4 Markers Flashcards
(14 cards)
Explain the concept of dynamic equilibrium in relation to the water cycle.
- Dynamic equilibrium refers to the tendency towards a natural state of balance within the hydrological cycle.
- The hydrological cycle is a closed system as no water enters or leaves; it is recycled within the system.
- The dynamic equilibrium can be easily upset by extreme events such as storms or droughts.
- Human activity can disrupt the dynamic equilibrium, e.g., by modifying a drainage basin.
- This disruption to the equilibrium can result in events such as flooding.
- Such extreme events or human interference cause sudden changes in the state of the system, disrupting the dynamic equilibrium, as seen with flooding.
Explain the role of cryospheric change in the water cycle.
Cryospheric change has a significant impact on sea levels (1). The cryosphere is a major store of water (1). In a period of cooling (glacial period) the cryosphere will grow in size (1). This is because the water cycle is slowed considerably as the ice restricts the return of the water to the sea and ocean (d). In a period of warming the cryosphere will add water to the cycle (1). As the water cycle restarts more of the ice melts and returns water to the sea (d). This increased the size of ocean store causing sea levels to rise through increased volumes of water (1) and thermal expansion (d).
Outline flows within the water cycle operating on a hill slope.
Surface runoff occurs when water runs directly over the ground (1). This may occur if the soil is saturated (or flow over impermeable surfaces). (1)(d) Infiltration occurs when the water moves from the surface and then down through the soil (1) until it reaches the groundwater or an impermeable layer in the soil (1) (d). Throughflow occurs when, under the force of gravity, water moves downslope through the soil until it reaches a water body (1). This movement is usually very slow due to the frictional effect of the soil particles (1) (d). Groundwater flow is the movement of water through permeable rock under the force of gravity (1). This is the slowest flow of water on a hillslope (1) (d).
Outline the process of decomposition in the carbon cycle.
Decomposition refers to the breakdown / decay of organic matter by bacteria or fungi (1). Animals (such as worms), bacteria and fungi are collectively termed decomposers (1)(d). During decomposition carbon dioxide is released (1). Most of the carbon released into the atmosphere is as a result of decomposition (1)(d). Decomposition is heavily temperature dependent (1). Warmer temperatures are characterised by much higher rates of decomposition as there is more microbial activity (1)(d). However, the presence of water is an equally key component in the rate of decomposition and the release of carbon (1)(d).
Explain the concept of carbon sequestration.
This process involves natural and/or artificial methods by which carbon is captured and stored in solid or liquid form (1). The purpose is to remove carbon from the atmosphere, thus reducing human induced contribution to CO2 levels and the possible link to global warming (1 + 1 with development). One artificial method involves the capture of CO2 from coal fired power plants. The captured carbon is then piped underground and stored in rock strata porous enough to hold CO2. (1 + 1 with development). One natural method involves working with natural processes to create natural carbon sinks. The development of peat bogs will stop vegetation decay. By creating new bogs or enhancing existing bogs, carbon sequestration will naturally occur (1 + 1 with development).
Explain the concept of a sediment cell.
A sediment cell is a closed system usually bounded by headlands or a change in longshore drift (1). Within a sediment cell, there is erosion, transport and deposition of sediment within a long-term cycle (1). The only inputs into the sediment come from erosion from the seabed or land (1). There is little or no movement of sediment between cells (1). Human activity such as beach management can interrupt the natural system creating imbalance within the cell leaving some areas at risk of erosion (1).
Outline the processes which lead to the development of barrier beaches.
A barrier beach is usually formed as an extension to a spit (1). Longshore drift moves sediment along the coastline until there is a change in the coastline (1). A spit develops, usually in a bay and once the spit develops across the whole bay, a barrier beach forms (1). Barrier beaches are unlikely to form in estuaries as the outcoming force of freshwater will always keep part of the estuary clear (1). Colonisation by vegetation can stabilise the barrier beach and trap further sediment keeping the barrier beach above sea even at high tide (1).
Explain the development of saltmarsh environments.
Salt marshes tend to develop in sheltered estuaries behind spits (1). As the spit develops, the area behind it becomes sheltered (d). Silt is deposited by the river which gradually builds up to form an inter-tidal mud flat (1). The mud flat continues to build and rise above sea level with the addition of further silt (1). Vegetation which is highly adapted to environment colonises the mud which itself traps further sediment (1). The salt marsh environment is colonised by halophytic vegetation (1).
Outline the process of sub-aerial weathering in the development of coastal landscapes.
Sub-aerial weathering involves the action of rainwater and insolation upon landforms in the coastal landscape (1). Here material is broken in situ, rocks are weakened and can contribute to sudden large-scale movements (1). Chemical weathering occurs when weak carbonic acid in rainwater attacks limestone cliffs (1). Mechanical weathering occurs when repeated freezing and thawing of water absorbed in pervious rock leads to the breakdown of rocks and the emergence of pronounced cracks in the bedding plain and rock strata (1). Biological weathering refers to the burrowing of plants and animals into the rock at the coast. This can lead to the break-up of rock as well as the weakening of the rock by species which attach to rock (1).
Explain the difference between eustatic, isostatic and tectonic sea level rise
Eustatic change is a global change in sea level, whereas isostatic is a more localised/regional change of the land relative to the sea level. Tectonic change is also a local/regional scale change in the land relative to the sea level (1 +1 with development). Eustatic change is brought about by a global change in the sea level relative to the land. During an ice age, sea levels drop relative to the land. Isostatic change results from the local impact of ice upon the land for example as ice melts, the pressure release can cause an isostatic rebound whereby the land rises above the sea level at a local level. Tectonic change is brought about by tectonic activity usually at plate boundaries. This can cause dramatic and immediate changes to the land relative to the sea (1 + 1 + 1 for development).
Outline processes which lead to the formation of fold mountains
Fold mountains are product of the convergence of tectonic plates (1). Continental and / or ocean plates are forced together (1). This may be as a result of opposing convection currents or as a result of slab pull and ridge push (d)(1). When continental crustal plates collide, there is a crumpling effect with uplift and a thickening of the continental mass e.g., the Himalayas (1). At subduction margins denser ocean crust is forced into the mantle beneath continental crust which is uplifted and crumpled to form fold mountains such as the Andes (1).
Outline the process of liquefaction.
Liquefaction occurs when compacted sediments loses strength and stiffness in response to an applied stress such as shaking during an earthquake (1). Material that is ordinarily a solid behaves like a liquid (1) (d). Liquefaction requires a degree of soil saturation to occur (1) (d). The phenomenon is most often observed in saturated, loose (low density or uncompacted), sandy soils (1). This is because a loose sand tends to compress when a load is applied (1) (d). The loss of soil structure causes it to lose its strength (the ability to transfer shear stress), and it may be observed to flow like a liquid (1) (d). Liquefaction can cause buildings and infrastructure to collapse as well as a significant risk to life as it acts like quicksand (1).
Outline the concept of positive feedback in the carbon cycle.
Positive feedback in the carbon cycle refers to processes that amplify or accelerate changes within the system, leading to a self-reinforcing cycle. Here’s an outline of the concept:
Definition: Positive feedback occurs when a change in one component of the carbon cycle leads to effects that enhance or amplify the original change, rather than dampening it.
Example - Ice-Albedo Feedback:
When temperatures rise due to increased atmospheric carbon, ice melts at the poles.
Melting ice reduces the Earth’s albedo (reflectivity), meaning more solar radiation is absorbed by the Earth’s surface rather than being reflected.
This leads to further warming, causing more ice to melt, which in turn accelerates the warming process. This creates a self-reinforcing cycle.
Example - Carbon Release from Permafrost:
Rising temperatures cause permafrost in the Arctic to thaw.
As permafrost thaws, carbon that has been locked in the frozen soil (in the form of organic matter) is released into the atmosphere as methane and CO2, both potent greenhouse gases.
The release of these gases further accelerates global warming, which causes even more permafrost to thaw, continuing the cycle.
Impact on the Carbon Cycle: Positive feedback loops in the carbon cycle can lead to significant and rapid changes in atmospheric CO2 levels, further intensifying climate change. These feedbacks highlight the potential for accelerating global warming, making it difficult to reverse the trend once certain thresholds are crossed.
Outline the formation of island arcs.
Island arcs are formed at convergent plate boundaries between oceanic crust. The denser oceanic crust sinks beneath the lighter oceanic crust via subduction and gravity assists as part of slab pull. The oceanic crust melts due to high temperatures and pressure in the Benioff zone, this forms magma. The magma is less dense than the rocks so it rises to the surface to form volcanoes. Overtime a series of volcanoes form along a subduction zone to form island arcs
