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CHALK and CLAY in the SOUTHDOWNS
Transcript of CHALK and CLAY in the SOUTHDOWNS
To understand chalk and clay landforms in the South Downs.
CHALK and CLAY in the SOUTH DOWNS
The chalks are created when
THE CHALKS IN THE SOUTH DOWNS.
PASTORAL FARMING: Mainly sheep, racehorses and some cows are farmed. Soils are too thin to allow much arable farming.
SETTLEMENTS: Where chalk meets clay, spring-line settlements (where a ridge of permeable rock lies over impermeable rock and a line of springs form along the boundary between the two) can be seen, eg Fulking in West Sussex. Due to the good access to London, the South Downs are popular as a location for commuters and retired people.
RACEHORSE TRAINING: For example, stud farms and stables are common at Epsom in Surrey.
QUARRYING: Chalk with flints is a strong building material used in cement manufacture.
What do you normally imagine if you hear someone saying "pass me the chalk, please?"
Chalk and clay are both sedimentary rocks but the landscapes they create are quite different.
Piece of chalk collected in South Downs.
On the South Downs: Hikers resting
Chalk is a sedimentary rock made of calcium carbonate.
It is weathered by chemical weathering called solution or carbonation
These are the most destinctive features found in chalk landscapes.
It consists of two parts a
Steep Scarp Slope
This is the much more gentle dip slope.
Two Conditions are required for formation of escarpments
1.Alternate layers of rock with a different level of resistants to erosion
2. Beds of rock that dip at an angle
Clay leads to large open vales that have abundant surface drainage. On the coast they form weak cliffs.
Chalk leads to outcrops like the white cliffs of Dover or Beachy Head in Sussex. Surface drainage is rare.
There is little surface drainage on chalk landscapes. Water permeates easily through the rock.
Streams once existed when the climate was much colder and here the water has cut deep to create dry valleys today.
During peiods of heavy rain temporary seasonal streams called bournes run out of the saturated rock.
Places like Winterbourne and Eastbourne take their names from these seasonal springs.