Coastal Landscapes and Change EQ1 Flashcards
What is the littoral zone?
The area of shoreline where land is subject to wave action. It’s subdivided into offshore, nearshore, foreshore and backshore.
What is the offshore?
The area of deeper water beyond the point at which waves begin to break. Friction between waves and the sea bed may cause some distortion of the wave shape.
What is the nearshore?
The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the waves sufficiently and causes it to break (breaker zone).
What is the foreshore?
The area between the high tide and low tide water marks.
What is the backshore?
The area above the high tide mark, affected by wave action only during major storm events.
What are the different types of coastal landscapes formed by the littoral zone?
- Rocky (cliffed coastline)
- Sandy coastline
- Estuarine coastline
What is the characteristics of a rocky coastline and where does it form?
Rocky coastlines usually form in areas with reistant geology, in a high energy environment were erosion is greater then deposition.
It creates areas of high relief varying from a few metres to hundred of meters
E.g. chalked cliffs at Flamborough Head Yorkshire
Where do Sandy coastlines form, and what are their characteristics?
Sandy coastlines form in areas of low resistant geology, low energy environments (constructive waves) were deposition is greater than erosion.
They are areas of low relief with sand dunes and beaches that are flatter.
Where do Estuarine coastlines form, and what are their characteristics?
They form in river mouths, low energy environments, less resistant rock where deposition is greater than erosion.
They are areas of low relief wiht salt marshes and mudflats.
Why is the littoral zone a dynamic zone of rapid change?
It can be described as a dynamic zone as
Short term > there are constantly changing inputs, through flows and outputs of energy and material. (Weather and high and low tide variations due to lunar month)
Long term > sea level variations due to climate change
How can coast be classified using long term criteria?
- geology (Rocky, Sandy or estuarine)
- changes in sea level (emergent or submergent)
How can geology help to classify coastlines?
Geology is all the characteristics of land such as lithology (rock type) and structure. It can be used to classify coastlines as
- rocky, sandy or estuarine
- concordant or discordant
How can sea level rise be used to classify coastlines.
Sea level change can be used to classify coasts as
- emergent or submergent
What are the short term criteria that can be used to classify a coastline?
- input from rivers
- inputs from waves
- inputs from tides
How can energy input be used to classify coastlines.
Coasts receive energy inputs mainly form waves but also from currents, rivers and gravity. It can be used to classify a coast as
- high energy or low energy
What is a high energy coastline?
- exposed coasts
- facing prevailing winds
- long wave fetches
- powerful destructive waves
What is a low energy coastline?
- sheltered coasts
- limited fetch
- low wind speeds
- small constructive waves
How can inputs from tides be used to classify a coastline?
Tidal range varies hugely in coastlines meaning coasts can be classified as
- Microtidal (tidal range between 0-2 metres)
- mesotidal (tidal range of 2-4 metres)
- macrotidal (tidal range greater than 4 m)
What are rocky coastlines?
Rocky coastlines are coastlines where solid rock is dominant. They occupy 1,000 km of the UKs coastline. Cliffs can vary in height from high relief areas to low relief areas.
Where do Rocky coastlines normally form?
Rocky coastlines from in areas of
- resistant geology(their lithology and structure means they erode and weather slowly)
- high energy environments (erosion is greater then deposition)
What are coastal plain landscapes?
Coastal plain landscapes include both Sandy and Estuarine coastlines. Their littoral zones consists of sand dunes, beaches, mudflats and salt marshes.
What are the characteristics of a coastal plain?
- relatively flat, low relief areas adjacent to the sea
- often contain freshwater wetlands and marshes due to the poor drainage of the flat landscape
- littoral zones in composed of sand dunes, mudflats and salt marshes.
Where do coastal plain landscapes form?
- low energy environments (deposition is greater than erosion) net accumulation of sediment
- low relief
How do coastal plains form?
They forms through the coastal accretion (continuous net deposition of sediment) from
- offshore sources (transported by waves, tides or current)
- terrestrial sources (rivers, glaciers, wind or mass movement)
They can also be formed through sea level change (falling sea level)
Why are coastal plains described and a dynamic equilibrium?
As there is a balance in the forces of
- deposition of sediment from river systems inland and deposition of sediment from offshore and longshore sources
- erosion by marine action at the coast
What two coastlines do geological structure form?
- concordant
- discordant
What is a concordant coastline?
When rock starts run parallel to the coast.
What are discordant coastlines?
When different rock strata intersects the coasts at an angle so geology varies along the coastline.
What does geological structure include?
It refers to the arrangement of rocks in 3D. It includes
- strata (differnt layers of rock within an area and how they relate to each other)
- deformation (degree of rock units that have been deformed by tectonic activity)
- faulting (major fractures)
What is morphology?
The shape of the landscape features. It is influenced by geological structure (headlands and bays, Dalmatian and Haff).
What landforms are formed along a concordant coastline?
- Dalmatian coastline
- Coves
- Haff coastlines
How does coves form?
At a concordance coastline with hard rock (limestone) forming a protective layer parallel to the sea, with a soft rock behind (clay).
1. The hard rock erodes very slowly retreating inland though undercutting
2. At points were the hard rock is weakened (faults/fractures) erosion can break through exposing the soft rock to rapid erosion.
3. This creates a serie of coves
E.g. Lulworth Cove on the Souht Dorset Coast (Portland limestone is the hard rock and Wealden clay the soft).
How do Dalmatian coast form? and example
At a concordant coastline, past tectonic forces has created folded ridges anticlines and down folded valleys synclines aligned parallel to the coast. Sea level rise has flooded the synclines producing lines of narrow island.
E.g. In Croatia on the Adriatic Sea (tectonic forces were the collision of the African and Eurasian plates)
How do Haff coastlines form?
On a concordant coastline Haff coasts forms through
1. Deposition produces up consolidated geological structures topped with sand dunes run parallel to the coastline just offshore
2. The sand ridges formed bars across some bays and river mouths, creating a lagoon behind filled with trapped water.
E.g. On the Southern fringes of the Baltic Sea