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a level geog- carbon and water > carbon and water > Flashcards

carbon and water Flashcards

1
Q

input

A

Material or energy moving into the system from outside
drainage baisin: precipitation
carbon cycle: precipitation with dissolved carbon dioxide

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2
Q

Output

A

Material or energy moving out of the system from the inside
Drainage basin: runoff
Carbon cycle: dissolved carbon with runoff

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3
Q

Energy

A

Power or driving force
Drainage basin: latent heat associated with changes in the state of water
Carbon cycle: production of glucose through the process of photosynthesis

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4
Q

Stores/ components

A

The individual parts or elements of a system
Drainage basin: trees, puddles, soil
Carbon cycle: trees, soil, rocks

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5
Q

Flows/ transfers

A

The links or relationships between the components
Drainage basin: infiltration, groundwater flow, evaporation
Carbon cycle: burning, absorption

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6
Q

Positive feedback

A

Sequence of events that increase change. Exacerbate the outputs of a system, driving it in one direction and promoting environmental stability

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7
Q

Negative feedback

A

Sequence of events that neutralises the effects of a system, promoting stability and a state of dynamic equilibrium

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8
Q

Dynamic equilibrium

A

Represents a state of balance within a constantly changing system

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9
Q

Positive feedback- drainage basin

A

Rising sea levels (due to thermal expansion and melting freshwater ice) can destabilise ice shelves increasing the rate of calving. This leads to an increase in melting, causing sea levels to rise further

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10
Q

Positive feedback- carbon cycle

A

Increased temperatures due to climate change cause melting of permafrost. Trapped greenhouse gases are released, enhancing the greenhouse effect, raising temperatures further

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11
Q

Negative feedback- drainage basin

A

Increased surface temperatures have led to an increase in evaporation from the oceans. This leads to more cloud cover. Clouds reflect radiation from the sun, resulting in a slight cooling of surface temperatures

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12
Q

Negative feedback- carbon cycle

A

Increased atmospheric CO2 leads to increased temperatures, promoting plant growth and photosynthesis. This in turn removes more CO2 from the air counteracting the rise in temperature

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13
Q

Stores in the water cycle

A

Most of the earths water is stored as saline water in the oceans

  • of the freshwater stores, ice sheets (Antarctica and Greenland) and groundwater are the main stores
  • rivers, lakes and the atmosphere contain remarkably small amounts of the global water stores
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14
Q

Transfers in the water cycle

A

Processes involved in transferring water between stores. E.g precipitation transfers water from the atmosphere to the earths surface. Evaporation moves it back to the atmosphere. Water may infiltrate the ground or percolate slowly through the rocks as groundwater flow.

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15
Q

Main stores in the water cycle

A

Lithosphere (land)
Atmosphere (air)
Cryosphere (frozen water- snow & ice)
Hydrosphere (liquid water)

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16
Q

What % of the earths water is saline?

A

97.4%

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17
Q

What percentage of the earths water is freshwater?

A

2.5%

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18
Q

What % of freshwater is stored in aquifers?

A

Just over 30%

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19
Q

What are aquifers?

A

Rocks deep below the ground surface forming vast underground reservoirs
-many aquifers are being exploited unsustainably as more water is abstracted

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20
Q

What rocks are aquifers most commonly found in?

A

Chalk and sandstone

-which are porous and permeable

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21
Q

Soil water budget

A

Soils vary enormously in their capacity to store and transfer water

  • porous, sandy soils hold little moisture as water is easily transferred through the pore spaces
  • clay soils tend to store water, with very limited water transfer
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22
Q

Water table

A

upper level of saturated rock
-this table rises and falls in response to groundwater flow, water abstraction by people, or by recharge (additional water flowing into the rock)
Through careful management the water table needs to be maintained at the same level- a state of equilibrium

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23
Q

Fossil aquifers

A

Aquifers in the deserts of Africa, the Middle East and Australia
-formed thousands of years ago when the climate in those regions was much wetter

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24
Q

Saline aquifers

A

Where sea water has has infiltrated into the rocks, often due to over-abstraction

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25
Q

How long does water remain in the water cycle stores?

A

Groundwater deep: 10,000 years
Soil: 1-2 months
Magnitude of water held in a store will vary over time and space e.g annual changes in Arctic (melting and freezing of the sea ice)

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26
Q

Sublimation

A

Transfer from a solid state (ice) to a gaseous state (water vapour) and vice versa

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27
Q

Overland flow

A

Transfer of water over the land surface

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28
Q

Infiltration

A

Transfer of water from the ground surface into soil where it may then percolate into underlying rocks

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29
Q

Throughflow

A

Water flowing through soil towards a river channel

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30
Q

Percolation

A

Water soaking into rocks

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31
Q

Climate change

A

At the peak of the last ice age 1/3 of the earths land was covered by glaciers and ice sheets
-with water ‘locked up’ such as snow and ice the mag. of this store increased significantly. With less liquid water reaching the oceans sea levels fell by over 100m compared with present day

During warmer periods in the past say about 3 million years ago ocean levels were about 50m higher than they are today as the amount of water stored as snow and ice declined

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32
Q

Driving force behind cloud formation and precipitation

A

Global atmospheric precipitation model;
3 interconnected cells (polar cell, ferrel cell, Hadley cell) & identifies latitudinal zones of rising and falling air

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33
Q

Cloud formation & causes of precipitation: equator

A

High temperatures result in high rates of evaporation. The warm moist air rises, cools and condenses to form towering banks of cloud and heavy rainfall in a low pressure zone called the ITCZ

34
Q

Cloud formation & causes of precipitation: mid latitudes

A

Cloud formation driven by the convergence of warm air from the tropics and cold air from the arctic. The boundary of these two distinct air masses- the polar front- results in rising air and cloud (and rain) formation. Strong upper-level winds (the jet stream) drives these unstable weather systems across the mid-latitudes, establishing the largely changeable conditions experienced in the UK

35
Q

Cloud formation- localised scale

A

e.g thunderstorms from intense convective activity

36
Q

Cryospheric processes

A

After oceanic water, the largest store of water on earth is frozen water - 95% is locked up in the worlds two great ice sheets covering Antarctica and Greenland

  • snow falls on glaciers and ice sheets become compressed and entering long term storage forming layers of glacial ice
  • on a shorter scale snow accumulated during the winter adds to the mass of a glacier or ice sheet. In the summer melting occurs or ice calves (breaks away). On a glacier the equilibrium line marks the altitude where annual accumulation and melting are equal. In recent decades the climate has warmed causing the equilibrium line to move to higher altitudes
  • most glaciers in the world are now shrinking and retreating
37
Q

Cryospheric processes: melting of freshwater ice

A

The total melting of freshwater ice has a profound impact on sea levels- the total melting of all the polar ice sheets could result in a 60m rise in sea level adding a great deal of water to the ocean store
(pos. feedback: rising sea levels trigger ice shelves, triggering calving and further melting)

38
Q

Processes of change at local scale

A

-Deforestation- reduces interception and infiltration. Overland flow increases
-Storms -inc amount of rainfall reaching ground
-Seasonal changes e.g frozen ground
Urbanisation- impermeable surfaces, water will flow quickly to nearby river channels
Farming-ditches drain the land and encourage water to flow quickly to rivers. Irrigation increases the amount of water on the ground

39
Q

Soil water budget

A

Wet seasons:
-precipitation exceeds evapotranspiration = water surplus
-ground stores fill with water (more surface runoff & higher discharge= river levels rise)
Drier seasons
-evapotranspiration exceeds precipitation = ground store depletion
-some flows into the river channel but is not replaced by precipitation
Back to wet season:
-deficit of water
-ground stores recharged

40
Q

Soil water budget

  • what happens in the autumn
  • what is field capacity
A
  • In the early autumn rates of evapotranspiration start to fall and the soil is replenished (recharge)
  • When the soil holds as much water as it can without any outputs occurring (therefore a water surplus occurs and water transfer processes will become active)
41
Q

How does the soil water budget vary from place to place?

A

Depends on type and depth of soil, its texture and its permeability

  • much of this is true of the underlying bedrock as its capacity to store and transfer water will depend on its lithology and its structure (porosity and permeability)
    e. g water will move much more slowly through older porous rock such as sandstone yet it will move very rapidly through widely jointed limestone.
42
Q

Drainage basin

A

Area of land drained by a river and its tributaries

  • edge of a river basin is marked by a by a boundary called the watershed
  • drainage basins vary enormously in size such as the Mississippi nile and the amazon
43
Q

Drainage basin: Precipitation

A

Water enters the drainage basin as precipitation

  • some of it may be intercepted by plants and trees where it may be stored before being evaporated. It takes time for the water to drip through the leaves or down the stems (stem flow) to the ground surface
  • here it is stored as puddles, flows over the ground as overland flow or infiltrates the soil. Some water may be taken up by plants before being transpired
44
Q

Drainage basin: groundwater flow

A

Groundwater flow feeds rivers through their banks and bed. Being generally a slow method of transfer it carries on supplying water well after an individual rainfall event has occurred. This explains why rivers continue to flow during long dry periods. Eventually water moves out of the system as runoff where the river flows into lakes or the sea, or evaporation

45
Q

Drainage basin: Infiltration

A

The INFILTRATION CAPACITY (rate of infiltration) is an extremely important factor- it will vary according to soil type and conditions (ie to what extent the soil is already saturated)

  • infiltration capacity is exceeded when soil is unable to absorb water at the rate which it is falling.
  • thin, frozen or already saturated soils will usually have a low infiltration capacity.
  • trees may promote infiltration as the roots form pathways for water to percolate underground.
  • water usually soaks into the coil by a combination of CAPILLARY ACTION (attraction of water molecules to soil particles) and gravity (which usually dominates)
46
Q

Drainage basin: Overland flow

A

If water is unable to infiltrate it may run off the surface as overland flow, flowing across a large surface area (SHEETFLOW) or concentrated into small channels called RILLS
-not common in ag. areas due to vegetation but is in urban areas

47
Q

Throughflow

A

Once in the soil water may either be stored as SOIL WATER or pass through as through flow

  • water passes through the soil until it reaches the water table (the upper layer of saturated rock ground) or the underlying bedrock. If the bedrock is impermeable no further downward movement will occur. If permeable water will seep into the cracks and holes in the rock.
  • however some jointed rocks such as limestone and granite can transmit water very quickly
48
Q

Throughflow: rate

A

Dependent on the depth and texture of the soil:
coarse, sandy soil absorbs and transfers soil rapidly, esp through discrete ‘pipes’ in the soil, caused by animal activity or the growth of plant roots. This contributes significantly to the flood hazard. Such soils are said to have a LOW FIELD CAPACITY (retain little water). Clay soils have a HIGH FIELD CAPACITY- these soils tend to be wet as they have tiny pore spaces which do not allow water to be transferred easily.

49
Q

Water balance

A

Precipitation = total run off + evapotranspiration +/- storage
Helps hydrologists to plan for future water supply and flood control by understanding the unique hydrological characteristics of an individual drainage basin

50
Q

Water balance : the river Wye - length

A

215km- 5th longest river in the UK

51
Q

Water balance : the river Wye.

A

Upper part: characterised by steep slopes, acidic soils and grassland. Must of this area was originally forested but this has been largely cleared to make way for pasture and sheep grazing. This has reduced interception and increased the potential for overland flow. Ditches have been dug to drain the land to make it more productive but this has increased the speed of water transfer, making the river more prone to flooding. The rocks here are impermeable mudstones, shales and grits. Further south the river flows over sandstones before cutting its way through a limestone gorge between Symonds Yat and Chepstow.
-because the underlying rock is mainly impermeable, groundwater flow is therefore limited throughout the basin: soils become quickly saturated and are unable to absorb excess water. This encourages overland flow, increasing the risk of flooding downstream- Hereford has been affected by flooding on many occasions.

52
Q

Discharge

A

Measurement of runoff at a moment in time

Discharge - cross sectional area x velocity

53
Q

Physical variations affecting change- the Californian drought

A

Rivers and lakes dried up, agricultural productivity declined and fires raged across tinder dry forests and grasslands

  • drought causes a reduction in water stores in rivers and lakes
  • vegetation dies back or is destroyed by fire- it affects processes such as transpiration, interception and infiltration
  • groundwater flow becomes more important, as it is a long-term transfer and not affected by short term weather extremes
  • heat and dry air causes initial high rates of evapotranspiration. This declines as water on the ground dries up (less water available to be evaporated) and trees transpire less
  • soils dry out-the soil water store is reduced and through flow ceases
54
Q

Evaporation- seasonal variations

A

In the summer higher temperatures encourage rapid evaporation (warm air can hold more moisture)
-lower temperatures in the winter reduce rates of evapotranspiration

55
Q

Vegetation- seasonal variations

A

In the summer vegetation grows rapidly increasing interception and transpiration
-in the winter vegetation dries back reducing interception and transpiration

56
Q

Human activities affecting change

A
  • Land use change
  • Water abstraction
  • Farming practices
57
Q

Land use change

A

Urbanisation- replacement of vegetated ground with impermeable concrete and tarmac. Water cannot infiltrate the soil, which increases overland flow and makes flooding more likely
Deforestation- removal of trees leading to surface runoff and soil erosion and reducing soil water stores.

58
Q

Farming practices

A

Farmers are able to control the local water cycle through irrigation or land drainage. Soils covered with plants have higher infiltration and soil water rates and therefore reduced runoff
-if desertification occurs the capacity to retain water is much lower

59
Q

Water abstraction

A

The extraction of water from rivers or groundwater aquifers

  • water that is abstracted for irrigation, industry and domestic purposes can have significant effects on the local water cycle
  • aquifers can become depleted
  • they can also become dominated by inflowing saltwater if the water table drops below sea level- this has become an issue with the chalk aquifer beneath London. Abstraction can result in low flow conditions in rivers which can have harmful impacts on ecosystems
60
Q

Carbon cycle: stores

A

lithosphere (rocks and soil)
hydrosphere (oceans)
cryosphere (snow and ice)
atmosphere and biosphere (plants)

61
Q

Carbon sink

A

A store that stores more carbon than it releases

62
Q

Carbon source

A

Releases more carbon than it absorbs

63
Q

Carbon transfers

A

The processes transferring carbon between the stores
For example the process of photosynthesis takes carbon out of the atmosphere into the form of carbon dioxide and converts it into carbohydrates such as glucose within plants. Transfers are the inputs and output that affect the magnitude of stores at any one time

64
Q

Fluxes

A

Amount of carbon held in each store is subject to changes over timescales

65
Q

Carbon stores: marine sediments and sedimentary rocks

A

Marine sediments and sedimentary rocks- largest store with rocks taking millions of years to form

66
Q

Ocean

A

Carbon dioxide is absorbed directly from the air and the river water discharges carbon carried in solution
-since the industrial revolution the oceans have absorbed more carbon dioxide from the air due to increased carbon emissions.

67
Q

Fossil fuel deposits

A

Hydrocarbons such as coal, oil and gas are important long term stores of carbon. Since the industrial revolution they have been exploited for heat and power. The resulting combustion has pumped huge quantities of carbon dioxide into the atmosphere causing climate change.

68
Q

Soil organic matter

A

Soils containing rotting organic matter are important carbon stores. Carbon can remain in the remain in the soils for hundreds of years. Deforestation, land use change and soil erosion can however release the stored carbon very rapidly.

69
Q

Atmosphere

A

Carbon is held in the atmosphere in the form of carbon dioxide. In recent decades the amount of carbon dioxide has increased due to emissions from power stations, vehicles and deforestation. This has led to the enhanced greenhouse effect and climate change.

70
Q

Terrestrial plants

A

Plants are vital for life on earth. They convert energy from the sun into carbohydrates that support life. Plants can store carbon for many years and transfer it to the soil. However through deforestation this carbon can be released back into the atmosphere very quickly.

71
Q

Global pattern of vegetation carbon storage

A

Scientists have identified that carbon uptake is increasing in the middle and high latitudes of the northern hemisphere, but less carbon is being absorbed in the tropics and Southern Hemisphere. A major cause of this is thought to be drought (possibly linked to climate change) impacting crop yields, timber production and expanses of natural vegetation.

72
Q

wood is … % carbon

A

50%

73
Q

A terrestrial carbon cycle: the lithosere

A
  • when rock is exposed for the first time (e.g after glacier retreat) it is vulnerable to the process of weathering
  • as the rock is slowly broken down carbon may be released, often dissolved in water
  • over time vegetation such as lichen and moss grow on the bare rock and carbon exchange starts to take place involving photosynthesis and respiration. Gradually, as organic matter is added to the broken fragments of rock, a soil develops that can support a wider range of plants
  • over hundreds of years the plant species becomes more diverse benefitting from the supply of carbon in the soil.
  • the sequence of change is called vegetation succession
  • eventually the final stage is reached when a state of environmental equilibrium or balance is achieved. This is usually in response to the climate and is therefore termed the climatic climax
  • the climax vegetation for a lithosphere in the UK will usually be a deciduous woodland
74
Q

Sere

A

A succession that relates to a specific environment

  • each stage in the succession can be referred to as a serial stage
  • a lithosere is a vegetation succession that occurs on bare rock.
75
Q

Main transfers operating in the carbon cycle

A
  • Photosynthesis
  • Respiration
  • Decomposition
  • Combustion
  • Burial and compaction
  • Carbon sequestration
  • Weathering
76
Q

Photosynthesis

A

The process whereby plants use the light energy from the sun to produce carbohydrates in the form of glucose

  • green plants absorb the light energy using chlorophyll
  • (a green substance found in chloroplasts in plant cells in their leaves)
  • the absorbed light energy converts carbon dioxide in the air and water from the soil into glucose. During this process oxygen is released into the air.
  • some glucose is used in respiration, but the rest is converted into starch, which s insoluble but can be converted back into glucose for respiration
77
Q

Respiration

A

A chemical process the happens in all cells and is common to both plants and animals. Glucose is converted into energy that can be used for growth and repair, movement and control of body temperature in mammals. Carbon dioxide is then returned to the atmosphere, mostly by exhaled air.

78
Q

Decomposition

A

When organisms die they are consumed by decomposers such as bacteria, fungi and earthworms. During this process of decomposition, carbon from their bodies is returned to the atmosphere as carbon dioxide. Some organic material passes into the soil where it may be stored for hundreds of years.

79
Q

Combustion

A

Organic material contains carbon. When it is burned in the presence of oxygen (e.g coal in a power station) It is converted into energy, carbon dioxide and water
-the carbon dioxide returning to the atmosphere might have been stored in rocks for millions of years

80
Q

Burial and compaction

A

Where organic matter is buried by sediments and becomes compacted. Over millions of years, these organic sediments sediments containing carbon may form hydrocarbons such as coal and oil

  • corals and shelled organisms take up carbon dioxide from the water and convert it to calcium carbonate used to build up their shells. When they die their shells accumulate on the seabed. Some of the carbonates dissolve, releasing carbon dioxide.
  • the rest becomes compacted to form limestone, storing carbon for millions of years.
81
Q

Carbon sequestration

A

An ‘umbrella term’ used to describe the transfer of carbon from the atmosphere plants, soils, rock formations and oceans.

  • sequestration is both a natural and human process
  • carbon capture and storage is a recent term used to describe the technological capturing of carbon emitted from power stations
  • smaller scale sequestration can also take place e.g by a change in farming practices.
82
Q

Weathering

A

Breakdown or decay of rocks in their original place or at close to the surface

  • when carbon dioxide is absorbed by rainwater it forms a mildly acidic carbonic acid.
  • through a series of complex chemical reactions rocks will slowly decompose with the carbon being held in solution. Transported via the water cycle to the oceans, this carbon can then be used to build the shells of marine organisms.

a level geog- carbon and water (1 decks)

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