Restless Earth

Restless Earth

1. Tectonic Plates

   • Structure of the Earth
     • The Earth is made up of 4 main layers
       • 1. Inner Core
         • In the centre of the Earth
         • The hottest part of the Earth
           • Temperatures of up to 5,500°C
         • Solid layer made up of iron and nickel
       • 2. Outer core
         • The layer surrounding the inner core
         • Liquid layer made up of iron and nickel
         • Extremely hot, temperatures similar to the inner core
       • 3. Mantle
         • Zone of hot rock in the interior of the Earth
         • Located between the crust and the outer core
         • Widest section of the Earth
           • thickness of approximately 2,900 km
         • Made of magma (semi-molten rock)
         • * Upper: Rock=Hard * Lower: Rock=Soft/ Starting to melt
       • 4. Crust
         • Outer layer of the Earth
         • Thin layer (0-60 km thick)
         • Solid rock layer
           • Includes continents + Ocean floor
         • There are 2 types of Crust
           • Continental Crust
             • Carries Land
           • Oceanic Crust
             • Carries water (ocean)
         • Broken up into pieces to form plates
   • Distribution
     • Convection Currents
       • Heat rising and falling inside the mantle creates convection currents
       • The convection currents move the plates
         • The point where two plates meet is called a plate boundary
           • Earthquakes and volcanoes are most likely to occur
           • The movement of the plates, and the activity inside the Earth, is called plate tectonics
           • There are different types of plate boundaries
             • Constructive=Continental and oceanic plates move apart
             • Destructive=oceanic plate is forced under continental plate
             • Conservative=plates slide past each other
         • Diverge=plates move apart
         • Converge=plates move towards each other
   • Plate Boundaries
     • Contructive Plate Boundaries
       • 1. Plates move apart (very slowly), magma rises from the mantle
       • 2. Magma erupts to the surface of the Earth, accompanied by earthquakes
       • 3. Magma reaches the surface, it cools and solidifies to form a new crust of igneous rock
       • 4. The new rock builds up to form a volcano
     • Destructive Plate Boundaries
       • 1. Plates move towards each other (very slowly)
       • 2. Oceanic plate is forced underneath the continental plate
       • 3. Oceanic plate melts to form magma and earthquakes are triggered
       • 4. These Earthquakes usually cause tsunamis

2. Earthquakes

   • Causes
     • An earthquake is the shaking and vibration of the Earth's crust due to movement of the Earth's plates (plate tectonics)
     • Earthquakes can happen along any type of plate boundary
     • Earthquakes occur when tension is released from inside the crust
     • Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake tends to occur
     • The focus is the point inside the Earth's crust where the pressure is released
     • The epicentre is the point above the focus, on the Earth's surface
       • The most severe damage will happen close to the epicentre
   • Measurement of earthquakes
     • seismometer
       • The power of an earthquake is measured using a seismometer
       • A seismometer detects the vibrations caused by an earthquake
         • It plots these vibrations on a seismograph
     • The magnitude (strength) of an earthquake is measured using the Richter scale
       • The Richter scale is numbered 0-10
         • An Earthquake measuring 7-8 can be devastating
   • Effects of an earthquake
     • Social impacts
       • Short-term
         • People may be killed or injured
         • Homes may be destroyed
         • Transport and communication links may be disrupted
         • Water pipes may burst and water supplies may be contaminated
       • Long-term
         • Disease may spread
         • People may have to be re-housed, sometimes in refugee camps
     • Economic Impacts
       • Short Term
         • Shops and business may be destroyed
         • The damage to transport and communication links can make trade difficult
       • Long-term
         • The cost of rebuilding a settlement is high
         • Investment in the area may be focused only on repairing the damage caused by the earthquake
     • Environmental impacts
       • Short-term
         • Fires can spread due to gas pipe explosions
           • Fires can damage areas of woodland.
       • Long-term
         • Important natural and human landmarks may be lost
   • LEDC
     • Suffer more from the effects of volcanoes and earthquakes
       • Weaker communication systems, lower standard of buildings and less funds for evacuation and eventual aftermath

3. Volcanoes

   • Key facts
     • formed by eruptions of lava and ash
     • usually cone shaped mountains or hills
       • When the lava cools, it forms rock
     • When magma reaches the Earth's surface it is called lava
     • Volcanic eruptions can happen at destructive and constructive boundaries, but not at conservative boundaries
     • Some volcanoes happen underwater, along the seabed or ocean floor
   • The formation of volcanoes
     • 1.Magma rises through cracks or weaknesses in the Earth's crust
       • 2.ressure builds up inside the Earth
         • 3.When this pressure is released, eg as a result of plate movement, magma explodes to the surface causing a volcanic eruption
           • 4.The lava from the eruption cools to form new crust
             • 5.Over time, after several eruptions, the rock builds up and a volcano forms
   • Inside a volcano
     • 1. magma chamber is a collection of magma inside the Earth, below the volcano
     • 2.main vent is the main outlet for the magma to escape
     • 3.crater is created after an eruption blows the top off the volcano
   • Activity
     • active and erupt frequently
     • dormant (temporarily inactive but not fully extinct)
     • extinct (never likely to erupt again)
   • Types of Volcanoes
     • Sheild
       • usually found at constructive or tensional boundaries
       • low, with gently sloping sides
       • formed by eruptions of thin, runny lava
       • Eruptions tend to be frequent but relatively gentle
     • Composite
       • made up of alternating layers of lava and ash (other volcanoes just consist of lava)
       • usually found at destructive or compressional boundaries
       • eruptions may be a pyroclastic flow rather than a lava flow
         • pyroclastic flow is a mixture of hot steam, ash, rock and dust
           • A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C