Geography- Restless Earth

Geography- Restless Earth

1. Tectonic Plates

   • The Earths Surface is separated into Tectonic Plates. The plates are made of two types of crust- Continental and Oceanic.
     • Continental crust is thicker and less dense and Oceanic crust is thinner and more dense,
   • Types of Plate Margin
     • Destructive Margins
       • Destructive margins are where two plates are moving towards each other. Where an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed. This often creates volcanos and ocean trenches. Where two continental plates meet, the plates smash together but no crust is destroyed.
     • Constructive Margins
       • Constructive margins are where two plates are moving away from each other. Magma rises from the mantle to fill the gap and cools, creating a new crust.
     • Conservative Margins
       • Conservative margins are where two plates are moving sideways past each other or moving in the same direction but at different speeds. Crust isn't created or destroyed.

2. Fold Mountains

   • Fold Mountains are formed when plates collide at Destructive Margins.
     • When tectonic plates collide, the sedimentary rocks that have built up are folded and forces upwards to form mountains. So Fold Mountains are found at Destructive Plate Margins and places where there used to be Destructive Margins e.g. South coast of North America You get Fold Mountains here a Continental Plate meets a Oceanic Plate e.g. Andes. You also get Fold Mountains where two Continental Plates collide e.g. Himalayas.
   • Uses of Fold Mountains
     • Farming: Higher slopes aren't great for growing crops and so they're used to graze animals. Lower slopes are then used to grow crops.
     • Hydro-Electric Power (HEP): Steep-sided mountains and high lakes make Fold Mountains ideal for generating HEP.
     • Mining: Fold Mountains are a significant source of metal ores and so there is lots of mining happening. The steep slopes make it difficult to access the mines and so roads are zig-zagged on the sides of the mountains.
     • Forestry: Fold Mountains are a good environment to grow certain types of trees e.g. conifers. They're grown on the steep valley slops and used for fuel, materials, etc.
     • Tourism: Fold Mountains have amazing views which attracts tourists. In Winter, people do sports like skiing, ice climbing etc. Communitcations have been improve through drilling tunnels in the mountains.
   • Case Study: Alps
     • Central Europe- It stretches across Austria, France, Germany, Italy, Liechtenstein, Slovenia and Switzerland. It was formed 30 million years ago by the collision of the African and European Plates. It's tallest peak is the Mont Blanc. There is a population of 12 million people.
     • Uses of the Alps
       • Farming: The steep areas are used to farm goats which provide milk, cheese and meat. Some sunnier slopes have been terraced to plant vineyards.
       • Hydro-Electric Power: The narrow valleys are dammed to generate HEP e.g. in Switzerland 60% of its electricity is from the Alps. The electricity is locally used and also exported to cities and towns further away.
       • Mining: Salt, iron ore, gold, silver and copper were mined in the Alps but mining has declined due to cheaper foreign sources.
       • Forestry: Scots Pine is planted all over the Alps because its more resilliant to the goats which kill native tree saplings. The trees are logged and sold to make things.
       • Tourism: 100 million tourist visit the Alps annually- huge impact on economy. 70% of tourists visit the steep mountains for sports. New viillages were built to cater for the quantity of tourist e.g. Tignes in France. Ski lifts, Ski runs, cable cars, holiday chalets and restaurants are spread across the landscape.
     • How have people adapted to the conditions?
       • Steep Relief: Goats are farmed because they're well adapted to live on steep mountains. Trees and man made defences are used to protect against avalanches and rock slides.
       • Poor Soils: Animals are grazed in high areas as the soil isn't good for growing crops.
       • Limited communications: Tunnels have been cut though the mountains to provide fast transport linkse.g. The Bernese Alps in Switzerland.

3. Volcanos

   • Volcano's are found at Destructive and Constructive Margins.
     • At Destructive Margins, the Oceanic plate goes under the Continental plate because its more dense. The oceanic plate goes into the mantle where its melted and destroyed. A pool of magma forms and the magma rises through cracks in the crust (vents). The magma erupts onto the surface, forming a volcano. At Constructive Margins the magma rises up into the gap created by plates moving apart.
   • Types of Volcano's.
     • Composite Volcano's: Made up of ash and lava that's erupted, cooled and hardened into layers. The lava usually thick and flows slowly. It hardens quickly to form the steep sides.
     • Shield Volcano's: Made up of only lava. The lava is runny and flows quickly, spreading over a wide area, forming a low, flat volcano.
     • Dome Volcano's: Made up of only lava, the lava is thick and flows slowly. It hardens quickly, forming a steep-sided volcano.
   • Predicting volcano's: Scientists can use tell-tell signs to predict volcanic eruptions. Things such as tiny earthquakes, escaping gas and changes in volcano shapes mean an eruption is likely.
   • Case Study- Soufriere Hills, Monserrat
     • 25th June 1997, 4-5 million m3 of rocks and gas released. 19 Killed.
     • Causes: Above a destructive plate margin, Atlantic plate being forced under the Caribbean plate. Magma rose through weak points forming an underground pool of magma. Rock above the pool collapsed, opening a vent.
     • Impacts
       • Primary Impacts: Large areas covered with volcanic material. Over 20 villages an two thirds of homes destroyed by pyroclastic flows. Schools, hospitals, the airport and the port destroyed. Vegetation and farmland destroyed. 19 people died and 7 were injured.
       • Secondary Impacts: Fires destroyed buildings including government offices and the police headquarters. Tourist stayed away and businesses destroyed- huge impact on economy. Population decline 8000 of the islands 12000 have left. Volcanic ash improved soil fertility. Tourism has now increased- people want to see the volcano.
     • Responses
       • Immediate Responses: People were evacuated from the south to safe areas in the north. Shelters were built to house evacuees. Temporary infrastructure was built. The UK provided £17 million of emergency aid. Local Emergency Services provided search and rescue.
       • Long Term Responses: A risk map and exclusion zones created. The UK provided £41 million to develop north of the island (docks, housing, airport). The Montserrat Volcano Observatory has been set up to try and predict eruptions.
   • Super volcano's (Massive volcano's)
     • Magma rises through cracks to form large magma basin below surface. Pressure of magma causes circular bulge on the surface. The bulge cracks, creating vents for lava to escape. The lava erupts causing earthquakes and plumes of ash and rock. When the eruptions finished, a caldera is left where the bulge collapsed. Sometimes these fill with water.
     • Characteristics: Flat, Large surface area, Caldera.
     • Consequences of a super volcanic eruption: Thousands of cubic kilometers of rock, ash and lava. A thick could of super heated gas and ash will flow, killing, burning and burying everything in its wake. Everything within tens of miles destroyed. Ash will shoot kilometers into air and block out almost all daylight over whole continents. This can trigger mini ice ages. Pyroclastic can cause tens of thousands of deaths, Sulfuric Acid reaches atmosphere- crops will fail/global cooling.

4. Earthquakes

   • Cause: Earthquakes caused by the tension that builds up at all three plate margins. Destructive Margins- tension builds up when one plate gets stuck as its moving down past the other. Constructive Margins- tension builds along cracks within the plates as they move away. Conservative Margins- tension builds when plates get stuck moving past each other. The plates will then jerk past, sending out shock waves. The waves spread out from the focus point. The epi-centre is the point on earths surfaces straight above the focus.
   • Measuring Earthquakes: The Richter scale is used to measure the amount of energy released by an earthquake. The magnitude is measured using a seisometer. The Mercalli scale: This measures the effects of an earthquake. Effects are measured using eyewitnesses. It's a scale of 1-12.
   • Case Study- Nepal
     • 25th April 2015. Magnitude of 7.8. Nepal is prone to earthquakes as it sits on two plate boundaries: Indo-Australian and Asian plates.
     • Causes: Two converging tectonic plates- The Indian plate and the overriding Eurasia plate.
     • Effects
       • Social Effects: Over 9000 people died and more than 23,000 were injured. Thousand of people are made homeless. Several churches were destroyed. Water was contaminated and people had no access. Survivors were being prayed on for Human Traffickers. Sewage everywhere made diseases more likely. The airport was closed.
       • Economic Effects: As one of the main incomes for Nepal, farmers land was destroyed and so therefore could sell or produce stocks. $5 billion was spent on rebuilding. (25% of the Nepal's GDP)
       • Environmental Effects: This earthquake caused avalanches on Mount Everest. Landslides occurred in the Lang Tang Valley. Many national heritage sites were lost and destroyed.
     • Responses
       • Short term responses: Emergency workers set up search and rescue parties. People donated blood for those injured. International agencies provided supplies such as food and water. Tents were set up to house people who were made homeless. Water purification tablets were used to purify contaminated water to make it safe to drink. People were evacuated to area's of safety.
       • Long term responses: Geohazards International (GHI) embarked on a project that focuses on improving earthquake disaster management and raising awareness of earthquake risks. Infrastructure is being rebuilt. Millions of pounds have been donated to aid the recovering effort.
   • Case Study- Tsunamis
     • An earthquake caused a Tsunami in the Indian Ocean on the 26th December 2004. It measured 9.1 on the Richter Scale.
     • The destructive plate along the west coast of Indonesia, that's moving down into the mantle, cracked and moved very quickly. This caused water to become displaced and triggered a Tsunami with waves up to 30 metres.
     • Effects
       • Around 230,000 people were killed or are still missing. Whole towns were destroyed-over 1.7 million lost their homes. The infrastructure was severely damaged. 5-6 million needed emergency aid. Millions of fishermen lost their livelihood and the economy suffered due to this and a lack of tourists. There was massive environmental damage.
     • Responses
       • Short Term Responses: Hundreds of millions of pounds was pledged by foreign governments, charities etc. to give survivors food, water, shelter and medical attention. Foreign countries sent ships, planes, soldiers and teams of specialists to help rescues, distribute food and water and begin the clear up.
       • Long Term Responses: Billions of pounds pledged to aid re-build infrastructure. Programmes have been set up to re-build houses and get people back to work. A Tsunami warning system has been put in place. Disaster Management Plans have been put in place abd volunteers have been trained so locals know what to do if one occurs again.

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