4.1 Geology and the UK Flashcards
Give a definition, approximate age, 3 examples and location in the UK of igneous rocks.
Igneous rocks are formed by the cooling of lava and magma. The magma/lava will cool and subsequently crystallise to form a rock, these tend to be very resistant to erosion and weathering. If the rock contains small crystals it has cooled and formed quickly, if it contains large crystals it has formed over a much longer period of time.
Igneous rocks tend to be around 300-600 million years old.
Common and well known igneous rocks include Basalt, Andesite and Obsidian.
In the UK igneous rocks are found commonly in Scotland, the Outer Hebrides and parts of Cornwall.
Give a definition, approximate age, 3 examples and location in the UK of sedimentary rocks.
When the carcasses/skeletons of creatures either sink to the sea/river bed or fall onto the ground they are usually, over time, trapped under layers of different material and sediment, these layers are called strata. As pressures compacts the rocks Calcium will crystallise and cement the strata into a rock type, sedimentary rocks.
Sedimentary rocks are young relative to the other rocks with an age of 210 million years or less.
Examples of sedimentary rocks include Chalk, Limestone and Clay.
Sedimentary rocks are commonly found in the UK Lowland in areas such as Sussex, Hampshire and London.
Compare Metamorphic and Igneous rock.
The formation of these rock types differ, igneous rocks are formed through the cooling and crystallisation of magma/lava whereas metamorphic rocks are formed when sedimentary and igneous rocks are placed under immense heat and pressure and form, through metamorphosis, metamorphic rock.
Compare the formation and characteristics of Granite and Carboniferous Limestone.
Granite (igneous) is formed by the slow cooling of magma (resulting in large crystals visible to the human eye). Carboniferous Limestone was formed in the Carboniferous Era, 360-300 million years ago, and is the product of material, sediment and skeletons/carcasses being compacted and cemented to form a rock type.
Granite is very resistant to weathering and erosion, this is why it is sometimes used in construction and design. Carboniferous Limestone is porous, allowing for weathering to damage it, it is also slightly alkali, this means acidic rain and seawater will erode this material.
Compare the formation and characteristics of Chalk and Slate.
Chalk was formed 100 million years ago (Cretaceous Period) and was formed by the compaction and cementation of rock and coral debris (shells and skeletons) at the bottom of tropical seas. Slate was formed through the metamorphism (melting and then solidifying again) of sedimentary rock (clay and volcanic ash).
Chalk is porous and not very resistant, it is also vulnerable to being dissolved through acidic material. Chalk is used to weaken acidic materials and as a tool for design and colouring. Slate, dud to its resistant to weathering and erosion is used for roofing and flooring, it is a very durable material.
Explain when and how active volcanoes shaped the Uplands of the UK.
420 million years ago the two plates Laurentia (England and Wales) and Avalonia (Scotland and Ireland) collided and created a collision boundary. Here large mountains were formed and magma rose up, some of it cooled and crystallised to form granite, other portions of the magma erupted and eroded the landscape, creating even more igneous rocks and sealing the two plates together.
Explain how glacial erosion and deposition shaped the Uplands of the UK.
As rocks and hollows were frozen over with glaciers in the previous Ice Ages, the most previous being 10,000 years ago, they left an unforgettable mark on the landscape. Many valleys, V-Shaped due to erosion from rivers, were widened drastically into U-Shaped Valleys with peaks and valleys forming due to the power of the glacier moving downwards (due to gravity) and to freeze-thaw weathering. Many misfit rivers were left behind, along with corries and aretes. Finally, moraines were left behind due to glacial deposition.
Explain when and how Sedimentary rock was formed across the UK Lowlands.
During the Carboniferous Era, 300-350 million years ago, coral fossils sunk to the sea-bed and over time were cemented by Calcium Carbonate to form sedimentary rock. Tectonic movements lead to these rocks (on their plate) moving towards the temperate climbing and during uplift the strata became visible. 30 million years ago the tectonic processes lead to this rock forming a domed anticlime which was eroded by glacial meltwater in the North. This took place across the Wealden area and created a scarp and vale topography.
Explain how glacial deposition shaped the UK Lowlands.
The Lowlands once consisted of a domed anticlime in the Wealden Area, an anticlime being a series of strata pushed upwards and domed. When the glaciers of the Uplands melted 10,000 years ago the glacial meltwater moved to the south and eroded the layers of the anticlime, on either side there are two escarpments, raised area with a dip-slope (remnants of a previously domed anticlime) and in the centre (low lying land) there is a vale.
Explain how scarp and vale topography forms in the UK Lowland.
In the Lowland, in the Wealden Area, there was a domed anticlime. Folded strata were pushed into this domed position from tectonic movement 30 million years ago. In the most recent Ice Age, 10,000 uears ago, the glacial meltwater eroded away this dome, the top layer faces the most erosion, it continues eroding until it reaches the Wealden Series (rock) below the anticlime. The lower area in the centre (what was previously the dome) is called the vale and the two higher areas are called escarpments (colloquially called scarps), these scarps will have a dip-slope, this is due to the scarps formally being part of a dome.
