coastal environment Flashcards
what physical processes affect coasts and their land forms?
- Marine and Sub-aerial processes.
- Marine processes include erosion, transportation, and deposition by waves.
- Sub-aerial processes include weathering, mass movement, and runoff.
what are “sub-aerial processes”?
- sub-aerial processes are land-based processes that shape the coast.
- They include weathering (the breakdown of rocks), mass movement (e.g., landslides, rockfall and slumping), and surface runoff (water moving overland).
- Unlike marine processes, they occur above sea level but impact coastal landscapes.
what are the three types of weathering, and when do they occur?
- Mechanical weathering- caused by physical forces like freeze-thaw action which breaks rocks into smaller pieces.
- Chemical weathering- occurs when rock minerals are chemically altered or dissolved, often by rainwater(e.g. acid rain)
- Biological weathering- caused by plants, animals, and microbes breaking down rocks, such as roots growing into cracks.
- These processes occur depending on the environment’s climate and biological activity.
what is “mass movement,” and what are its types?
The downhill movement of material due to gravity.
examples:
* Rotational slumping: material moves along a curved surface, common on clay cliffs.
* Landslides: material moves suddenly down a slope, often triggered by heavy rain or coastal erosion.
what are the processes of coastal erosion?
- Corrasion/Abrasion: waves hurl rocks and sediment against cliffs, wearing them down (acts as a sandpaper)
- Attrition: rocks and pebbles are smashed together, becoming smaller and smoother.
- Solution: sea water dissolves soluble minerals in the rocks.
- Hydraulic action: the force of waves compresses air into cracks in the cliff, causing pressure and leading to rock breakage.
what is longshore drift?
- Transportation of sand and pebbles along the coast.
- It occurs when waves hit the shore at an angle, moving material in a zig-zag pattern along the coastline.
- This process shapes beaches and spits.
when does coastal deposition occur?
- When the sea loses its energy and drops the sediment it is carrying.
- This can occur in sheltered areas, such as bays or where the energy decreases due to shallow water or a change in the coastline’s shape.
What are the differences between constructive and destructive waves?
- Constructive waves: low energy, long wavelength and low frequency (6-8 per minute). They build up beaches by depositing material.
- Destructive waves: High energy, short wavelength, and high frequency (10-14 per minute). They erode coastlines by removing sediment.
how do erosion processes form coastal landforms?
Coastal erosion shapes the following landforms:
- Headlands and bays: formed when softer rock erodes faster than harder rock, leaving headlands.
- Cliffs and wave-cut platforms: Waves erode the base of a cliff, causing it to collapse and retreat, leaving a flat platform.
- Caves, arches, stacks, and stumps: Erosion widens cracks in cliffs, forming caves.
- Continued erosion can create arches, which eventually collapse to leave stacks and stumps.
How are depositional landforms such as beaches, spits, and bars formed?
- Deposition occurs when the sea loses energy and drops sediment.
- Beaches: formed by the accumulation of sand and pebbles from the constructive waves.
spits: formed when longshore drift deposits sediment along a coastline, extending out into the sea. - Bars: formed when a spit connects two headlands, cutting off a bay from the sea.
how does geology affect coastal landscapes?
- The type of rock(lithology) and its structure(such as the presence of joints and faults) influence erosion rates.
- Harder rocks like granite erode slowly, forming steep cliffs, while softer rocks like clay erode quickly, forming bays.
What is the impact of vegetation on the coast?
- Vegetation, such as grasses and mangroves anchor soil with roots.
- Reduces Erosion
- Sand dunes, for example, are often stabilised by plants like marram grass, which can withstand harsh coastal conditions.
how do human activities impact the coast?
- Human activities, such as coastal development, tourism, and industry, can accelerate erosion, disrupt ecosystems, and lead to coastal degradation.
- Structures like groynes and sea walls can also interfere with natural processes, sometimes worsening erosion elsewhere.
How does sea-level rise impact the coast?
- Flooding of low-lying areas
- Increased coastal erosion
- loss of habitats.
- Submergent features, such as rias and fjords, occur as land sinks or sea level rise.
What are the features of global coastal ecosystems?
Coral reefs
Mangroves
Sand dunes
Salt marshes
