KQ3

• Changes to the Carbon Cycle: Volcanic Activity ☆ Carbon is transferred from lithosphere to the atmosphere ☆ When crustal plates colide, one sinks beneath the other and the rock melts under extreme pressure and heat. Heated rock recombines into silicate minerals releasing CO2 ☆ Destruction of vegetation leads to reduction in carbon sequestration ☆ Ash clouds block out sunlight limiting photosynthesis
• Changes to the carbon cycle: Wildfires ☆ Occurs where lots of vegetation is. (Leaf and plant litter) ☆ If this is dry enough, it can be ignited by lightning strikes and make a fire. These wildfires release carbon into the atmosphere and clear vegetation ☆ Over time a new ecosystem will form with new vegetation and it'll absorb carbon.
• Changes in the carbon cycle ☆ Diurnal changes: temperature, precipitation and evaporation ☆ Seasonal changes: temperature, location, storage ☆ Volcanic activity ☆ Wildfires ☆ Glacial & Interglacial cycle
• How many tonnes of carbon is emitted per year due to burning fossil fuels? 8 Billion
• How much did historic forest cover reduce by due to deforestation? 50%
• How much did global temperatures rise by between 1901 and 2020? 1 degree
• How much has the amount of CO2 in the atmosphere risen by since 1958? 25%
• How much water is stored in the oceans? 97% of global water
• How much water is needed to make a smartphone and a laptop? 14,000 litres for the smartphone, 190,000 for the laptop.
• Diurnal changes in the water and carbon cycles When it is day time it will be warmer so processes like evaporation and precipitation will be more evident. Photosynthesis rate would increase meaning more carbon is sequestered in the plants.
• Seasonal change in the water and carbon cycles In summer the temperature will be higher meaning more evapotranspiration, precipitation and potentially more infiltration. Photosynthesis will increase which will raise the amount of carbon stored in the biosphere
• Orbital cycles affecting the water and carbon cycles Milankovitch cycles affect the eccentricity, obliquity and precession of the Earth which can affect temperature and processes such as infiltration, photosynthesis, evapotranspiration and precipitation
• Volcanic activity affecting the water and carbon cycles Volcanic eruptions produce ash which block the sun's radiation from reaching the Earth which reduces temperatures. The sulphur dioxide also reflects the sunlight back into the atmosphere. The eruption of Mount Tambora in 1816 is an example of short term global decrease in temperature. Temperatures decreased by 0.4 to 0.7 degrees
• Sunspots affecting water and carbon cycles The sun's energy changes over time. Sunspots are dark patches on the surface of the sun where solar flares occur. Maximum sunspot activity increases temperatures on Earth while minimum sunspot decreases the Earth's temperature.
• Glacial & Interglacial cycles affecting water and carbon cycles Since the middle quaternary, glacial-interglacial cycles have lasted for about 100,000 years each. Glacial cycles are categorised by the presence of large ice sheets and interglacial the absence of them. Interglacials tend to occur when there are periods of peak solar radiation.
• How does urbanisation affect the carbon cycle? 10% of the carbon released globally comes from changing land-use with the replacement of countryside with built-up areas. It is estimated that 2.4% of global carbon emissions are caused by cement production, CO2 is a by-product of the chemical conversion of limestone to lime. Cities consume as much as 80% of energy production worldwide.
• How does agriculture affect the carbon cycle? Livestock release methane when they ruminate. 20% of the USA’s methane emissions originate from cattle. Methane is also a bi-product of rice cultivation. Methane is emitted from flooded rice fields as bacteria in the waterlogged soil produce it in large quantities.
• How does deforestation affect the carbon cycle? 20% of global carbon dioxide emissions is caused by deforestation. Although deforestation is occurring around the world, it is particularly concentrated in tropical regions. Clearing forests speeds up the decay of leaf litter on the forest floor, releasing even more carbon to the atmosphere. Soil carbon is exposed to the atmosphere, speeding up soil erosion, removal of carbon into the hydrosphere by rainwater and rivers and even the release of stored soil carbon through decomposition into the atmosphere.
• How does forestry affect the carbon cycle? Forest trees extract CO2 from the atmosphere and sequester it for hundreds of years. Though forests trees only absorb more carbon than they release for the first 100 years after planting; after this the amount of carbon being absorbed through photosynthesis is balanced out by the decomposition of leaves.
• Dynamic equilibrium The lack of overall change in a system, if changes happen feedback occurs which corrects the system to its original state
• Positive feedback loop A positive feedback loop is a feedback loop which amplifies the initial change which leads to repetition of the cycle.
• Negative feedback loop A negative feedback loop is a feedback loop where the process occurring is counteracted by another process
• Example of a positive feedback loop in the water cycle Increasing temperatures mean increased rates of evaporation which increases the atmospheric concentrations of water vapour which enhances the greenhouse effect and increases temperatures
• Example of a negative feedback loop Increased precipitation means enhanced percolation of water into aquifers which reduces evapotranspiration because water is stored underground which reduces precipitation.