geo

• Erosion is greatest when:  

  • river is fast / has lots of energy
  • rivers is transporting lots of sediment (abrasion and attrition)
  • river has low pH (solution)
  • river is eroding soft rock 
  • outside of a meander (bend)
•  

  Transport

   Traction

  Big rocks roll along the river bed

   Saltation

  Smaller particles ‘bounce’ along the river bed

   Suspension

  Sediments that float in the flow of the river

   Solution

  Sediments dissolve in the water 
• Transport is greatest when:  

  • river is fast / has lots of energy
  • rivers has a large volume of water (discharge is great)
  • there is lots of sediment
• Deposition - Rivers drop the load it is carrying due to a drop in energy (speed). This happens when:

  • river loses speed
  • rivers flow into a sea / lake
  • when the gradient becomes less steep
  • Inside of a meander (bend)
  • there is less water in the river 
  • there is more friction (eg flood)
• 2. River erodes soft rock at a faster rate, creating a step in the river bed. 3.Waterfall retreats upstream to form a gorge
• • As the overhang of the waterfall collapses, it retreats upstream. 
  • This creates a gorge, which is a valley with a steep sides.
• • A valley with steep sides
  • River is high above base level and therefore erodes vertically creating a steep valley
  • Sides are weathered creating a V shape
• • Circular depression in the river bed. 
  • Stone gets trapped in depression in river bed
  • Eddies swirl stone around in hollow
  • Stone grinds out a pothole in the river bed
• Meanders This a bend in the river
• Meanders

  • Helical flow in the river (corkscrew motion) sends the energy to the sides. 
  • The fastest flow is therefore on the outside of the bends
  • Because it is faster on the outside, this means there is more erosion on the outside.
  • On the inside where flow is slower there is more deposition. 
  • This makes the river more sinuous (bendy)
• Oxbow lake

  • Continued erosion on the outside and deposition on the inside results in the neck of the meander narrowing
  • Eventually the channels join together to form a cut off channel and an oxbow lake.
  • An oxbow lake is a horseshoe shaped lake.
• floodplains

  • A floodplain is the flat area of land next to the river which is prone to flooding
  • The river meanders migrate across (laterally) and downstream.
  • The edge of the floodplain is marked by sides called bluffs
  • The river floods and deposits its load because energy falls due to friction
• • Levees are raised embankments on the banks of the river
  • The river floods and the speed slows down due to friction
  • The river loses energy and deposits its load on the floodplain.
  • The coarsest (largest) material is deposited first. 
  • The finest (smallest) material is deposited further away
• Delta

  • River meets the still sea / lake at its mouth
  • The river slows down and loses energy
  • The river deposits its load, creating land which extends out to sea
  • Channel splits into distributaries due to deposition in the channel. 
  • They often have a fan shape, due to ocean currents.
• Opportunities on floodplains and deltas People live on the floodplains and on deltas because: 

  • The river is a source of water for drinking, washing, cleaning
  • Water can be used for irrigation (water for farming)
  • There are fertile soils, which are great  for farming
  • Land is flat = easy to build on and easy to farm on. 
  • River can be used to transport goods eg crops and trade
  • Rivers can be used for fishing
• Stratovolcano Infrequent, violent,  explosive eruptions ,Sticky lava (high viscosity) flows slowly,  creating steep sides and a narrow base when it cools.
• Shield Volcano Gentle, frequent, non-explosive eruptions , Fluid lava (low viscosity) flows a long way before cooling creating shallow sides.
• Earthquake and volcanoes distribution

  • Not evenly distributed, found together
  • Around edges of continents/oceans
  • Especially ring of fire around the Pacific
  • Found on plate boundaries
• Destructive / Convergent Boundary VOLCANOES 1 - An oceanic and continental plate move together. 2 - The denser oceanic plate sinks, this is known as subduction 3 - The plate melts to form magma
• 4 - Magma rises through the crust 5 - Lava erupts at the surface and  creates a stratovolcan
• Ash Clouds. Bubbles of lava burst explosively and cool to form pyroclastic (solid) materials. Ash is smaller than 4mm.

  • Breathing problems
  • Fields covered
  • Buildings can collapse
  • Lakes and rivers polluted
  • Flights disrupted
  • Costs to rebuild
• Lava flows

  • Destroy buildings and businesses
  • Cover fields
  • Destroy roads etc
  • Costs to rebuild
  • Death
  • Injuries
  • Cause explosions
• Volcano Gases

  • Can make climate cooler affecting farming
  • Breathing problems
  • Can mix with water in clouds to make acid rain damaging plants, fish and buildings
  • In extreme cases can suffocate people causing death
•  Pyroclastic Flow

  • Destroy whole towns
  • Destroy roads etc
  • Death and injuries
  • Costs to rebuild
  • Forests destroyed
• Lahars

  • Destroy whole towns
  • Destroy roads etc
  • Death and injuries
  • Costs to rebuild
  • Forests destroyed
• Earthquake Effects

  • Buildings collapse, killing many and affecting businesses and services eg schools. Many can be left homeless and live in camps
  • Broken water pipes mean there is little water and can lead to disease
  • Roads and bridges collapse affecting transport and businesses
  • Fires, started by gas leaks, destroy many buildings
  • Tsunamis destroy houses in coastal areas
  • Landslides kill many people in rural areas.
  • Electricity pylons topple over leaving people with no power
• Positives of Volcanoes


  • Mining - when magma cools it can contain valuable minerals
  • Ash contains nutrients and minerals, which makes soil very fertile and good for farming
  • Tourism - volcanoes are a tourist attraction creating jobs eg guide, hotels
  • Geothermal energy - water pumped into hot rocks, evaporates into steam, turns a turbine for electricity or to heat water
• Protection

  Make more resistant buildings:

  • Computer controlled weights / pendulum a t top to reduce movement
  • Automatic window shutters to stop glass falling
  • Deep foundations to make it stable
  • Rubber shock absorbers to absorb energy and reduce shaking
• Prediction

  • Almost impossible to predict earthquakes
  • Animals act strange eg frogs before the earthquake
  • Small tremors may be recorded before the big earthquake
• Prediction

  • Tiltmeters - Measure swelling of volcano
  • Boreholes to measure temperature. It increases as lava rises
  • Measure volcanic gases. This increases before the eruption. 
  • Seismographs measure earthquakes as lava rises through volcano
• Preparation

  • Concrete shelters to protect from ash and lava bombs
  • Evacuation routes signed
  • Train emergency services and stockpile supplies.
• Nyiragongo


  A volcano located in Democratic Republic of the Congo, a country in Africa
• Nyiragongo is located in eastern DRC near the border with Rwanda
• Nyiragongo is located near the large city of Goma
• Nyiragongo


  • Created at a constructive boundary
  • The African plate is being split apart into the Nubian to the west, and the Somali plate to the east
  • Has a 2 km wide crater with an active Lava lake
• 2002 Nyiragongo eruption


  1. A huge fissure opened on the volcano on the 17th January 2002, caused by earthquakes

  2. Lava drained from the lake, through the fissure, flowing towards the city of Goma at speeds of 60 km/hr
• The destruction of residences and businesses meant many people lost their livelihoods
• Unemployment levels increased to 95 percent, from 80 percent prior to the eruption
• 120,000 people were made homeless
• 250 people died through carbon dioxide asphyxiation, collapsing buildings, burns, and the lava-triggered explosion of a gas station