Restless Earth

Restless Earth

1. Structure of the earth

   • Inner core
     • Outer core
       • Lower mantle
         • Upper mantle
           • Crust
             • Continental Crust
               • Granite
               • 30km - 50km thick
               • Low density/igneous rock
             • Oceanic Crust
               • Basalt
               • 6km - 8km thick
               • Higher density

2. Plate boundaries

   • Destructive: 2 plates collide one plate subducts the other(goes under). This creates volcanoes and earthquakes
   • Collision; 2 plates collide and the 2 plates buckle which creates mountain ranges
   • Constructive: 2 plates move apart forming volcanic ridges
   • Conservative: 2 plates slide past and rub against on another. This causes earthquakes

3. Volcanoes

   • Shield
     • found at constructive plate boundries
     • Gentle sloping sides and wide base
     • Not explosive
     • Runny lava low gas content
   • Composite
     • Tall with steep sides
     • Form at destructive plate boundries
     • Explosive which creates ash clouds
     • Volcanic bombs
     • Pyroclastic flow: mix of ash, gases and rock
     • Very high gas content
   • States of volcanoes
     • Active
     • Extinct
     • Dormant(A sleep)
   • How to predict an eruption
     • Tunnels: have seismometers which monitor earthquake activity.
     • Boreholes: Measure water temperature of water(increase in water temp = rise in magma)
     • Tiltmeters: Detect when the volcano swells as it fills with magam
     • Aircraft: measure the amount of gas given of by the volcanoes
   • How to protect from a volcano
     • Concrete shelter: protect from volcanic bombs
     • Concrete channels: direct dangerous mudflow
     • Evacuation routes + regular drills

4. Earthquakes

   • Key terms
     • Epicentre: where earthquake was first noticed on earth surface
     • Focus: Where the earthquake happened directly in the earth
     • Seismic waves: Waves of energy
     • Seismograph: Graph that shows vibrations from an earthquake
     • Magnitude: amount of energy released from the earthquake
     • Richter scale: measure the strength of the earthquake and magnitude
     • Mercalli scale: measures the scale of damage
   • Effects of an earthquake
     • Human factors that effect earthquake damage
       • Tourism
       • Building quality
         • Material of structure
       • Population
       • Warning systems
       • Response team
       • Preperation
         • Grab bags
       • Nuclear power stations
     • Physical factors that effects earthquakes damage
       • Time since last earthquake
       • Rock type
       • Depth of focus
       • Location of epicentre
         • Sea: could cause tsunami
         • Land: no tsunami
       • Distance from plate boundary
       • If it diggers another disaster
       • Magnitude of earthquake
       • Number of aftershocks
   • Earthquake proof building often have ...
     • Shock absorbers
     • Strong steel frame: flexible stops cracking
     • Strong double glazing: stops glass falling into streets
     • A damper: acts like pendulum reduces building sway
     • Cross bracing: stops floors collapsing
     • Ball bearings: building rolls on them reduces pressure on structure
     • Re-enforced walls: help take strain of earth movement
     • Floating designs: structure doesn't touch floor moves with earthquake e.g Emergancy operations centre in LA

5. Case studies

   • Volcanic: Iceland
     • Causes
       • Constructive plate boundary
         • North american and Eurasian plates
       • High pressure resulted in eruption
       • Magma cooled very quickly
         • Due to glacier on top of volcano
           • Caused a massive ash cloud
       • Small earthquakes triggered eruption
     • Effects
       • Primary
         • Giant ash cloud
         • People's health at risk from ash
         • Flash floods
         • Volcanic bombs
         • Local area covered in ash
         • Evacuation
       • Secondary
         • Shut down aerospace
         • 17,000 flights cancelled on first day
         • Stock shares in airlines dropped by 4%
         • Airlines lost $200 million a day
         • Increased use of ships/ferries
         • Less fruit and veg at supermarkets
         • More fertile ground a year after(had best harvest ever)
         • Live stock died
         • People stuck aboard
     • Response
       • Short term
         • Text message sent to everyone within 30 mins of eruption
         • Icelandic volcano response team started evacuations
         • Bulldosed road to save the ridge
       • Long term
         • Reduced amount of ash so planes could fly
         • Monitoring of nearby volcano(kalta: erupts every 50 years long over due)
   • Earthquake(with tsunami): Japan