2.1 Earth's systems and processes

Earth's systems are interconnected networks that shape our planet. The geosphere, hydrosphere, atmosphere, and biosphere work together, exchanging matter and energy through various processes. Understanding these systems is crucial for grasping how our planet functions.

Biogeochemical cycles, like carbon and nitrogen, move essential elements through Earth's systems. These cycles maintain balance and support life. Human activities have disrupted many of these cycles, leading to environmental challenges we face today.

Earth's Systems: Components and Interactions

Geosphere: Solid Earth

Top images from around the web for Geosphere: Solid Earth

• 

  What are the Earth's Layers? - Universe Today View original

  Is this image relevant?

• 

  1.5 Fundamentals of Plate Tectonics – Physical Geology View original

  Is this image relevant?

• 

  What are the Earth's Layers? - Universe Today View original

  Is this image relevant?

• 

  1.5 Fundamentals of Plate Tectonics – Physical Geology View original

  Is this image relevant?

1 of 2

Top images from around the web for Geosphere: Solid Earth

• 

  What are the Earth's Layers? - Universe Today View original

  Is this image relevant?

• 

  1.5 Fundamentals of Plate Tectonics – Physical Geology View original

  Is this image relevant?

• 

  What are the Earth's Layers? - Universe Today View original

  Is this image relevant?

• 

  1.5 Fundamentals of Plate Tectonics – Physical Geology View original

  Is this image relevant?

1 of 2

• The geosphere consists of the solid Earth, including the crust, mantle, and core
• Source of minerals (gold, silver, copper), rocks (granite, limestone, basalt), and soils that support life on Earth
• Processes within the geosphere, such as plate tectonics and volcanic activity, shape Earth's surface and create diverse landscapes (mountains, valleys, plains)
• Interactions with other Earth systems include the formation of soil through weathering and erosion, the release of gases from volcanoes into the atmosphere, and the storage of groundwater in aquifers

Hydrosphere: Water on Earth

• The hydrosphere encompasses all water on Earth, including oceans, lakes, rivers, groundwater, and water vapor in the atmosphere
• Plays a crucial role in regulating Earth's climate by absorbing and redistributing heat through ocean currents (Gulf Stream, Antarctic Circumpolar Current)
• Supports diverse aquatic ecosystems, such as coral reefs, kelp forests, and wetlands, which are home to a wide variety of plant and animal species
• Interactions with other Earth systems include the exchange of water vapor with the atmosphere through evaporation and precipitation, the erosion and transport of sediments by rivers, and the dissolution of minerals from rocks

Atmosphere: Gaseous Envelope

• The atmosphere is the gaseous envelope surrounding Earth, composed primarily of nitrogen (78%) and oxygen (21%)
• Provides the air we breathe, which is essential for the survival of most living organisms on Earth
• Protects Earth from harmful solar radiation, such as ultraviolet (UV) rays, through the ozone layer in the stratosphere
• Influences weather and climate patterns through the uneven heating of Earth's surface, the formation of high and low-pressure systems, and the circulation of air masses
• Interactions with other Earth systems include the exchange of gases with the biosphere through photosynthesis and respiration, the transport of moisture and pollutants by winds, and the absorption and emission of heat by greenhouse gases

Biosphere: Zone of Life

• The biosphere comprises all living organisms on Earth, including plants, animals, and microorganisms
• Divided into distinct ecosystems, such as forests, grasslands, deserts, and tundra, each with its characteristic flora and fauna adapted to specific environmental conditions
• Plays a vital role in the cycling of nutrients and energy through food chains and food webs, with primary producers (plants) converting solar energy into chemical energy and consumers (animals) transferring energy to higher trophic levels
• Interactions with other Earth systems include the exchange of gases with the atmosphere through photosynthesis and respiration, the formation of soil through the decomposition of organic matter, and the uptake and release of water by plants through transpiration

Interconnections and Feedback Loops

• Earth's systems are interconnected and exchange matter and energy through various processes, such as the water cycle, carbon cycle, and rock cycle
• The water cycle involves the continuous movement of water through evaporation, transpiration, condensation, precipitation, infiltration, and surface runoff, connecting the hydrosphere, atmosphere, and biosphere
• The carbon cycle involves the exchange of carbon between the atmosphere, biosphere, hydrosphere, and geosphere through processes such as photosynthesis, respiration, decomposition, and the burning of fossil fuels
• The rock cycle describes the transformation of rocks through processes such as weathering, erosion, deposition, metamorphism, and igneous activity, linking the geosphere with other Earth systems
• Feedback loops, both positive and negative, play a crucial role in regulating the interactions between Earth's systems and maintaining a state of dynamic equilibrium
• Positive feedback loops amplify changes in a system (melting of Arctic sea ice reduces Earth's albedo, leading to increased absorption of solar radiation and further warming)
• Negative feedback loops counteract changes in a system (increased atmospheric CO2 levels lead to enhanced plant growth, which removes more CO2 from the atmosphere, mitigating the initial change)

Biogeochemical Cycles: Balance of Earth's Systems

Essential Elements and Their Pathways

• Biogeochemical cycles are the pathways through which essential elements, such as carbon, nitrogen, phosphorus, and water, move between the living and non-living components of Earth's systems
• These cycles involve the transfer of elements through various reservoirs, such as the atmosphere, biosphere, hydrosphere, and geosphere, and are driven by physical, chemical, and biological processes
• The cycling of elements is crucial for the growth and development of living organisms, as well as for the maintenance of ecosystem structure and function
• Disruptions to biogeochemical cycles, such as those caused by human activities, can lead to imbalances in Earth's systems and have far-reaching consequences for the environment and human well-being

Carbon Cycle: Photosynthesis to Fossil Fuels

• The carbon cycle involves the exchange of carbon between the atmosphere, biosphere, hydrosphere, and geosphere
• Key processes in the carbon cycle include photosynthesis (conversion of atmospheric CO2 into organic compounds by plants), respiration (release of CO2 by living organisms), decomposition (breakdown of dead organic matter), and the burning of fossil fuels (release of stored carbon into the atmosphere)
• The atmosphere serves as a major reservoir of carbon in the form of carbon dioxide (CO2), while the biosphere stores carbon in living organisms and dead organic matter (soil, peat)
• The hydrosphere, particularly the oceans, acts as a significant carbon sink, absorbing atmospheric CO2 and storing it as dissolved inorganic carbon (carbonic acid, bicarbonate, and carbonate ions)
• The geosphere stores carbon in the form of fossil fuels (coal, oil, natural gas) and carbonate rocks (limestone, dolomite), which are formed over millions of years through the burial and compression of organic matter
• Human activities, such as the burning of fossil fuels and deforestation, have significantly altered the natural balance of the carbon cycle, leading to increased atmospheric CO2 concentrations and global climate change

Nitrogen Cycle: Fixation to Denitrification

• The nitrogen cycle encompasses the processes by which nitrogen is converted between its various chemical forms, such as nitrogen fixation, nitrification, and denitrification
• Nitrogen fixation is the process by which atmospheric nitrogen (N2) is converted into biologically available forms, such as ammonia (NH3) and nitrate (NO3-), by nitrogen-fixing bacteria and cyanobacteria
• Nitrification is the process by which ammonia is oxidized into nitrite (NO2-) and then nitrate by nitrifying bacteria, making nitrogen available for uptake by plants
• Denitrification is the process by which nitrate is reduced back into atmospheric nitrogen by denitrifying bacteria, completing the nitrogen cycle
• The biosphere plays a crucial role in the nitrogen cycle, with plants assimilating nitrates and animals obtaining nitrogen through the consumption of plants or other animals
• Human activities, such as the use of nitrogen-based fertilizers and the burning of fossil fuels, have greatly increased the amount of biologically available nitrogen in the environment, leading to problems such as eutrophication and acid rain

Phosphorus Cycle: Weathering to Decomposition

• The phosphorus cycle describes the movement of phosphorus through the environment, including weathering of rocks, uptake by plants, and decomposition of organic matter
• Phosphorus is a limiting nutrient in many ecosystems, meaning that its availability often determines the growth and productivity of living organisms
• The geosphere serves as the primary source of phosphorus, with phosphate minerals (apatite) being released through weathering and erosion
• In the biosphere, plants take up dissolved phosphate ions from the soil and incorporate them into organic compounds, which are then consumed by animals and passed through food chains
• The decomposition of dead organic matter by microorganisms releases phosphorus back into the soil, where it can be taken up again by plants or leached into aquatic ecosystems
• Human activities, such as the use of phosphate-rich fertilizers and the discharge of sewage and industrial waste, have led to the accumulation of excess phosphorus in aquatic ecosystems, causing eutrophication and algal blooms

Water Cycle: Evaporation to Infiltration

• The water cycle, also known as the hydrologic cycle, involves the continuous movement of water through evaporation, transpiration, condensation, precipitation, infiltration, and surface runoff
• Evaporation is the process by which water changes from a liquid to a gas, primarily from the surface of oceans, lakes, and rivers, and enters the atmosphere
• Transpiration is the process by which water is released into the atmosphere from the leaves of plants through stomata, contributing to the overall evaporation from land surfaces
• Condensation occurs when water vapor in the atmosphere cools and forms liquid water droplets, leading to the formation of clouds and fog
• Precipitation is the process by which water falls from the atmosphere back to Earth's surface in the form of rain, snow, sleet, or hail
• Infiltration is the process by which water on the ground surface enters the soil, recharging groundwater aquifers and providing moisture for plant growth
• Surface runoff is the flow of water over land surfaces, which occurs when the rate of precipitation exceeds the rate of infiltration or when the soil is saturated
• The coupling of the water cycle with other biogeochemical cycles is essential for the transport and distribution of nutrients and the maintenance of ecosystem functions

Coupling of Cycles and Ecosystem Stability

• Biogeochemical cycles are driven by a combination of physical, chemical, and biological processes, and they play a vital role in recycling nutrients and maintaining the stability of Earth's systems
• The coupling of biogeochemical cycles occurs when the processes or components of one cycle influence or depend on those of another cycle
• For example, the carbon and nitrogen cycles are closely linked through the processes of photosynthesis and decomposition, with plants requiring both carbon dioxide and nitrogen compounds for growth, and decomposers releasing these elements back into the environment
• Similarly, the water cycle is coupled with the carbon cycle through the processes of evapotranspiration and precipitation, which influence the distribution and availability of water for plant growth and carbon uptake
• The phosphorus cycle is coupled with the carbon and nitrogen cycles through the uptake and release of phosphorus by living organisms, as well as through the weathering and erosion of phosphate-rich rocks
• The coupling of biogeochemical cycles helps to maintain the stability and resilience of ecosystems by ensuring the continuous recycling and availability of essential nutrients
• Disruptions to one biogeochemical cycle can have cascading effects on other cycles and the overall functioning of Earth's systems, highlighting the importance of understanding and managing these interconnections

Energy Flow and Nutrient Cycling in Earth's Systems

Solar Energy: Driver of Earth's Processes

• Energy from the sun drives most of the processes on Earth, including the water cycle, atmospheric circulation, and photosynthesis in the biosphere
• Solar radiation is the primary source of energy for Earth's systems, with the amount of incoming solar radiation varying based on latitude, season, and atmospheric conditions
• The uneven heating of Earth's surface by the sun creates temperature and pressure gradients, which drive atmospheric and oceanic circulation patterns, such as the Hadley Cell and the Gulf Stream
• Solar energy also powers the water cycle by providing the energy needed for evaporation and transpiration, which in turn leads to cloud formation, precipitation, and the recharge of freshwater resources
• In the biosphere, solar energy is captured by primary producers (plants and algae) through the process of photosynthesis, converting light energy into chemical energy stored in organic compounds

Energy Flow in Ecosystems

• The flow of energy through ecosystems follows the laws of thermodynamics, with energy being transferred from one trophic level to another and ultimately dissipating as heat
• Primary producers, such as plants and algae, form the foundation of food chains and food webs by converting solar energy into chemical energy through photosynthesis
• Consumers, such as herbivores (primary consumers) and carnivores (secondary and tertiary consumers), obtain energy by feeding on other organisms and transferring energy to higher trophic levels
• Decomposers, such as bacteria and fungi, break down dead organic matter and release nutrients back into the environment, playing a crucial role in energy flow and nutrient cycling
• Energy transfer between trophic levels is inefficient, with typically only about 10% of the energy being passed on to the next level, while the remaining 90% is lost as heat or used for metabolic processes
• This inefficiency in energy transfer limits the number of trophic levels in an ecosystem and influences the abundance and biomass of organisms at each level

Nutrient Cycling: Biotic and Abiotic Processes

• Nutrients, such as carbon, nitrogen, and phosphorus, cycle through Earth's systems via biogeochemical cycles, which involve both biotic and abiotic processes
• Biotic processes are those carried out by living organisms, such as photosynthesis, respiration, and decomposition, which play a crucial role in the uptake, storage, and release of nutrients
• Abiotic processes are non-living physical and chemical processes, such as weathering, erosion, and atmospheric and oceanic circulation, which influence the distribution and availability of nutrients
• The cycling of nutrients is essential for the growth and maintenance of living organisms, as well as for the overall productivity and stability of ecosystems
• Nutrient imbalances, such as those caused by human activities (fertilizer use, fossil fuel combustion), can lead to environmental problems, such as eutrophication, acid rain, and climate change

Decomposition: Recycling of Nutrients

• Decomposition is a critical process in nutrient cycling, as it breaks down dead organic matter and releases nutrients back into the environment for uptake by other organisms
• Decomposers, such as bacteria and fungi, secrete enzymes that break down complex organic compounds into simpler inorganic forms, such as carbon dioxide, water, and mineral nutrients
• The rate of decomposition is influenced by factors such as temperature, moisture, oxygen availability, and the chemical composition of the organic matter
• In terrestrial ecosystems, decomposition plays a key role in the formation and maintenance of soil fertility, as the released nutrients are essential for plant growth
• In aquatic ecosystems, decomposition is crucial for the recycling of nutrients and the support of primary productivity, although excessive decomposition can lead to oxygen depletion and the formation of dead zones

Coupling of Energy Flow and Nutrient Cycling

• The coupling of energy flow and nutrient cycling is essential for the functioning and sustainability of Earth's ecosystems
• Energy flow provides the necessary power for the biotic processes involved in nutrient cycling, such as photosynthesis, respiration, and decomposition
• Nutrient availability, in turn, influences the productivity and structure of ecosystems, as the growth and reproduction of organisms depend on the sufficient supply of essential elements
• The efficiency of energy transfer between trophic levels affects the amount of biomass and the cycling of nutrients within an ecosystem, with more efficient energy transfer supporting greater biomass and nutrient retention
• Disruptions to energy flow or nutrient cycling, such as those caused by human activities or natural disturbances, can have cascading effects on ecosystem functioning and stability
• Understanding the coupling of energy flow and nutrient cycling is crucial for the management and conservation of Earth's ecosystems, as well as for predicting the impacts of global environmental changes

Human Impact on Earth's Systems and Processes

Alteration of Natural Balances

• Human activities, such as fossil fuel combustion, deforestation, and land-use changes, have significantly altered the natural balance of Earth's systems
• The burning of fossil fuels has increased atmospheric concentrations of greenhouse gases, primarily carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)
• Deforestation and land-use changes have reduced the capacity of ecosystems to absorb and store carbon, further contributing to the increase in atmospheric CO2 levels
• These alterations have led to global climate change, which is characterized by rising global temperatures, changes in precipitation patterns, and more frequent and intense extreme weather events
• Human activities have also disrupted biogeochemical cycles, such as the nitrogen and phosphorus cycles, through the excessive use of fertilizers and the release of pollutants into the environment

Climate Change and Its Impacts

• The increasing atmospheric concentrations of greenhouse gases, driven by human activities, have led to global climate change and its associated impacts on ecosystems, sea levels, and weather patterns
• Rising global temperatures have caused the melting of glaciers and ice sheets, leading to sea-level rise and the inundation of coastal areas and low-lying islands
• Changes in precipitation patterns, including more frequent and intense droughts and floods, have affected the availability of freshwater resources and the productivity of agricultural systems
• Shifting climate zones and changes in the timing of seasonal events (phenology) have impacted the distribution and abundance of species, leading to the disruption of ecological communities and the loss of biodiversity
• Ocean acidification, caused by the absorption of excess atmospheric CO2, has negative effects on marine organisms with calcium carbonate shells or skeletons (corals, mollusks), compromising the health and resilience of marine ecosystems

Biodiversity Loss and Habitat Degradation

• Deforestation and land-use changes have reduced biodiversity, disrupted habitats, and altered the carbon cycle by reducing the capacity of ecosystems to absorb and store carbon
• The conversion of natural habitats, such as forests and wetlands, into agricultural or urban areas has led to the fragmentation and loss of ecosystems, endangering many plant and animal species
• Habitat degradation, caused by pollution, overexploitation, and invasive species, has further contributed to the decline of biodiversity and the disruption of ecological processes
• The loss of biodiversity has far-reaching consequences for the functioning and resilience of ecosystems, as well as for the provision of essential ecosystem services, such as pollination, pest control, and nutrient cycling
• Efforts to conserve biodiversity and restore degraded habitats, such as the establishment of protected areas and the implementation of sustainable land management practices, are crucial for mitig