- Created by: Francesca
- Created on: 20-04-13 17:29
Because of logging - tree roots secure the soil to the bedrock,
Maintains land stability by absorbing rain.
Logging increased due to population pressures
More area needed for food to grow
Coconut trees- shallow roots
Heavy rainfall - up to two weeks before. 200cm in 10 days.
Mild earthquake could have triggered it
1500-2500 buried in mud
Waist deep mud - 19 died
'Everything was buried' schools and houses swamped. Buried pupils
Secondary hazard - another mudslide
Malham Cove - Yorkshire.
Karst scenery? Well developed features on dry limestone.
Clints - rectangular shaped slabs of rock.
Grykes - gaps between clints.
Limestone weathers easily - calcium carbonate.
Permeable - water seeps through dissolving it.
More acidic water the more solution.
Calcium rich water drips from the ceiling and leaves behind calcium.
Stalactites - from top of cave
Stalagmites - from bottom of cave.
Tropical karst - Jamaica.
Cockpit - landscape pitted with smooth sided soil covered depressions. Uniform in height. Develop as a result of solution.
Tower - variable in size. Steep sides with cliffs and overhangs. Caves and solution notches at base.
Greater physical strength. Resistant to erosion.
Contain quartz, mica and feldspar.
Freeze thaw and hydrolysis occur.
Tors - isolated masses of bare rock.
Bornhardts - large isolated dome like hills standing above an extensive plain. Often made of granite and formed by exfoliation.
Abrasion or corrasion - wearing away of the bed and bank by the load carried by a river.
Attrition - wearing away of the load carried by the river creating smaller rounder particles.
Hydraulic action - force of air and water on the sides of the river and in cracks.
Solution or corrosion - removal of chemical ions causing rocks to dissolve.
Load - heavier load.
Velocity and discharge - more.
Gradient - steeper
Geology - soft rock
pH - more acidic
Human impact - deforestation, dams.
Suspension - small particles held up by turbulent flow
Saltation - heavier particles bounced and bumped along bed
Solution - chemical load carried dissolved in water
Traction - heaviest material rolled or dragged along bed
Floatation - leaves and twigs carried on surface
Floodplains and leveés
Area covered by water when river floods
Leveés - when a river floods it's speed is reduced by friction.
The river had to deposit some of its load.
Drops coarser heavier material first to form raised banks or leveés
Deltas - large volume of sediment needs to be carried by river.
Velocity falls as it enters a still body of water.
Deposition occurs - heaviest particles first.
If water is salty deposition is increased.
Meanders eventually join together and separate to form a new river and an oxbow lake.
It will eventually be taken over by vegetation because it is no longer moving.
The water will evaporate.
Access to fresh water and fish.
Flooding more common.
Annual floods - 4 million tonnes of sediment full of nutrients deposited.
A dam was built - Aswan Dam
People had to relocate.
It stops damage and controls flooding.
Millions of tons of fertiliser now have to be used.
Long shore drift.
Direction of wind causes wave to hit shoreline at an angle.
Wave carries swash at an angle.
Backwash carried back into sea at a 90 degree angle.
Smaller material is deposited.
Hydraulic action - as waves break cliff face. Trapped air in cracks is put under great pressure and as the wave retreats pressure is realised with explosive force.
Abrasion - process of a braking wave hurling material - pebbles or shingles against cliff face.
Attrition - eroded material such as broken rock is worn down to produce smaller rounded beach material.
Solution - occurs on limestone or chalk. Calcium carbonate dissolves in acidic water.
Wave cut platform, arches, stumps, stacks.
Waves attack base of cliff.
Abrasion, solution, hydraulic action and solution.
Over time the cliff will be under cut and a wave cut notch is formed.
Eventually the cliff collapses and further cliff retreat forms a wave cut platform.
Waves erode cracks in the headland.
Eventually erodes to form an arch.
Arch becomes unsupported and collapses to form a stack.
Stump forms from collapsed stack.
Beach of sand or shingle linked at one end to land.
Curved? Wind direction changes and moves spit inland.
Rivers current stops deposition across the estuary.
Wave energy reduced along a coast where headlands and bays are common.
As waves undergo refraction spit becomes curved.
Tombolo - spit that joins land to an island - Chesil Beach
Bar - Spit that joins mainland to mainland - ordfordness in Devon
Salt marshes - form because water becomes sheltered
Mud is deposited and plants begin to grown forming salt marshes.
Green algae colonises first.
Plants increase deposition rate,
Borth - Wales
300000 tonnes of rock used as a coastal defence.
Man made reef in Borth.
Some shipped in from Norway.
Problems with coastal erosion.
Absorb natural energy of wave and allow build up of beaches.
Attract tourists and are a natural defence.
Expensive to maintain
Expensive to transport large boulders.
Twigs and leaves fall to ground to become litter.
Decomposition by fungi and bacteria.
Nutrients enter soil.
Soil is fertile.
If trees are cut down less twigs and leaves fall to floor so less decomposition less nutrients and therefore less growth.
Desertification The Sahel
Land turned into desert.
500km from Senegal.
Covers a fifth of Africa.
Sun heats earth - latitude.
Earth heats air above it.
Hot air rises - less dense.
As it rises water vapour in air cools and condenses into water droplets.
They collect to form clouds.
Become heavy and fall as rain.