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examBoard: Cambridge
examType: IGCSE
lessonTitle: Beach Formation and Characteristics
Beaches are dynamic coastal features that form where waves deposit sediment along the shoreline. They're constantly changing - sometimes slowly over seasons and sometimes dramatically during storms. Understanding how beaches form and their characteristics helps us appreciate these amazing coastal environments and how they respond to natural processes and human activities.
Key Definitions:
Beaches form when waves transport and deposit sediment along the coast. The material comes from:
A typical beach has several distinct zones:
The type of waves reaching a beach has a huge impact on its shape and characteristics. There are two main types of waves that create distinctive beach profiles.
Characteristics:
Effect on beaches: Build up beaches by depositing material. The strong swash pushes sediment up the beach, while the weak backwash means less material is pulled back to sea.
Characteristics:
Effect on beaches: Erode beaches by removing material. The powerful backwash drags sediment back to sea, creating steeper, narrower beaches.
Beaches change their shape throughout the year in response to changing wave conditions. This creates distinctive summer and winter profiles.
Characteristics:
During summer, calmer conditions mean constructive waves dominate, building up a wide, flat beach with a pronounced berm.
Characteristics:
Winter storms create destructive waves that remove sediment from the beach, creating a steeper profile. The sediment is often stored in offshore bars until summer conditions return.
Beaches can be made up of different materials, which affect how they look and behave. The size, shape and sorting of sediment tells us about the beach's history and the processes at work.
Boulder: >256mm
Cobble: 64-256mm
Pebble: 4-64mm
Gravel: 2-4mm
Sand: 0.0625-2mm
Silt/Clay: <0.0625mm
Angular: Recently broken, little transport
Sub-angular: Some transport and abrasion
Sub-rounded: Significant transport
Rounded: Extensive transport
Well-rounded: Very long transport history
Well-sorted: Similar sized particles, indicating consistent energy conditions
Poorly-sorted: Mixed sizes, indicating variable energy conditions
Sorting improves with distance from source as waves selectively transport different sized particles
Beaches can be classified by their material composition, which affects their appearance and behaviour.
Characteristics:
Characteristics:
Several factors influence the shape, size and characteristics of beaches:
Chesil Beach is an 18km long shingle barrier beach in Dorset, southern England. It's famous for its perfectly sorted sediment - pebbles are largest (up to 10cm) at the western end (Portland) and gradually decrease in size to small pebbles (2mm) at the eastern end (West Bay).
This sorting occurs because of the prevailing south-westerly waves. As waves approach at an angle, they create longshore drift that moves sediment eastward. The largest pebbles require more energy to move, so they travel shorter distances than smaller ones, creating a natural grading system.
Local fishermen were historically able to tell their location along the beach in foggy conditions just by examining the pebble size - a remarkable example of how beach characteristics can be distinctive!
Beaches often feature distinctive landforms that develop through wave action and sediment movement:
Spits are elongated ridges of sand or shingle that extend from the land into the sea, often with a curved end. They form where the coastline changes direction and longshore drift continues to transport sediment past this point.
Bars are similar but connect two headlands across a bay, sometimes enclosing a lagoon behind them.
Example: Hurst Castle Spit, Hampshire, UK
Beach cusps are regularly spaced, crescent-shaped indentations along the shoreline. They form through complex interactions between waves and the beach face, creating a scalloped pattern.
Ridges (or berms) are raised platforms of sediment marking the limit of high tide or storm waves. Multiple ridge lines often indicate past storm events.
Human activities can significantly affect beach environments:
For your IGCSE Geography fieldwork, you might study beaches using these techniques:
These techniques help geographers understand beach processes and how they change over time.
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