You must know and be able to describe and explain:Physical weathering
Freeze-thawExfoliation
Chemical weatheringLimestone solution
IgneousSedimentaryMetamorphic
Formed by fire – magma in the interior of the Earth
Formed by the cooling of lava or magma
Examples – Basalt and Granite
Made up of small particles transported by water, ice and wind
As more sediment accumulates the weight causes the rock to form
Weak rock generallyExamples –
Sandstone, clay, limestone and chalk
Originally igneous or sedimentary rock which have been altered by heat and/or pressure
ExampleLimestone into
MarbleClay into Slate
All the Granite rocks in the UK are found to the north and west of the Tees-Exe line
The rock which forms tors is that which remains after the surrounding rocks have been weathered and carried away.
Where tors occur, the joints in the granite are wider apart than in the rock around them
Freeze-thaw weathering can operate more effectively and blocks of rock break off more quickly where the joints are close together, because there are more cracks in the rock for the water to fill
Each time the water freezes and expands within a joint, more pressure is put on the surrounding rock and the crack widens.
Where there are fewer joints, it takes longer for the blocks of rock to be broken off and the block are left upstanding as Tors
ReservoirsPoor grazing land for Cattle and SheepDartmoor – PoniesBuilding materials and gravestones
In the Uplands of England and WalesThe Yorkshire Dales – Malham and IngletonPeak District near CastletonThese rocks are very susceptible to chemical
weathering
Limestone pavements – flat surfaces of bare rock broken up into separate block
The flat surfaces of the blocks are clints and the gaps are grykes
Rivers disappear underground either through small holes in the rocks called sink holes or down larger holes with a funnel shape above called swallow holes
Underground limestone is full of holesForms large chambers, caves and cavernsStalactites made of lime hang down from the
roofs like long iciclesStalagmites are the thicker columns built up
from the floor
Good for sheep farming – grazing the short turf-like grass which grows
Limestone landforms are attractive to visitors – tourist attractions – Gift shops in Castleton etc
Farmers can ear extra income from campsites and bed and breakfasts
Used as a building material – St. Paul’s CathedralWhen crushed it can be used for fertiliserUsed a cleanser in many industries – power
stationsQuarrying
Chalk is a soft, white, porous form of limestone composed of the mineral calcite. It is relatively resistant to erosion so forms tall steep cliffs where chalk ridges meet the sea e.g. Beachy Head along the south coast of England
Chalk is porous which means that water can pass through and be stored in the pore spaces between the particles of rock. When it rains, water infiltrates into the chalk layers and saturates the chalk. The upper level of saturation is called the water table.
Many water companies drill boreholes into the chalk rock to supply water to nearby settlements.
Chalk forms distinctive landscapes with steep escarpments and gentle dip slopes. The hills may have dry valleys which show the characteristics of a river valley but have no water flowing along them. The North and South Downs in south-east England (UK) show all these features
There are two requirements before an escarpment can be formed:Alternate outcrops of different types of rocks.
One rock needs to be soft and the other needs to be more resistant to erosion
Beds of rock dip at an angle to the ground surface. Instead of being horizontal, the beds were tilted by earth movements so that they lie at an angle to the surface
The clay is eroded more quickly than the chalk
As the clay is eroded down into the vale, the chalk is left standing up because of its greater resistance
The scarp slope forms a prominent feature where the layer of chalk reaches the surface
The dip slope is more gentle following the tilt of the beds of rock
Settlement - see Fulking case studiesGood for pasture and training racehorsesGood building materialUnderground water supply – called aquifers
Top Related