Flashcards in Why are coastal landscapes different and what processes cause these differences? Deck (37)
what is meant by the littoral zone?
the wider coastal zone, including coastal land areas and shallow parts of the sea just off shore.
what can the littoral zone be divided into?
-coast: land adjacent to the sea, usually largely populated and urbanised
-backshore zone: above high tides and only effected in storms or exceptionally high tides
-foreshore: where processes occur between high and low tide marks
-nearshore: shallow water areas near to land (used in fishing, leisure and coastal trade)
-offshore: the open sea
what are the two main types that coasts can be divided into.
-rocky (or cliffed) coastlines with cliffs varying in height from few metres to hundred of metres.
-coastal planes (with no cliffs) where the land has gently sloped towards the sea across am area of deposited sediments, often in the form of sand dunes and mud flats.
what are the different coastal classifications?
-relative sea level change
how do formational processes impact the classification of a coast?
>primary coasts: dominated by land-based processes, such as deposition at the coast from rivers or new coastal land formed from Laval flows
>dominated by marine erosion or deposition processes.
how does relative sea level change impact the classification of a coast?
>emergent coasts: where the coast is rising relative to sea level, for example as a result of tectonic uplift.
>Submergent coasts: flooded by the sea either because of sea level rise or subsiding land.
how does tidal range impacts the classification of the coast?
tidal range varies hugely on the coastline meaning coasts can be:
-microtidal (tidal range of 0-2m)
-mesotidal (tidal range of 2-4m)
macrotidal (tidal range of 4m+)
how does wave energy effect the classification of the coats?
>low energy: sheltered coast with limited fetch and low wind speeds resulting in small waves
>high energy: exposed coasts, facing prevailing winds with long wave fetches resulting in powerful waves.
what kind of cliff face occurs after marine erosion?
cliffs tend to be steep, unvegetated with little debris at the bottom of the cliff
what are subaerial processes and what kind of cliffs do they leave behind?
subaerial processes include weathering processes (mechanical, chemical and biological), mass movement processes (landslides and rock falls) and surface run off erosion.
tend to leave behind shallower, curved slopes and lower reliefs; surface runoff erosion and mass movement are responsible for the cliff shape.
what are some geological structures?
jointing (fracture diving rock)
faulting (cracks in crust)
folding (overlapping to create ridges)
deformation (tilting and folding by tectonic activity)
strata (different layers of rock exposed by the cliff)
what are geological structures responsible for the formation of?
concordant coastlines: same rock type running parallel to the coast.
discordant coastlines: bands of rock that run perpendicular to the coast
describe a typical coastal recession
bedrock is made of igneous, sedimentary and metamorphic rocks which determines the erosional recession.
-erosion occurs at the foot of the cliff creating a notch. material above the notch collapses and is washed away. repeated collapsing causes the rock to retreat further away. the rate of this erosion depends on the strata of the rock (discordant or concordant)
what are some ways you can identify a coast?
-geology (rocky coast, muddy coast, sandy coast etc)
-changes to sea level.
what is wave refraction?
Friction with the sea bed as waves approach the shore causing the wave crest to become distorted or refracted as velocity is reduced (when wave approaches shoreline)
discordant coasts- why do headlands and bays change over time?
the effect the coast has on the wave crest
-in deep water wave crests (highest point on the wave) are parallel
-in bays, wave crests curve to fill the bay and wave height decreases.
-the straight wave crests refract, becoming curved, spreading out in bays and concentrating on headlands.
-the effect of wave refraction is to concentrate powerful waves at headlands (so greater erosion) and creates lower diverging wave crests in bays so reduces erosion.
what is a Dalmatian coast? and an example
When the valleys are flooded by the rise in sea level, the tops of the valleys remain above the surface of the sea and appear to be a series of islands that run parallel to the coastline.
Dalmatian coast in Croatia.
what are Anticlines and Synclines?
types of geological folds caused by tectonic compression. Anticlines forms crests and Synclines cause troughs.
what is a cliff profile?
the height and angle of the cliff face, plus its features such as wave-cut notches or changes in slope angles.
what are the two main features that determine the geology and the cliff profile?
1. the resistance to erosion of the rock
2. the dip (angle) of rock strata in relation to the coastline
what are some cliff profiles you may find **** tweak from book ****
-horizontal dip (vertical or near vertical profile with notches reflecting strata that are more easily eroded)
-seaward dip high angle (sloping, low-angle profile with one layer facing the sea; vulnerable to rock-slides)
-seaward dip low angle (profile may exceed 90˚ producing areas of overhanging rock; very vulnerable to rock falls.
-landward dip (steep profile on 70-80˚ and producing very stable cliffs with reduced rock falls.
what are other geological features that influence cliff profiles and rate of erosion?
-faults (major fractures in rock caused by tectonic forces)
-joints (divides strata up into blocks of regular shape)
-fissures (much smaller cracks that bring about weaknesses in the rock)
-folded rocks (often heavily fissured or jointed meaning they are more easily eroded)
what are micro-features?
small-scale coastal features such as caves and wave-cut notches which form part of a cliff profile
what is meant by coastal recession? and what is the key influence of this erosion?
how fast a coastline is moving inland
lithology (sedimentary igneous and metamorphic rock)
describe igneous rock and give examples
examples: granite, basalt and dolerite
VERY SLOW- erosion rate of less than 0.1 cm annually
they're crystalline meaning the interlocking crystals make for strong, hard and resistant rock
often have few joints, so there is limited weakness that erosion can exploit
describe Metamorphic rocks and give examples
examples: slate, schist, marble
SLOW- erosion rates of 0.1-0.3 cm annually
crystalline metamorphic rock are resistant to erosion. many metamorphic rocks exhibit features called foliation when all the crystals are orientated in one direction, which produces a weakness. metamorphic rocks are often folded and heavily fractured forming weaknesses that erosion can exploit
describe sedimentary rocks and give examples
examples: sandstone, limestone, shale
MODERATE TO FAST- erosion rate pf 0.5-10 cm annually
most sedimentary rocks are clastic (broken up and older) and eroded faster than crystalline igneous and sedimentary rocks. geologically young sedimentary rocks tend to be weaker and rocks with many bedding planes and fractures are often most vulnerable to erosion.
what is unconsolidated material?
sediment that has not been cemented to form solid rock, a process known as lithification
what is the difference between clastic or crystalline rocks?
clastic rocks consist of sediment particles cemented together.
crystalline rocks are made up of interlocking mineral crystals.