geo

• Earthquake


  Triggered from below the Earth's surface where rocks under great stress and pressure reach breaking point and make sudden jerking movement
• Epicentre


  • Location at the surface of the ground above the focus
• Focus


  • Location of the source of an earthquake below the ground
• Seismic waves


  1. Shock waves sent to the focus -> surface of the Earth starts to shake and break

  2. Shock waves spread in places thousands of kilometres away

  3. Damages are done depending on the pressure of the focus & whether there are people & buildings within the range of earthquake
• Volcano


  A hole, crack or vent in the Earth's crust that allows molten rock (magma), solid rocks, steam and other gases to escape onto Earth's surface and into the air
• Strato-volcanoes


  • Composite cone volcano
  • Erupt with great violence, causing death and destruction
  • Usually occur in mountain regions (great pressure can build beneath the ground)
  • Steep sides as the acid lava - not suitable for agriculture - is more vicious and cools quickly
  • Rocks are also thrown (volcanic bombs)
  • Secondary vent formed when lava leak from the sides
• Shield volcano


  • Flatter and less violent, dramatic & damaging
  • No great build-up of pressure, erupt more often and are less explosive
  • Lava contains less acid, is less vicious & runny and flows for some distance from the vent -> when cooled, slopes are gentle
  • Created beneath the ocean and their peaks form islands
• Crust

  Collection of solid tectonic plates that join together like a jigsaw puzzle
• Mantle

  A layer of molten lava that flows through convection current
• Convection currents

  Differences in temperature of material beneath the plates of the Earth's crust leads to the creation of currents to transfer heat, moves plates above them -> giving rise to earthquakes, volcanoes and fold mountains
• Tectonic plates

  • Meet at plate boundaries where earthquakes, volcanoes and fold mountains are created
  • rigid segments of rocks that make up the Earth's crust
• Plate boundaries

  The edge of a tectonic plate where earthquakes, volcanoes and fold mountains formed or take place
• Classification of Volcanoes

  • active : regular eruptions
  • dormant : has not erupted for many years but activity can be detected inside
  • extinct : will not erupt again as no activity can be detected
• Crust bin

  Oceanic crust (heavy) sinks beneath continental crust (light) and melts, creating heat & pressure & magma (molten rock)
• Crust factory

  • new crust as magma cools from mantle
  • sea floor spreads as plates move apart/diverge
• Continental plate


  • Mostly made of granite, a light rock than basalt (25-100km thick)
  • mostly above ocean, forming land
• Oceanic plate


  • Mostly below the ocean
  • Mainly made of basalt (5-10km thick)
  • Dense and heavy so it sinks below continental plate
• divergent boundary

  • movement : spreading
  • effect : constructive - new crust created
  • relief : ridge
  • activity : earthquakes and shield volcanoes
• convergent boundary

  • movement : subduction
  • effect : destructive - old crust destroyed
  • relief : trench
  • activity : earthquakes and stratovolcanoes
• conservative boundary

  • movement : plates slide sideways by each other
  • effect : crust neither destroyed nor created
  • relief : no major effect
  • activity : earthquakes
• glacial

  to do with ice, its movement and the features formed by it
• mudflow

  a mass movement of rocks and soil down a slope that is often triggered by heavy rain and developed by volcanic ash
• lahars

  a volcanic mudflow containing a mixture of rocky debris, ash and water, and usually flows down a river valley from a volcano
• volcono's opportunities

  • light ash from the volcano gives nutrients to the soil, making it fertile for an abundant of crops - good for farmers
  • volcanic heat provides the energy for hot springs, steaming geysers and thermal areas, and produce renewable electricity
  • volcanic activity produced much of the world's mineral wealth
  • tourism
• Earthquake


  • Causes death to both humans and animals
  • Causes destruction through landslides, tsunamis, fires & rock movements
  • Destroys buildings and infrastructure
• precipitation:

  • any form of water falling on the Earth's surface from the atmosphere
  • for example: dew, fog, frost, hail, mist, rain, sleet and snow

  discharge :

  • the amount of water flowing across the width of a river at a given point
• once clouds have released the precipitation, many different routes and destinations are possible for water. it may:

  • evaporate back into the atmosphere
  • be transpired by plants
  • stay for a time in lakes, glaciers or reservoirs
  • infiltrate into the ground to become groundwater
  • run off the surface immediately into rivers
• RIVER TERMINOLOGY:

  width - how wide the water in the river is. the distance from bank-to-bank of the surface water of the river

  depth - how deep the water in the river is -> varies across the river, so an average usually taken from several measurements of the width

  velocity - the speed at which the river is flowing -> varies with depth and width

  wetted perimeter - length of the wet part of the channel cross-section containing water flowing

  cross-section area - area of flowing water when measure from bank to bank
• drainage basin :

  • the area of land drained by a river and its tributaries - known as catchment area

  watershed:

  • the boundary of a drainage basin - known as divide
• How does evaporation occur in the water cycle?

  As temperature increases, water in the sea changes from liquid to gas and rises into the atmosphere
• What happens during condensation in the water cycle?

  Water vapor cools and changes back to water droplets, forming clouds
• What is the role of prevailing winds in the condensation process?

  They blow water vapor towards the mountains where it cools
• What happens to rainfall after it is intercepted by plants and trees?

  Some falls on land and infiltrates the ground or flows on the surface
• What is overland flow in the water cycle?

  Upland streams flow downhill and join to form wider rivers
• What happens to rivers formed by overland flow?

  They eventually discharge into lakes
• transpiration: water from the roots is returned to the atmosphere from leaves
• erosion: the wearing away and removal of rocks by the action of the agents of erosion - wind, water, ice, gravity
• main processes of erosion

  1. hydraulic action - the force and impact of flowing water alone can remove material from the bed and banks of rivers
  2. abrasion (corrasion) - the effect of the load grinding away at the bed and banks of a river like sandpaper
  3. attrition - as materials wears away the bed and banks, it also becomes smaller and more rounded and less effective in carrying out erosion
  4. solution (corrosion) - some rocks dissolve in the presence of water
• materials are transported by the river by:

  1. solution load: minerals are dissolved and carried in solution
  2. suspension load: very light materials are carried near the surface giving the river its colour
  3. saltation load: small pebbles and stones are bounced along the riverbank
  4. traction load: heavy boulders and rocks are rolled along the riverbed
• deposition - the laying down of solid material such as mud or sand on the seafloor and river or lake beds

  • a river deposits materials when energy decreases - no longer competent to transport its load -> gradient of the river channel becomes more gentle