Topic 4: UK's Evolving Physical Landscape Flashcards
How have tectonic processes shaped the UK’s physical landscape?
- Convection currents have caused uplift of some land, pushing it upwards and further out to sea
- Slowly moved to its current position from Antartica 500 millions years ago
- Between collisions, huge volcanoes occurred erupting masses of lava and forming mountains
How has glaciation shaped the UK’s physical landscape?
- As the Pennines were uplifted, rivers like the Wharfe eroded into them, creating V-shaped valleys.
- But the most recent Ice Age, over 10 000 years ago, brought huge glaciers to the Pennines. They had two effects:
• altering river valleys, making them deeper and widening them into U-shaped troughs using corrosion, abrasion, freze thaw
• as they melted, the glaciers left features like Malham Cove
How has geology shaped the UK’s physical landscape?
- As tropical dosn amd coral died, skeletons fell to the sea floor, forming horizontal layers (stratas)
- As skeletons fell, they crushed those beneath them, eventually squeezing out water and compacting them into rock
- Other rock strata deposited on top of limestone- resists erosion so it forms high peaks and protects weaker sands
- Calcium Carbonate crystallises around the fragments, cementing together
What is igneous rock?
Magma cools amd hardens. Rock form crystals as it cools down. Usually hard
What is sedimentary rock?
Layers of sediment are compacted together until they become solid rock:
Limestone and chalk form from tiny shells and skeletons of sea creatures. Limestone is hard, chalk is softer rock
What is metamorphic rock?
Sedimentary rocks that were heated and compressed during igneous activity. Heating and compression harden them and make them resistant - shale becomes slate and limestone becomes marble.
What are the locations of upland in Uk?
North West- Peak District, Lake district
What are the locations of lowland
South East/ Central UK- North and South Downs
What rock types are in upland?
Resistant igneous and metamorphic- Carboniferous limestone, granite
What rock types are in lowland?
Sedimentary- Limestone, chalk, clay
What are features of the upland?
Valleys, glacial deposits, volcanoes
What are features of the lowland?
Wide valleys, forest historically, farmland
What is an example of sedimentary rock and its properties?
Limestone:
Coral/ sediment and pressure over time. Made up of layers
Permeable, underground rivers
Generally resistant
What is an example of igneous rock and its properties?
Granite:
Magma cools deep underground
Crystals of quartz
Very resistant
What is an example of metamorphic rock and its properties?
Slates:
Heated mud or shales
Very resistant
How does seasonality impact coastal erosion?
Through changing seasons, storm frequency may vary, often highest in winter. Increases in storm frequency result in the erosion and saturation of cliffs through increasing winds and rainfall. Temperature also varies with seasons. Differences in temperature have an impact on processes along the coast (eg: Increasing rate of salt weathering as water evaporates quickly
How does storm frequency impact coastal erosion?
Storms are very frequent in many parts of the Uk, especially in winter. Stronger winds create high energy, destructive waves which increase erosion pf the cliffs. Intense rainfall cause cliffs to become saturated- thus makes mass movement more likely
How does prevailing wind and fetch impact coastal erosion?
The prevailing winds in the UK are mostly warm south Westerlies which bring storms from the Atlantic Ocean. The Uk’s South is exposed to these winds and storms, further resulting in the erosion of coasts
How does mass movement impact coastal erosion?
Mass movement is the shifting of rocks and loose material down a slope, e.g. a cliff. It happens when the force of gravity acting on a slope is greater than the force supporting it. Mass movements cause coasts to retreat rapidly. They’re more likely to happen when the material is saturated — it acts as a lubricant and makes the material heavier and unstable. In rotational slumping, the material shifts with a rotation as material closer to the surface is more stable; less of it collapses. Layers of impermeable rock means it can slump. Rock slides occur as it slides quickly along a bedding plane
How does weathering impact coastal erosion?
Weathering is the breakdown of rock. This may occur through mechanical weathering (seawater gets into cracks, evaporates, salt crystals form and expand, widens cracks causing it to break up), chemical weathering (Water have dissolved CO2, making them weak carbonic acids, reacts with rock containing calcium carbonate so rocks are dissolved), biological weathering- living things (plant roots break down rocks by growing into cracks and pushing apart)
What is abrasion?
eroded particles in the water scrape and rub against rock, removing small pieces
What is hydraulic action?
waves crash against rock and compress the air in the cracks. This puts pressure on the rock. Repeated compression widens the cracks and makes bits of rock break off.
What is attrition?
eroded particles in the water smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together.
What are the characteristics of destructive waves?
- Destructive waves are high, steep, and have a high frequency
- Their backwash (the movement of the water back down the beach) is more powerful than their swash (the movement of the water up the beach). This means material is removed from the coast.
- The backwash flows under the next incoming wave, forming a rip current. These can be strong and drag swimmers out to sea.
- Storms increase the erosional power of destructive waves, which can lead to increased rates of coastal retreat.
What are the characteristics of constructive waves?
- Constructive waves are low, long, and have a low frequency
- The swash is powerful and it carries material up the coast, meaning they deposit material along the coast
- The backwash is weaker and it doesn’t take a lot of material back down the coast.
What are joints?
Small, usually vertical cracks
What are faults?
Larger cracks caused by past tectonic movements
How do headlands and bays form?
- Headlands and bays form where there are alternating bands of resistant and less resistant rock along a coast.
- The less resistant rock (e.g. clay) is eroded guickly and this forms a bay — bays have a gentle slope.
- The resistant rock (e.g. chalk) is eroded more slowly and it’s left jutting out, forming a headland — headlands have steep sides.
How does an arch form?
Arch:
* Large crack, opened up by hydraulic action
* Cave becomes larger through further erosion
* Cave breaks through the headland forming a natural arch
How does a stack form?
Stack:
* The arch erodes and collapses,
* This leaves a tall rock stack- an isolated rock that’s separate from the headland
How does a stump form?
Stump:
The stack is eroded, forming a stump
How do wave cut notches and platforms form?
- Wave power is concentrated at the cliff base where abrasion forms a wave-cut notch.
- As the notch grows, a cliff overhang develops.
- The overhang becomes unstable and eventually collapses, forming a pile of rock debris. The debris protects the cliff base from further erosion.
- Over time, the rock debris is eroded by attrition, exposing the cliff to erosion again.
- Over thousands of years, a succession of wave-cut notches form, and the cliff collapses again and again, retreating inland.
- A level area of smooth rock is left where the cliff line once was, stretching out to sea, called a wave-cut platform.
What is deposition?
Deposition is when material being carried by the seawater is dropped on the coast. It occurs when water carrying sediment slows down so that it isn’t moving fast enough to carry so much sediment
How does longshore drift move material?
- Waves follow the direction of the prevailing wind.
- They usually hit the coast at an oblique angle (any angle that isn’t a right angle)
- The swash carries material up the beach, in the same direction as the waves.
- The backwash then carries material down the beach at right angles, back towards the sea.
- Over time, material zigzags along the coast.
How does a split form?
- Spits form at sharp bends in the coastline, e.g. at a river mouth.
- Longshore drift transports sand and shingle Material past the bend and deposits it in the sea.
- Strong winds and waves can curve the end of the spit (forming a recurved end).
- The sheltered area behind the spit is protected from waves — lots of material accumulates in this area, which means plants can grow there.
- Over time, the sheltered area can become a mud flat or a salt marsh.
How does a split turn into a bar?
- A bar is formed when a spit joins two headlands together.
- The bar cuts off the bay between the headlands from the sea.
- This means a lagoon can form behind the bar.
What is solution?
Soluble materials dissolve in the water and are carried along
What is suspension?
Small particles like salt and clay are carried along by the water
What is saltation?
Pebble-sized particles are bounced along the river bed by the force of the water
What is traction?
Large particles like boulders are pushed along the river bed by the force of the water
What os the rock alignment of disconcodent
alternating bands of hard and soft rock that are at right angles to the coast
What is the rock alignment for concordant?
the alternating bands of hard and soft rock (strata) are parallel to the coast
What are features caused by discordant rock structure?
Long headlands, bays
harder sandstones as headlands.
Softer limestone
What are features caused by concordant rock structure?
Coves, steep cliffs, a gap through the limestone, exposing less resistant sands and clays behind, Stair Hole
