Tectonics

Tectonics

1. Volcanoes

   • Montserrat
     • Island in the Caribbean population 11,000, main eruptions took place 1995-97 and have continued. Lies on a destructive plate margin.
       • Primary effects - 23 deaths, pyroclastic flow burned buildings and trees, ash buried 2/3rds of the island, 60% of capital city (Plymouth) housing destroyed, ash buried airport and roads destroyed.
       • Responses - As volcano had not erupted for 400 years government had no plans in place. People evacuated to north of island, 8,000 people fled to UK and neighbouring islands. UK given £35m in aid by 2010, little farmland left, Plymouth still uninhabited, tourism slowly returning, hazard of the island shows dangerous areas and limited access.
       • Secondary effects - hospitals and schools closed, impossible to farm as land buried under ash, ash washed into the sea destroyed coral reefs

2. Plate Boundaries

   • Constructive
     • This is where the plates move away from each other.
       • Where two oceanic plates move apart, ocean trenches are formed and undersea volcanoes form mid-ocean ridges, such as the Mid- Atlantic Ridge.
       • Where continental plates pull apart, rift valleys are formed and lava erupts to create shield volcanoes, such as Skjaldbreidur in Iceland. Minor earthquakes can occur here
   • conservative
     • This is where plates are pushed in different directions, e.g the San Andreas Fault
       • Plates remain locked together until the rock breaks along a fault line. Major earthquakes occur as stored energy is released.
   • Destructive
     • This is where plates push together
       • Earthquakes occur when the plates move
       • Lighter continental crust made of granite is compressed to form fold mountains such as the Andes.
       • The denser oceanic crust, made of basalt,is forced down into the mantle(Subduction). This forms an Oceanic trench

3. Earthquakes

   • Key terms
     • Shaking and vibration of Earth's crust
       • Movement of TECTONIC plates
         • TENSION RELEASE and PRESSURE BUILD UP causes earthquakes
           • Point inside the crust where pressure is released is called the FOCUS
             • Energy is released in SEISMIC WAVES
               • Felt most strongly at the EPICENTRE
   • Haita (LEDC)
     • Primary effects - President's palace collapsed. Hospitals collapsed. Houses collapsed. Infra-structure destroyed and after shocks.
     • Secondary effects - missing people, increase in cholera, tense situation, no food or water, no doctors or hospitals, no long term support structure.
   • Sichuan,China
     • Earthquake registered 8.0 on the Richter Scale. The area is densely populated and the Earthquake struck at 4am. Caused by the movement of the indian plate against the Eurasian plate.
       • Secondary effects- relief effort were hampered because roads were destroyed. 700 schools were destroyed. Water and electricity supplies were cut off. Fires broke out in the collapsed buildings.
       • Responses- 50,000 Army troops were sent to help. International aid and experts were bought in. 1.47m people were evacuated from the worst affected areas. Temporary camps were set up with 34,000 tents erected. Government passed strict building regulations to help prevent future damage.
       • Primary effects- buildings collapsed and many thousands were under rubble. 70,000 people were killed. 5 million people were left homeless. 374,000 people were injured. Many farm animals were lost and crops destroyed.

4. Advantages of living in tectonic areas

   • Advantages - Volcanic soils are very fertile. e.g Mount Elgon Coffee . Volcanic landscapes attract tourism. Volcanic processes create valuable mineral resources. Deep water trenches of subtraction zones provide rich fishing grounds

5. Prediction and prevention

   • Prediction
     • Remote sensing, satellite monitoring of volcanic temperature and gas emmissions
       • Tiltmeters - monitor changes in shape of a volcano
         • Gas emissions indicate increased risk
           • Ultrasound - used to detect movements of magma
     • Seismometers - measure the increase in earthquake activity
       • Laser beams detect earthquake plate movements
   • Prevention / Preparation
     • Exclusion zones, evacuation plans, readiness of emergency supplies, communication systems, information provided in risk areas.