rocks and weathering

• What is pinning?

  It is literally a huge pin up to 6 meters long which is drilled into the ground and consolidated the loose and firm soil together to stop the slope slipping on itself
• What is netting?

  Placing nets to collect scree and loose rocks to catch them if they fall is often used in tourist areas or in areas near a road. Supports loose rock face
• What are gabions?

  A wall of wire cages filled with rocks usually built at the foot of cliffs used to stabilise the toe of a landslip
• What is drainage?

  A cause of mass movement is excess water on a slope which increases sheer stress and provides lubrication. To prevent this, trenches are dug and filled with gravel so the water moves into them and off the slope
• What is grading?

  Grading is cutting gently graded platforms into a slope so when it rains rocks do not move as far. It makes the slope more gentle.
• What is afforestation?

  Planting vegetation to increase interception and reduce soil erosion and surface runoff making the slopes less saturated.
• What is grouting?

  Grouting is when permeable rocks are filled with cement to reduce pore water and increase strength.
• What is Shotcrete?

  Shotcrete is when loose rock is sprayed with concrete to stabilise it.
• What is hazard mapping?

  Using past events to predict where and how big a future event is likely to be, and using this information to plan for the future e.g. not building near on a weak slope plain.
• What is soil creep?

  - A slow but continuous process

  -1-3cm per year

  - slopes over 5 degrees

  - Repeated expansion and contraction of soil particles due to precipitation and climate

  - Lifts to a right angle of a slope then falls
• What is evidence of soil creep?

  - Terracettes (Ribbed pattern on slopes)

  - Leaning poles and bent trees
• What are mud/soil flows?

  - Slopes 5-15 degrees

  - Defining hourglass shape

  - Soil gets saturated, and material liquidifes, due to an increase in sheer stress break away from base of the slope forming a bowl shape at start of the flow

  - Loses momentum, further elongates shape, creating the tow of the flow

  - Pulls down vegetation
• What is a rotational slump?

  - Common on coastlines due to undercutting

  - The toe of a slope has been removed

  - permeable soil overlaying and impermeable bedrock

  - Water infiltrates permeable rock creating a zone of lubrication

  - portions of the slide drop and rise for the adjacent slopes, leaving behind a curved slip plane
• What is a Translational Slide?

  - A plane of weakness between overlying and underlying material

  - Results in a block of material sliding down the slope, retaining its shape until it hits the ground
• What is a rockfall?

  - Occurs of slopes 40 degrees and over

  - Often a result of extreme rapid weathering

  - Large angular rocks

  - Hot weather can cause soil to shrink, destabilising rocks
• What is freeze-thaw weathering?

  - When water gets into cracks in the rock.

  - The water freezes and expands, putting pressure on the joints of the rock.

  - The ice then thaws releasing the pressure. If this is repeated, bits of the rock will fall off.

  - The stress produced by the expansion is greater than the resistance of the rock
• What is cystallisation weathering?

  - Salt solutions (sodium) in the joints of rock crystalise due to evaporation and expansion, forcing the force apart

  - Effective at 27 degrees where temperature fluctuations produce expansion rates of 300%
• What is exfoliation?


  -the peeling off of curved layers of rock

  - When rocks are exposed to sunlight and harsh temperatures, it expands.

  - When the temperature falls at night, it contracts.

  - Due to the temperature fluctuations and pressure, the layers of the rock begin to crack

  - the outer layers start to peel away layer by layer.

  - Darker rocks more vulnerable due to albedo
• What is carbonation?


  - a form of chemical weathering

  - weak carbonic acid reacts with calcium carbonate-rich rocks. - Therefore rock types that have calcium carbonate such as chalk and limestone will be more affected It can encourage carbonation, where rocks such as limestone are disintegrated through carbonic acid resulting in calcium carbonate, as evidenced by Old Harry’s rock
• What is oxidation?


  - When the oxygen in water reacts with iron in rocks

  - Can be seen through a red/orange hue
• What is dilation?


  - Pressure release is where the material overlying the rock is removed

  -allowing the rock to expand

  -causing fractures/joints to be formed
• What is Chelation?


  - Weathering through organic subtances

  - Like humic acid
• What is hydration?


  - Minerals in a rock expand due to water absorption

  - Increasing pressure on rock
• What is hydrolysis

  hydrolysis is also encouraged by the presence of water as granite granite-containing feldspar reacts with CO2 and water, resulting in Kaloinite.
• What are the factor's effecting rates of weathering?

  -Climate

  - Structure

  - Texture

  - Composition

  - Vegitation

  - Relief

  - Human activity