Presentation on theme: "Living in an Active Zone Use this PowerPoint to complete the brainstorm on the topic of ‘Living in an active zone’"— Presentation transcript:
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 - ates_video.shtml ates_video.shtml Video - ates_video.shtml ates_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 Margins Oceanic 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
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 - video.shtml video.shtml Video - video.shtml 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?
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 - video.shtml video.shtml Video - video.shtml 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 monitored Preparing 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 planprotect 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 - Volcanoes Predicting 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 magma Preparing Exclusion zones created around volcanoes Authorities must be ready to evacuate Emergency supplies of basic provisions must be gathered Good communication systems in place
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.
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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