The Uk Eveolving Physical Lamdscape Flashcards
What is an igneous rock
Earth oldest rock formed from lavas resistant to erosion
What is an sedimentary rock
Some are resistance
Formed by sediments left by rivers
What is metamorphic rock
Sediment rocks that were heated and compressed
What is mass movement
It is the shifting of the rocks and loose material down a slope it happens when the force of gravity is greater than the force supporting it
What does erosion mean
The wearing away of the landscape
What does carbon dating use
Radioactive testing to find the age of rock contained living materials
Geology 112
Geologists know that fossils at Malian cove are just like the coral species living in the Great Barrier Reef
By testing fossils from malham cove using carbon dating, they know that they lived during a geological period called the Carboniferous
At the time the uk was covered by tropical seas just like the barrier reef
Tropical fish and corals thrived, as they died skeletons fell to the sea floor, forming horizontal layers
Two processes turned them into solid rock
As skeletons fell, they crushed those beneath, eventually squeezing out water and compacting them into rock.
Calcium carbonate crystallised around the fragments this cemented them together and even preserved some fossils intact
Later other rock strata were deposited on top of the lime stone eg sandstone and shale.
Milestone grit it resist erosion so well that it formes the highest peaks of the Pennines and protects weaker sands and shales beneath
Tectonic processes
Over 300 million years three tectonic processes affection rocks in the Pennines
The plate on which the uk sits shifted away from the tropics
Convection currents beneath the plate up lifted rock from below the sea becoming land
During uplift some rocks snapped and moved along faults in a series of earthquakes over thousands of years each movement disturbed the strata so that they tilted
Sometimes the faults form a steep edge where uplift has raised some parts more than others
GLACIATION
As the Pennines were uplifted rivers like the wharfe eroded into them creating a v shaped valley but the most recent ice age over 10000 years ago bought huge glaciers to the Pennines they had two effects
Alter Ning river valleys making them deeper and widening them into a u shaped troughs
As they melted the glaciers left features like malham cove with a spectacular waterfall
Upland and lowland landscapes
Upland areas of the uk consist of resistant igneous metamorphic and some sedimentary rocks
Lowland
Lowland areas of the uk generally consist of generally younger and less ristiatand sedimentary rocks
Britain’s geology 116
Cornwall has large amounts of tin and copper which made it wealthy
Huge strata of coal helped to make Britain the world first industrial nation
HOW DO ROCKS DIFFER
IGNEOUS the earths oldest rocks formed from lavas and deep magmas they were once molten then cooled and crystallised most igneous-rocks are resistant to erosion
SEDIMENTARY formed from sediments eroded and deposited by rivers the sea to the sea bed some are resistant limestone and some crumble easily shale
METAMORPHIC sedimentary rocks that were heated and compressed during igneous activity heating and compression harden them and make them more resistant shale becomes slate and limestone becomes marble
ROCKS AND LAND SCAPE
To the north and west are uplands of England wales and Scotland
South and east of the line are lowlands of central and southern England
North and west of the line
Most rocks are older
Most resistant igneous and metamorphic rocks are found here
There are more faults where upland areas were uplifted by tectonic activity
To the south and east of the line rock are
Younger
Weaker sedimentary rocks which erode easily lime stones are found there too but they are younger and less resistant then Carboniferous limestone
The Lake District an upland landscape
Like the Pennines the Lake District was once glaciated glaciers creat deep u shaped valleys and hollows now filled by lakes today rivers flow in the valley instead bottom instead of glaciers
These rivers are small compared to their valleys and are known as misfits the deposit silt and mud in the valley bottoms making them fertile for farming
Weathering and slope proces
What makes the ground rough are oak fragments known as scree. Scree consist of angular rock pieces created by freeze thaw weathering each winter temperatures are often below freezing at night and warmer during the day rainwater gets into cracks in the rock freezes and expands by 10% expansion widens the crack and eventually the rock breaks into pieces
Scree fragments are unstable and move easily during rock falls increasing dangers for walkers
Land slides are common the Lake District is the UKs wettest region rain adds to the weight of wet herd rock so it slides easily
What is weathering
Is the physical chemical or biological breakdown of solid rock by the action of weather or plants
The Weald lowland landscape
Although southern England is much lower than the Lake District some parts consist of undulating hills one such area the Weald in Kent and Sussex the land scape is also affected by geology the Weald was once a dome of folded rocks forming an arch called anticline
Resistant rocks like chalk form steep escarpments
Behind the escarpment gentle slopes follow the angel at which the rocks were tilted known as the dip slope
Softer clays are lower and flatter forming the valves
Weathering
Because southern England is warmer than the Lake District different types of weathering occur
Chalk is calcium carbonate an alkaline so is affected by solution Chemical weathering
Tree and shrub roots break up solid rock biological weathering
Post glacial and slope processes
Chalk is porous so it is unusual to find rivers in chalk areas except when its saturated after wet weather however clay is impermeable so rivers are common in valves during and after the last ice age water in chalk froze making it impermeable then fresh water formed rivers and valleys as the climate warmed water seeped through the chalk once again leaving dry valleys where rivers had once flowed
Slope processes are slower then in the Lake District the most common is soil creep its caused by rain dislodging soil particles
What is mechanical weathering
It is the breakdown of rock without changing its chemical composition
What are the main types of mechanical weathering
The seawater gets into cracks in the rock
When water evaporates salt crystals form as the salt crystallises they expand which puts pressure on the rocks
This widens he cracks and causes the rocks to break up
What is chemical weathering
Is the break down of rocks by changing its chemical composition
What happens during chemical weathering
Seawater and rainwater have carbon dioxide dissolved in them which makes weak carbonic acids
Carbonic acid reacts with rock that contains calcium carbonate so the rocks re dissolved by the rainwater
