4.1 Geology and past processes have influenced the physical landscape of the UK Flashcards
What role has glaciation played in the shaping of the UK’s physical landscape?
As water froze within hollows to become glaciers previously uplifted rocks were eroded by these glaciers. The last Ice Age, 10,000 years ago, led to glaciers eroding into valleys, widening valleys into a U-Shape and creating troughs. The glaciers also left marks on the landscape of the UK including misfit rivers and corries and when the ice finally melted multiple features including waterfalls were left.
What role did Tectonic Processes play in the shaping of the UK physical landscape?
Many thousands of years ago the plate on which England and Wales is situated shifted away from the tropics as a result of climate change. The convection currents moved this plate until it collided with a separate plate on which Ireland and Scotland were situated. The collision boundary led to the sea-bed between to uplift (rise) and form mountains.
What role did Geology play in the shaping of the UK physical landscape?
During the Carboniferous Era (200-350 million years ago) the UK was situated in the tropics. When coral and animals died it would sink to the sea-bed and be trapped by other layers of rock and sediment called strata. Here the compression and cementation by Calcium Carbonate (CaCO3) lead to these strata becoming sedimentary rock. As the plates collided (explained in previous Flashcard) this strata was uplifted and was visible above sea level. These strata are highly resistant because the weak sands and shales are protected by layers of more resistant rock, such as limestone.
How have these three past processes acted together to create the UK’s physical landscape?
(Formation of valleys and peaks)
Tectonic processes will lead to the movement of plates (due to convection currents) which will subsequently collide. The sea-bed (which conntains fossils and multiple layers of strata) will then uplift to form mountains. Then, during an Ice Age, a glacier, which has formed in a hollow, will erode through the strata and pre-existing valleys. The weaker sedimentary rocks, such as sands and shales, will erode quickly creating a wide valley but harder rock, such as Millstone Grit will not erode and remains as peaks. The lower layers of strata, usually consisting of limestone, will not be eroded by the glaciers and instead water will enter the porous rock and slowly erode it as a result of freeze-thaw weathering.
Igneous Rock
- formation
- examples
- characteristics
Igneous rocks are formed when lava, above ground, and magma, below ground, cool and solidify. The lava/magma will crystallise and if the crystals are large it cooled slowly and if they are large it cooled and solidified slowly.
Examples include: Granite, Basalt and Andesite
Igneous rocks are usually very resistant to erosion and to forms of weathering, they will also contain crystals (a result of their formation).
Sedimentary Rocks:
- formation
- examples
- characteristics
Sedimentary rocks are formed as dead plants and animals sink to the sea-bed or their skeletons are left on the ground. Over time, as layers are built up, the depth increases. There are now multiple layers called strata. As the strata is compressed and the various sands and rocks cemented by Calcium Carbonate (CaCO3) the strata become one rock, a sedimentary rock.
Examples include: Chalk, Clay and Limestone
Sedimentary rocks tend to be alkali and sometimes can be resistant against erosion, such as limestone, or very susceptible to erosion, such as chalk and clay, and this is a result of their formation, if there is greater compression and cementation they will be much more resistant to erosion and forms of weathering but compared to igneous rocks they are much weaker.
Metamorphic Rocks:
- formation
- examples
- characteristics
Metamorphic rocks are formed when either igneous or sedimentary rocks are exposed to intense heat and intense pressure, normally deep underground close to the Mantle. The rocks are compressed and heated and become metamorphic.
Examples include: Schist and Slate
Metamorphic rocks tend to usually be very resistant and many are formed though metamorphosis when they are melted and solidify again.
Distribution of rock types around the UK’s physical landscape.
Upland: The UK Upland Area is considered north of the Tees-Exe Line which runs from Kingsbridge, Devon, to Middlesborough, Yorkshire. The rocks here tend to igneous and metamorphic and are very resistant to erosion. Many have an age exceeding 360,000 years and the area has a very tumultuous landscape with areas of both high and low relief.
Lowland: The UK Lowland Area is south of the Tees-Exe Line and include London. This area mainly consists of sedimentary rocks, many with an age under 210,000 years and there is very low relief. This area usually isn’t covered in glaciers or ice during Ice Ages.
