Paper 1 (2024) Flashcards
How can recurrence intervals be used in flood prediction and prevention?
Helps calculate probability of floods based on past events
Used to predict how often an event may happen
It is a probability often based on little data
Used to predict size as well as frequency
Predicts likelihood of volume
Can give consideration to where prevention takes place
Explain two ways a slope may be modified to reduce mass movement
Afforestation
Netting
Pining
Grading
Terracing
Shotcrete
Slope drainage channels
Gabions at base to stabilise slope vase
Describe a river levee
Raised banks along a river
Parallel to river channel
Usually composed of sediment
With coarser grained material nearer the river channel
May be an artificial feature
May be vegetated
Explain the formation of meanders and oxbow lakes
Starts from straight channels
Irregularities on the river bed cause turbulence
Production of alternating riffles and pools
Leading to thalweg swinging back and forth
Leading to helicoidal flow from outer/inner/outer banks
Erosion on outer bank (river cliff) and deposition on inner bank (slip off slope)
Sinuosity increases until river cuts through at high flows
Deposition at mouth of old channel
To leave an oxbow lake
Explain why not all incoming solar radiation reaches the surface of the Earth
Reflected by clouds
Absorbed by clouds
Scattered by dust, aerosols and air molecules
Absorbed by ozone
Explain the causes of precipitation
Evaporation is a requirement of most processes to produce moist air that can then undergo uplift, cooling, reaching dew point and condensation. Cooling by conduction can lead to the formation of dew. Growth of water droplets, collision theory and processes leading to hail or snow and the role of condensation nuclei
Explain the formation of an oxbow lake and lakes
Development of meander (erosion and deposition)
Low gradient (lateral erosion dominant)
Helicoidal flow (pools and riffles)
Increased sinuosity (narrowing the neck of meander)
Cut off during period of high discharge (new course)
Deposition (oxbow lake forms)
Oxbow lake infilled over time (evaporation)
Suggest reasons for different patterns of cloud cover
Orographic uplift. The air is forced to rise through the process of adiabatic cooling, condensation takes place. The temperature difference between land and sea causing air to cool. Cooler surface temperature leads to condensation. The evaporation over the ocean so moist air is carried towards islands or forms over sea. Rivers are a source of moisture leading to convection
Explain the differences between slides and flows
Internal displacement
Velocity of the movement in relation to other factors
Water content
Presence of a slip plane
Causes such as water content
Nature of movement
Differences on type of material
Geological structure
Describe how land/sea distribution affects the seasonal variation of temperature
The sea has higher thermal heat capacity than the land which means sea heats up more slowly in summer but loses heat more slowly too. Land areas in the summer heat up more quickly and so in those latitudes the isotherms are displaced poleward. Land heats more quickly but also cools more quickly. Therefore the sea has a moderating impact on temperatures, milder winters and cooler summers. Continental areas have higher summer temperatures and lower winter temperatures than areas close to the sea
Explain the formation of volcanic island arcs
Convergence of two oceanic plates
Heavier and denser plate subducts
Magma rises leading to oceanic underwater activity
The arc pattern of upwelling is related to the curvature of the Earths surface
Explain how changes in land use might cause a river to flood
Any land use change that will lead to increased flow to the river channel
Housing construction. Impermeable surfaces reduces infiltration, increases runoff and a flashy flood response
If trees are replaced by arable crops this diminishes infiltration and interception causing rapid runoff
Changing land use upstream is likely to increase flooding downstream
Explain the formation of snow
Evaporation to water vapour
If temperatures are cold enough vapour changes directly into small ice crystals
Ice and super cooled water droplets exist together
Water attracted to ice crystals which grow
Become heavier as updraughts move them through large clouds
If heavy enough they start to fall
Will remain as ice crystals if air temperature is low enough
If fall through moist air, melt around the edges and stick
Describe how through-flow occurs on slopes
After infiltration of water from the surface, percolation through the soil in a downslope direction parallel to the ground surface as a result of gravity. More permeable soils or steeper gradients have a faster through-flow
Describe and explain the formation of gorges
Gorges are steep side river valleys where river downcutting has exceeded lateral erosion
The headward extension of waterfalls creating a gorge as the fall retreats
River and mass movement processes also lead to steep slopes
Can also be formed by tectonic uplift or changes in sea level where the river is rejuvenated and rapid vertical erosion occurs to reach base level
Describe the atmospheric process of convection
As the sun heats the earths surface the air above it heats up and rises. If conditions allow this air can continue to rise, cooling as it does, forming clouds by condensation
Explain how fog can form
Radiation fog occurs in winter with clear skies and calm conditions. The land cooling overnight by thermal radiation cools air near the surface, reducing ability to hold moisture, allowing condensation
Advection fog occurs when moist, warm air from the sea passes over the colder land surface and is cooled
Valley fog forms when cold dense air settles into the lower valley, condensing and forming fog
Upslope fog forms when winds blow air up a slope, cooling and condensing
Describe and explain how energy is transferred in the atmosphere by wind belts
The main wind belts are the trade winds, westerlies and easterlies. These move from high to low pressure. The north/south westerly wind belts move energy from the equator via the subtropical air masses towards polar regions. When the ITCZ moves north the trade winds move north and heat to northern latitudes. Reverse when ITCZ moves south. Hot air rises at the equator and moves north and south with the ITCZ transferring heat. Winds travelling over oceans are affected by sea temperatures and ocean currents
Describe and explain the formation of volcanic island arcs
Formed by the subduction of one oceanic tectonic plate under another oceanic plate. Subduction leads to melting of the subducted plate and the magma then rises through the non-subducted plate to form a chain of volcanoes called a volcanic island arc. The movement of the plates cause the volcanic islands to curve
Explain why annual hydrograph’s might vary from year to year
Increase or decrease in temperature affecting runoff
Precipitation varying in amount and intensity
Land use changes affecting runoff
Human management strategies
Explain the enhanced greenhouse effect
The effect of a greenhouse gas which allows incoming shortwave radiation but absorbs outgoing longwave radiation leading to increased atmospheric temperatures. An increase in the amount of these gases as a result of industrial processes or other human activities
Explain how the mass movement process of heave may occur
Wetting and drying
Freezing and thawing
Soils expand when wet and contract on drying
During cold temperatures small ice crystals form in wet soil leading to expansion with contraction on thawing
Soils expand on freezing and contract on melting
Soil is lifted upwards and falls back downslope
Describe the main features of a braided river channel
Many separate channels
Eyots, some vegetated
Wide, flat and shallow main channel
Vertical banks
Visible sediment in the channels
Explain the formation of river cliffs
Formed on the outside of meanders
Where the velocity and energy are greatest with the thalweg swinging towards the banks
Erosion of the banks by hydraulic action and cavitation
Lead to further development of the river cliff
