1. KS3 Geography – plate tectonics Student outcomes: Describe the structure of the earth Examine the processes for the 3 plate margins State differences between continental and oceanic crust Explore the distribution of earthquakes and volcanoes Investigate the basics of earthquakes and volcanoes Explain how the impacts of earthquakes are reduced

2. Part A – The earths structure For the exam, you need to know these below structures, and the simple basics of them: The crust The crust is a 7-50 km thick crust, made out of solid rock. The further down the crust, the hotter it is. The mantle The mantle is a molten rock layer of the earth, and the largest layer in the earth, the further down the mantle, the hotter the magma is The core The core is split into the outer core and inner core, the outer core is liquid iron and nickel, at very hot temperatures, and the inner core is solid iron and nickel, the core is a spherical shape. You need to state the difference between oceanic crust and Continental crust Oceanic crust is more dense than continental crust, and has a more thinner layer (It is more dense because water is very dense Continental crust is less dense and has a thicker layer

3. Part B – Types of plate boundary There are 3 main plate boundaries you need to know, as well as knowing them, you need to learn how they work, and be able to give an example of where they are. Types of plate boundary: Constructive boundary At a constructive boundary, the plates here pull away from eachover, allowing the magma from the mantle to rise and fill the gaps, an example of a constructive plate boundary is the Mid-Atlantic Ridge. Constructive plate boundaries mainly cause volcanic eruptions Conservative boundary At conservative boundaries, two plates create friction in the crust, as this friction eventually creates a crack, allowing the plates to shift across eachover, causing earthquakes, at conservative plates, no crust is lost or made. An example of a conservative plate boundary is the San Andreas Fault in Western North America. Destructive boundary At destructive boundaries, the plates are colliding with eachover, there are different causes for the collision of a type of crust, the most common is an oceanic crust colliding with a continental crust, here a subduction zone is formed (Where the more dense oceanic plate is subducted by the continental plate, sliding into the mantle) creating underwater trenches, as well as underwater volcanic chains. As two continental crusts collide, the land is crumpled upwards, creating fold mountains, and sometimes earthquakes, and where two oceanic crusts collide, islands called archipelagos can form, and create underwater volcanoes and earthquakes. An example of a destructive plate boundary is along the Himalayas mountain range

4. Part C – Basics of Earthquakes Earthquakes occur at all 3 types of boundaries, but mostly occur on conservative and destructive plate boundaries. An earthquake is a tremor caused in the earths crust when the plates move. The plates move a few mm a year, and they move because of convection currents in the mantle. A diagram of an earthquake zone: Fault Line Seismic waves The focus is the point in the earths crust where the plates move, and the earthquake occurs. The epicentre is the point directly above the focus on the earths surface. The fault line is a weak point in the earths crust, prone to earthquakes, for example the San Andreas Fault. Seismic waves are waves carrying energy created at earthquake zones, which can travel long distances.

5. Part C – Basics of Earthquakes Seismic waves are energy waves which are distorted by earthquakes and explosions, they are strong waves which travel long distances, and are the main energy of detecting earthquake occurrence. The image shows an instrument that measures earthquakes – called a Seismometer. When an earthquake is detected, the seismic waves are detected by the seismometer, causing a vibration to move the spring, which moves a pen, creating a graph (called a Seismograph) on paper on a drum, the larger the recording, the stronger the seismic waves detected, so if they seismograph looked like this: Then the seismic waves detected are strong, but if the seismograph looked like this: The earthquake would of lasted a very short while, and would continue small.

6. Part C – Basics of Earthquakes From the seismograph, the strength of an earthquake is recorded on a scale, called the Richter Scale. The Richter scale is a scale from 1-10 which measures the strength of earthquakes on magnitude. For your exam, you need to be able to interpret information from earthquakes, to predict and understand the strength of an earthquake. Below shows the richter scale from 1-10 The higher up on the Richter scale, the stronger the earthquake is, most strong earthquakes are from 6.2-10, on average the most frequent strong earthquakes are around 7.7-7.9 magnitude. Below 4.5, the earthquake may not be noticeable, and above is obviously noticeable. There is also the Mercalli scale, which measures damage of an earthquake from 1-10

7. Part D – Basics of Volcanoes Volcanoes are mountains, or parts of the earth that magma escapes from. Volcanoes occur on destructive and constructive plate boundaries. Volcanoes are classified into 3 types, Extinct, Dormant, and Active, you need to know atleast 3 examples of active volcanoes. Extinct Volcanoes are those which have not erupted in over a 1000 years, they are called extinct because wildlife or nature may have closed and shut the crater. Dormant volcanoes are those which haven't erupted in a long while, but are the shape and look of a normal volcano. Active volcanoes are those which frequently erupt. You need to know different examples of these volcanoes. Examples: Mount Etna, Italy is an active volcano Mount St Helens, USA is an active volcano Masaya Volcano, Nicaragua is an active volcano Mosaya Volcano, Nicaragua

8. Part D – Basics of Volcanoes As well as classification of Volcanoes, you will also need to learn the 3 different types of volcanoes, and an example of each. There are 3 types of Volcanoes, Composite Volcanoes, Dome Volcanoes and Shield Volcanoes. Composite Volcano: These volcanoes are steep conical volcanoes, made from ash, mud and rock deposited from previous eruptions, when Composite volcanoes erupt, they give out ash, rock, lava and gas, when all these substances are together they are called Pyroclastic flows. Composite volcanoes have large craters at the top. An example of a Composite Volcano is Soufriere Hills, Montserrat Dome Volcano: Dome volcanoes are volcanoes which are basically dome shape, they are steep volcanoes, but not conical, when Dome volcanoes erupt they give out gas and Lava, and result in Lava flows, Dome volcanoes give out acidic Lava which is slow and thick. An example of a Dome volcano is Mt St. Helens in the USA A Shield volcano gives out lava only, but the lava is more runny, and cools quicker, the lava is also Alkaline in a Shield Volcano. Shield Volcanoes are mostly flat, eg Kilauea in Hawaii

9. Part E – Impacts of Tectonic hazards As well as knowing the basics of volcanoes and Earthquakes, you also need to know the impacting result on humanity, as well as nature. Earthquakes and volcanoes have primary and secondary impacts, the primary impacts occur during the earthquake, whereas the secondary impacts occur after the earthquake or volcano. Type of hazardPrimary impactsSecondary impacts EarthquakeDeaths, injuries, infrastructure damaged, buildings destroyed, bridges destroyed, schools and medical centres destroyed Fires caused, people remain homeless, spread of disease, deaths still occur, unemployment, road blockages, tsunamis and landslides caused, psychological problems Volcanic EruptionPyroclastic flows destroy settlements, deaths, toxic gases released, wildlife nearby killed off, some crops destroyed, lava flows cause fires Survivors remain homeless, unemployment, agricultural land can be rendered useless, diseases spread, landslides and mudslides, psychological problems, sulfur dioxide causes acid rain

10. Part E – Impacts of Tectonic hazards Remember, these impacts can be high or low, and the main impacts, such as death, damage, etc are triggered by the following 3 factors: Population Rural/Urban area structure Preparation If population in an area prone to earthquakes is high, its obvious there will be a high death toll, but these factors can be reduced, see part F, if the disaster occurs in an urban area, not prepared for a disaster, and highly populated the impacts can be tragic. If the disaster occurs in a Rural area where the population is smaller, and less buildings are around, the disaster will not be as devastating. Of course in LEDCs the money and preparation is poor, but in areas prone to earthquakes, preparation such as training, earthquake drills etc people know what to do. In MEDCs, although the area is rich, they may not be well prepared, but they can repair and respond much quicker than LEDCs mainly because LEDCs have fewer money and expertise than MEDCs.

11. Part F – Reducing Tectonic Hazards You need to know how MEDCs and LEDCs respond to earthquakes and volcanoes, and how areas prone to these hazards can reduce the impacts. Reducing the impacts of Earthquakes: Obviously, if scientists were able to successfully predict the exact time and place of an earthquake things would be much different, but it is impossible, so instead scientists come up with ideas to reduce earthquakes. Signs of earthquakes: Looking at fault lines and suggesting where earthquakes can occur Animal behaviour Toxic gases released Well water levels change But these signs can not successfully predict an earthquake, so other ways of reducing the impacts are set up, see slide 12 for these ways.

12. Part F – Reducing Tectonic hazards Reducing Earthquakes can be done by many methods, one popular method is building earthquake resistant buildings, which are designed to absorb the energy of earthquakes, reducing the damage and impacts, the image below shows a diagram of an earthquake proof building: Other methods of reducing earthquakes include planning, such as teaching people what to do in an earthquake situation, this is done in Japan a lot as Japan is very prone to earthquakes. In volcanic hazards, volcanoes are easier to predict, and scientists can tell when a volcano may occur, so evacuation can be done, but in earthquakes, evacuation isn't as easy. In earthquake prone areas, people are given emergency kits, and survival kits, with all the needs for an earthquake. Whats in an earthquake survival kit? A Torch, a bottle of water, food supply (simple tinned food), Radio, for news reports, batteries for the radio and torch, clothing, and blankets, medication for the ill, money and possibly a fire extinguisher, a gas mask will also be needed. MEDCs have access to Radio and TV more than LEDCs, so people are more alert when a volcano may occur

13. Part F – Reducing Tectonic Hazards You need to know why people may still live in Tectonic areas, such as volcanic zones. People may live near volcanoes for different reasons, below shows some of these reasons: Close to family Like there home, and just will not leave Area is rich in minerals and needs Geothermal energy is provided As well Scientists can predict volcanoes easier, for example they can tell by the release of toxic gases, and mini earthquakes. Responding to hazards MEDCs can respond to LEDC disasters by giving aid, but this can not completely help, as LEDCs may take up to 10 years to fully recover from a disaster, MEDCs take less time, but the recovery is still long, such as using the money for expensive infrastructure, and rebuilds Scientists continue to research evidence to help find out when earthquakes will happen as well