Please enable JavaScript.
Coggle requires JavaScript to display documents.
THE UK'S EVOLVING PHYSICAL LANDSCAPE: INTRODUCTION (Landscape…
THE UK'S EVOLVING PHYSICAL LANDSCAPE: INTRODUCTION
Rock Types
Igneous
Igneous rocks are formed when magma from the mantle cools and hardens.
The rock forms crystals as it cools
Igneous rocks are usually really hard eg. basalt and granite
Magma erupts as lava and cools to form volcanic landforms (extrusive rocks)
If magma cools inside the earth it form intrusive rock, which may later be exposed by erosion and weathering
Sedimentary
Sedimentary rocks are formed when layers of sediment are compacted together over millions of years until they become solid rock
There are two main types in the UK:
Carboniferous limestone and chalk are formed from tiny shells and skeletons of dead sea creatures. Limestone is quite hard, but chalk is a much softer rock.
Clays and Shale are made from mud and clay minerals. They are very soft
eg. sandstone, limestone, chalk and clay
Lithification - turning into rock
Metamorphic
Metamorphic rocks are formed when other rocks are changed by heat and pressure.
The new rocks become harder and more compact eg. Shale becomes Slate, and with further heat and pressure, Slate becomes Schist
eg. marble, which originates from limestone and slate, which originates from clay
Tees-Exe Line
A generic split between the Rivers Tees and Exe that divides between resistant rock in the north and less resistant rock in the south
Upland Areas
The UK's main upland areas tend to be in the north-west of the country
Gramphian mountains
Part of the Scottish higlands and home to Ben Nevis - the highest mountain in the UK
The Gramphians are steep, rocky and sparsley populated
Snowdonia
A glaciated upland area formed from rock from extinct volcanoes
Contains steep mountaines and glaciated valleys
The Lake District
Mourne Mountians
The Pennines
Landscape Processes: Physical
Weathering
The breakdown of rock into smaller pieces
Biological - the disintergration of rock as a result of action by living organisms
Chemical - any of the variouse weathering processes that cause rock to undergo chemical decomposition, changing the chemicaal and mineralogical composition of the rock
Mechanical - any of the various wethering processes that cause physical disintergration of exposed rock without any change to its chemical composition
Erosion
Erosion wears away rock. During the last glacial, ice eroded the landscape. Rivers and the sea now constantly erode the landscape
Post-Glacial river processes
Melting ice at the end of glacial periods made rivers much bigger than normal with more power to erode the landscape. The ice also left distinctive landforms when it melted e.g hnging valleys (little valleys that are left at a higher level than the main valley)
Slope processes
Including mass movements eg. rockfalls, slides, slumps, and soil creep
Physical process are affected by climate
A cold climate increases the likelihood of freeze-thaw weathering
A wet climate increases the number of streams and rivers
Distinctive Upland Landscapes: Snowdonia
An upland landscape - maps of Snowdonia show tightly packed contour lines and lots of rocky crags
Llyn Idwal is a tarn. It sits in a corrie (basin) that was hollowed out by ice during glacial time.
Freeze-thaw weathering occurs on the steep back wall of the corrie. As the rocks are broken up there are rock falls, which form scree slopes
This large U-shaped valley was eroded by ice - it has a flat floor and steep sides. They valley contains a misfit river that looks too small to have created it
There is lots of rain in Snowdonia and the rocks are mostly impermeable. This means there are lots of streams that are eroding the steep sides of the corrie anfd forming gullies
Distinctive Lowland Landscapes: The Downs and The Weald
Are a lowland landscape - chalk escarpments (the Downs) lie either side of a large flat area of clay (the Weald). The valley is flat (the contour lines on a map are widely spread apart)
Large rivers eg. the River Arun, meander on the impermeable clay, widening the valley floor
The UK has a wet climate - heavy rain can lead to flooding. The overflowing river deposits silt on the vlley floor forming a flood plain
Dry valleys are found in the UK lowland landscapes. These are valleys with no streams visible. (they flow undergrounf in the permeable chalk). They formed during glscisl periods when the colder climate led to more freeze-thaw weathering and glacial snow melt meant that streams had much more melt water in them than theu do today
Lowland Areas
The UK's main lowland areas tend to be in the south-west
The Cheshire Plain
An area of flat, low lying land formed by the deposition of eroded material
Land is very fertile and is used for dairy farming
The Downs and Weald
A lowland area with a wide valley situated between the parallel hills of the Downs
The area used to be covered by forest but is now mainly used for agriculture
Characteristics of different rock types create different landscapes
Granite
Granite is very resistant and forms upland landscapes
It has lots of cracks which aren't evenly spread. The parts of the rock where there are more cracks wear down faster. Areas that have fewewr joints are weathered more slowly than the surrounding rock and stick out at the surface forming tors.
Granite is impermeable - it doesn't let water through. This creates moorlands - large areas of water-logged land and acidic soil, with low-growing vegetation
Slate and Schist
Slate forms in layers creating weak planes in the rock. It is generally very hard and resistant to weathering but it is easily split into thin slabs
Schist has bigger crystals than slate and also splits easily into small flakes.
Slate and Schist often form rugged upland landscapes. They are impermeable, which can lead to waterlogged and acidic soils
Carboniferous Limestone
Rainwater slowly eats away at limestone through carbonation weathering. Most weathering happens along joints (cracks) in the rock, creating some spectacular features eg. limestone pavements (flat areas with deep weathered cracks), caverns and gorges
Limestone is permable, so limestone areas can also have dry valleys and resurgent rivers (rivers that pop out at the surfacewhen limestone is on top of impermeable rock)
Chalk and Clay
Chalk is harder than clay. It forms escarpments (hills) in UK lowlands and cliffs at the coast. One side of the hill is usually steep and the other side is more gentle
Chalk is permeable - water flows through it and emerges as a spring where it meets impermeable rock
Clay is very soft and easily eroded. It forms wide flat valleys in the UK lowlands. It is impermeable so water flows over the surface - there are lots of streams, rivers and lakes
Tectonic Activity
Active Volcanoes
520 million years ago the land that now makes up the UK used to be much closer to a plate boundary than it is now. Active volcanoes forced magma through the Earth's crust which cooled to form Igneous rocks
Plate Collisions
Plate collisions caused the rocks to be folded and uplifted, forming mountain ranges. Many of these remain as uplands, eg. the Scottish Uplands, the Lake District and North Wales - the igneous rock is hard and more resistant to erosion
The intense heat and pressure caused by plate collisions formed hard metamorphic rocks in Northern Scotland and Northern Ireland
Plate Movements - UK Position
Plate movements meant that 345-280 million years ago Britain was in the tropics and higher sea levels meant that it was partly underwater - carboniferous limestone formed in warm shallow seas. This can be seen in the uplands of Peak District, South Wales, and South-West England
The youngest rocks in the UK are the chalkks and clays found in Southern England. They formed in shallow seas and swamps. Chalks and clays are softer rocks that are more easily eroded - they form lowland landscapes
Glacial periods
There have been lots of glacial periods during the last 2.6 million years
During some glacial periods, part of the UK was covered in a massive ice sheet
At its maximum, ice-covered most of Scotland, Ireland and Wales and came as far south as the Bristol Channel in England
Ice is very powerful, so it was able to erode the landscape, carving out large U-shaped valleys in upland areas such as the Lake District
Glaciers also deposited lots of material as they melted. Landscapes formed by glacial meltwater and deposits extended south of the ice sheets eg. large parts of Eastern England are covered in till (an unsorted mixture of clay, sand and rocks) deposited by melting glaciers
Limit of maximum glaciation - where the ice in the last ice age extended to
Landscape Processes: Human
Agriculture
People have cleared the land of forest to make space for farming
Over time hedgerows and walls have been put in to mark out fields
Different landscapes are best used for different types of farming
Arable - flat land with good soil eg. East England, is used for arable farming (growing crops)
Dairy - warm and wet areas, eg. South-West England, are good dairy farming. There are lots of large, grassy fields
Sheep - sheep farming takes place in the harsher conditions in the uplands. Sheep farming has led to a lack of trees on the hills
OS maps show the influencs of agriculture, including filed boundaries and drainage ditches (dug to make the land dry enough for farming)
Forestry
Forestry is the management of areas of woodland - they can be used for timber, recreation or conservation
The UK used to be covered in deciduous wookdland, but there is very little natural woodland left
Coniferous (evergreen) forests have been planted for timber . The trees are often planted in straight lines - the forests don't look natural. When areas are felled, the landscape is left bare
In some places, deciduous woodland is being replanted to try to return the area to a more natural state
OS maps show forestry plantations and areas that are being managed
Settlement
Lots of factors influence where settlements have develope. For example, early settlers needed a water supply, somewhat that could easily be defended or that was sheltered from wind and rain
Other factors such as bridging oints over rivers and the availibility of resources eg. wood for building, also played a part
As settlments grew they further influenced the landscape
Land was concreted over for roads and building, which affected drainage patterns
Some rivers were diverted through underground channels
Some river channels were straightened or had embankments built to prevent flooding
Most of the biggest cities are ports and industrial area eg. London, West Midlands, Manchester and Portsmouth. These landscapes are more urban thana rural
Look for buildings, railways, canals and embankments to identify settlements on OS maps