Coasts - 2B.1 Flashcards
Coast definition
the land adjacent to the sea and is often heavily polluted and urbanised
Backshore definition
Above the high tide level and is only affected by waves during high tide and major storms
Foreshore definition
wave processes occurs between low and high tide marks
Nearshore definition
shallow water areas close to land and used exclusively for fishing, coastal trade and leisure
Offshore definition
The open sea
The coast is a system…
it has inputs, outputs and processes which are balanced and equal. Because they are in a dynamic equilibrium (ever changing, never in a constant state)
Coastal inputs
- people (human activity, coastal management)
- land (rock type and structure, tectonic activity)
- marine (waves, tides, storm surges)
- atmospheric (weather/climate, climate change, solar change)
Coastal outputs
- erosional landforms (arch, stack, stump, bay, headland)
- depositional landforms (tombolos, spits, beaches)
- different types of coast (coastal wetlands and sandy beaches)
Coastal processes
- deposition - dropping off of sediment
- transport - movement of sediment
- weathering - wearing away of material in situ
- erosion - wearing away of material
- mass movement - movement of surface material
What are coasts?
the narrow zone where the land and sea interact
Types of coastline: rocky vs coastal plains
This is the most straightforward type of classification
Rocky coastlines
cliffs, with visible rocks and break in the angle of the beach
Coastal plains
gentle and the edge of the littoral ones can be hard to distinguish. Often fins dunes on sandy beaches when they aren’t underwear and they give a hint about a boundary
Rocky cliff profiles: sub-aerial dominated
- most erosion is done by surface processes (wind, rain, rivers etc)
- cliff tends to be curved with accumulated debris at the base of the cliff and a little undercutting
Rocky cliff profiles: marine dominated
- most erosion is done by the sea
- abrupt transition from land to sea
- steep cliff with undercutting (wave-cut notch)
- little beach, mainly rocks revealed at low tide (wave cut platform)
Coastal plains
- low lying areas, generally containing sand dunes, marshes and wetlands
- form sue to a fall in sea level exposing what was a shallow continental shelf or due to accretion (build up) by material dropped by rivers
- dependant on a state of dynamic equal
Long term - geology
- classify - rocky, sandy, estuarine, concordant, discordant
- land characteristics
- lithology (rock type)
- structure (arrangement of rock units)
Long term sea level change
- classify - emergent and submergent coastline
- Caused by: Tectonic processes (lift sections of land = local sea fall. Land subsides = local sea rise) and Climate change (sea level rise - emerging from ice age and surface ice melts. Sea level fall - 90,000 years during glacials)
Short term - energy inputs
- receive energy from tectonic currents, mass movement, tides (ebb and flow over a 12-15 hour cycle), gravity, waves (main input)
- classify - high and low
advancing/retreating coastlines
- long term processes - emergent/submergent
- short term processes - erosion/deposition
Sediment inputs
- get sediment from tides, waves, wind (vary constantly), currents, mass movement, tectonic processes
- Added to a coastline (deposition), removed (erosion)
Eroding coastline
erosion > deposition
net loss of sediment
coastline retreats
deposition coastline
deposition > erosion
net gain of sediment
coastline advances
Littoral zone definition
the wider coastal zone including adjacent land areas and shallow parts of the sea just offshore
- exposed to the air at low tide and is under water at high tide
- the back shore and foreshore areas are where physical processes and the greatest amount of human activity occurs
