TYPES OF ROCKS
- formed by the COMPACTION and CEMENTATION of sediments usually deposited in the sea.
- In layers called BEDS. Contains fossils but some rocks can be tough, most are weaker than igneous and metamorphic rocks.
- Sandstone, limestone, shale, cale and mudstone.
- Formed by the cooling of molten magma either underground (intrusive) or on the ground (extrusive) by volcanic acitivity.
- Composed of interlocking crystals. Generally tough rocks and are resistant to erosion.
- Basalt, granite, gabbro
- Formed by the alteration of pre-exisiting igneous, sedimentary or metamorphic rocks by heat and pressure.
- Crystalline, in layers called cleavage and banding. Tend to be tough and resistant to erosion.
- Slate, gneiss and schist.
KEY TERMS 1
Permeability: allowing water to pass through
Porous: rock that allows water to soak into it via spaces between particles.
Igneous rocks: rocks formed from the cooling of molten magma
Sedimentary rocks: most ocmmonly, rocks formed from the accumulation of sediment on the sea floor.
Metamorphic rocks: rocks that have undergone a change in their chemistry and texture as a result of heating or pressure.
Rock cycle: connections between the three rock types shown in the form of a diagram.
Geological timescale: the period of geological time since life became abundant 542 million years ago, which geologists have divided into eras and periods.
GEOLOGICAL TIMESCALE AND POSITION OF I,S & M ON IT
The boundaries between the different periods represent critical stages in the earth's history, such as periods of mountain building or widespread sea level change.
GRANITE- FORMED ABOUT 280 MILLION YEARS AGO
CARBONIFEROUS LIMESTONE- FORMED SOME 340 MILLION YEARS AGO
CHALK- FORMED DURING THE CRETACEOUS PERIOD
CLAY- FORMED DURING JURASSIC, CRETACEOUS AND TERTIARY PERIODS.
THE ROCK CYCLE
- Weathering(the breakdown of rock) of all three rock types create loose sediment.
- This makes it easier for erosion(the removal of rock) to occur.
- The Sediment is transported away(e.g. by Rivers) and deposited on the sea bed.
- Sediment is compacted on the sea bed through lithifaction to form Sedimentary Rocks.
- Heat and Pressure (e.g. from overlaying layers of rock) can change any rock type to new Metamorphic Rock.
- Melting of any rock typ (e.g. in the mantle) creates magma. When the magma cools, Igneous Rocks are formed.
- The whole process repeats and keeps on repeating. It is still happening today, but it takes so long to happen that we don't notice.
DISTRIBUTION OF THE 4 ROCKS AND LOCATIONS
WEATHERING: the break up or decay of rocks in their original place at or close to the earth's surface.
EROSION: process of weathering and transportation of rocks
MECHANICAL WEATHERING (PHYSICAL WEATHERING)
- involves the disintegration of rocks without any chemical changes taking place. Often results in piles of fragments called scree found at the foot of bare rocky outcrops.
1) FREEZTHAW WEATHERING: involves the action of water as it freezes and thaws in a crack or hole in the rock.
- In some areas, the temperature is above 0 degrees in the day and below 0 degrees at night.
- During the day, water seeps into cracks in a Rock.
- At night the water Freezes, expanding by about 9%, which puts pressure on the rock.
- The water Thaws the next day, releasing the pressure from the Rock.
- The process repeats every day and night unti the cracks are wide enough to cause the rock to break.
WEATHERING 1 CONTINUING
2) EXFOLIATION: FLAKING OF THE OUTER SURFACE OF ROCKS MAINLY CAUSED BY REPEATED CYCLES OF HOT AND COLD.
- In some areas, the temperature has a large range. In the desert the temperatures reach 40 degrees in the day and 5 degrees at night.
- Each day the surface layers of the rock heat up and expand faster than the inner layers.
- At night the surface layers of the rock coold down and contract faster than the inner layers.
- This creates pressure within the rock and causes the surface layers to peel off, much like an Onion Skin.
The presence of water is important for exfoliation to take place as it weakens the rock, making it more vulnerable to flaking.
CHEMICAL WEATHERING-WEATHERING THAT INVOLVES A CHEMICAL CHANGE TAKING PLACE.
SOLUTION: dissolving of rocks or minerals by rainwater
- Some minerals that make up rocks are soluble in water(rock salt)
- The minerals dissolve in rainwater, breaking down the rock.
CARBONATION: weathering of limestone and chalk by acidic rainwater.
- Carbon Dioxide dissolves in rainwater to make a weak Carbonic Acid.
- Carbonic Acid reacts with Calcium Carbonate in rocks(Carboniferous Limestone), so the rocks are dissolved by the rainwater.
BIOLOGICAL WEATHERING- WEATHERING CAUSED BY LIVING ORGANISMS SUCH AS TREE ROOTS OR BURROWING ANIMALS.
- Plant roots break down rocks by growing into cracks and expanding them by forcing them apart. (flora and fauna)
- Burrowing animals may loosen small amounts of rock material.
DIAGRAMS OF WEATHERING PROCESSES
WHAT ARE THE CHARACTERISTICS OF GRANITE LANDSCAPES
CHARACTERISTICS OF GRANITE:
- Tough rock, resistant to the processes of weathering and erosion.
- Contains cracks or joints,
- Vertical joints formed when the granite cooled and contracted.
- Horizontal joints in granite resulted from pressure release as the overlying rocks were removed by erosion.
- The rock expanded as the pressure was released, causing the joints to form roughly parallel to the ground surface.
- Granite is an impermeable rock
TYPE OF WEATHERING IT IS VULNERABLE TO:
- The presence of the joints makes it vulnerable to freeze-thaw weathering and sometimes exfoliation.
WHAT ARE THE CHARACTERISTICS OF GRANITE LANDSCAPES
THE APPEARANCE OF A TOR:
- Horizontal cracks caused by pressure release.
- Zone of widely spaced joints.
- Rounded edges, vertical/ horizontal joints, broken rocks at the foot, enlarged joints.
HOW A TOR IS FORMED:
- The granite seen on Dartmoor originated as a granite batholith, under the surface of the earth. A batholith is an area of molten rock that has cooled very slowly within the crust, creating a rock with large crystals.
- Over time the material above the batholith was weathered and removed by rivers and glaciers. As this material was removed there was a reduction of pressure on the granite as there was less above it. This caused it to crack creating joints and bedding planes.
- Where the joints were close together the most rapid weathering occurred, and quickly broke down the rock. However there were also areas where there were very few joints and so slower weathering occurred. The main form of weathering is freeze-thaw.
- As this process continued over millions of years, the overlying material was totally removed, leaving behind the tors and valleys seen on Dartmoor.
WHAT ARE THE CHARACTERISTICS OF GRANITE LANDSCAPES
HUMAN USES OF GRANITE LANDSCAPES (DARTMOOR):
Economic purposes, environmental and social uses:
- Main settlements: Ashburton, Buckfastleigh, Chagford, Moreton Hampstead
- Farming- employs 2,000 people in the National Park
- Koolin, china clay extraction
- Tourism- national park, popular for walking, camping and pony trekking- 10 million peole visit each year.
- Princetown- prison
- Used by MOD- control over 30,000 acres, land between Okehampton and two bridges, used for land firing, began in the 19th century, unpopular and several local views.
- Used for water supply- 8 reservoirs (e.g. Burrator), created by the urban populations particularly by Plymouth, Exeter, total area covered by water to nearly 200 hectares.
- Used for historically- tin mining since 12th century, works continued till 1920s, quarrying of Dartmoor granite- important source of employment.
WHAT ARE THE CHARACTERISTICS OF CARBONIFEROUS LIME
CHARACTERISTICS OF LIMESTONE:
- sedimentary rock
- composed largely of the minerals: calcite and aragonite
- composed of skeletol fragments of marine organisms
- the sollubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years
- most cave systems are through limestone bed rock.
FORMATION OF LIMESTONE PAVEMENTS
- Rainwater is a weak carbonic acid as it has carbon dioxide dissolved in it
- A reaction takes place between the calcium carbonate and the slightly acidic rainfall and the limestone dissolves
- This happens most where the rainfall can gain easy access- through the joints
- These are therefore enlarged to form the grykes of the limestone pavement, leaving behind the clints- slabs of limestone
- These vary in size due to the pattern of the joints.
FORMATION OF SWALLOW HOLES
- They are large funnel shaped opening leading from the surface underground
- They are formed by enlarged joints dissolved by carbonation
- And eroded by hydraulic action
- EXAMPLES: Gaping Gill in Yorkshire Dales
FORMATION OF DRY VALLEYS
- Formed by the streams on the surface of the limestone
- Happened at the end of the Ice Age when the limestone was frozen and so was impermeable
- As glaciers melted there was a lot of water and this stayed on the surface
- This carved out river valleys
- As the ice melted, the supply of water reduced and the limestone thawed because of the warming
- As a result, the river disappeared underground, leaving the valley that had been carved- without the stream.
FORMATION OF GORGES
- It's a great limestone gorge approximately 150m deep
- It is believed to be the remains of a huge underground cavern whose roof collapsed around the time of the last ice age
- They are very steep sided valleys formed by cave roofs collapsing
FORMATION OF RESURGENCES/ SPRINGS
- Rivers will abandon the underground caverns as it tries to find a lower level
- Should the river meet an underlying impermeable rock, it will have to flow over this rock until it reaches the surface as a resurgence.
- EXAMPLE: Malham beck in Malham Cove- huge natural limestone cliff which once had a waterfall
LAND FORMATION OF STALACTITES/ STALAGMITES
- Rainwater is weak carbonic acid and limestone is soluble in this
- Therefore water present in the cave has flowed through limestone and so has dissolved calcium carbonate in it.
- As the water drips from the roof, some evaporates leaving behind small amounts of re-dposited calcium carbonate
- This process continues for many years to build up the stalacite which is suspended from the ceiling
- Drops of water drip from the roof to the floor below, calcium carbonate is deposited when evaporation occurs
- This leads to the build up of stalagmite that grows from the ground.
LAND FORMS OF CURTAINS AND PILLARS
CURTAINS: A broad deposite of calcite usually formed when water emerges along a crack in a cavern.
Usually formed when water flows over a rock face or drips occur in many places along a crack in a wall. This can result in the formation in the sheet like curtain rather than an individual stalacite.
PILLARS: A calicte feature stretching from floor to ceiling in a cavern.
LAND FORMATION OF UNDERGROUND CAVERNS
- These develop when water flows underground through joints or swallow holes
- And then weathers and erodes the limestone beneath
- Eventually large cave systems can form
- Gaping Gill is an example.
LIMESTONE LANDSCAPE CASE STUDY- MALHAM, YORKSHIRE
- Quarried to be manufactured into cement
- Source of lime for industry, farming and to neutralise acidic soils
- Used in building stone and in dry stone walls as field boundaries.
- Popular stones for gardens
- Generally thin, upland soils so mostly used for sheep
- Spring water flowing out of limestone is good water source
- Attractive upland scenery
- Popular with tourists- national parks- good for walking, biking, climbing and potholing- fell running over 301m Cawden
COSTS AND BENEFITS OF USING THE LANDSCAPE FOR TOUR
- Traffic jams
- Farm gates left open
- Animals worried by dogs
- High shop prices, high house prices due to demand for holiday homes
- Visitors spend money on local shops, cafes and hotels
- Jobs for locals are created in restaurants, hotels
- Local craft shops and farms gain extra income
WHAT ARE THE CHARACTERISITCS OF CHALK AND CLAY?
- Two examples of sedimentary rocks
- Both formed under the sea and then uplifted by tectonic activity to form rocks
- Chalk is permeable rock meaning there are few rivers around it- it is heavily jointed and porous.
- Formed 70-100 million years ago
- Cretacious limestone
- Soft white rock
- Porous rock
- Product of chemical weathering and erosion
- Impermeable when wet
FORMATION OF ESCARPMENT/ CUESTA AND VALE
- Harder chalk is next to the softer rock
- The layers are tilted at an angle to the surface due to the earth movements.
- They start at similar heights but erosion affects them both- carbonation on the chalk
- Chalk is more resistant to erosion than the clay as it is harder and therefore erodes mroe slowly
- Lies above the the surrounding clay in the lower lying vale
- 2 parts to the escarpment
- Steeper slope that cuts across the diagonal organisation of the rock layers and the gentler dip slope that is parallel with it
- The rock structure is important in the formation of landforms with its characteristics scarp slope at right angles to the tilt and the dip slope that follows.
FORMATION OF DRY VALLEYS (CHALK AND CLAY)
EXAMPLE: Devil's dyke
- Formed in periglacial times when the ground froze
- Melt water rivers ran over the surface of the chalk rather than flowing down through it
- These rivers carved out steep sided valleys
- Once the climate had warmed again, the dry valley was left behind
FORMATION OF SPRING LINES
- Springs form at the bottom of the escarpment, where the chalk meets the clay
- This is why many settlements can be found along the spring lines
LANDSCAPE FEATURES ASSOCIATED WITH CHALK AND CLAY
HUMAN USE OF CHALK AND CLAY LANDSCAPE 1
- Sheep, racehorses and cows are farmed
- Soils are too thing to allow arable farming to happen
- Clay is used for farming- high nutrient content- accessible to farming machinery
- Chalk meets clay, spring line settlements can be seen (Fulking in West Sussex)
- Due to the good access to the London, the South Downs are popular as a location for commuters and retired people
- Stud farms and stables are common at Epsom
- Chalk with flints is a strong building material used in cement manufacture.
- Clay is used to make pots and bricks and in the manufacturing of paper
HUMAN USE OF CHALK AND CLAY LANDSCAPE 2
Underground aquifers act as a store for water within the chalk and are used as a natural water supply for London
WHY IS LIMESTONE VALUABLE FOR THE BUILDING INDUSTR
Limestone, quicklime and slaked lime are all used to neutralise excess acidity - which may be caused by acid rain - in lakes and in soils. Limestone is used as abuilding material, and to purify iron in blast furnaces. It's also used in the manufacture of glass, and of cement (one of the components of concrete).
GENERAL ADVANTAGES AND DISADVANTAGES OF QUARRYING
- You get the follwing rock that you need- provides raw materials
- Good economic factor- significant economic contribution both locally and nationally
- More jobs created in rural areas
- Can lead to improvement in communication
- Damages the environment, disturbs the wildlife
- Visual/ noise pollution- local people annoyed by the noise or destruction of the place
- Turns away tourists.
- Affects housing prices
- Respiratory / diseases caused by the dust
- Blasting leaves a scar in the hillside
- Heavy traffic becomes a disturbance
- Large, ugly scar left on the landscape
- Local damage maybe disturbed
HOPE QUARRY CASE STUDY 1
Hope Quarry is a limestone quarry located close to Castleton. It began extraction in 1948, just before the area was desgined to be a national park
2 million tonnes of limestone are extracted each year, used to produce 10% of the ULC'S cement.
Now employs about 200 local people, many of whom live in nearby
The quarry is now estimated to have resources for the next 30 years
ADVANTAGES OF HOPE QUARRY:
- Economic: Provides 200 jobs, multiplier effect and it's the cheapest way of getting resources
- Social: Jobs mean people don't have to commute
- Improved road communications, At Hope Quarry 15 million has been spent trying to reduce the impact of heavy traffic.
- Environmental: With modern techniques, effects are minimised. There is estimated to be enough reserves for 30 years.
- As quarrying is a large scale.
HOPE QUARRY CASE STUDY 2
DISADVANTAGES OF HOPE QUARRY:
- Loss of agriculture
- High transport costs (far from market)
- Extracting and treating rock creates noise and dust
- Heavy traffic along quiet country roads creates hazards, noise and dust.
RESTORATION OF QUARRIES DURING/ AFTER EXTRACTION 1
CASE STUDY: DRAYTON QUARRIES IN CHICHESTER
- Has now been turned into a habitats for natural value
- Before the extraction commenced- trees and shrubs were planted and an avenue of oak trees
- During the extraction (takes 3-4 years) each regressive restoration scheme will commence. No dewatering is necessary.
- Freshwater lake with scalloped, graded margins, reed beds, shallows, deep pools, gravel beaches and islands.
- 2.3ha of grassland margins
- Bird nesting boxes and bat boxes
- 1ha of woodland and scrub
RESTORATION OF QUARRIES DURING/AFTER EXTRACTION 2
CASE STUDY: DRAYTON SOUTH
IMPORTANCE OF LAKE:
- Attracts birds
- Shallows where the warmer water mean quatic plants can colonise and deeper areas for diving birds.
- It will provide space for recreation and protect archaeological interest
The impact of quarrying can be reduced by careful, sustainable management and restoration schemes may have a positive impact.
DIFFERENT USES FOR RESOTRATION OF QUARRIES
- CAR PARKING- multi-storey car park spaces which will provide parking for local attractions and facilities. Revenue earned from parking charges would go to the National Park Authority.
- RESERVOIR- Flooding the quarry can be used for water sports such as jet skiing. Potential fishing and provides a wetland habitat for aquatic plants
- NATURE RESERVE AND WILDLIFE CONSERVATION AREA- Site will be re- landscaped and a range of habitats will be brought in. Variet of plants and trees would encourage biodiversity.
- RECREATION AREA- A built for purpose recreation area would include mountain bike tracks and walking paths
- FARMLAND- Put to agriculture use and sold off to local arable and pastoral farmers in the area. Quarry will be filled with soil and sown with grasses for pasture.