Coasts Flashcards
Discordant Coastlines
Definition: Coastlines where rock structures meet the coast at an angle, perpendicular to oncoming waves.
Features: Alternating rock types leading to the formation of headlands and bays.
Example: Atlantic coasts.
Concordant Coastlines
Definition: Coastlines where rock structures run parallel to the coast.
Examples: Dalmatian and Haff coastlines.
Explain why coastal zone is a dynamic zone which undergoes rapid change
The coastal zone is considered a dynamic zone because it undergoes continual change, driven by factors like wave action and erosion, sea level rise, sediment transport, human intervention, and climate change.
Abrasion
Sediment and stones are picked up by the waves and wear away at the cliff/headland
Hydraulic action
This is the shear force of the waves forcing air at high pressure into cracks in the cliff. Over time this weakens the rock and causes the joint to widen
Corrosion
Weak acids in seawater dissolve the rock particles
Attrition
As rocks are moved around by the water they knock into each other becoming gradually smaller and rounder
Differential erosion
Differential erosion between sedimentary and igneous rocks is driven by variations in their resistance to weathering and erosion. Sedimentary rocks, like sandstone, often possess a weaker interlocking structure, making them more susceptible to rapid erosion, whereas igneous rocks, such as granite, typically have a stronger interlocking and crystalline structure, resulting in slower erosion rates. This discrepancy in erosion rates along coastal cliffs leads to the formation of wave-cut platforms. As softer sedimentary rocks erode more quickly than harder igneous rocks, a step-like profile develops in the cliff face. Over time, this process causes the retreat of the cliff and the creation of a flat, wave-cut platform at its base, where the more resistant igneous rock remains relatively intact while the softer sedimentary rock erodes away.
Freeze-Thaw Weathering
A type of mechanical weathering where water seeps into cracks in rocks, freezes, and expands. The expansion exerts pressure on the surrounding rock, causing the cracks to widen and eventually leading to the fragmentation of the rock.
Carbonation Chemical Weathering
A form of chemical weathering where carbon dioxide from the atmosphere or dissolved in water reacts with minerals in rocks, particularly carbonate minerals like limestone or marble, forming soluble compounds such as calcium bicarbonate. This reaction weakens the rock structure and leads to its dissolution.
Biological Weathering
As the plant grows the roots enter the cracks in the rock under the soil. As the plant and roots grow the roots cause the crack to get larger. Rock breaks away–> rock fall
Eustatic sea level change
A global change in sea level resulting from an actual fall or rise in sea level
Isostatic sea level change
Local changes in sea level resulting from the land rising or falling relative to the sea
Eustatic sea level rise
Eustatic sea level rise, driven by climate change-induced warming, leads to the melting of glaciers and ice caps. This increased volume of water in the oceans causes sea levels to rise globally. As a result, coastal areas experience inundation, leading to the formation of distinct landforms such as rias, characterized by drowned river valleys, and fjords, which are deep, glacially-carved coastal valleys
Isostatic Sea Level Fall
Conversely, as glaciers and ice caps melt, the weight previously borne by the land is redistributed as water, causing the land to rebound or rise isostatically. This rebounding land results in a relative decrease in sea level in areas where glaciers were present, rather than a global increase
Eustatic Sea Level Fall
A decrease in global sea levels due to factors such as cooling climate conditions or the growth of glaciers and ice caps. This reduction in ocean volume results in the exposure of previously submerged coastal areas and the formation of distinctive landforms such as emerged beaches and coastal terraces.
Mass movement
The downhill movement of material under the influence of gravity
Types of mass movement
Landslides
Rockfalls
Rockslides
Slumps
Creep
Landslides
Landslides are the movement of a mass of rock, debris, or earth down a slope. They can be triggered by various factors such as heavy rainfall, earthquakes, volcanic activity, or human activities like construction and deforestation.
Rockfalls
Rockfalls involve the sudden detachment and freefall of individual rocks or clusters of rocks from a steep cliff face. They often occur due to weathering and erosion processes, such as freeze-thaw cycles, which weaken the rock and make it susceptible to detachment.
Rockslides
Rockslides are similar to landslides but involve the rapid movement of large masses of rock down a slope. They typically occur on steep slopes and are often triggered by factors such as heavy rainfall, seismic activity, or the undercutting of slopes by rivers or coastal erosion.
Slumps
Slumps are a type of rotational mass movement where a mass of material moves downhill along a curved surface. They often occur in cohesive (clay-rich) soils and are characterized by the backward rotation of the mass as it moves downslope. Slumps are commonly triggered by heavy rainfall, saturation of the soil, or undercutting of slopes.
