Earth's Life Support Systems Flashcards
What is a systems approach?
A model used to help explain phenomena where relationships are examined between a number of components that are linked.
What is an open system?
A type of system whose boundaries are open to both inputs and outputs of energy and matter.
What is a closed system?
A system with inputs and outputs of energy, but without any movement of materials across system boundaries.
Define inputs
An addition of energy and/or materials to a system. E.g light energy from the sun and materials from comets
Define outputs
The transfer of energy and/or materials out of a system. E.g. astronauts have left materials in space
Define stores
The amount of the total material held within parts of the system.e.g. Fossil fuels are energy stores and crust is a material one
Define flows/transfers
The transfers of energy or material between the stores. E.g. rivers transfer water and energy
Define flux
Measurement of rate of flow/transfer between stores. Usually measured in petagrams(Pg)/gigatonnes(Gt) (billion tonnes) per year.
Define processes
The physical mechanisms that drive the flows of energy and material between stores.
Define feedback
The return ‘loop’ where the outputs and consequences have a positive or negative impact on the inputs, altering the subsequent operation of the system.
Define negative feedback
An automatic response to change in a system that restores equilibrium.
Define positive feedback
An automatic response to change in a system that generates further change
Define dynamic equilibrium
A system displaying unrepeated average states through time. Even if it is modified by geomorphic processes the general state does not change - it remains in balance. E.g. rivers will always follow essentially the same route every time.
Define mass balance
Calculation of inputs versus outputs eg water balance would measure rainfall versus evaporation and runoff. Can be +ve or -ve.
What is geomorphology?
the study of the physical features of the Earth’s surface, i.e. the landscape and the different landforms that are contained within it.
Which type of systems are water and carbon cycles at a global and local scale?
At global scale = closed systems ( only energy crosses boundaries). Time scales vary from days to millions of years.
On smaller scales water and carbon cycle = open systems (material and energy can cross boundaries).
Oceans contain 97% of all water. Other stores include polar ice and glaciers (cryosphere), groundwater, lakes, soils, atmosphere and the biosphere
Why is water important for supporting life on the planet?
A medium that allows organic molecules to mix/form complex structures. Ubiquity of water due to ‘Goldilocks zone’ from the Sun. more water = more lifeforms. Helps create benign thermal conditions for the earth. Oceans moderate temperatures by absorbing, storing and releasing heat. Clouds containing water particles reflect 1/5th of solar radiation and lower surface temperatures. Water vapour (greenhouse gas) absorbs longwave radiation from the earth to maintain average global temperatures.
Why is water important for flora, fauna and people
Makes up 65-95% of all living organisms. Crucial for growth, reproduction and metabolic functions. Plants need it for photosynthesis, respiration and transpiration and to maintain rigidity and transport mineral nutrients from the soil. In mammals water is the medium used for all chemical reactions in the body including the circulation of oxygen and nutrients. Sweating and panting cools mammals.
Why is water important economically?
Used to generate electricity, irrigate crops, provide recreational facilities and satisfy public demand (drinking water, sewage disposal). Used in many industries such as: food manufacturing, brewing, paper and steel making.
Describe evaporation, what is net evaporation?
The process by which liquid water is converted into a gaseous state. Large proportion of pathway from liquid to vapour. 90% moisture in atmosphere from oceans, seas, lakes and rivers. 10% transpiration. Heat energy breaks bonds. Net evap = rate of evap > rate of condensation. If equal called saturation state. Amount evaporated = amount falling but only 10% falls on land. Used to desalinate water and extract minerals from lakes.
Describe sublimation
The phase change of water from ice to vapour without becoming a liquid. Low humidity and dry winds preferable. Happens more at high altitudes. Needs energy
Describe transpiration
Evaporation of moisture from pores on the leaf surfaces of plants.
Describe run-off
The movement of water across the land surface.
Describe evapotranspiration
Combined loss of water at the surface through evaporation and transpiration by plants. Water evaporated from ground surface and transpiration of groundwater. Varies depending on factors such as temperature, wind, soil, plant and sunlight.
Describe infiltration
Vertical movement of rainwater through the soil. Dependent on ground condition, precipitation amount, soil saturation. Some remains in shallow soil layers moving vertically and horizontally, others recharge aquifers deeper underground.
Describe condensation
The phase change of water vapour to water. Forms clouds as moisture particles combine with dust and smoke. Happens higher where it is less dense and cooler. Clouds regulate solar energy flow to the earth meaning any changes can have huge impacts. Fog forms when high humidity causes a cooler surface. Occurs at dew point.
Describe precipitation
Moisture (rain, snow, hail) falling from the clouds towards the ground.
Describe percolation
The movement of surface and soil water into underlying permeable rock. Primary connection that provides an input to the earth.
Describe ablation
The loss of ice and snow, especially from a glacier, through melting, evaporation and sublimation.
Describe groundwater flow
The horizontal movement of water within aquifers. Major contributor to flow in streams and rivers. Some infiltrates to aquifers (where spaces between soil and rock particles can be totally filled with water). Flow depends on layers of rock and soil permeability.
How do we calculate the global water budget?
INPUTS = OUTPUTS
Precipitation = evaporation & transpiration + surface & sub-surface flows
Why does air rise?
convection (surface heated by solar radiation) or orographic uplift.
Why does air cool?
if it comes into contact with a cool surface: by moving horizontally across the surface (advection - could form stratiform clouds) or by radiation cooling (ground rapidly loses heat through terrestrial radiation by conduction). When air cannot absorb any more water vapour (at dew point) the water is contains will condense an form clouds. Some do not produce precipitation as small particles are kept buoyant by rising air currents. When particles aggregate reach a critical size they will fall to earth.
What is adiabatic expansion?
parcel of air warmed by ground so it is warmer than surrounding air. Rises by convection as it is less dense. Becomes cooler due to the expansion of a parcel of air due to a decrease in pressure which causes cooling. Dew point is reached and at this altitude base of clouds form or will rise further is dew point not reached.
What is ELR?
(Environmental Lapse Rate) - vertical temperature profile of the lower atmosphere at any given time. On average temp falls by 6.5 degrees for every km of height gaines. Due to decrease in atmospheric pressure with height and particles get further apart and cooler.
What is DALR?
(Dry Adiabatic Lapse Rate) - rate at which a parcel of dry air cools. Cooling caused by adiabatic expansion is 10 degrees/km.
What is SALR?
(Saturated Adiabatic Lapse Rate) - the rate at which a saturated parcel of air (condensation is happening) cools as it rises through the atmosphere. Requires latent heat for condensation (7 degrees/km). Lower than DALR. heat released into atmosphere and rate of temperature decrease is less.
Describe absolute instability of a parcel of air?
Parcel of air warmer than surroundings so is less dense and rises (unstable). Ability to hold water decreases with altitude so dew point reached and becomes saturated (cloud base). Lapse rate decreases but air is still water so still rises (unstable). Produces cumulonimbus clouds on hot British days.
Describe absolute stability of a parcel of air?
Temperature of surroundings higher than more dense air particle. Will not rise and stays close to the surface (stable). Typical summer conditions with cumulus clouds with no rain.
Describe conditional instability of a parcel of air?
The temperature of the parcel of air is cooler than the surroundings so will not rise and is stable. eventually it will pass through the dew point and will decrease temperature more slowly. The parcel of air then becomes warmer and less dense and will rise. If the air is forced upwards (e.g. a mountain) high enough it will become warmer than the surroundings and it condenses it will become unstable. This is called conditional instability. Common in Britain.
What is a catchment area?
(drainage basin) - an area of land that contributed water to a particular stream or river. Can be large (Thames) or small scale.
What is a watershed/drainage divide?
boundary between 2 adjacent drainage basins
What 4 factors affect the amount of water in a catchment area?
- Type of precipitation (rain or snow) - Most rain on reaching the ground flows quickly into streams and rivers. But at high latitudes and mountainous catchments, precipitation often falls as snow and can remain on the ground for months so there may be a lot of time between snowfall and run-off.
- As intensity increases water moves rapidly overland into streams and rivers.
- Duration of precipitation - Prolonged events, linked to depressions and frontal systems may deposit exceptional amounts of rain and cause river flooding.
- Seasonal variation- In some parts of the world (e.g. East Africa) precipitation is concentrated in the rainy season. During this season river discharge is high and flooding is common. In the dry season ricers may cease to flow altogether.
Describe interception (store)
Trapping and temporary storage of precipitation on surfaces if plant leaves, stems and branches. Occurs in urban areas on roofs etc.
Loss of water by interception annually = 30-60% grass, 30-35% coniferous forest, 7-15% cereal crops in season.
Factors affecting vegetation type- larger from grasses than crops. Trees (large SA and aerodynamic roughness) higher. Greater from evergreen conifers than deciduous. Have leaves all year and water adheres t spaces between needles = increased evap. Increases with wind speed. Initially as rainfalls onto dry surfaces most is intercepted but as it becomes saturated output through stemflow etc increase. Depends on duration and intensity of a rainfall event.
Describe surface stores
Depression storage- water collects in small hollows or depressions on the ground surface.
Describe the soil moisture store
Water stored temporarily near to the ground surface in the soil.
Describe groundwater stores
Water stored underground in permeable and porous rocks known as aquifers. A saturated zone below the water table. Varies seasonally, falls in summer with increased evaptran.
Describe groundwater flow
The horizontal movement of water within aquifers.
The slow lateral transfer of water through saturated soil or rock (below the water table).
This is very slow as water usually flows through solid rock (few pores). It can be rapid in highly permeable rocks. Water enters river channels through banks and begs. Mountains channel flow during droughts
Describe throughfall (flow)
Water drips from leaves and branches onto the ground.
Describe stemflow
Water flows down the trunk or stem of a plant.
Describe overland flow
what are the two different types?
Rainfall that runs off the ground surface either because the soil is saturated or the intensity of rainfall exceeds the soil’s infiltration capacity. Movement of water over the land surface as sheet flows or in small channels (rills). This is a very rapid transfer and uncommon in the UK. It will cause flooding.
Saturated overland flow- if the soil is saturated or frozen meaning water can’t infiltrate the soil and so flows over the surface. There is a link to antecedent precipitation (rainfall over previous days).
Infiltration excess overland flow - Happens when the intensity of precipitation is greater than the infiltration capacity of the soil. This is rare but could occur in thunderstorms or if the ground is bare and compacted.
Describe infiltration (flow)
What factors affect the rate of infiltration?
The vertical movement of rainwater through the soil. Infiltration capacity- the maximum rate at which water can enter the soil (mm/hour).
Factors affecting: soil type, land use - sandy soil has higher infiltration than clay as macropores allow faster transfer than micropores. Crop use for land will increase as roots act as channels. Saturates land will reduce infiltration and can cause flooding. Antecedent precipitation- lots of rain will reduce it as saturated soil cannot absorb any more. Dry soil is better. Start of rain will infiltrate better before saturation.
Describe throughflow
Water flowing horizontally (lateral transfer) through the soil to stream and river channels. This occurs in a downslope direction parallel to the ground surface and above the water table. This is slow compared to overland flow and accounts for the majority of transfer to river channels. It may flow through pore spaces or more quickly as pipe flow along routeways formed by roots, burrows or cracks
Describe percolation (flow)
The movement of surface and soil water into underlying permeable rocks.
