Slides in this set
·Slopes are defined as any part of the solid land surface where there is an incline.
Processes and Factors- Slope processes- Slow movements
·Processes operating on slopes have a major impact on fluvial landscapes.
·Slope processes transfer material downslope to the river.
Individual soil particles are pushed or heaved to the surface by wetting or freezing
of water. Terracettes are created, these are small terraces from a few centimetres
to 0.5m across the face of a slope caused by soil creep or solifluction.
Particles move at right angles to the surface. They fall under gravity once the
particle has dried, or the ice has melted. Net movement downslope tends to be
Rain- Splash erosion-
This is when individual raindrops compact the soil and dislodge particles equally in
all directions. In some cases solifluction can take place. Solifluction- flowing soil-
soil is affected by the freezing and thawing in cold periglacial environments.
On a flat surface the soil will dislodge particles in all equal directions however, if
the process takes place on a slope the downward component will be more
Processes and Factors- Slope processes- flow movements
Sheetwash is the un-channelled flow of water over a soil surface. On most
slopes sheetwash is divided into areas of high velocity separated by areas
of lower velocity. Occurred during Boscastle floods of 2004
This occurs when the soil's infiltration capacity has been exceeded and
can lead to the formation of gullies
Through flow is water moving down through the soil. It is channelled in to
natural pipes in the soil, this gives it sufficient energy to transport
Fast Mass Movements
Processes and Factors- Slope processes- Fast mass movements
Sliding material maintains its shape and cohesion until it impacts at the bottom
of a slope and leads to large, slumped Terracettes.
Mini Case Study- The Vaiont Dam, Italy (9 Oct 1963)- over 2000 died
Prolonged heavy rainfall led to landslides in Central and East Java (Indonesia)
killing 120 people
Fast Mass Movements
Slumps occur when weaker rocks especially clay, and have a rotational
movement along a curved slip plane. Clay absorbs water, and becomes
saturated, and exceeds its liquid limit. It then flows along the slip plane.
It is affected by Sheer strength.
Mini Case study- Folkestone Warren. Also Holbeck Hall hotel, Scarborough-
human activity impacted the sheer stress and strength and caused the whole
hotel to be destroyed.
Fast Mass Movements
Rock falls occur on steep slopes. The initial cause of the fall may be weathering for
example, freeze thaw.
Mini Case Study- Wastwater in the Lake District. Falls lead to scree slopes and
large slumped terraces. In upland areas falls and slides are an important
sediment source for rivers.…read more
Slopes vary with climate. In general, slopes in temperate environments are
rounder, due to chemical weathering. Whereas slopes in arid environments are
jagged or straight because of mechanical weathering and overland run-off.
Processes and Factors- Factors affecting slopes
Rock Type Structure
Slopes are influenced by rock type. North and West are resistant rock such as
Granite and Limestone which are not easily eroded. To the South and East, softer
rocks such as, chalk and clay which are easily eroded.
Aspect is the direction a slope faces. In the UK, north facing slopes remain in the
shade. During cold periglacial times, temperatures rarely rise above freezing.
However, the south facing slopes experience many cycles of freeze-thaw due to
the temperature. Solifluction and overland run-off lower the level of the slope.
Mini Case study-
The result of this is an asymmetric slope such as, the River Exe in Devon.…read more
Processes and Factors- Weathering- Mechanical Weathering
Water gets in joints and cracks and freezes at 0°C, expands by 10% and then
exerts pressure which cracks rocks and causes them to break and fracture. It is
most effective in environments where the temperature fluctuates above and
below freezing point, such as periglacial and alpine regions.
Salt Crystal Growth
This occurs in two ways: One, in areas where temp fluctuates around26-28°C,
sodium sulphate, and sodium carbonate expand by 300%
The second is, when water evaporates, salt crystals may be left behind to attack
the structure. Both methods are frequent in hot desert areas.
This occurs in hot dessert areas. Rocks heat up by day and contract by night. AS
rock is a poor conductor of heat, stresses take place only in the outer layers and
causes peeling or exfoliation to occur.
This is the process where overlying rocks removed by erosion cause underlying
rocks to expand and fracture parallel to the surface.…read more