Physical Case Studies AQA Revision notes - Ice, rivers and volcanoes.

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The Restless Earth…

Fold Mountains- The Andes…

  • Longest range of fold mountains in the world at 7000km long
  • FARMING: Much of the land is used for farming, using terraces to create areas of flat land on the slopes. These terraces help to retain water and limit the downward movement of the soil where the soil is thin in the first place. Most of the crops are grown in the lower valleys e.g. soybeans, rice and cotton
  • LLAMAS: Llamas can carry up to 25% of their body weight and are used to carry materials for irrigation to inaccessible areas
  • MINING: The Yanacocha gold mine in Peru is the largest in the world. The nearby town of Cajamarca has seen the population increase by eight times since the mines opened. The mines provide a source of jobs; however the growth brings an increased crime rate.
  • HYDROELECTRIC POWER: The steep slopes and narrow valleys are an advantage for HEP especially with the melting snow in spring e.g. the Yuncan project dams the Paucartambo and Huachon rivers in northern Peru
  • TOURISM: There are many natural attractions of the Andes, such as mountain peaks, volcanoes, glaciers and lakes and Machu Picchu and the Inca trail which attract tourists

Volcano in a MEDC- Mt St Helens

  • Washington State, USA, fold mountains at a destructive plate margin 
  • 20th March 1980 an earthquake under the mountain caused by moving magma 
  • 3rd April 1980, a bulge appeared on the side of the mountain
  • 18th May 1980- eruption! Gas, steam and ash blasted out of the top and of the side of the volcano, causing a pyroclastic flow moving at 300km/h, killing 61 people. Then hot magma melted the snow and flowed down the mountain at 35 m/s.
  • SHORT TERM RESPONSES: The president visited the area, diggers cleared the ash off roads, snowploughs were used in Ritzville to clear ash, 2000 stranded people cared for in nearby schools and churches, helicopters used to locate casualties
  • LONG TERM RESPONSES: Logging was hard hit by the lateral blast, but there was enough logs recovered to build 85000 three bedroom homes, the US government gave $951m to rebuild industry and compensate residents, 10 million trees replanted, National Park established in 1982 to celebrate the miraculous return of life to the area
  • LONG TERM EFFECTS:, Increased risk of flooding due to new landscape, area more wealthy due to rise in tourism, , 12% of crops ruined

Volcano in a LEDC- Montserrat

  • An island belonging to an archipelago in the Caribbean
  • First eruptions began in July 1995 and has been erupting ever since
  • SHORT TERM RESPONSES: Scientists monitored the volcano and set up warning systems e.g. loudhailer, sirens, charities like the Red Cross set up temporary schools, the UK government sent emergency aid, some people evacuated on boats, charities sent emergency food for animals, people evacuated to the north of the island, troops from USA sent to help evacuation
  • LONG TERM RESPONSES: The south of the island still remained out of bounds 10 years later, the Red Cross built a home for the elderly, people moved back to the island, mainly elderly population, the volcano itself may become a tourist attraction, the UK government funded a 3 year redevelopment programme including offering mortgages, some vegetation began to re-grow on the south of the island, which will soon become very fertile
  • POSITIVE IMPACTS: Fertile lands, tourism industries set up- new jobs, geothermal energy potential, cheap land in unwanted “danger zones”, dramatic scenery, volcanic material used for building
  • NEGATIVE IMPACTS:  Lack of services, danger of death, risk of repeat eruptions, high insurance costs
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Supervolcano- Yellowstone, Montana, USA

  • The caldera is bulging up beneath Lake Yellowstone, up to 70cm in some places
  • The Yellowstone magma chamber is 80km long, 40km wide and 8km deep
  • An eruption today is likely to destroy 10 000km2 of land, kill 87 000 people, 15cm of ash would cover buildings within 1 000 km and 1 in 3 people affected would die. Also, global climates would change, crops would fail and many people die as a result

Measuring Earthquakes- The Richter Scale

  • A logarithmic scale, from 1- no upper limit, based on scientific recordings
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