♻️AP Environmental Science Unit 4 – Earth Systems & Resources

Earth's Structure and Composition

• Earth consists of several layers: crust, mantle, outer core, and inner core
  • Crust is the thin, outermost layer (~5-70 km thick) composed of solid rocks (basalt, granite)
  • Mantle is the thick, middle layer (~2,900 km thick) composed of hot, dense rocks (peridotite)
  • Outer core is a liquid layer (~2,200 km thick) composed primarily of iron and nickel
  • Inner core is a solid layer (~1,200 km thick) composed primarily of iron and nickel
• Earth's composition includes a variety of elements and minerals
  • Most abundant elements in Earth's crust include oxygen, silicon, aluminum, and iron
  • Common rock-forming minerals include quartz, feldspar, mica, and olivine
• Earth's interior is divided into lithosphere and asthenosphere based on mechanical properties
  • Lithosphere includes the crust and uppermost mantle, behaves as a rigid layer
  • Asthenosphere is a portion of the upper mantle that behaves plastically, allows for plate movement
• Earth's magnetic field is generated by convection currents in the outer core
  • Magnetic field deflects charged particles from the solar wind, protecting Earth's atmosphere
• Earth's structure and composition have been shaped by various processes over its ~4.6 billion year history
  • Differentiation of Earth's layers occurred early in its history due to density differences
  • Plate tectonics and volcanic activity continue to modify Earth's surface and interior

Plate Tectonics and Geological Processes

• Plate tectonics is the theory that Earth's lithosphere is divided into several large, rigid plates that move and interact
• Plates move due to convection currents in the mantle, driven by heat from Earth's interior
• Three main types of plate boundaries: divergent, convergent, and transform
  • Divergent boundaries occur where plates move apart, creating new oceanic crust (mid-ocean ridges)
  • Convergent boundaries occur where plates collide, resulting in subduction or mountain building (trenches, volcanic arcs)
  • Transform boundaries occur where plates slide past each other, causing earthquakes (San Andreas Fault)
• Geological processes shape Earth's surface and create various landforms
  • Weathering breaks down rocks through physical, chemical, and biological processes
  • Erosion transports weathered materials by wind, water, or ice
  • Deposition occurs when eroded materials are laid down, forming sedimentary rocks
• Volcanic activity occurs when magma rises to Earth's surface, creating various features
  • Shield volcanoes have gentle slopes and are formed by fluid lava flows (Mauna Loa)
  • Composite volcanoes have steep slopes and are formed by alternating layers of lava and ash (Mount Fuji)
• Earthquakes occur when stress builds up along plate boundaries or faults, causing sudden movement
  • Seismic waves generated by earthquakes can be used to study Earth's interior structure
• Geological processes operate on various timescales, from sudden events to gradual changes over millions of years

Atmosphere and Climate Systems

• Earth's atmosphere is a thin layer of gases that surrounds the planet, composed primarily of nitrogen (78%) and oxygen (21%)
• Atmosphere is divided into several layers based on temperature changes: troposphere, stratosphere, mesosphere, thermosphere
  • Troposphere is the lowest layer where weather occurs, temperature decreases with altitude
  • Stratosphere contains the ozone layer, which absorbs harmful UV radiation
• Greenhouse gases in the atmosphere trap heat, contributing to Earth's climate
  • Main greenhouse gases include water vapor, carbon dioxide, methane, and nitrous oxide
  • Increasing greenhouse gas concentrations due to human activities are causing global climate change
• Climate is the long-term average of weather conditions in a particular area
  • Factors that influence climate include latitude, altitude, ocean currents, and atmospheric circulation patterns
• Earth's climate system involves complex interactions between the atmosphere, oceans, land, and biosphere
  • Positive feedback loops can amplify climate changes (ice-albedo feedback)
  • Negative feedback loops can dampen climate changes (carbon cycle)
• Global climate patterns are driven by uneven heating of Earth's surface and the transfer of energy
  • Hadley, Ferrel, and Polar cells are large-scale atmospheric circulation patterns
  • Jet streams are fast-moving air currents that influence weather patterns
• Climate change can have significant impacts on ecosystems, human societies, and the economy
  • Rising sea levels, more frequent extreme weather events, and shifts in species distributions are some potential consequences

Hydrosphere and Water Cycle

• Hydrosphere includes all of Earth's water in various forms: oceans, lakes, rivers, groundwater, ice
• Oceans cover ~71% of Earth's surface and play a crucial role in regulating climate and supporting life
  • Ocean currents transport heat and nutrients, influencing global climate patterns
  • Upwelling brings nutrient-rich deep water to the surface, supporting marine ecosystems
• Water cycle describes the continuous movement of water through Earth's systems
  • Main processes in the water cycle include evaporation, transpiration, condensation, precipitation, and runoff
  • Water cycle connects the hydrosphere with the atmosphere, biosphere, and geosphere
• Freshwater resources are essential for human societies and ecosystems
  • Surface water includes lakes, rivers, and wetlands, which support biodiversity and provide water for various uses
  • Groundwater is water stored in porous rock or sediment, accessed through wells or springs
• Water scarcity is a growing concern in many regions due to population growth, climate change, and pollution
  • Sustainable water management practices include conservation, efficiency improvements, and wastewater treatment
• Water quality is affected by various pollutants, such as nutrients, chemicals, and pathogens
  • Eutrophication occurs when excess nutrients stimulate algal growth, leading to oxygen depletion in water bodies
  • Water treatment processes remove contaminants and ensure safe drinking water supplies
• Hydrosphere interacts with other Earth systems through processes like weathering, erosion, and sedimentation

Biosphere and Ecosystems

• Biosphere encompasses all life on Earth, including organisms and their interactions with the environment
• Ecosystems are communities of organisms and their abiotic environment, linked by energy and nutrient flows
  • Examples of ecosystems include forests, grasslands, deserts, and coral reefs
  • Ecosystem services are benefits provided by ecosystems, such as carbon sequestration, water purification, and recreation
• Biodiversity refers to the variety of life at all levels, from genes to ecosystems
  • High biodiversity is associated with ecosystem stability and resilience
  • Biodiversity loss is a major concern, caused by habitat destruction, overexploitation, and climate change
• Energy flow in ecosystems follows a hierarchical structure, from producers to consumers
  • Primary producers (autotrophs) convert solar energy into chemical energy through photosynthesis
  • Consumers (heterotrophs) obtain energy by feeding on other organisms
• Nutrient cycling involves the transfer of essential elements like carbon, nitrogen, and phosphorus through ecosystems
  • Decomposers break down dead organic matter, releasing nutrients back into the environment
  • Human activities can disrupt nutrient cycles, leading to imbalances and pollution
• Ecological succession describes the gradual changes in species composition over time
  • Primary succession occurs on newly exposed surfaces, like volcanic islands or glacial moraines
  • Secondary succession occurs following a disturbance, like a forest fire or abandoned agricultural land
• Biosphere interacts with other Earth systems through processes like carbon sequestration, oxygen production, and soil formation

Natural Resources and Energy

• Natural resources are materials or substances that occur naturally and can be used for economic gain
  • Renewable resources can be replenished on a human timescale (solar, wind, hydropower)
  • Non-renewable resources are finite and cannot be easily replaced (fossil fuels, minerals)
• Fossil fuels (coal, oil, natural gas) are the primary energy sources for modern societies
  • Burning fossil fuels releases greenhouse gases, contributing to climate change
  • Peak oil refers to the point at which maximum extraction rates are reached, followed by a decline
• Renewable energy sources are increasingly important for reducing greenhouse gas emissions and ensuring energy security
  • Solar energy can be harnessed through photovoltaic cells or solar thermal collectors
  • Wind energy is captured using wind turbines, which convert kinetic energy into electricity
  • Hydropower generates electricity by harnessing the energy of falling or flowing water
• Nuclear energy is derived from the splitting of atomic nuclei (fission) or the fusion of light atoms (fusion)
  • Nuclear fission is used in current nuclear power plants, but generates radioactive waste
  • Nuclear fusion has the potential to provide abundant, clean energy, but technical challenges remain
• Mineral resources are non-renewable and extracted through mining operations
  • Metals like iron, copper, and aluminum are used in construction, transportation, and electronics
  • Rare earth elements are critical for clean energy technologies, but their extraction can have environmental impacts
• Sustainable resource management involves balancing economic, social, and environmental considerations
  • Circular economy approaches aim to minimize waste and maximize resource efficiency
  • Life cycle assessment evaluates the environmental impacts of a product or process from cradle to grave

Human Impacts on Earth Systems

• Human activities have significant impacts on Earth's systems, often leading to environmental degradation
• Land use changes, such as deforestation and urbanization, alter ecosystems and biogeochemical cycles
  • Deforestation contributes to biodiversity loss, soil erosion, and climate change
  • Urbanization can lead to habitat fragmentation, increased pollution, and altered hydrological processes
• Agriculture has transformed large areas of land and has impacts on soil, water, and biodiversity
  • Intensive farming practices can lead to soil degradation, nutrient depletion, and pesticide pollution
  • Irrigation can cause water scarcity and salinization of soils
• Industrial activities release pollutants into the air, water, and soil
  • Air pollution from factories and vehicles can cause respiratory problems and contribute to acid rain
  • Water pollution from industrial effluents can harm aquatic ecosystems and human health
• Overconsumption of resources and generation of waste strain Earth's capacity to absorb and regenerate
  • Plastic pollution is a growing concern, with impacts on marine life and potential human health risks
  • Electronic waste contains toxic substances and is often improperly disposed of in developing countries
• Climate change, largely driven by human activities, has far-reaching consequences for Earth's systems
  • Rising temperatures, changing precipitation patterns, and more frequent extreme events affect ecosystems and human societies
  • Ocean acidification, caused by increased absorption of atmospheric CO2, threatens marine biodiversity and food webs
• Human impacts are interconnected and can have cascading effects across Earth's systems
  • Feedback loops can amplify or dampen the effects of human activities on the environment
  • Addressing human impacts requires a systems thinking approach that considers the complex interactions between social and ecological systems

Sustainability and Conservation Strategies

• Sustainability aims to meet the needs of the present without compromising the ability of future generations to meet their own needs
  • Three pillars of sustainability: environmental, social, and economic
  • Sustainable development seeks to balance economic growth with environmental protection and social equity
• Conservation strategies aim to protect and preserve natural resources, biodiversity, and ecosystems
  • Protected areas, such as national parks and wildlife reserves, safeguard important habitats and species
  • Ecosystem-based management considers the interactions between species and their environment
• Renewable energy transition is crucial for reducing greenhouse gas emissions and mitigating climate change
  • Policies and incentives can support the deployment of renewable energy technologies
  • Energy efficiency measures can reduce energy demand and associated environmental impacts
• Sustainable agriculture practices can help to feed a growing population while minimizing environmental harm
  • Agroecology applies ecological principles to agricultural systems, promoting biodiversity and soil health
  • Precision agriculture uses technology to optimize resource use and minimize inputs
• Sustainable water management is essential for ensuring water security and ecosystem health
  • Integrated water resources management considers the multiple uses and users of water resources
  • Water conservation measures, such as efficient irrigation and low-flow appliances, can reduce water demand
• Circular economy approaches aim to minimize waste and maximize resource efficiency
  • Designing products for durability, repairability, and recyclability can reduce resource consumption
  • Industrial symbiosis involves the exchange of waste materials and energy between industries
• Education and awareness-raising are important for promoting sustainable behaviors and decision-making
  • Environmental education can foster knowledge, skills, and values for sustainability
  • Public engagement and participatory processes can help to build support for sustainability initiatives
• International cooperation is necessary for addressing global environmental challenges
  • Multilateral agreements, such as the Paris Agreement on climate change, set shared goals and commitments
  • Technology transfer and capacity building can support sustainable development in developing countries