PAL Coasts

Created by

Niki Patel

Cards (150)

What is the littoral zone?
Coastal zone in which sediments are moved around between the land, beach and sea
What does the littoral zone contain?
Coastal sediments (pebbles and sand particles) that are moved by waves, currents and tides, which is from highest sea level line (linked to high tides and storm waves) to shallow offshore waters (where the base of a wave first encounters friction with the sea bed)
What is the backshore?
Area sitting above high tide level. Coastal processes only affect the backshore when there is an extreme weather event, such as a storm
What is the foreshore?
Marks the zone between the high and low tide marks. Many wave processes take place here
What is the nearshore?
An area just off the coastline, consisting of shallow sea water
What is the offshore?
Open sea
What is the effect of geology?
Can create rocky, sandy and estuarine coasts, as well as concordant and discordant coasts
What is the effect of energy?
Levels of energy can create high or low energy coastlines
What is the effect of balance?
Between erosion and deposition, creating either erosional or depositional coasts
What is the effect of sea level change?
Creates either emergent or submergent coastlines. More broadly, we can classify coastlines into rocky and coastal plains
What are rocky coastlines?
Vary in height, formed from hard rock, dominated by marine and sub-aerial processes
What are coastal plains?
Low-lying, low-relief, contain wetland and marshlands, poor drainage, flatter landscapes
What are concordant coastlines?
Generated when rock strata run parallel to the coastline
What are discordant coastlines?
Form when different rock strata intersect the coast at an angle, so geology varies along the coastline
What type of coasts are bays and headlands associated with?
Discordant
What are bays and headlands?
When alternate bands of hard and soft rock erode at right angles. Softer rock erodes more rapidly, forming a bay. Harder rock is more resistant and juts out as a headland. Headlands are vulnerable to wave refraction. Coves form on concordant coastlines. Once waves erode through harder out rock, softer rock begins to erode
What is wave refraction?
The bending of a wave as it spreads over different depths along a coast
How is a dalmatian coastline formed?
Where geology creates valleys parallel to the coast so that when the sea level rises, a series of elongated island remain offshore
What is a haff coastline?
Where sand dunes and spits run parallel to the coastline
What is lithology?
Refers to physical characteristics of particular rocks
What are the 3 main types of rocks?
Igneous, sedimentary, and metamorphic, as well as unconsolidated (loose) material such as clau
What does the type of rock influence?
Permeability which affects rates of erosion, affecting features formed
What are igneous rocks?
Granite, diorite, basalt
Crystalline, resistant, impermeable
What are sedimentary rocks?
Limestone, chalk, sandstone, shale
Formed in strata
Jointed sedimentary rocks (limestone and sandstone) are permeable
Other sedimentary rocks (chalks) have air spaces between their particles so are porous
Shale is fine and compacted making it impermeable
What are metamorphic rocks?
Marble, schist, slate
Very hard and resistant
Impermeable
What are unconsolidated materials?
Glacial till or boulder clay e.g on Holderness coast
Loose and easily eroded
If compacted, particles can stick together and form an impermeable layer within a cliff strata
What is coastal morphology?
Refers to the shape and form of coastal landscapes and their features
What is coastal morphology determined by?
Lithology or physical characteristics of the rock
Relief and slope (cliff profiles)
Rock type and its permeability
How resistant to erosion the rock is
What characteristics contribute to geological structure?
Strata - layers of rocks and their positioning, often with many different types
Bedding planes - splits in rocks, creating horizontal blocks
Joints - splits in rocks, creating vertical blocks
Folds and dips - deformations in rock due to tectonic activity; susceptible to pressure
Faults - weaknesses in rock geology that is susceptible to erosion
What is a cliff profile?
Cross section of a cliff from a low water mark to top of cliff
What causes different structures to emerge on coastlines?
Interactions between geological structures and lithology
What is a horizontal dip?
Uniform horizontal layers and bedding planes can produce steep sided cliffs. Notches will appear in the cliff face
What is a seaward dip, high angle?
Where dipping is steep, rockslides become common due to large slabs of rock sliding down
What is a seaward dip, low angle?
Joints opened by weathering and pressure releases slabs to form cliffs that dip seaward
What is a landward dip?
Bedding planes dipping inland, producing steep and stable cliffs
What affects coastal recession?
Geology and lithology affect rates of erosion and speed at which coastline recedes and retreats
Weathering and mass movement processes also affect rate of erosion
Most cliffs are formed of more than one rock type and will produce complex cliff profiles
What is the role of vegetation?
Stabilise sediment
How plants stabilise sediment?
Plants growing in sediment provide an extra layer of protection, so the surface of sediment is not as exposed
Plants protect sediment from aeolian (wind) erosion by reducing wind speed due to friction with vegetation and binding sediment together
What do plants growing in coastal and estuarine environments tend to be?
Halophytic (salt tolerant) and xerophytic (drought tolerant)
Outline salt marshes
Form in sheltered, low energy estuarine environments. Rivers and tides deposit silt and mud, causing mudflats to develop. These are colonised by vegetation that are halophytic. Vegetation growth and deposition of silt and mud over time causes a salt marsh to emerge