Geograophy - Rocks

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  • Created by: mollyhgs
  • Created on: 22-04-15 16:54

Geological time Periods and Eras

Geological time Periods and Eras

We measure time in weeks, minuets and years wheras geological time is measured in terms of millions and billions of years as it is very vast.

Period - basic unit of geological time in which a single type of rock is formed.

Era - they are longer and are made up of 2 or more periods

Carboniferous Limestone was formed 340 million years ago -  P-Carboniferous E-Palaeozoic

Granite was formed 280 million years ago-  P-Permian E-Palaeozoic

Chalk and Clay were formed 65-145 million years ago-  P-Cretaceous E-Mesozoic

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Rock Formation 1

Rock Formation 1

Igneous

  • Formed from magma that has either cooled underground or erupted from a volcano
  • When magma cools at the surface (volcano) it cools very quickly and forms tiny crystals (eg. Basalt)
  • When magma cools underground it coold slowly and forms large crystals (eg. Granite)
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Rock Formation 2

Rock Formation 2

Sedimerntary

  • Forms from rock particles that are worn off other rocks
  • The wearing of the rocks is called weathering
  • The rocks are carried away by wind or water and they eventually settle to form layers called strata
  • As these layers build up the pressure from the layers above makes them become rock
  • Most sedimentary rocks are formed underwater
  • Egs. Limestone
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Rock Formation 3

Rock Formation 3

Metamorphic

  • These rocks are ones that have morphed into other rocks
  • They are formed when igneous or sedimentary rocks undergo great pressure and heat below the earths surface causing them to change.
  • The types of metamorphic rocks made depends on the original rock it came from
  • Eg. limestone becomes Marble
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The Rock Cycle

(http://image.slidesharecdn.com/rockcyclepdf-150226150727-conversion-gate01/95/50-rock-cycle-6-638.jpg?cb=1424984913)

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Rock Distribution UK

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Freeze-Thaw

  • When the temperature is 5+ water collects in the cracks of the rock.
  • Then when the temperature is less thank -5 the water turns to ice, the cracks widened because it occupies a larger volume.
  • After freezing and thawing many times scree falls off.
  • The line of weakness in the rock is a bedding plane because it runs in a horizontal direction between the beds of rock. The line of weakness within the bed of rock is called a joint. Bedding planes and joints are the first places to be attacked by weathering. the rocks that form scree have sharp edges because they have not moved after being broken off.
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Exfoliation

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Biological Weathering

As the tree grows into the rock beneath the soil and the rock will move away to make space for the roots.

This is biological weathering as the plants are living things

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Weathering

Weathering- the breaking up of rocks

Erosion-the travelling of the rocks

Mechanical- when rocks are broken down without any chemical reaction

  • Freeze-Thaw
  • Exfoliation

Chemical- the break down of rocks due to chemical reaction

  • Solution
  • Carbonation

Biological- the break down of rocks by living things

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Chemical Weathering

Chemical Weathering

Solution-
Some rocks dissolve in exposure to rainwater

Carbonation-

  • Rainwater picks up CO2 from the air
  • Rainwater becomes a weak carbonic acid
  • Acidic rainwater reacts with calcium carbonate(limestone) to form calcium bicarbonate which then dissolves.

RAINWATER + CO2 = CARBONIC ACID

CARBONIC ACID + LIMESTONE(calcium carbonate) = CALCIUM BICARBONATE

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Granite Landscapes

Granite Landscapes are found in clusters in Scotland and Cornwall (SW)

If it was formed underground there will be a huge dome shaped mass of magma called a Batholiths

As the rock on the top gets weathered and eroded the batholiths becomes exposed on the surface.

STAGE 1 - as granite cools underground joints form close - wide - close

STAGE 2  - the climate is warmer. The soil and other rocks have been weathered and eroded away. The joints are chemicaly weatheredin the warm, wet conditions. the closely spaced joints are weathered first as there are more lines of weakeness.

STAGE 3 - Today the climate is cooler leading to more freeze-thaw weathering.The water gets into the roch and freeze-thaw weathering takes place continuing to weaken and break up the rock. The soil and other rocks have been weathered and eroded away exposing the Tor above the surface.

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Dartmoor Case Study

  • Dartmoor is in the south west of England
  • The tors are 5 - 10 meters tall
  • Tors are surrounded by boulders of all sizes (called scree)
  • Tors were formed by freeze-thaw weathering
  • Haytor is 456 meters high
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Uses of Granite Areas

  • Farming-as the areas are large enough for sheep, cattle and ponies. its not used for crops as granite soil is to thin and acidic to grow on.
  • Building-granite is strong and resistant to weathering and erosionso used for building, gravestones,roads, walls and fireplaces
  • Tourism-stunning sceneary, walking, cycling, outcrops are great for climbers as large crystal cracks are good hand/foot holds.eg. Dartmoor national park is popular for horse riding and camping, over 10 million people visit there each year.
  • Military Training-bleak isolated moorland, away from large populated areas. eg north dartmoore is used as an army firing range with a large base camp
  • Water Storage-as granite is impermeable it makes reservoirs. in granite areas there are deep valleys which are used to store water. upland areas has high rain fall.dartmoor has 8 resovoirs which provides drinking water to towns like plymouth
  • Quarrying-quarried for china clay. china clay is used for pottery and is important for manufacturing paper, paint and make up. china clay is also important for employment and the local economy.
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Chalk and Clay

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Formation of Enscapment and Dry Valleys

Enscapment

STAGE 1- under the surface ther are horizontal layers of clay then chalk then clay (repeated)

STAGE 2 - because of plate tectonics the layer get in to an angle - still layered

STAGE 3 - as the clay is less resistant it wears away leaving a steeper slope called the scarp slope. The peak between the chalk and clay is called an enscapment. The vale is the lowest point.

Dry Valleys

STAGE 1 -In glacial times when the climate was really cold all of the ground was frozen

STAGE 2 -Water couldnt soak into the ground so it crept up the dip slope

STAGE 3 -when the climate warmed up masses of water in rivers flowed down the slope eroding a deep, steep sided valley in the dip slope.

STAGE 4 -The water table then lowered and the water flowed down and dried up leaving a dry valley.

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Charecteristics of Chalk and Clay

Chalk

  • Permeable (allows water to pass through)
  • Porus (pores in rock often making it wate logged)
  • Rainwater soaks through and reaches the water table
  • where the water table reaches the surface, springs are formed

Clay

  • Weak
  • Impermeable
  • Easily eroded by water
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Limestone

Located

  • Mainly in Ireland
  • Tends to be away from the coast
  • Vertical bands in Northen England
  • Small clusters in S Scotland and SW England

Charecteristics

  • Strong, tough and resistant
  • Forms upland areas and cliffs on the coast
  • Chemically weak
  • Made of Calcium Carbonate therefore dissolved by carbonation
  • Permeable (allows water in)
  • lots of joints and bedding planes
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Landscape Keywords

SWALLOW HOLES-a cavity in the ground, caused by water erosion and providing a route for surface water to disappear underground.

STALACTITES-a structure hanging like an icicle from the roof of a cave, formed of calcium deposited by dripping water.

STALAGMITES-a mound rising from the floor of a cave, formed of calcium deposited from water dripping from above

CAVERN - underground cave

GRIKES - the deep cracks between the clints on a limestone pavements

CLINTS- the main slabs in a limestone pavement

RESURGENCE - the place where water reappears from being underground

PILLAR -  when a stactite and a stalagmite meet

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Gorges and Resurgence

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Swallow hole (Gaping Gill) and Limestone Pavements

Swallow hole (Gaping Gill)

  • Gaping Gill is a swallow hole in the Yorkshire Dales
  • Its where a surface stream disapears underground
  • Gaping Gill drops 110 meters into a giant chamber
  • Water would flow and erode a crack in the weak weathered rock and it will continue to erode downwards

 Limestone Pavements

At the end of the iceage glacier meltwater exposed the bare rock in upland areas leaving large slabs of limestone called clints and the gaps between the are called grikes.

As the rainwater falls from the sky it mixes with C02 to make a weak carbonic acid which dissolves limestone (chemical weathering - carbonation)

Over thousands of years the grikes widen and deepen causing and uneven surface. vegetation grow in the grikes.

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Limestone - Underground Features

CAVERNS -As water from the swallow holes uses chemical weathering to slowly erode the joints and bedding planes finally the rock becomes really weak and collapses inleaving a large cavern when the roof has eroded.

STALACTITE- As water drips down the C02 evaporates back into the atmosphere leaving molecules of Calcium Carbonate behind which builds up hanging from the ceiling.

STALGMITE - As water repetivly drips in the same place it splashes making it wider.C02 evaporates leaving molecules of Calcium Carbonate behind which builds upfrom the ground

PILLARS - Stalactites and stalagmites join/fuse after tousands of years. If calcium carbonate is still dripping within the water the pillar will become wider.

CURTAINS - The ceiling has cracks in causing water seeps down along the length of a joint it produces a type of stalactite at an angle which resembles a curtain. They can be very thin and fragile and after many years they can reach the ground.

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Quarrying (advantages and disadvantages)

Quarrying is the extraction of rocks and other material from the earths surface by blasting. Frequently quarried materials include sand and limestone.

Advantages

  • jobs
  • we need materials
  • tourism
  • local buisnesses

Disadvantages

  • Pollution
  • noise
  • dust=mess
  • visual pollution
  • dangerous
  • lorries cause congestion
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Hope Quarry Map

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Hope Quarry (A's and D's)

Advantages

  • Hope quarry produces 2 million tonnes of Limestone each year (Economic)
  • Hope quarry can be used for another 30-35 years (all 3)
  • Employees use the shops and services in hope porviding money for the local economy(economic)
  • It produces a source of money for the local council (Economic)
  • Employ 300 local people each year (Economic and Social)
  • £15 million been spent on imporoving transport for lorries and local people (Social)

Disadvantages

  • Wildlife and habitats have been destroyes as the quarry has expanded (Enviromental)
  • Hope Quarry produces 1 million tonnes of C02 each year (Enviromental)
  • huge amounts of dust are being produced- causing asthma and polluting local water supplies (Social and Enviromental)
  • Loud explosions - noise pollution (Social and Enviromental)
  • Heavy lorries cause congestion and likely accidents. roads need to be repaired more often (all 3)
  • Noise pollution can effect wildlife and animal population (enviromental)
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Hope Quarry- Reducing and Restoring

Reducing impacts while open

  • over 75,000 trees have been planted there since opened in 1948 (env)
  • the 2.5 million tonnes of limestone that could not have been used was used to conceal the enterence(env+econ)
  • in 2003 they began to use recycled materials instead of fossil fuels(env)
  • landscaping and tree planting has been a noise barrier and reduced visual impact(env+soc)
  • road are being sprayed with water after lorries go on them to reduce the dust(env)
  • rail is used instead of road for 70% of the limestone. 1 train is equal to 57 lorries on road(env)

Restoring after extraction

  • recreation and tourist oppotunities (filling with water and used as fishing lakes)(soc)
  • landscaping can be used(soc + env)
  • topsoil can fill them and then be used for farming -introducing species again(env)
  • land has been contured and landscaped to create golf courses(soc)
  • land has been contured and landscaped with lakes to make them more attractive and encourage a natural habitat and increase biodiversity(env)
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How are chalk and clay areas used?

FARMING CHALK: scarp slopes are used for sheep farming. soil on chalk is fertile.wheat, barley and vinyards are grown. horses trained on chalk hills (eg. epsom race course)

FARMING CLAY: as clay id impermeable it is often water logged. crops are not grown on clay fields as its so wet. flatter clay areas are used for cattle as the grass is longer and its better suited for dairy farming

SETTLEMENTS:spring line settlements are common as they provide water. flat clay id easy to build on (eg. barton le clay

BUILDING: clay is sometimes made into bricks and is commoly used in pottery

QUARRYING:chalk is a main componant for making cement so its quarries for that.

WATER STORAGE: chalk id permeable and porus (water cant soak in) therefore its a great underwater stone. about 70% of the SE Englands water supplies come from underground resvoirs

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How limestone areas are used?

BUILDING: limestone is easily worked and carved therefore used for onate things like churches and statues. eg, st.pauls cathedral, houses of parliament and buckingham palace

QUARRYING AND INDUSTRIAL USE:once limestone has been quarried it gets crushed and is then used to make concrete or cement. limestone is spread on fields as fertiliser as it neutrilises acidic soil. its used as a cleaner too as it absorbs sulfur dioxide and is used for steel smelting.

FARMING:limestone soil is thin so it cant be farmed on. short grass is used for sheep farming. income from sheep is low so farmers have widened their operations to camping sites or opening B and B's to make more income. this is common in the peak district and the yorkshire dales.

TOURISM: limestone areas are attractive to tourists for walking, cycling and caving. unique scenery takes people to places such as the peak district for 'Treak Cliffe cavern' and to see famous formations such as 'dream cave' and 'fairytale'. most tourists stay in local villages providing buisness for B and B's and shops ect.

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