Geography CP&L: Systems & Processes Flashcards
What is Mass Movement?
The downhill movement of material under the influence of gravity known as mass movement. It can range from being extremely slow - less than 1cm a year (e.g. soil creep - to really fast (e.g. rockfalls and landslides). Mass movement at the coast is common.
Examples of Mass movement:
- Soil creep
- Solidification
- Earth Flow
- Mud Flow
- Slumping
- Landslide
- Rockfall
Why is Upwelling beneficial?
(Currents)
Subsurface water that rises to the surface as a result of upwelling is typically colder, rich in nutrients, and biologically productive. Therefore, good fishing grounds typically are found where upwelling is common. For example, the rich fishing grounds along the west coasts of Africa and South America are supported by year-round coastal upwelling.
Wind Upwelling
(Currents)
Winds blowing across the ocean surface often push water away from an area. When this occurs, water rises up from beneath the surface to replace the diverging surface water. This process is known as “upwelling.” Upwelling occurs in the open ocean and along coastlines. The reverse process, called down welling, also occurs when wind causes surface water to build up along a coastline. The surface water eventually sinks toward the bottom.
Longshore Drift
(Currents)
Waves do not typically approach the beach perfectly parallel to the shoreline. rather, they arrive at a slight angle, called the “angle of wave approach.” When a wave reaches a beach or coastline, it releases a burst of energy that generates a current, which runs parallel to the shoreline. This type of current is called a “longshore current”.
Wave Refraction
(Wind & Waves)
Wave refraction is the distortion of wave fronts as they approach and indented shoreline. This causes energy to be concentrated at headlands and dissipated in bays. Consequently, features of erosion and deposition are created. As the wave front nears the the coast, the base of the wave begins to slow due to friction caused by shallower water in front of the headland. The Bathymetry of the sea floor generally flowers the shape of the coastline and therefore directly in front of the headland the sea floor is shallower. As the base of the wave slows, the wave height increases and the wave length shortens. The section not the wave front still in deep water has not slowed down as the base of the wave has not yet been significantly affected by friction. This causes the wave front to start to bend. This called wave refraction. As the waves move closer to the headland, the ‘bending’ becomes more produced as the section of the wave front in front of the headland continues to slow down whereas the section of the wave front in front of the bay is still be to travel at it’s original speed.
Thermohaline circulation
(Ocean Currents)
- Near the poles, the water is chilled. It also gets saltier because as ice is formed, more salt is left in the ocean.
- This cold salty water is denser and sinks. As it sinks, surface water moves in to replace it creating a current.
- The dense cold water moves down towards the equater when it is warmer and then moves back up towards the pole.
- This movement drives global nutrient cycles and carbon dioxide cycles.
Spring Tides
(Tides)
Moon and sun are aligned
Gravitational pull of sun and moon are combined = highest tide, lowest low tide & high tidal range
Every 14-17 days
Neap tides
(Tides)
Moon and sea are at a right angle
Gravitational pull of sun and moon counteract each other = lowest high tide and highest low tide, low tidal changes
Every 14-17 days
Tidal Range
(Tidal)
Macrotidal - more than 4m
Mestidal - 2 to 4m
Microtidal - less than 2m
Tidal Bore
(Tidal)
Occurs along coast where a river empties into an ocean or sea. A tidal bore is a strong tide that pushes up the river, against the current.
Physical Weathering
(Sub-aerial Weathering)
The disintegration of rock without any significant change in the chemical or mineral composition of the rock e.g. Freeze Thaw Weathering, Salt Crystallisation
Freeze Thaw Weathering
(Physical Weathering)
- Water collects in between cracks and joints
- Water freezes into ice exterior pressure on rock
- Rock disintegrates into large boulders
Salt Crystallisation
(Physical Weathering)
-Water collects in between cracks
- Evaporation leaves salt crystals behind
- Rocks eventually break apart
Chemical Weathering
(Sub-aerial Weathering)
The decomposition of rocks by the action of air, water or acid
Oxidation
(Chemical Weathering)
Causes rocks to disintegrate when the oxygen dissolved in water reacts with some rock minerals, forming oxides and hydroxides. It especially affects ferrous, iron-rich rocks, and is evident by a brownish or yellowish staining of the rocks surface.
Hydration
(Chemical Weathering)
A form of chemical Weathering in which chemical bonds of the mineral are changed as it interacts with water. In the process of hydrolysis, a new solution (a mix of two or more substances) is formed as chemicals in rock intent with water.
Carbonation
(Chemical Weathering)
Occurs where carbon dioxide dissolved in rainwater makes a weak carbonic acid (H2CO2) reacts with calcium carbonate (CaCO3) in rocks like limestone and chalk to create calcium bicarbonate (Ca(HCO3)2) which the dissolves easily in water. Carbonation is more effective in locations with cooler temperatures as this increases the amount of carbon dioxide that is dissolved in the water.
Solution
(Chemical Weathering)
Is the main chemical process and it combines with erosion to produce many distinctive features.
Biological Weathering
(Sub-aerial Weathering)
The breakdown of rocks and minerals as a result of the activities of plants, animals and micro-organisms.
Marine Organisms
(Biological Weathering)
Some marine organism, such as the piddock (a shellfish), have specially adapted shields that enable them to drill into solid rock. They are particularly active in areas with chalk geology where they can produce a sponge-like rock pitted with holes.
Seaweed
(Biological Weathering)
Seaweed attached itself to rocks and the action of the sea can be enough to cause swaying seaweed to prise away lose rocks from the seafloor.
Algae
(Biological Weathering)
Algae secretes chemicals capable of promoting solution
Animals
(Biological Weathering)
Animals can weaken cliffs as they burrow or dig into them, such as rabbits or some cliff-nesting birds
What is weathering?
Is when material is broken down is situ, remaining in or near its original position
Hydraulic action
(Marine Processes of Erosion)
THe sheer force of the water impacting upon rocks (without debris). Steep waves have considerable energy. When they break as they hit the foot of the cliffs or seas walls, they may generate shock - waves of up to 30 tonnes per square metre.
Abrasion
(Marine Processes of Erosion)
This is the wearing away of the cliffs by sand, shingle (pebbles) and boulders hurled against them by the waves. In addition, the beach material may be rubbed against the base of the cliff by the swash and backwash resulting in a smooth, polished abrasion notch at the base of the cliff.
Attrition
(Marine Processes of Erosion)
Wave bash pebbles into each other making them smaller and more rounded in shape
Solution
(Marine Processes of Erosion)
This includes the dissolving of limestone by carbonic acid in the sea water and the corrosion of other rocks by the action of the salt in the sea water
Soil Creep
(Mass Movement)
Extremely low form of movement of individual soil particles downhill. The precise mechanism of movement often involves partials rising towards the groundstroke due to wetting or freezing and the then returning vertically to the surface in response to gravity as the soil fires out or thaws. The zigzag movement is similar to that of longshore drift. Soil Creep cannot be seen operation but its action can be implied by the formation of shallow terracettes, the build-up of soil on the upslope side of walls and the bending of tree trunks.
Mudflows
(Mass Movement)
A mudflows involves earth and mud flowing downhill, usually over unconsolidated or weak bedrock such as clay, often after heavy rainfall. Water gets trapped within the rock, increasing pore water pressure, which forces rock participles apart and leads to slope failure. Pore water pressure is a form of energy within the slope system and it is an extremely important factor in determining slope instability. Mudflows are often sudden and fast-flowing so can represent a significant natural hazard.
Landslide
(Mass Movement)
A landslide involves a block of rock moving very rapidly downhill along a planar surface (a slide plane), often a bedding planes that is roughly parallel to the ground surface. Unlike a mudflows, the moving block of material in a landslide remains largely intact. Landslides are frequently triggered by earthquakes or very heavy rainfall, when the slip surface becomes lubricated and friction is reduced. Landslides tend to be very rapid and pose a considerable threat to people and property. In 1993, 60m of cliff slid into the beach near Scarborough in North Yorkshire taking with it part of the Holbeck Hall Hotel
Rockfall
(Mass Movement)
A rockfall involves the sudden collapse or breaking away of individual rock fragments (or a block of rock) at a cliff rock. They are most commonly associated with steep or vertical cliffs in heavily jointed and often quite resistant rock. A rockfall is often triggered by mechanical weathering (particularly freeze-thaw) or an earthquake. Once broken away from the source, rocks fall or bounce down the slope to formscree (also know as talus) at the foot of the slope. Scree often forms a temporary store within the coastal system, with material gradually being removed and transported elsewhere by the sea. When this occurs the scree forms an input into the sediment cell.
Runoff
(Mass Movement)
Runoff is a good illustration of the link between the water cycle and the coastal system. When Overland flow occurs down a slope or cliff face, small particles are moved downslope to enter the literal zone, potentially forming an input into the sediment cell. Runoff can be considered a type of flow that transfers both water and sediment from one store (the rock face) to another (a beach/the sea). Toxic chemicals can contaminate stormwater and cause threats to coastal ecosystems, illustrating yet another link between natural systems.
Solifluction
(Mass Movement)
Essentially, solifluction is similar to soil creep but specific to cold periglacial environments. In the summer, the surface layer of soil thaws out and becomes extremely saturated because it lies on top of impermeable frozen ground (permafrost). Known as the active layer, this sodden soil with its blanket of vegetation slowly moves downhill by a combination of heave and flow. Solifluction characteristically forms features called solifluction lobes.
Landslip or slump
(Mass Movement)
A landslip or slump differs from a landslide in that its slide surface is curved rather than flat. Landslip commonly occur in weak and unconsolidated clays Nd sands, often when permeable rock overlies impermeable rock, which causes a build-up of pore water pressure. Landslips or slumps are characterised by a sharp break of slope and the formation of a scar. Multiple landslips can result in a terraced appearance on the cliff face.
Aeolian Transport
Sediment can also be transported by the wind. Processes of transportations and deposition by the wind are called Aeolian processes. This is important in the formation of sand dunes.
If prevailing winds are blowing on shore and there is a supply of dry sediment, Aeolian transport will occur.
Suspension
(Aeolian Transport)
Sediment is picked up and carried by the wind. Makes up 1% of movement
Salutation
(Aeolian Transport)
Sediment bunches along as it is repeated picked up and dropped by the wind. Makes up 95% of movement.
Creep
(Aeolian Transport)
Sediment grains collide and push each other along. Makes up 4% of movement.
Deposition
Deposition occurs when the velocity of the water or wind falls below a critical value for particular size of particle and can therefore no longer be transported.
This critical value helps to explain why higher energy coastlines have pebbled beach (because the waves have enough energy to move them) and lower energy coastlines have sandy beaches (because the waves only have enough energy to move smaller particles).
