Wednesday, 14 January 2009

Rocks and Landscapes - Overall classifications:

IGNEOUS ROCKS - formed from magma (2 types)
extrusive - magma spills onto surface then cools (small crystals + fine texture) - basalt used for roads (Giants causeway + Fingals cave) large hexagonal columns

intrusive - cools slowly below surface (large crystals and course texture) - Granite used for building, pottery (Dartmoor Tors)

SEDIMENTARY ROCKS - laid down in layers e.g. sandstones, shales, clays are made from tiny particles of sand and clay eroded from past landscapes and deposited in layers.
These layers = beds or strata - separated by bedding planes.
Carboniferous limestone and chalk are formed from the tiny shells of micro-organisms and microskeletons. They are made of CACO3 (Calcium Carbonate) and react with dilute Hydrochloric Acid.Softer + usually more porusCoal is made from carbonaceous remains of tropical plants.

METAMORPHIC ROCKS - physicals altered sedimentary and igneous rock.
Can be changed from volcanic activity, radioactive decay, tectonic earth movements and the intense heat and pressures.Rocks are harder, more compact and crystalline.
During the physical alteration of rock:


An impermeable rock is one which does not let water pass through it, in contrast to a permeable rock, which does allow water through. Permeable rocks may either:
1) consist of tiny pores through which water can pass - such rocks which include chalk, are said to be porous (stores water) or
2) contain areas of weakness, such as bedding planes, along which water can flow. Horizontal bedding planes, which separate individual layers of rock, can be seen in sandstone and carboniferous limestone (are said to be pervious)

1. Limestone areas are weathered when limestone reacts with rainwater (a weak carbonic acid - due to CO2) creating limestone solution.
Dissolved limestone is removed in solution, by running water, erodes, along weaknesses (e.g. joints and bedding planes) forming solution features. Such as; caves swallow holes, clints and grykes.
Water droplets leave the dissolved rock (calcite) behind, after evaporation, on cave roofs and floors to form stalactites and stalagmites. e.g. Malvern, North Yorkshire or Cheddar Gorge, Somerset.
2. Granite areas react chemically; rotting-down to produce kaolin as china clay (e.g. in Cornwall).

Physical Weathering - breaks down surfaces

1. FREEZE THAW Water gets trapped in cracks (usually along joints) and expands when it freezes, pressuring the sides of the rock.
During the day the water melts and contracts; releasing the pressure.
Alternating expansion and contraction weakens the rock and pieces break off. This is called frost shattering.
The process produces scree on steepslopes and blockfields on gentler ones.

In very warm climates, where exposed, non vegetated rock is repeatedly heated and cooled.
The surface layers heat-up and expand, more rapidly than the inner ones, during the day, and also contract and cool quicker too.
This sets up stresses in the rock and the surface layers start to peel off. This creates rounded rocks and hills (e.g. Ayers Rock, Australia).

3. TREE ROOTS (biological weathering)
Tree roots penetrate and widen bedding planes, and other weaknesses in the rock, until blocks of rock become detached (prevalent in Cumbria)
Also (in decaying plants) and (animal remains) make acids which eat away, through chemical reaction, at the rocks below.

CASE STUDY 1 - GRANITE - Characteristics and formation - DARTMOOR, UK

Resistant to erosion, forms distinctive landscape features e.g. tors and rocky outcrops.
Granite is impermeable, does let water soak through = lakes and rivers and marshy areas (on its landscape)
Granite weathers to produce very poor, very acidic soil.

Click Here for Year 10 Dartmoor pictures

Other landforms associated with granite are:
Deep, steep v-shaped valleys, created as the water has exploited and eroded through the cracks in the rock.
Marshes and bogs form due to the underlying impermeable granite preventing water from seeping away, and the high rainfall that many of these areas encounter.
Exfoliated domes can occur in warmer climates, producing spectacular scenery, as seen in Yosemite National Park

Granite is quarried as a building materialDramatic features attract touristsSoil is unsuitable for farming, but good for hunting grouse and army training.Usually a treeless area, although trees do grow in pockets; and valley floors.Sparsely populated due to infertile soil e.g. Dartmoor, Yosemite Valley Nevada (Sierra Nevada) and the Cairngorms.
Granite areas themselves have limited economic uses.
The soil is usually poor and thin, so little farming takes place, probably just some sheep and cattle grazing.
Because granite is impermeable, and the soil is poor, areas such as Dartmoor are ideal sites for reservoirs.
Historically granite areas were mined, especially in the South-West,for things such as copper, tin and arsenic. Nowadays quarrying occurs, taking a way china clay for pottery and of course granite itself, which is used in building (an excellent example being the city of Aberdeen, which is known as "the Granite City"). Granite is also used for things such as hearths,fireplaces, and gravestones.
Tourism is increasingly becoming important in granite areas. Many tourists just come to take in the fresh air and beautiful scenery, but the towns and villages of these areas are trying to cash in by opening guesthouses, cafes and other tourist facilities.
The Northern half of Dartmoor is also used as an army firing range, with a large camp based just outside of Okehampton. The military uses of the moor have caused conflicts with local farmers, residents and tourists.

Granite has 3 minerals: Quartz, feldspar and Mica - feldspar is affected by hydrolysis, but once one mineral is weakened, they all suffer:
1. Tors occur when there is underlying granite e.g. a batholith (Dartmoor)
2. High levels of vertical and horizontal joints, of varied density.
3. Water percolates into the joints and rots the rock via hydrolysis.
4. Weathering is concentrated where joints are most densely packed.
5. Overlying rock is stripped away by erosion.
6. Through weathering the joints are expressed and widened.
7. Later erosion takes away the weathered granite; frost action dislodges larger blocks of granite frost action dislodges larger blocks of granite from the tors.
8. The blocks of rock where the joints are widely spread leave blocks of stacked rock.
9. Frost action may further weather the joints - emphasizing the effects.
10. The unweathered sections (without joints) form our tors.

Check out this film which the Year 10's made to help with revision:


- (produces landscape with: thin grassy soil; good for sheep.)
The landscape produced by limestone is called karst.
Limestone is a pervious rock (lets water pass through it) so there are very few surface streams.
Formed from the remains of organic matter, usually seashells and plants.It was formed under the sea 220-280 million years ago.
It is a hard, grey sedimentary rock, with a large number of joints(vertical cracks) and bedding planes (horizontal cracks)
Carboniferous limestone is an example of a pervious rock, as it allows water to flow through the joints and bedding planes.
The main processes, which affect it, are carbonation and solution.
The two best areas of carboniferous limestone in Britain are the Yorkshire Dales and the Peak District.

1. Swallow holes: various acids in the water of the surface streams begin to dissolve and widen surface joints to form swallow holes.
2. Caverns once underground the river will continue to widen joints and bedding planes through solution. Where solution is more active caverns will form.
3. Stalactites and Stalagmites - dissolved limestone may be deposited as dripstone, in the form of stalactites and stalagmites, where continual drips from the roof of the cave forms these features. (The water in the dripstone evaporates, leaving calcite behind). Other collections of water that don't form features are called sumps.
(Flowing water across the floor of the cave is called 'calcite flowstone'.)
4. Resurgent springs - permeable limestone meets impermeable underlying rock (granite or basalt) - it flows over this rock until it emerges as a spring on the surface.
5. Shakes holes - funnel shaped hollows where limestone has a cover of peat as boulder clay. Shake holes are formed when the peat/clay; collapses into the joints widened by solution.
6. Dry valleys - they have normal characteristics of drainage systems but do not currently carry rivers. Previously water would have flowed over the areas due to frost or due to increased discharge (allowing a river to maintain its flow across a limestone area).
7. Gorges- when limestone collapses over an underground river, gorges are formed. If it collapses over a small cave, then a depression called a dolvie is formed.
Year 10 Homework Question:

Look at the image below and answer the question that was given out on the past paper sheet:

The tourist industry is a very important source of income to limestone areas. Most people come to walk in the hills and see the spectacular karst sceney. The local people are cashing in on this by opening café, guest houses and other tourist facilities.
Limestone is an excellent building stone, and has been used in some very well known buildings, such as the Houses of Parliament. Obviously this mean that there are often a large number of quarries.
Limestone, whether crushed or used as lime, can be very useful in a number of areas. It is used as an industrial cleanser, farmers use it as fertiliser and it forms an important ingredient in cement making.
Here is a revision video on all you need to know about Carboniferous Limestone landscapes from the Year 10's! Enjoy

Case Studies: YORKSHIRE DALES - National Park and CHEDDAR GORGE
Attract tourists: Sight of Special Scientific Interest (SSSI)
e.g. Aysgarth falls and Malham Cove.
8 million visitors per year. (mostly in August). Brings in £46 million per year. Malham cove is a honeypot site - 0.5 million people go to Malham alone.This causes many problems: Traffic (and pollution), Overcrowding, Litter and Footpath erosion.

The "Pennine Way" has been protected from erosion through:resurfacing with limestone chips, (hoping to reduce step erosion).
1. Locally gathered/extracted2. Hard wearing3. Matches scenery4. Lets rainwater soak into it.
Malham cove: a glacier formed and the water eroded the rock and when it melted, it created a waterfall, which then created a cove. The water gradually soaked into the ground because the limestone defrosted.
Traffic Causes problems: Spoils wildlife (pollution and dirt). Walls get destroyed (cost to repair).
Stakeholders in the area, include:
Residential stakeholders (affected by traffic and noise), Tourists (want to enjoy beauty but destroy it in doing so), Environmentalists (preserve the area), Shopkeeper (seasonal business - unsustainable), National Park Authority (use beauty to bring tourism) andQuarry owners (need land for resources but destroy it and pollute area).

Characteristics of Chalk: Formed 70 to 100 million years ago, chalk is also called cretaceous limestone.It is a soft, white rock.
Chalk is an example of a porous rock, as it has pore spaces, which can store water. It does not have joints and bedding planes like carboniferous limestone.
Is a product of chemical weathering and river erosion.
Clay is porous, but becomes impermeable when wet, as the particles expand and fill the pore spaces.
The main areas of chalk and clay in this country are in the South and East of the country. Places like the North and South Downs are good examples.

Rock Layout: the chalk is tilted because of tectonic plate movement. The chalk is a giant upfold.

Chalk and clay landforms
Bournes are streams that occasionally flow down the dry valleys in times of prolonged wet weather, when the ground may have become saturated.

Clay vales are the valleys between the chalk escarpments. The clay, when drained is a fertile soil suitable for a range of farming methods. Clay vales are flat, and have a number of streams meandering through them.

Dry valleys, such as Devil's Dyke, were formed in periglacial times, when the ground froze, so 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 a dry valley was left behind. These also are common features of limestone landscapes.

Escarpments or cuesta's are the main landform of chalk and clay areas. Initially the layers of chalk and clay were tilted by the collision of the African and Eurasion plates. The soft clay was then eroded faster than the more resistant chalk, leaving escarpments (chalk hills) behind. Because of the angle of the tilt, these escarpments have two distinctive sides. The steeper side is called the scarp slope, whilst the gently sloping side is called the dip slope.

Springs form at the bottom of the escarpment, where the chalk meets the clay. This is why many settlements can be found along spring lines in chalk and clay areas.

Escarpment Formation:
> Weathering removes the layer of rock on top of the chalk. The chalk is also partially eroded.
> It has a steep scarp slope and a dip slope.

Settlements: Located at the bottom of the scarp and dipslopes (not on the chalk). They are near to springs and clay soil which is good for crops. Because they are on the spring line, they are away from the risk of flooding.
Water stored in the chalk hill can be used as a natural reservoir.
Quarried for cement and lime.Soil is suitable for sheep farming and cereal crops like wheat and barley.

Clay is very fertile, but must be drained first. Once that has been done farming includes dairying, sheep grazing, and some arable farming. On the chalk escarpments the main agriculture is sheep grazing.
Many settlements were built at the bottom of the scarp or dip slope, as the land was less likely to flood, there was a good water supply, and there was good farming land nearby. Very early settlements would have been higher up the chalk escarpment for defensive purposes.
Chalk is a main ingredient in cement making, and is quarried for thatpurpose. Clay can be used in pottery.
Underground aquifers act as a store for water within the chalk and are used as a natural water supply for London.
Check out this revision video on Chalk and Clay:


Quarrying is one of the biggest industries in the areas where granite, limestone, chalk and clay are found. Unfortunately these areas are, in many cases, also areas of great natural beauty and of tenpart of a National Park. There are therefore many positive and negative impacts of quarrying.
The impacts of quarrying - sort the following into ADVANTAGES and DISADVANTAGES

Quarries provide much needed employment opportunities in areas where jobs are often hard to come by.
Noise pollution from the blasting needed to extract rock.
The increased income means that more money is likely to be put into the local economy.
Visual pollution from the quarry pit itself, as well as the buildings and slag heaps.
The increase of industry and need for access for large lorries may lead to infrastructure (roads mainly) improvements.
Dust pollution from the rock blasting.
Good landscaping of the quarry site once it has been exhausted could enhance the area's natural beauty further.
Noise and dust pollution from the many heavy lorries that will be travelling to and from the quarry every day. These lorries may also block country roads and damage wildlife.
Pollutants from the quarry can run-off into the local rivers and cause problems for local people and wildlife.
Wildlife habitats are initially lost when the quarry opens.

Possible solutions to the problems of quarrying
Trains could be used instead of lorries, which would cut down the traffic and damage to roads.
Landscaping could be used during quarrying to diminish the visual scar,and also once quarrying has been completed, to try to return the area to nature as best as possible.
The quarry could be restricted in size, so that it does not engulf the surrounding area.
Lines of trees can be used to reduce noise pollution and try to improve the look of the area.

Quarrying positives: Building materials (cement) and lime (fertilisers), Employment (in quarry and associated businesses), Wildlife reserves (after).
Quarrying negatives: Noisy, dirty, eyesores (makes area ugly), increase traffic, when quarrying stops; they are often used as landfill sites.

No comments: