4.2 Uplands and Lowlands (4.2 A number of physical and human processes work together to create distinct UK landscapes). Flashcards
There is an annual race above Wastwater, which is 34km long and involves climbing a total of 2750m over several peaks of hard igneous rock.
What has happened in the past that made that rock hard and rough?
Name features and additional events that make it dangerous for people .
What makes the ground so rough are rock fragments i.e. Screes, which consist of angular rock pieces that are created by a type of weathering called freeze thaw weathering and happens as follows:
Each winter, temperatures are often below freezing at night and warmer during the day. Rainwater gets in the cracks in the rock, freezes overnight, and expands by 10%, causing the crack to widen and melts in the day.
Refreezes at night, expanding by another 10%, widening the crack again and thawing in the daytime (when the temperature is a lot higher).
This repeated process causes pressure in the rocks to increase
And finally after this continuos cycle the rock finally breaks off, leaving angular rock pieces which in time, followed by angular rock pieces from many other rocks , form screes.
An example of a scree is on the edge of Wasdale.
As a brief reminder,freeze thaw weathering would not have been as effective or common in the ice age, as the conditions around that time, were mostly very cold. Therefore not forgetting that freeze thaw weathering requires hot and cold temperatures, it would have therefore not have happened that often.
Every winter more scree is added.
In addition, rapid slope processes occur, affecting valley sides.
Scree fragments are not stable (unstable) and move easily during rockfalls; this creates an increase in danger for walkers even cause death.
Landslides are also common. The Lake District for instance is the wettest region (over 2000mm of rain a year). Rain adds to the weight of weathered rock so it slides easily, increasing dangers of walkers in that area, as the GROUND THERE IS VERY SLIPPERY MAKING IT DANGEROUS.
FREE THAW WEATHERING PROCESS AND DANGERS OF LAND SLIDES AND SCREES.
Just like the Pennies, Lake District was once ‘what’ and what was the aftermath? (Post-glacial river processes).
They were once glaciated and glaciers created deep U-shaped valleys and hollows filled now by lakes. Today, rivers flow in the valley bottom instead of glaciers. These rivers are small compared to their valleys, and are known as “misfits” (misfit river(s)).
Why are misfit rivers, like in the Lake District, beneficial for us?
Misfits deposit silt and mud, which is called alluvium, in the valley bottoms.
And that alluvium is beneficial for us because they are fertile for farming.
Why do different types of weathering occur in southern England and what are their fully detailed processes?
Different types of weathering occur in southern England because it is warmer than the Lake District and they are as follows:
Biological weathering (when tree shrub roots and burrowing animals break up solid rock):
Plant roots can grow down through cracks into rock surfaces and push them apart, loosening fragments, and as a result larger cracks are formed.
Decaying plants and animal remains make acids which eat away at the rocks below.
Rabbits and worms, that are burrowing creatures , these animals burrow in holes in the rock, breaking up softer rocks like clay.
Both the animals and the plant roots put pressure on the rock in doing this.
And after continuous cycles… the burrowing animals and plants cause a breakdown in the rock and finally break down the structure of the rock.
Chemical weathering (when chalk is affected by solution because of the fact it is calcium carbonate, an alkali):
Rainwater absorbs CO2 as a by-product from pollution
The rain/surface water becomes a weak carbonic acid.
Acid reacts with calcium carbonate in limestone/chalk
The rocks are dissolved
What or who is responsible for dry valleys in southern England ( the lowlands)? (Post- glacial river processes)
Chalk is porous, so it’s unusual to find rivers in chalk areas, except when it’s saturated after wet weather. But clay is impermeable (doesn’t let fluid pass through it) so rivers are therefore common in vales. During and after the last ice age, which was responsible for the dry valleys in southern England, water in the chalk froze making it impermeable.
Then, fresh water formed rivers and valleys.
And as the climate warmed, which we might have or still be making happen quicker, water seeped through the chalk once again leaving DRY VALLEYS where rivers had once flowed.
But the water isn’t gone; it hasn’t all dried out; it is just not visible above the surface like water far beneath the desert floor.
What is difference between the slope processes in southern England and Lake District, which is most common and how is it caused?
Slope processes are slower than in the Lake District; the most common is soil creep, which is caused by rain dislodging soil particles.
What caused East Anglia (lowlands) to have sand, clay and chalk as their main geology and how have we benefitted from it?
Glaciation eroded the area producing fertile soil , arable, which benefitted us because farmers can now grow more crops in the area, many villages have been built there and trees (12%) have been cut down for large farmlands.
Which is lowland and upland for Lake District and East Anglia?
Lake District- upland
East Anglia- lowland.
Define weathering and name each type and describe each process.
Weathering is the breakdown of rock into smaller pieces. The different types are: mechanical, chemical and biological.
Mechanical weathering is the breakdown of rock without changing its chemical composition. The main one that affects coasts is salt weathering:
The seawater gets into cracks in the rock
When the seawater evaporates, salt crystals form. As the salt crystals form they expand, which puts pressure on the rock.
Repeated evaporation of saltwater and the forming of salt crystals widens the cracks and causes the rock to break up.
Chemical weathering is the breakdown of rock by changing its chemical composition. Carbonation weathering is a type of chemical weathering that happens in warm and wet conditions:
Seawater and rainwater have carbon dioxide dissolved in them, which makes them weak carbonic acids.
Carbonic acid reacts with rock that contains calcium carbonate, so the rocks are dissolved by the rainwater.
Biological weathering is the breakdown of rock by living things e.g. plant roots break down rocks by growing into cracks on their surface and pushing them apart.
