Physical processes (Edexcel GCSE Geography A): Revision Notes

Physical processes in changing UK landscapes

Introduction to physical processes

The distinctive upland and lowland landscapes we see across the UK today have been shaped by various physical processes working together over thousands of years. These processes include glacial activity, weathering, climate effects, and river action. Understanding how these processes interact helps us explain why different parts of Britain look so different from each other.

Upland landscape formation

Upland areas in the UK show clear evidence of past glacial activity combined with ongoing weathering processes. The Lake District provides an excellent example of how these processes have worked together to create today's mountainous landscape.

Glacial erosion

During the Ice Age, massive glaciers moved across the landscape, carving out distinctive features that we can still see today. In places like Stickle Tarn in the Lake District, glaciers carved out bowl-shaped depressions called corries. These deep, circular hollows were formed as glaciers rotated and scraped away the bedrock beneath them. The steep back walls and relatively flat floors of these features provide clear evidence of glacial erosion.

Glacial erosion also created the characteristic U-shaped valleys found throughout upland Britain. Unlike river valleys which tend to be V-shaped, glacial valleys have wide, flat floors and steep sides where the ice carved away the landscape.

Weathering processes

Weathering continues to shape upland landscapes today, particularly through freeze-thaw action. When water gets into cracks in the rock and freezes, it expands, widening the cracks. Over time, this process breaks off fragments of rock that fall down the mountainside. These broken rock pieces collect at the bottom of cliffs to form sloping piles of debris called scree slopes.

The exposed rock faces in upland areas are particularly vulnerable to this type of weathering because they experience frequent temperature changes around the freezing point, especially during winter months.

Climate effects

The high rainfall typical of upland areas creates additional challenges for the landscape. Water cannot soak into impermeable rocks, so it flows rapidly over the surface, creating numerous streams and contributing to erosion. The combination of high precipitation and steep slopes means that surface water moves quickly, carrying away loose material and continuing to modify the landscape.

Post-glacial rivers

An interesting feature of many upland valleys is that the streams running through them today seem too small for the valleys they occupy. This is because these U-shaped valleys were carved by glaciers, not by the relatively small streams we see now. The valley floors are much wider than the current streams could have eroded, providing evidence of the much more powerful glacial forces that once shaped these landscapes.

Lowland landscape formation

Lowland areas of the UK have been shaped primarily by river processes operating over thousands of years. The landscape of Herefordshire demonstrates how rivers create wide valleys through erosion and deposition.

River erosion

As rivers flow through the landscape, they gradually erode the land around them, particularly as they meander from side to side. Over time, this lateral erosion widens valleys and creates the gently rolling terrain characteristic of lowland Britain. Rivers like the Lugg and Wye have carved broad valleys between low hills through this process of gradual erosion and sediment transport.

The meandering nature of lowland rivers means they constantly change course slightly, eroding material from the outside of bends while depositing it on the inside. This process slowly widens valleys and creates the flat-bottomed profile typical of river valleys.

River deposition

When rivers flood during periods of heavy rainfall, they deposit the sediment they have been carrying across the surrounding land. Over many flood events, this process builds up layers of fertile silt, creating wide, flat floodplains. These floodplains are characteristic features of lowland landscapes and explain why many lowland areas have such flat, productive farmland.

The alternating processes of erosion during normal flow and deposition during floods work together to create the gentle, undulating landscapes typical of lowland Britain.

Case study: Bowerman's Nose, Dartmoor

Dartmoor's granite tors, such as Bowerman's Nose, provide excellent examples of how multiple physical processes work together to create distinctive landscape features. The formation of these impressive rock stacks involves several stages of geological and weathering processes.

Formation process

The story of Dartmoor's tors begins deep underground around 290 million years ago. A large body of molten rock (magma) formed what geologists call a batholith beneath the surface. As this magma cooled very slowly, it formed granite - a hard, crystalline rock with a distinctive jointed structure.

Over millions of years, the rocks above the granite were gradually worn away, exposing the granite at the surface. Once exposed, the granite became vulnerable to weathering processes, particularly chemical weathering which attacked the joints in the rock, gradually widening them.

Weathering and erosion effects

Chemical weathering works particularly effectively on granite because it attacks the minerals that hold the rock together. As the joints in the granite widened, blocks of rock became loose and were gradually removed by erosion and mass movement processes.

The areas of granite most affected by weathering and erosion were worn away, leaving behind the more resistant blocks that now form the tors. Freeze-thaw weathering also played a role, particularly in breaking up the surface layers of granite and creating the scattered boulders found around many tors.

This combination of processes - underground formation, exposure, chemical weathering, and physical erosion - working together over millions of years created the dramatic granite landscapes we see on Dartmoor today.