LEDC MEDCDeaths

Injuries

Damage

Homelessness

Cost

Likely to be high, thousands Probably fairly low

Many, lots from aftershocks and people trying to rescue others

Lower number due to good rescue services and education of people

Extensive, especially to buildings

Structures more likely to be ‘earthquake proof’

Potentially a long term problem.

Quite low as people are more likely to be insured, so be able to rebuild

Not too high, but more of a problem in an LEDC. More likely to need aid

Very high due to greater amount of possessions, and insurance claims

How does where you live affect the impact of an Earthquake?

Measuring the magnitude of earthquakes Each level goes up by a magnitude of 10.

Kobe Earthquake, Japan,1995, MEDC

Tuesday January 17th at 5.46am, measuring 7.3 on the Richter scale. The epicenter was on Awaji Island just across from Kobe. The focus was 14 km deep. There is a fault running through the Kobe area, which had not moved for 50 years, so a lot of pressure had built up.

Nearly 6,500 people lost their lives; 4,600 of these were from Kobe – the closest city to the epicentre. 300,000 people lost their homes.

$200 billion damage – 2.5% of Japan’s GDP at the time

Within 5 weeks there had been 50 aftershocks. There were 1350 After shocks in total

Fires caused by ruptured gas lines caused secondary damage.

Water mains burst and roads were blocked. 130km of bullet train track was closed. 12 trains were derailed.

Most collapsed structures did adhere to building codes, but only to out-dated 1960’s standards

1 in 5 of the buildings in the worst affected area of the city collapsed. Buildings collapsed or were damaged. 85% of schools were destroyed, 12% of industry was lost and 90% of the port.

The soil liquefied and many building sank at strange angles.

Army led relief effort. Vital supplies flown in, e.g. tents medical supplies, food, water and rescue teams.Government criticized for not doing enough to help. Army took to long to arrive. They also turned down help from other countries.

COPING WITH EARTHQUAKESPeople cope with hazards in a number of ways. • At an individual level three important factors affect how a person copes: • Experience: people with more experience of hazards are better able to

adjust to them.• Levels of wealth: people with more money have more choices open to them.• Personality: is the person a leader or a follower, a risk-taker or very cautious?

The three basic options from which they can choose are:• to do nothing and accept the hazard.• to adjust to living in a hazardous environment.• to leave the area.

The first and last options are the most extreme actions. In most cases, the middle option is used.

How people adjust to the hazard depends on:• the type of hazard.• the risk (probability) of the hazard - several factors influence how people view the risk.• the likely cost (loss) caused by the hazard.

Ways of managing the consequences of a hazard include:• sharing the cost of loss, through insurance or disaster relief.• modifying the hazard event, through building design, building location and emergency procedures.• improved forecasting and warning.

METHOD EXPLANATION

Rubber block building: The house is built on rubber blocks which absorb the movement in the ground. They separate the house from the ground.

Building held with wire: The building is supported at the top with soft wires that run deep into the ground. This stops the top of the building shaking so it all moves in one go.

LEDC wall: This is a method of strengthening walls, used in LEDC’s. The barbs on the wire stick into the wood and hold it firmly.

LEDC ‘I’ bar: These are used in LEDC’s. They are heavily welded strong steel bars used to support buildings. The problem with these is that small earthquakes and tremors cause micro fractures in the steel, which weakens them for when a big earthquake strikes.

Dome shaped building: The dome is a very safe shape for buildings but it costs a lot and there is a lot of wasted space.

Houses spread apart: Houses in LEDC’s need to be a good space apart so that if an earthquake strikes, it does not produce a ‘domino’ effect.

Chinese house: This house is not directly attached to the floor but if it is built around a bamboo pole, which is in the ground, when an earthquake strikes, the house will simply move around the pole, instead of moving away.

Computerised weight: The computerised weight on the building moves to the opposite side of the building shifts. This will balance the weight, keeping the top of the building straight, to stop it from wobbling.

Cross bracing: Cross bracing is used in LEDC’s. The wall is strengthened at each corner to prevent it from collapsing.

Legs on the house: This method is sometimes used to separate the house from the ground.

LEDC house: In LEDC’s, houses are safest if they are made of light weight materials, such as wood and corrugated iron. The lower the building, the safer it is.

Volcanoes Warm Up

• The plate boundary which causes the most volcanoes.

Plate 1 Plate 2

Oceanic trench Continental crust

Asthenosphere

Oceanic crust

Lithosphere

Destructive margin (subduction)Processes•The oceanic crust moves towards the continental crust and sinks beneath it due to its greater density.•Deep sea trenches and island arcs are formed.•Volcanic activity is common.•Example: Nazca sinks under the South American plate.

3 TYPES OF VOLCANO

Inside the Volcano• The magma chamber is a collection of magma inside the

Earth, below the volcano. • The main vent is the main outlet for the magma to escape. • Secondary vents are smaller outlets through which magma

escapes. • The crater is created after an eruption blows the top off the

volcano. • An eruption occurs when pressure in the magma chamber

forces magma up the main vent, towards the crater at the top of the volcano. Some magma will also be forced out of the secondary vent at the side of the volcano.

Causes

• Volcanoes form when magma reaches the Earth's surface, causing eruptions of lava and ash. They occur at destructive and constructive plate boundaries

• The immediate effects of volcanic eruptions can be devastating, but they may be beneficial in the long term

How They Form

• Magma rises through cracks or weaknesses in the Earth's crust.

• Pressure builds up inside the Earth. • When this pressure is released, eg as a result of

plate movement, magma explodes to the surface causing a volcanic eruption.

• The lava from the eruption cools to form new crust. • Over time, after several eruptions, the rock builds

up and a volcano forms

EFFECTS

Primary• Destroyed by fire• Explosions• Weight of ash• Crops/Livestock destroyed

Secondary• Mudflows• Changes in landscape/climate• Food/water supply• Homelessness• Businesses Close• Insurance Claims• Unemployment• Premiums increase• Tourism depleted

Why Live Near A Volcano

• Geothermal Energy• Tourism• Fertile Soils• Mineral Extraction• Raw Materials

• Would you live near a volcano?

Complete the TableReason For Living

Near A Volcano WHY?Fertile Soils RICH IN MINERALS, WHEN WEATHERED THEY

ARE VERY FERTILE. IDEAL FOR FARMERS TO GROW CROPS.

Geothermal Energy STEAM FROM WATER HEATED BY ROCKS BELOW THE SURFACE DRIVES TURBINES TO GENERATE ELECTRICITY.

Mineral Extraction MANY VALUABLE MINERALS FORM WHEN VOLCANIC ACTIVITY OCCURS.

Raw Materials THE RAW MATERIALS FOR MANY PRODUCTS COME FROM VOLCANOES. THESE INCLUDING BUILDING MATERIALS AND CHEMICALS USED IN INDUSTRY

Tourism VOLCANIC LANDSCAPES CAN HAVE BEAUTIFUL SCENERY THAT ATTRACTS MANY VISITORS.

WHAT CAN YOU SEE THEN?

Territory size shows the proportion of all people killed by volcanoes between 1975 and 2000, that died there

Case Studies

LEDC – Montserrat

MEDC – Mt. Etna

Mount Etna, MEDC 2001

• Europe’s most active Volcano• NE Coast of Sicily, Italy• Located on Destructive plate boundary

(Eurasian & African plates)• African subducted under the Eurasian plate• 12th July 2001• Gas & Steam escape• Volcanic Bombs• Lava & Pyroclastic Flows (lava reached 1000oc)

Details

• Lava swallowed up, houses, cars, car parks, ski lift & pylons,

• Earthen dams protect tourist base of Rifugio Sapienza

• Army equipment blocked and diverted lava flows• Tourism affected (snow couldn’t settle – skiing)• £5.6m available in immediate financial assistance• Planning & emergency services worked together• Tax breaks

Montserrat, LEDC 1997

• Small Island in Caribbean• Poor population who rely on subsistence farming• Before 1995, 12000 people lived there, now less than

5000 live there• Destructive plate boundary, oceanic pushed below

continental• 2/3 of island covered in ash• 50% of island evacuated to North (temporary

accommodation)• 23people died in 1997• The capital – Plymouth – became a ghost town

Primary Effects

• Floods as valleys were blocked with ash

• The airport and port were closed

• Farmland was destroyed

• Forest fires caused by pyroclastic flows

• Many schools and hospitals were destroyed

The Secondary effects of the Eruption

• As most of the southern area was destroyed any remaining inhabitants have had to endure harsh living conditions in the North.

• Transport remains a problem for people travelling to the island as the port and airport remained closed.

• The tourist industry is still suffering with few visitors except for cruise ships looking at the volcano

• Over half the population left the island and have not returned

Responses

• £41 million was given in aid by the British Government.• Money was given to individuals to help them move to

other countries. • Riots occurred as locals complained that the British were

not doing enough to help the island • The MVO (Montserrat Volcano Observatory) was set up

to study the volcano and provide warnings for the future • A Risk assessment was done to help islanders

understand which areas are at risk and reduce problems for the future.