Living in an Active Zone Use this PowerPoint to complete the brainstorm on the topic of

‘Living in an active zone’

Cross section of the Earth

Structure of the earth

• Earth is made up of four distinct layers• Crust (oceanic/ Continental)• Mantle • Outer core• Inner core

Structure of the earth

• Crust is broken up piece called tectonic plates • 7 large plates and 12 small plates• These plates move because of Convection

Currents in the magma• Where two plates meet is a plate margin

Video - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/tectonic_plates_video.shtmlVideo - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/tectonic_plates_video.shtml

Why do the plates move?

Constructive Plate Margins

• Two oceanic plates move away from each other shield volcanoes form creating mid ocean ridges e.g. mid Atlantic ridge.

• When two continental plate move apart a rift valleys are formed. Shield volcanoes found here e.g. Iceland

Constructive plate boundary

Constructive Plate Margins

Destructive Plate MarginsOceanic and continental Crust •Where it involves oceanic and continental crust, the oceanic crust is always subducted below the continental because it is denser. •The subduction of the oceanic crust creates a deep sea trench and earthquakes are formed at the subduction zone. •Fold mountains are created on the continental crust . •The subducted oceanic crust melts in the mantle rising up into the fold mountain to create composite volcanoes•E.g. Mount St Helens

Destructive plate boundary

Destructive Plate Margins

Oceanic crust only •Destructive plate margins also can involve two oceanic plates•Here island arcs are formed in the oceanic crust•E.g. Montserrat, Caribbean

Destructive Plate Margins

Plate definitions

Types of Volcanoes

• Shield Volcanoes found on constructive plate margins. Lava is hot and runny. Not as explosive. Not very high. Very wide base

• Composite volcanoes found on destructive plate margins. Thick stick lava. Erupt explosively. Very tall cone shaped.

Video - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/volcanoes_video.shtmlVideo - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/volcanoes_video.shtml

Active volcano – liable to erupt e.g. Mt Etna.

Dormant (sleeping) volcano – a volcano which has not erupted for many years. For example, Mt Pinatubo erupted in 1991 after 500 years of dormancy.

Extinct volcano – a volcano which has not erupted for many thousands or millions of years e.g. Edinburgh.

However, it is often very difficult to tell whether a volcano will erupt again…El Chichon, Mexico erupted in 1982 after being dormant for approximately 1200 years!

Do all volcanoes erupt?

Volcanic hazards

• Lava flow• Ash • Lahars • Lava bombs• Pyroclastic flow

Volcanic Hazards

Volcanic emissions

Earthquakes – Causes

• Earthquakes are cause by shock waves travelling through the earth crust

• The source of the earthquake is called the focus, the epicentre is the point immediately above it on the surface

• Size of an earthquake can be measured by a seismometer along the Richter scale

• Tsunamis are a secondary hazard of an earthquake

Epicentre Focus

Seismic waves

Video - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/earthquakes_video.shtmlVideo - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/earthquakes_video.shtml

Why do earthquakes happen?

How can we measure earthquakes?

This measures the magnitude of a tremor (how powerful it is) using an instrument called a seismograph. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. Although the Richter Scale has no upper limit, the largest earthquake ever recorded was in 1960 in Chile. It measured 9.5 on the Richter Scale.

The Richter Scale

Earthquakes - Factors• Strength of the earthquake (magnitude) – more shaking means more

damage will be caused • Distance from epicentre – closer to the epicentre the more damage will

be caused. • Depth of the focus – the shallower an earthquake the more damage will

caused • Number of people living in an area (population density)- the epicentre is

close to a city then more people will be affected. • Type of rock – softer rocks are likely to shake more and fro longer causing

more damage • Time of day – if more people are in building more people are likely to die.• The extent of preparation – some countries are well prepared for

earthquakes and therefore have little impact (see later on how to prepare for an earthquake

Why do people live there?500 million people live in active zones• Dramatic scenery created attracts tourists, bringing income to an area e.g.

Mount Vesuvius, Italy• Lava and ash provide nutrients to the soil, making the land near volcanoes

very fertile and good for agriculture. E.g. Mount Etna, Italy • Opportunities to generate electricity using the heat from the earth

(geothermal energy) E.g. Iceland • Volcanic rock is a good building stone• Many people cannot afford to Move (LEDCs) E.g. Mount Pinatubo,

Philippines• Tectonic hazards are rare and often to affect an area in a persons lifetime

E.g. Montserrat volcano had not erupted for 300yrs until recently • Prediction and earthquake resistant building are improving. E.g. Kobe

Japan has many earthquake proof buildings

• DON’T FORGET YOU NEED TO GIVE EXAMPLES

Predicting and preparing - Earthquakes

Predicting• Laser beams used to detect plate movements• Seismometer used to pick up vibrations• Radon gas – escape from the cracks in the crust

before an earthquake – this can be monitoredPreparing• Educating people via TV or in schools what to do• Earthquake drills to prepare• Earthquake proof buildings, designed to absorb the

energy of an earthquake and withstand movement

predict plan protect

Predict

water levels can rise in wells and lakes because of cracks in the rock

foreshocks before the main quake can be detected by a seismometer

animals can act strangely before the earthquake

a tiltmeter can check any movement within the rocks

How can we limit earthquake damage?

Plan and protect

How can we limit earthquake damage?

This is San Francisco in the USA.

San Francisco is near the San Andreas Fault and therefore the city experiences earthquakes.

Building in earthquake zones

This skyscraper has been built to be ‘earthquake-proof’. Its wide base lowers the centre of gravity of the building and makes it more stable.

Predicting and preparing - VolcanoesPredicting • Remote sensing – satellites monitor temperature and gas

emissions• Seismometers – measures earthquakes activity that occurs

before an eruption• Tiltmeters – monitor changes in the shape of a volcano as it

fills with magma• Gas emissions – indicate an increased risk• Ultra sound – to detect movements of magmaPreparing• Exclusion zones created around volcanoes• Authorities must be ready to evacuate • Emergency supplies of basic provisions must be gathered • Good communication systems in place

Predicting eruptions

The problem of prediction

Volcanologists (people who study volcanoes) are skilled at predicting the likelihood of an eruption.

However, it's very difficult to pinpoint exactly when an eruption will happen. Often, moving magma doesn't result in an eruption, but instead cools below the surface. Monitoring potential eruptions is expensive. With many volcanoes erupting only every few hundred years, it's not possible to monitor every site.

Video - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/managing_hazards_video.shtmlVideo - http://www.bbc.co.uk/schools/gcsebitesize/geography/natural_hazards/managing_hazards_video.shtml

This is an alternative

casestudy - Miss Kingdom’s class

had two different casestudies (New

Zealand and Pakistan). It is up to you which one

you lean