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Rocks, Resources and Scenery
Transcript of Rocks, Resources and Scenery
quarrying. This is an important issue and
has led to conflict and debate. Impact of quarrying on the environment can be reduced by careful, sustainable management. Their formation is linked by the rock cycle. The period of geological time since life became abundant 542 million years ago, which geologists have divided up into eras and periods. Limestone was formed in the Jurassic Period Rocks belong to one of three groups. Metamorphic Sedimentary Igneous rocks form when molten rock (Magma if it is below the surface or lava if it has erupted from a volcano) solidifies. These rocks can be identified by the following tell-tale clues:
Igneous rocks contain a minerals randomly arranged in crystals (Remember CRYSTALS )
If the rock has small crystals this means that it had rapidly cooled, possibly because it was erupted into the ocean. We call it an EXTRUSIVE IGNEOUS rock. If the rock has large crystals it means that it slowly cooled, the molten rock solidifies deep down within the crust without ever reaching the surface via an eruption. We call it an INTRUSIVE IGNEOUS rock.
The rock are usually tough and hard (With the most famous exception being pumice stone). Extrusive igneous rock formed when magma (lava) cools outside the earth's crust. Intrusive igneous rock forms when magma cools inside the earth. Igneous Layers of sediment are deposited at the bottom of seas and lakes.
Over millions of years the layers get squashed by the layers above.
The salts that are present in the layers of sediment start to crystallize out as the water is squeezed out. These salts help to cement the particles together. Rocks that have undergone a change in their chemistry and texture as a result of heating and / or pressure. Sedimentation creates layers or rock particles Compaction and cementation presses the layers and sticks the particles together. This creates sedimentary rock. Rocks underground that get heated and put under pressure are changed into metamorphic rock. Rocks underground that get heated so much they melt turn into magma. Magma is liquid rock. Magma also comes from deeper inside the Earth, from an region called the mantle. Pressure can force magma out of the ground. This creates a volcano. When the magma cools it turns into solid rock, called extrusive igneous rock. Magma that cools underground forms solid rock called intrusive igneous rock. Areas of rock can move slowly upwards, pushed up by pressure of the rocks forming underneath. This is called uplift. Weathering breaks down rocks on the surface of the Earth. There are three types of weathering - physical, chemical and biological. Wind and water move the broken rock particles away. This is called erosion. Rivers and streams transport rock particles to other places Rock particles are deposited in lakes and seas, where they build up to form layers. This starts the process of sedimentation which will create sedimentary rock. How can you spot a Sedimentary rock?
Sedimentary rock will often have layers or bands across them.
It will often contain fossils which are fragments of animals or plants preserved within the rock. Only sedimentary rocks contain fossils.
The rock will tend to scrape easily and often crumble easily. Sandstone Limestone Shale Earth movements can push all types of rock deeper into the Earth. These rocks are then subjected to massive temperatures and pressures causing the crystalline structure and texture to change. THEY DO NOT MELT. The high pressure involved are often associated with mountain building processes. Slate Marble Schist Basalt Pumice Granite 3 types of weathering Chemical Biological Mechanical Exfoliation Freeze-thaw Solution Carbonation This is where the rock is broken into smaller pieces by the effects of temperature and sometimes water. Weathering is the breakdown and alteration of rocks and minerals at or near the Earth's surface into products that are more in equilibrium with the conditions found in this environment. The effect of living things on the rock Chemical weathering changes the composition of rocks, often transforming them when water interacts with minerals to create various chemical reactions. A process by which minerals in the rocks dissolve directly in water. A process by which dissolved carbon dioxide in rainwater or moisture in surrounding air forms carbonic acid and reacts with the minerals in the rock. This process weakens the rock thus breaking it down in the process. Water - eg from rainfall or melting snow and ice - becomes trapped in a crack or joint in the rock.
If the air temperature drops below freezing, the water will freeze and expand by 9-10 per cent putting pressure on the rock.
The ice will melt when the temperature rises above freezing.
If this process happens repeatedly, the rock will weaken and eventually shatter into angular fragments.
The fragments may then be deposited as scree at the foot of a slope.
It is most effective where the temperature fluctuates around 0°C, eg on north-facing high altitude slopes in Snowdonia. Exfoliation occurs mainly in hot desert areas. This includes places like Arizona in the USA and Alice Springs in Australia. In these places, the temperature can get as high as 40°C. As rock is made up of layers (especially in sedimentary types like sandstone and metamorphic types like marble), in the intense heat, the top layer of rock expands. However, the inner layers remain cool. At night, when temperatures drop, the top layer contracts. Repeated heating and cooling causes the surface of the rock to peel off like an onion skin. Case Study How can the impact of a quarry be reduced? During extraction What happens at a limestone quarry? What impact do quarries have upon their local environment? After extraction Quarrying is...the extraction of rocks and other materials from the earths surface through blasting. Frequently quarried materials include sand, gravel, limestone etc.
Limestone Quarrying in the Peak District
The Peak District is a major area of limestone quarrying, including works at Hope Quarry and Wirksworth Quarry.Hope Quarry is located close to Castleton. It began extraction in 1948, just before the area was designated a national park. 2 million tonnes of limestone are extracted each year, used to produce 10% of the UK's cement. The Peak District is a major area of limestone quarrying, including works at Hope Quarry and Wirksworth Quarry. Hope Quarry is located close to Castleton. It began extraction in 1948, just before the area was designated a national park. 2 million tonnes of limestone are extracted each year, used to produce 10% of the UK's cement What is limestone used for?
aggregate or crushed rock
chemical production - fertiliser etc.
iron and steel
lime blasting for quarrying releases large amounts of dust (problem for asthma sufferers and pollutes water supplies)
leaves an ugly scar in the land when abandoned (an eyesore)
heavy lorries transporting limestone cause congestion on narrow roads and increase the likelihood of accidents
wildlife and habitats are destroyed and lost
noise pollution from the blasting disturbs both wildlife and local people
heavy lorries cause more frequent costly repairs to roads to be made. Advantages of quarrying creates job opportunities (10% of male employment in the Derbyshire Dales is in Quarrying and 300 people are employed at Hope Quarry).
multiplier effect, created by creation of jobs, more money in the area and more services supported
great demand for limestone for building purposes as well as other products such as cement .
it is a raw material needed to support both the local and national economy
roads improved to cope with the large lorries (benefits the local community)
the quarry provides a source of money for the local council through taxes and rates 1. Earth Mounds - this are built around the quarry to reduce the impact of noise from blasting on the local area
2. Water sprays - these can be used to reduce the spread of dust from the quarry
3. Restrictions are put on the size of the quarry that is allowed
4. Blasting is only allowed during designated areas to minimise impact on locals
5. Quarry's are often screened off e.g. by trees etc.. to reduce visual impact
6. Restoration plans are often put in place following the decommissioning of a quarry - examples have included the development of wetland habitats, lakes and other conservation / recreation areas. Drayton North and South Even before extraction had started, restoration had begun.
Hedgerows were planted and an avenue of oak trees between the two quarries was created.
Once quarrying is completed it will have reed beds providing a range of habitats. The edges will be woodlnd and grasslands. The result is expected to be an area rich in biodiversity. Hollow Banks Quarry was a 20 ha quarry in North Yorkshire. Following its closure in 2003 the owners began a restoration:
Site contoured to create a gently undulating landscape with ponds, grass and woodlands.
Soil was added and the land was divided up to form farm land and woodland.
Woodland areas were fanced off to protect them.
20,000 trees and shrubs were planted (2004 - 2005)
Aquatic plants at the edges of ponds.
Footpaths established. Aggregate Aquifer Batholith Biological weathering Carbonation Cavern Cement Chemical weathering Cliff Crust Curtain Dry valley Escarpment/ cuesta Exfoliation Freeze-thaw weathering Geological timescale Gorge Igneous rocks Joints Limestone pavement Mass movement Mechanical weathering Metamorphic rocks Permeable rock Pillar Pores Quarry restoration Resurgence Rock cycle Scree Sedimentary rocks Solution Spring Stalactite Stalagmite Swallow hole Syncline Tor Vale Water table Weathering