Plate tectonics. Temperature increases towards the centre

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1 Temperature increases towards the centre Plate tectonics Structure of the Earth Crust Two layers of rock that move on top of the mantle 1. Oceanic Lithosphere heavy rock created at constructive plate boundaries thinner than continental crust 2. Continental Lithosphere less dense (lighter) rock thick Mantle solid largest part of the inside of the Earth where convection occurs part nearest the crust is partially molten which allows plates to move across it Asthenosphere. Outer core liquid rotates giving the Earth it magnetic field Inner Core Solid made of iron and nickel. Main Tectonic Plates The North American Plate The South American Plate The Eurasian Plate The Pacific Plate The Nazca Plate The Indian Plate How does plate tectonics occur? 1. Heat from the core heats the mantle. 2. The heated rock rises up because it is less dense than the cooler rock above. 3. As it rises it begins to cool as it reaches the crust. This rock is now more dense than the hotter rock. This causes it to sink. 4. This rising and sinking rock creates convection currents. 5. These convection currents drag the tectonic plates causing them to move along the surface. This movement is called plate tectonics.

2 Plate margins Destructive Plate Boundaries E.g. the boundary between the Nazca and South American Plates Two plates collide oceanic crust subducts underneath the continental crust. Many earthquakes and composite volcanoes. Collision Plate Boundaries E.g. The Himalayas, China Two continental plates collide with each other Lots of earthquakes No volcanoes Constructive Plate Boundaries E.g. the boundary between the Eurasian and North American Plates Convection currents pull the plates apart forming a volcanic ridge. Lots of volcanoes and some earthquakes Conservative Plate Boundaries E.g. San Andreas Fault, California Two plates slide past each other Lots of friction created which Causes earthquakes

3 Fold mountains The formation of fold mountains Case study of human activity in fold mountains: The Alps Winter sports such as skiing in resorts such as Chamonix. Climbing and hiking in the summer months. Summer lakeside holidays, eg Lake Garda. Agriculture - takes place mainly on south facing slopes and includes cereals, sugar beet, vines and fruits. Forestry - coniferous forests for fuel and building. Communications - roads and railways follow valleys. Hydroelectric power (HEP) - steep slopes and glacial meltwater are ideal for generating HEP. Hydroelectric accounts for 60 per cent of Switzerland's electricity production. The challenges of living in the Alps include: the relief (high mountains and steep slops give little flat land for farming), the climate (temperature drops with height), soils (infertile) and accessibility (difficult to cross the mountains).

4 Earthquakes The magnitude of earthquakes is measured on the Richter Scale. The visual impact of earthquakes is measured on the Mercalli Scale. KEY TERMS: The focus is the point at which the earthquake happens beneath the ground. The epicentre is the point on the surface above the focus. This is where the effects of the earthquake are worst. Shockwaves radiate in all directions from the focus. Location Port-au-Prince, Haiti Christchurch, New Zealand Facts Magnitude 7 12 January 2010 Primary impacts Secondary impacts Response dead homes destroyed offices and factories destroyed Roads blocked 1 in 5 lost their jobs Morgues and cemeteries overflowed Spread of disease eg cholera Looting of destroyed houses $440 million given in aid 810,000 people in aid camps 4.3 million people needing food rations Magnitude February dead injured 50% of city buildings damaged 80% of city with no electricity Businesses out of action Christchurch could not host the Rugby World Cup Schools had to share classrooms Chemical toilets provided for 30,000 residents Temporary housing provided 80% of roads repaired

5 Volcanoes Volcanoes Composite Volcanoes e.g. Etna, Italy and Krakatoa, Indonesia Destructive plate boundaries Thick, highly viscous andesitic lava that does not flow very far Steep sided cone shape Alternating layers of ash and lava Erupt rarely but are very explosive Shield Volcanoes e.g. Surtsey island, Iceland Constructive plate boundaries Thin, low viscous, runny basaltic lava that flows a long way Gently sloping sides with a very wide base Erupt frequently but less explosive and dangerous Shield Volcano Montserrat: Fact file Montserrat is an island located in the Caribbean, south of the USA. The composite volcano, in the south east of the island, had been dormant for hundreds of years. It erupted in 1995 and Main hazards were ash fall and pyroclastic flows. Primary effects: 20 people were killed evacuated. Two thirds of homes destroyed. Secondary effects: Cost of rebuilding. Tourist industry disrupted. Immediate responses: Evacuation. Emergency aid for shelter. Long-term responses: UK aid to rebuild infrastructure. Volcano observatory built to monitor. Attempts to re-attract tourists. Composite Volcano A supervolcano eruption is 1000 times bigger than a normal volcano.

6 Tsunamis are a secondary affect of an earthquake under the ocean Tsunamis Case study: The Asian Tsunami (2004) Sri Lanka: 32,300 dead or missing. 97,000 houses destroyed. Over a million left homeless. India: 16,400 dead of missing. 157, 000 houses destroyed fishing boats destroyed. Thailand: 5400 dead or missing homes destroyed. Loss of income as tourism industry destroyed.

7 Managing earthquakes and volcanic hazards It is hard to predict when earthquakes or volcanoes will happen because we do not know When it will happen Exactly where it will happen How big it will be What other impacts (secondary effects) there might be how many people will be effected Things that can help us predict them are Animals and birds leaving the area An increase in ground gas emissions An increase in rock/ soil temperature The volcano might swell (get bigger) Increasing numbers of small earthquakes Water stores (lakes and ponds) getting warmer Earthquake proof buildings We can reduce the impacts of earthquakes by making buildings stronger. Here are some ways of doing this. Prediction, protection and preparation How to reduce the impacts of earthquakes or volcanoes Volunteers and emergency services to clear away debris and look for survivors Food and clean water to prevent the spread of disease Radio communication in case phones no longer work Medical help to aid survivors An evacuation plan to relocate people after the event

8 Test yourself. What causes tectonic plates to move? Why do earthquakes happen? What are the different types of volcanoes? What are the impacts of earthquakes? How could we predict volcanic eruptions? What causes tsunamis?