Topic 6: EQ1 Flashcards

Question

What are the 5 key processes in the geological carbon cycle?

Answer 1

1) mechanical, chemical and biological weathering of rocks on land in Situ. 2) Decomposition 3)Transportation 4) Sedimentation 5) Metamorphosis

Answer 2

-Mechanical weathering causes the breakup of rocks by frost; shattering and exfoliation produces small, easy-to-transport particles. -Chemical weathering causes the breakdown of rocks by carbonic acid in rain, which dissolves carbonate-based rocks. -Biological weathering by the burrowing animals and the roots of plants can break rocks up.

Answer 3

Plant and animal particles that result from decomposition after death and surface erosion store carbon.

Answer 4

Rivers carry particles (ions) to the ocean, where they are deposited.

Answer 5

Over millennia these sediments accumulate, burying older sediments below, such as shale and limestone.

Answer 6

The layering and burial of sediment causes pressure to build, which eventually becomes so great that deeper sediments are changed into rock: shale becomes slate and limestone becomes marble.

Answer 7

In the oceans today, 80% of carbon-containing rock is from shell-building organisms and plankton. These are precipitated on to the ocean floor, form layers, are cemented together and lithified into limestone. The remaining 20% of rocks contain organic carbon from organisms that have been embedded in layers of mud. Over millions of years heat and pressure compress the mud and carbon, forming sedimentary rock such as shale.

Answer 8

They were made up to 300 million years ago from the remains of organic material. Organisms, once dead, sank to the bottom of rivers and seas, were covered in silt and mud, and then started to decay anaerobically. This occurs over millennia. The deeper the deposits, the more heat and pressure which build up on the deposits. When the organic matter builds faster than it can decay, layers of organic carbon become oil, coal or natural gas instead of shale.

Answer 9

-This is formed from the remains of tiny aquatic animals and plants. Gas and oil occur in ‘pockets’ in rocks, migrating up through the crusts until meeting caprocks. -Natural gas, such as methane, is made up of the fractions of oil molecules, so small they are in gas form not liquid, and usually found with crude oil. -Other hydrocarbon deposits include oil shales, tar sands and gas hydrates.

Answer 10

Carbon fossil fuels (e.g. coal) were made up to 300 million years ago from the remains of dead organic material. Organisms once dead, sank to the bottom of rivers and seas, were covered in silt and mud, and then started to decay anaerobically. This process operates over millennia. When organic matter builds up faster than it can decay, layers of organic carbon become fossil fuels instead of shale.

Answer 11

Between 100-200 million years. On average 10-100million tonnes of carbon moves through this slow carbon cycle annually.

Answer 12

This is faster than the geological processes. At 10^16 g for the ecosystem cycle and 10^15 grams annually for the anthropogenic cycle.

Answer 13

1) water reacts with atmospheric CO2 and carbonic acid forms. When this weak acid reaches the surface, it reacts with some surface minerals, slowly dissolving them into their component ions, 2) Transportation of calcium ions by rivers from the land into oceans. These combine with bicarbonate ions to form calcium carbonate and precipitate out as minerals such as calcite (CaCO3). 3) Deposition and burial turns calcite sediment into limestone. 4)Subduction of the sea floor under continental margins by tectonic spreading. 5) Some of the carbon rises back up to the surface within heated magma and returns to the atmosphere as CO2. Diamonds have also been discovered to form 700km below the surface, proving carbon is cycled between Earth’s Surface and the lower mantle.

Answer 14

Outgassing occurs at: active or passive volcanic zones associated with tectonic plate boundaries (including subduction zones), places with no current volcanic activity (e.g hot springs in Yellowstone National Park USA), and direct emissions from fractures in the earth’s crust. Volcanoes currently emit 0.15-0.26 Gt CO2 annually, compared to the 35 Gt humans emit, this makes volcanic degassing fairly insignificant.

Answer 15

About 70 surface volcanoes are currently active. An example of major degassing as a pulse is the 1991 eruption of Mt Pinatubo in the Philippines, part of an island arc created by a subduction zone, such eruptions not only return CO2 to the atmosphere, but the fresh silicate rock erupted starts the carbon cycle again.

Answer 16

Increase in volcanic activity -> Rise in CO2 emissions and loss of carbon from rocks -> Temperature rises -> More uplift of air, condensation and rain -> More chemical weathering and erosion of rocks -> More ions deposited on ocean floors -> More carbon stored in rocks.

Answer 17

The oceans are the Earth’s largest carbon store, being 50x greater than that of the atmosphere; 93% of CO2 is stored in undersea algae, plants and coral, with the remainder being in a dissolved form. Small changes oceanic carbonic cycling can have significant global impacts. The CO2 gas exchanged flux between ocean and atmosphere operates on a timescale of several hundred years. There is also a significant input of both organic carbon and carbonate ions from continental river run-off. Only a small proportion of this carbon is eventually buried in ocean sediments, but these are important long-term carbon stores with fluxes operating over millennia.

Answer 18

When looking at the carbon cycle pump: the biological pump, and the actions of the linked carbonate pump involving thermohaline circulation. This circulation is part of a third important process called the physical pump. These pumps flux surface ocean CO2 to the deep ocean. The definition of the carbon cycle pumps is the processes operating in oceans to circulate and store carbon.

Answer 19

The global system of surface and deep water ocean currents is driven by temperature (thermo) and salinity (haline) differences between areas of oceans.

Answer 20

-The organic sequestration of CO2 to oceans by phytoplankton. These marine plants float near the ocean surface to access sunlight to photosynthesise. Despite being the base of the marine food web, their huge numbers make up half of the planets biomass. -Phytoplankton have rapid growth rates, called net primary productivity. This is especially in the shallow waters of continental shelves, where rivers carry nutrients far our to sea. Arctic and southern oceans are very productive. -Carbon is then passed up the food chain by consumer fish and zooplankton, releasing CO2 back into the water and atmosphere.

Answer 21

2 billion metric tonnes annually.

Answer 22

This relies on inorganic carbon sedimentation. Marine organisms make hard outer shells and inner skeletons from calcium carbonate. These include coral, oysters and lobsters. When organisms die and sink, many shells dissolve before reaching the sea floor sediments. This carbon becomes part of deep ocean currents. Shells which don’t dissolve build up on the sea floor slowly, forming limestone sediments, e.g the white cliffs of Dover.

Answer 23

-Based on the oceanic circulation of water including upwelling, downwelling and the thermohaline current. -CO2 in the oceans is mixed much more slowly than in the atmosphere, so there are large spatial differences in CO2 concentrations. -CO2 can be absorbed more in colder waters. Concentration is 10% higher in the deep ocean than at the surface. Polar oceans store more than tropical oceans. -Warm tropical waters release CO2 to atmosphere, but high-latitude oceans take it in. More than 2x the CO2 can dissolve in cold polar waters than equatorial waters. -As ocean currents carry the water towards the poles, it cools and absorbs more CO2. This increases its density, causing the water to sink which takes accumulated CO2 downwards.

Answer 24

It is a vital component of the global ocean nutrient and carbon dioxide cycles. The ocean currents circulate carbon, with water flows equivalent to over 100x the Amazon river. In the 1000 year process for a cubic metre of water to travel the whole system, the water is depleted of CO2 and nutrients in warm surface zones, and then enriched in the colder deeper layers. The planets food chain system relies on the cool, nutrient rich waters which support algae and seaweed growth. The circulation also helps shift carbon in the carbonate pump cycle from.upper to deeper waters.

Answer 25

The carbon uptake (92PgC) and carbon loss (90PgC) from the oceans is dependent on organic and inorganic processes acting at both surface and deep ocean locations. Until the 20th century began, oceans were able to sequester increased CO2 emissions, but evidence now suggests a slowing of this storage. Increased oceanic acidification, due to increased CO2, reduces the capacity for extra CO2 storage.

Answer 26

-Primary producers - plants - take carbon out of the atmosphere through photosynthesis and release CO2 back into the atmosphere through respiration. -When consumer animals eat plants, carbon from the plant becomes part of its fats and proteins. -Microorganisms and detritus feeders such as beetles feed on waste material from animals, and this becomes part of these micro-organisms. -After this plant and animal death, tissues such as leaves decay faster than more resistant structures, such as wood. Decomposition is fastest in tropical climates with high rainfall, temperatures and oxygen levels; it is very slow in cold, dry conditions or where there is a shortage of oxygen. In arctic biomes, ecosystems are locked down by extreme cold for substantial periods of time.

Answer 27

Tropical forests, the savannah and grasslands, which together account for half of global net primary productivity (NPP). Storage is mainly in plants and soils, with smaller amounts in animals and microorganisms such as bacteria and fungi. The largest store is in trees, which can live tens, hundreds and even thousands of years.

Answer 28

Diurnally - during the day the fluxes are positive, from the atmosphere to the ecosystem; at night the flux is negative, with loss from the ecosystem to the atmosphere. Seasonally - in the northern hemisphere winter, when few land plants are growing and many are decaying, atmospheric CO2 concentrations rise; during the spring, when plants begun growing again, concentrations drop.

Answer 29

These are one of the largest organic stores of carbon on Earth. The Amazon rainforest alone, which covers 5.3million sq km, sequesters 17% of all terrestrial carbon, more than any other land-based biome. Some species, such as Brazil nut trees, dominate this process. 1% of the Amazons 16,000 tree species store 50% of its carbon, removing CO2 from the atmosphere for centuries.

Answer 30

Wetlands that contain peat, an organic sediment, are important carbon stores. Many peat lands formed during the Holocene have been a store for thousands of years; with climate change and overuse, however, they are becoming net carbon sources.

Answer 31

Soils store 20-30% of global carbon, sequestering about 2x the quantity of carbon as the atmosphere and 3x that of terrestrial vegetation. However, whether it sequesters or actually emits CO2 depends on the local conditions.

Answer 32

Arid and semi-arid soils, and those developed on limestone, contain inorganic carbon. But the most important store is from organic sources through plant photosynthesis and subsequent decomposition both above and below ground, living organisms represent about 5% of the total soil organic matter. They have seasonal as well as daily patterns, and not all are active at the same time.

Answer 33

As all plants are made of carbon, any loss to the ground means a transfer or flux from the plant to the soil. Litterfall and branch litter includes whole plants, leaves and branches shed during any year. Roots may also be shed. Carbon is stored as dead organic matter in soils for years, decades or even centuries in colder climates or wetland environments, before being broken down by soil microbes and released back to the atmosphere.

Answer 34

The formation of humus is the most long-term process in the soil decomposition process. Humus is seen easily in soils as it has a dark, rich colour. Humus soils are 60% carbon and are important for sequestration as well as for water storage.

Answer 35

Carbon cycling and formation is most active in topsoil horizons. Stabilised carbon, with longer turnover times, is located in deeper soil layers. In permafrost regions, over 61% of carbon is stored deeper than 30cm. An additional long-term carbon store in many soils is pyrogenic carbonaceous matter, formed from biomass burned and carbonised during wildfires. This resists microbial decomposition and can remain in soils for long periods.

Answer 36

-Climate: this dictates plant growth and microbial and detritivore activity. Decomposition is rapid at high temps or in waterlogged soils. High rainfall increases potential carbon storage. Arid soils also only store 30 tonnes per hectare compared to 800tonnes per hectare in cold regions. -Soil type: clay-rich soils have a higher carbon content than sandy soils. Clay protects carbon from decomposition. -Management and use of soils: Since 1850, soils globally have lost 40-90Gt of carbon through cultivation and disturbance. Current rates of carbon loss due to land-use change are 1.6 +- 0.8 Gt of carbon/year.

Answer 37

It does this by affecting vegetation and little stores and flows. For example, the Arctic biome contains 1/3 of the earth’s soil but with a rapidly warming climate and rising CO2, so its net storage function may have already ‘flipped’ from a store to a source.

Answer 38

The carbon stores of the atmosphere, ecosystems and soils are in constant exchange. The carbon balance in soils is regulated by plant productivity, microbial activity, geology, erosion, climate and the amount of upwards and downwards (leaching) water movement in soil.

Answer 39

Sustaining other global systems. The carbon cycle plays a key role when regulating the Earth’s global temperature and climate by controlling the amount of CO2 in the atmosphere, which then affects the hydrological cycle. Ecosystem development and agriculture depends on the carbon cycle. Carbon stores and fluxes involve natural processes which have helped to regulate the carbon cycle and atmospheric CO2 levels for millions of years.

Answer 40

The sun is the natural driver of almost all of the earth’s atmospheric energy. Short-wave solar radiation comes from the sun and then dark surfaces on the earth absorb this and radiate it back as heat. One of the most vital roles in the carbon cycle is the release of CO2, and other gases such as methane (CH4) into the atmosphere. Some of the long-wave length radiation emitted from the earth is absorbed and reflected by the greenhouse gases back towards earth, and some passes back out into space. Retaining this heat causes the earth’s temps to be 16°C warmer than it would be otherwise, allowing life to be sustained.

Answer 41

-CO2 - makes up 89% of greenhouse gas produced. 30% increase since 1850. -Methane (CH4) - makes up 7% of greenhouse gases produced and is 21x more powerful than CO2. 250% increase since 1850. -Nitrous oxide (N2O). Makes up 3% of greenhouse gases produced. From jet engines and car pollution. 250x more powerful than CO2. 16% increase since 1850. -Hydrocarbons. 1% greenhouse gases produced. Used in industry. 3000x more powerful than CO2.

Answer 42

The concentration of several greenhouse gases in the atmosphere have increased by 25% since 1750, when industrialisation began in the UK. Since the 1980s, 75% of CO2 emissions have come from burning fossil fuels. Most researchers believe this is the cause of increased global temps. Human activity, such as burning fossil fuels and deforestation, release natural stores of carbon and nitrogen, which combine with oxygen in the air to form greenhouse gases. Global temps also increase the amount of water Vapor in the atmosphere, leading to greater condensation and cloud cover, trapping heat in the atmosphere.

Answer 43

-Approx 31% reflected by clouds, aerosols and gases in the atmosphere and by the land surface. -The other 69% is absorbed at the earth’s surface, especially by oceans. -69% of what is absorbed at the surface is re-radiated to space as longwave radiation. Some of this is re-reflected back towards the earth’s surface by clouds and greenhouse gases, ‘trapping’ the radiation.

Answer 44

-Different latitudes experience different concentrations of solar radiation, which in turn influences temperature. Solar insulation is most concentrated at the equator, but more dispersed at the Poles, causing the cooler pole temps. -Earth surface characteristics also have implications, e.g snow reflects a lot of sunlight and dark forests will absorb it. -Air movement, ocean currents and atmospheric circulation also distributes heat around the world.

Answer 45

-Solar radiation (insolation) is most intense over the Equator, convection and low-pressure systems dominate meaning rainfall is high all year. - At 30° N/S precipitation decreases and high pressure conditions means clouds rarely form. -Different air masses meet at the mid latitudes, and the low pressure systems bring rainfall. -Closer to the poles, precipitation falls as the air cools further and is dense and dry - creating polar deserts.

Answer 46

The effects of topography and migration of global pressure and wind systems (such as the movement of the ITCZ N and S of the equator) can cause regional variation.

Answer 47

-Phytoplankton sequesters CO2 through photosynthesis, transferring it from the atmosphere to the ocean stores. Known as the biological pump. This transfers 5-15 Gt of carbon from atmosphere to ocean each year. -Terrestrial photosynthesis allows for 100-120 Gt of carbon to be sequestered each year. Respiration and decomposition then releases this back into the atmosphere.

Answer 48

-Anything which affects the level of phytoplankton in the world’s oceans, or area of land covered by forest will have an impact on carbon sequestration, which in turn affects composition of the atmosphere. -Tropical rainforests climates are ideal for plant growth, and this promotes photosynthesis. -In oceans, warm tropical shallow waters are the ideal homes from coral reefs and mangroves, the marine equivalents of rainforests in terms of plant growth. -Deserts have sparse vegetation and offer little in terms of CO2 sequestration. -Melting arctic sea ice means that greater expanses of ocean are exposed to direct sunlight, and seasonal thaws now last longer. Increasing photosynthesis by phytoplankton now results in algal blooms in Arctic waters, so more CO2 is now being stored there.

Answer 49

Soil health depends on the amount of organic carbon which is stored in the soil. This depends on its inputs and outputs (decomposition, erosion and use in plant and animal productivity). Carbon is the main component of soil organic matter and helps to give soil its water-retention capacity, its structure and fertility. This is the opposite to ‘active’ soil carbon found in topsoil. Organic carbon is concentrated in the surface soil layer as easily eroded small particles, which is why soil erosion is a major threat to carbon storage and soil health.

Answer 50

Changes from a carbon source to a carbon sink. The deforestation, resource destruction and soil erosion which was occurring globally still occurs, but afforestation and reforestation efforts in North America, Europe and China as well as improvements in agricultural practice is helping to reform plant stores as carbon sinks. 2015 onwards could see warmer temps trigger faster decomposition and recycling of carbon in dead plants and soils, possibly causing them to become a carbon source again.

Answer 51

About 1% of solar insolation reaching earth is captured by photosynthesis and used by plants to produce organic material or biomass. The rate at which plants produce biomass is called primary productivity. Net primary productivity (amount of biomass produced by plants minus energy lost through respiration) is high in tropical rainforests with warm and humid conditions, and a year-round growing season. Tundra ecosystems, with a cool and dry climate, grow much more slowly and have a much lower level of productivity.

Answer 52

Highest: -Tropical rainforest (≈2200g/m2/yr) -Temperate deciduous forest -Savanna -Taiga -Temperate grassland -Tundra -Desert and scrubs (≈100 g/m^2/yr)

Answer 53

Since the Industrial Revolution in Europe, coal, oil and natural gas have been taken from the ground and used by industries, power stations and machinery. Compared to the natural carbon cycle, this happened very quickly, and atmospheric CO2 is the highest it has been in the past 800 000 years (over 400ppm).

Answer 54

-Temperate and tropical areas may have stronger storms because atmospheric heat and moisture has increased. -Fewer extreme cold events but more extreme warm events due to average temps increasing. -Biggest increase in average temps will be in the Arctic due to more heat being transferred from the tropics. -Precipitation patterns will change, higher near poles and lower near subtropics as warmer air can hold more soil moisture.

Answer 55

-10% of land species face extinction because of a lack of a ability to adapt to rising temperatures. Especially in polar areas. -80% of coral reefs could be bleached by warm seawater and suffer chemical erosion due to oceans becoming more acidic. -Warmer winters will allow the season for pests and disease to thrive to increase. -Biodiversity will change and habitats move further north to cooler regions, which will change food webs.

Answer 56

Organic matter helps retain soil moisture and nutrients, which in turn improves the productivity of an ecosystem by providing water and dissolved nutrients for plants to absorb through their roots to grow (increasing biomass).

Answer 57

-The shift of subtropical high pressure areas towards poles will increase drought conditions in Mediterranean climate zones. -Permafrost will melt, adding more water to Arctic rivers and streams. -River discharges will decrease in areas with lower precipitation and lower effective precipitation (where evaporation rates increase). -Cryosphere stores will decrease as glaciers retreat or surface ablation increases, this will increase river discharges in the short-run but decrease them in the long-run.

Answer 58

As carbon can be stored in soils as dead organic matter, in some regions this will be a process which takes thousands of years. Mangroves have thick layers of organic litter, humus and peat, all containing high levels of carbon. And as twice a day these soils are submerged below water by high tide, the soils are anaerobic and thus means decomposition is slow as microbes and bacteria cannot survive, so carbon is stored for thousands of years.

Answer 59

Their drainage and clearing, which causes their once anaerobic conditions preventing the biota needed for decomposition to be removed. This will cause significant amounts of carbon to be released into the atmosphere.

Answer 60

-Subduction zones, where carbon sources are oxidised and and vented back into the atmosphere or ocean. -Divergent plate boundaries, where rising magma releases CO2. -Hotspots (e.g Yellowstone), where non-erupting volcanoes passively diffuse CO2 into the atmosphere.