Geomorphic Processes In Coastal Landscapes

Question 1

How are coastal landscapes developed

Answer 1

Key idea ⮕ Coastal landforms develop due to a variety of interconnected climatic and geomorphic processes.

Question 2

Geomorphic processes

Answer 2

-Weathering (Physical or mechanical, Chemical, Biological)
-Mass movement (Rock fall, Slides)
-Erosion (Wave processes)
-Transportation (Wave processes)
-Deposition (Wave processes)

Question 3

Weathering

Answer 3

-Physical or mechanical
-Chemical
-Biological

Question 4

Weathering definition

Answer 4

definition
Energy used to produce physically or chemically altered materials from the surface or near surface rock. In coastal environments some types of weathering are particularly significant and influence the formation of coastal landforms.

Question 5

Physical or mechanical weathering

Answer 5

The breakdown of rock is largely achieved by physical weathering processes that produce smaller fragments of the same rock. No chemical alteration takes place during physical weathering. By increasing the exposed surface area of the rock, physical weathering allows further weathering to take place.
In many coastal landscapes, such as western Europe, the presence of the sea results in the moderation of temperatures and so air temperatures may seldom drop below 0ºC, reducing the extent of fluctuations and rendering some of the processes ineffective

Question 6

Freeze thaw physical weathering

Answer 6

Water enters cracks/joints and expands by nearly 10 per cent when it freezes. In confined spaces this exerts pressure on the rock causing it to split or pieces to break off, even in very resistant rocks.

Question 7

Pressure release physical weathering

Answer 7

When overlying rocks are removed by weathering and erosion, the underlying rock expands and fractures parallel to the surface. This is significant in the exposure of sub-surface rocks such as granite and is also known as dilatation. The parallel fractures are sometimes called pseudo-bedding planes

Question 8

Thermal expansion physical weathering

Answer 8

Rocks expand when heated and contract when cooled. If they are subjected to frequent cycles of temperature change then the outer layers may crack and flake off. This is also known as insolation weathering, although experiments have cast doubts on its effectiveness unless water is present.

Question 9

Salt crystallisation physical weathering

Answer 9

Solutions of salt can seep into the pore spaces in porous rocks. Here the salts precipitate, forming crystals. The growth of these crystals creates stress in the rock causing it to disintegrate. Sodium sulphate and sodium carbonate are particularly effective, expanding by about 300 per cent in areas of temperatures fluctuating around 26-28ºC.

Question 10

Chemical weathering

Answer 10

The decay of rock is the result of chemical weathering, which involves chemical reactions between moisture and some minerals within the rock. Chemical weathering may reduce the rock to its chemical constituents or alter its chemical and mineral composition. Chemical weathering processes produce weak residues of different material that may then be easily removed by erosion or transportation processes.

Question 11

Oxidation chemical weathering

Answer 11

Some minerals in rocks react with oxygen (O2), either in the air or in water. Iron is especially susceptible to this process. It becomes soluble under extremely acidic conditions and the original structure is destroyed. It often attacks the iron-rich cements that bind sand grains together in sandstone.

Question 12

Carbonation chemical weathering

Answer 12

Rainwater combines with dissolved carbon dioxide from the atmosphere to produce a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate, which is soluble. This process is reversible and precipitation of calcite happens during evaporation of calcium rich water in caves to form stalactites and stalagmites.

Question 13

Solution chemical weathering

Answer 13

Some salts are soluble in water. Other minerals, such as iron, are only soluble in very acidic water, with a pH of about 3. Any process by which a mineral dissolves in water is known as solution, although mineral specific processes, such as carbonation, can be identified.

Question 14

Hydrolysis chemical weathering

Answer 14

This is a chemical reaction between rock minerals and water. Silicates combine with water, producing secondary minerals such as clays. Feldspar in granite reacts with hydrogen in water to produce kaolin (china clay).

Question 15

Hydration chemical weathering

Answer 15

Water molecules added to rock minerals create new minerals of a larger volume. This happens when anhydrite takes up water to form gypsum. Hydration causes surface flaking in many rocks, partly because some minerals also expand by about 0.5 per cent during the chemical change because they absorb water.

Question 16

Biological weathering

Answer 16

Biological weathering may consist of physical actions such as the growth of plant roots or chemical processes such as chelation by organic acids. Although this, arguably, does not fit with the precise definition of weathering, biological processes are usually classed as a separate type of weathering.

Question 17

Tree roots biological weathering

Answer 17

Tree roots grow into cracks or joints in rocks and exert outward pressure. This operates in a similar way and with similar effects to freeze-thaw. When trees topple, their roots can also exert leverage on rock and soil, bringing them to the surface and exposing them to further weathering. Burrowing animals may have a similar effect. This may be particularly significant on cliff tops and cliff faces.

Question 18

Organic acids biological weathering

Answer 18

Organic acids produced during decomposition of plant and animal little cause soil water to become acidic and react with some minerals in a process called chelation. Blue-green algae can have a weathering effect, producing a shiny film of iron and manganese oxides on rocks. On shore platforms, molluscs may secrete acids which produce small surface hollows in the rock.

Question 19

Wave processes

Answer 19

-Erosion (Abrasion (or corrasion), Attrition, Hydraulic action, Pounding, Solution (or corrosion))
-Transportation (Solution, Suspension, Saltation, Traction)
-Deposition

Question 20

Wave processes definition

Answer 20

Waves are a source of energy in coastal landscape systems, and when they break onshore, the energy can be expended through geomorphic processes to shape landforms. They can also supply material to the system in the form of sediment, which is either deposited in, or transported within, the coastal system.

Question 21

Erosion (waves processes) definition

Answer 21

Breaking waves are able to erode the coastline with a range of processes.

Question 22

Abrasion (or corrasion) (Erosion (waves processes))

Answer 22

When waves armed with rock particles scour the coastline; rock rubbing against rock

Question 23

Attrition (Erosion (waves processes))

Answer 23

Occurs when rock particles, transported by wave action, collide with each other and with coastal rocks and progressively become worn away. They become smoother and more rounded as well as well as smaller, eventually producing sand.

Question 24

Hydraulic action (Erosion (waves processes))

Answer 24

Occurs when waves break against a cliff face, and air and water trapped in cracks and crevices becomes compressed. As the wave recedes the pressure is released, the air and water suddenly expands and the crack is widened. The average pressure exerted by breaking Atlantic waves is 11,000 kg per m³.

Question 25

Pounding (Erosion (waves processes))

Answer 25

Occurs when the mass of a breaking wave exerts pressure on the rock causing it to weaken. Forces of as much as 30 tonnes per m² can be exerted by high-energy waves.

Question 26

Solution (or corrosion) (Erosion (waves processes)

Answer 26

Involves dissolving minerals like magnesium carbonate minerals in coastal rock. However, as the pH of sea water is invariably around 7 or 8 this process is usually of limited significance unless the water is locally polluted and acidic. Even then, only coastal rocks containing significant amounts of soluble minerals are likely to be affected by this.

Question 27

Transportation (waves processes)

Answer 27

-Solution
-suspension
-Saltation
-Traction

Question 28

Transportation (waves processes) definition

Answer 28

Waves, as well as tides and currents, can move material shorewards in a variety of ways.

Question 29

Solution (Transportation (waves processes))

Answer 29

Minerals that have been dissolved into the mass of moving water. This type of load is invisible and the minerals will remain in solution until water is evaporated and they precipitate out of solution.

Question 30

Suspension (Transportation (waves processes))

Answer 30

Small particles of sand, silt and clay can be carried by currents; this accounts for the brown or muddy appearance of some sea water. Lager particles can also be carried in this way, perhaps during storm events.

Question 31

Saltation (Transportation (waves processes))

Answer 31

This is a sense of irregular movements of material which is too heavy to be carried continuously in suspension. Turbulent flow may enable sand-sized particles to be picked up (entrained) and carried for a short distance only to drop back down again. Similarly, other particles may be dislodged by the impact, allowing water to get beneath them and cause entrainment.

Question 32

Traction (Transportation (waves processes))

Answer 32

The largest particles in the load may be pushed along the sea floor by the force of the flow. Although this can be called rolling, again the movement is seldom continuous. Large boulders may undertake a partial rotation before coming to rest again.

Question 33

Deposition (waves processes)

Answer 33

Material is deposited when there is a loss of energy caused by a decrease in velocity and / or volume of water. Depositional tends to take place in coastal landscape systems that follow a number of traits:
-Where the rate of sediment accumulation exceeds the rate of removal
-When waves slow down immediately after breaking
-At the top of the swash, where for a brief moment the water is no longer moving
-During the backwash, when water percolates into the beach material
-In low-energy environments, such as those sheltered from winds and waves, e.g. estuaries.

Question 34

Settling velocity deposition

Answer 34

The velocity at which sediment particles are deposited. The larger and heavier particles require more energy to transport them. As flow velocity decreases, the largest particles being carried are deposited first and so on, sequentially until the finest particles are deposited (see image).