1033576120.pdf

# Earth's surface systems and energy flow Earth's surface systems are fundamentally driven by the flow of energy from both solar radiation and Earth's internal heat, influencing key geological and biogeochemical cycles [2](#page=2) [3](#page=3) [4](#page=4). ### 1.1 Energy drivers of Earth's surface systems The primary driver of most processes on Earth's surface, including the water cycle and land erosion, is the Sun's energy. Electromagnetic radiation from the sun is the principal source of energy for Earth's surface geologic system processes. Energy primarily leaves the Sun's photosphere as electromagnetic radiation. Latitude is the factor that most significantly affects climate zones on Earth. Increasing altitude generally leads to colder climates [12](#page=12) [2](#page=2) [3](#page=3) [4](#page=4). > **Tip:** Understanding the energy budget, which is the balance between incoming solar radiation and outgoing heat energy at Earth's surface, is crucial for comprehending climate and surface processes [5](#page=5). The internal engine, driven by the flow of heat out of Earth, is also a critical driver, particularly for the rock cycle and processes like mountain building and the formation of igneous rocks from magma. The formation of igneous rock from magma and mountain building from uplift are both pathways driven by Earth's internal heat. The rock cycle is powered by two "dueling engines": the internal engine (plate tectonics) and the external sun-powered water cycle [13](#page=13) [4](#page=4) [5](#page=5). ### 1.2 Residence time in Earth's reservoirs The term for the average amount of time a molecule spends in any of Earth's reservoirs is **residence time** [2](#page=2). ### 1.3 Feedback mechanisms in Earth systems Earth systems can experience different types of feedback mechanisms that influence their stability and change. #### 1.3.1 Reinforcing feedback Reinforcing feedback amplifies a change in an Earth system. For example, meanders in a river can grow larger as water flows faster on the outside of a curve, eroding the bank, which is an example of reinforcing feedback. Warmer temperatures melting an ice shelf and darker rock absorbing more energy after a glacier melts are also examples of processes that amplify change [3](#page=3) [4](#page=4). #### 1.3.2 Counterbalancing (negative) feedback Counterbalancing feedback works to stabilize a system by counteracting a change. An example of counterbalancing feedback is when meanders grow so large that they cut themselves off, forming an oxbow lake and returning the river to a straighter path [3](#page=3) [4](#page=4). > **Tip:** Distinguishing between reinforcing and counterbalancing feedback is key to understanding how Earth systems respond to disturbances. #### 1.3.3 Tipping points Tipping points are thresholds that can lead to sudden and irreversible changes within a system [2](#page=2). ### 1.4 Major Earth cycles Several interconnected cycles govern the movement of essential elements and water through Earth's systems. #### 1.4.1 The rock cycle The rock cycle describes the transformation of rocks through various processes. * **Igneous rock formation:** Igneous rocks are formed from the cooling and crystallization of magma [3](#page=3) [4](#page=4) [5](#page=5). * **Metamorphism:** Metamorphism is primarily a chemical process where increasing temperature and pressure alter the shape and composition of minerals. This process can transform sedimentary rocks into metamorphic rocks, for instance, by increasing pressure and temperature to alter existing minerals [3](#page=3) [4](#page=4). * **Sediment fate:** Sediments carried away by erosion, often by the water cycle, typically end up in the ocean [5](#page=5). #### 1.4.2 The water cycle The water cycle, powered by the sun's energy, involves the movement of water through evaporation, condensation, precipitation, and streamflow. Evapotranspiration is a water cycle process that requires energy input from the sun [3](#page=3) [4](#page=4). #### 1.4.3 The carbon cycle The carbon cycle involves the exchange of carbon between Earth's atmosphere, oceans, land, and living organisms. * **Photosynthesis:** Photosynthesis is a vital process for plants, enabling them to create and store energy from sunlight and is a significant contributor to the reduction of atmospheric carbon dioxide over geological time. Primitive life forms and the expansion of photosynthetic plant life altered Earth's early atmosphere by absorbing carbon dioxide [12](#page=12) [13](#page=13) [3](#page=3). * **Respiration:** Respiration is a process that returns carbon dioxide from living organisms (ocean life, vegetation) back to the atmosphere [4](#page=4). * **Erosion and carbon:** Erosion can release carbon dioxide from rocks into the atmosphere. Chemical weathering of rocks has a significant effect on Earth's atmosphere by removing carbon dioxide [12](#page=12) [13](#page=13). ### 1.5 Natural climate change factors Several factors influence natural climate change over geological time. * **Solar output:** Changes in the Sun's energy output can contribute to natural climate change [12](#page=12) [13](#page=13). * **Volcanic activity:** Volcanic activity is a factor in natural climate change [13](#page=13). * **Tectonic events:** Tectonic events also contribute to natural climate change [13](#page=13). > **Example:** Smartphone usage is NOT a factor contributing to natural climate change according to the geologic record [13](#page=13). --- # Atmospheric systems and climate factors Atmospheric systems and climate factors involve the processes that govern Earth's climate, including energy transfer within the atmosphere, the water cycle, global circulation patterns, and feedback mechanisms that influence long-term climate trends. ## 2. Atmospheric systems and climate factors ### 2.1 Earth's energy budget The balance between incoming solar radiation and outgoing heat energy at Earth's surface is crucial for maintaining temperatures. Earth's surface energy budget is primarily driven by incoming solar radiation, which is mostly in the form of visible light [5](#page=5) [6](#page=6). #### 2.1.1 Albedo Albedo refers to the proportion of incoming sunlight that reflects off an object's surface. Surfaces like fresh snow generally have a high albedo, reflecting a significant amount of sunlight. Conversely, surfaces such as water typically have a low albedo, absorbing more sunlight [11](#page=11) [9](#page=9). #### 2.1.2 Greenhouse effect The greenhouse effect is the process where infrared energy is absorbed by atmospheric gases and then re-radiated back toward the surface. This absorption and re-radiation trap heat, warming the planet. Factors that can increase Earth's surface temperature include an increase in incoming sunlight, an increase in energy trapped by greenhouse gases, and a decrease in the amount of sunlight reflected back into space [6](#page=6) [9](#page=9). #### 2.1.3 Role of clouds During the daytime, clouds primarily have a cooling effect on Earth's temperature by reflecting sunlight back into space [10](#page=10). ### 2.2 Atmospheric layers and processes Earth's atmosphere is divided into several layers, each with distinct characteristics and processes. #### 2.2.1 Troposphere The troposphere is the lowest layer of the atmosphere and contains most clouds and weather phenomena [6](#page=6). #### 2.2.2 Stratosphere In the stratosphere, ozone absorbs ultraviolet radiation from the sun, leading to an increase in temperature within this layer [7](#page=7). #### 2.2.3 Dew point and condensation The dew point is the temperature at which air becomes saturated with water vapor, initiating condensation. Condensation is a key process in cloud formation and precipitation [6](#page=6). ### 2.3 Global atmospheric circulation The global pattern of air circulation is influenced by Earth's size and rotation, resulting in a system of interconnected atmospheric cells [8](#page=8). #### 2.3.1 Pressure zones Places where air is rising in the global atmospheric circulation model are classified as low-pressure zones. In a low-pressure region at the surface, air is rising and cooling, leading to the formation of clouds and precipitation [7](#page=7). #### 2.3.2 Circulation cells The global atmospheric circulation is broken up into six cells due to Earth's size and rate of rotation. Most of Earth's rain falls in the Hadley cells, where warm air rises and cools, influencing trade winds. Ferrel cells and polar cells are also components of this global circulation system [8](#page=8). #### 2.3.3 Storm systems Cyclones are large, rapidly rotating storm systems characterized by high winds, a low-pressure center (the eye), and spiraling arms of thunderstorms [8](#page=8). ### 2.4 The water cycle The water cycle describes the continuous movement of water on, above, and below the surface of the Earth. #### 2.4.1 Evapotranspiration The water cycle begins with evapotranspiration, which is a combination of evaporation and transpiration from the leaves of plants. Processes within the water cycle that require energy input from the sun include evapotranspiration [3](#page=3) [7](#page=7). #### 2.4.2 Precipitation The type of precipitation that reaches the ground is influenced by the temperature of the air it falls through and the temperature near the surface [8](#page=8). ### 2.5 Climate factors and feedback mechanisms Long-term climate is influenced by various factors and is subject to feedback mechanisms that can amplify or dampen changes. #### 2.5.1 Latitude and altitude Latitude is the factor that most significantly affects climate zones on Earth. Increasing altitude generally leads to colder temperatures [12](#page=12). #### 2.5.2 Feedback loops * **Reinforcing feedback (Positive feedback):** This type of feedback amplifies a change in an Earth system [3](#page=3). * **Example:** The melting of sea ice creates a reinforcing feedback for warming because the exposed dark ocean water absorbs more sunlight than ice, accelerating the warming process [10](#page=10). * **Example:** Forming meanders in a river can represent reinforcing feedback [3](#page=3). * **Example:** Warmer temperatures melting an ice shelf is an example of reinforcing feedback [4](#page=4). * **Example:** Darker rock absorbing more energy after a glacier melts is a reinforcing feedback [4](#page=4). * **Counterbalancing feedback (Negative feedback):** This type of feedback works to reduce or counteract a change in an Earth system [3](#page=3). * **Example:** When meanders grow so large that they cut themselves off, forming an oxbow lake and returning to a straighter river path, this represents counterbalancing feedback [4](#page=4). #### 2.5.3 Specific feedback examples * The ocean's absorption of carbon dioxide (CO2) from the atmosphere is an example of counterbalancing feedback [9](#page=9). * Biomass feedback for global warming can involve plants absorbing CO2 [10](#page=10). #### 2.5.4 Tropical deforestation The overall net result of tropical deforestation on climate is warming [9](#page=9). #### 2.5.5 Ocean currents The global convection cycle of deep ocean currents is driven by temperature and salinity, where cold, salty water is denser than warm freshwater [10](#page=10). #### 2.5.6 Early Earth atmosphere Early Earth's atmosphere changed due to primitive life forms; the expansion of photosynthetic plant life captured oxygen and released carbon dioxide [12](#page=12). #### 2.5.7 Erosion and the carbon cycle Erosion can release carbon dioxide from rocks into the atmosphere, thereby relating to the carbon cycle [12](#page=12). ### 2.6 Solar energy The Sun is the primary source of energy for many Earth systems. #### 2.6.1 Solar processes Energy is generated in the Sun's core through nuclear fusion. The Sun converts approximately 6.2 billion tons of hydrogen into helium each second. Due to extreme temperatures, atoms in the Sun exist as plasma, with electrons stripped off the nuclei. Energy primarily leaves the Sun's photosphere as electromagnetic radiation [11](#page=11) [12](#page=12). --- # Feedback loops and system changes Feedback loops significantly influence Earth's systems, driving changes that can range from gradual adjustments to abrupt, irreversible shifts known as tipping points. Understanding these mechanisms is crucial for comprehending the dynamics and potential future states of our planet [2](#page=2). ### 3.1 Types of feedback loops Earth's systems are governed by two primary types of feedback loops: reinforcing (positive) and counterbalancing (negative) feedback [3](#page=3). #### 3.1.1 Reinforcing feedback (positive feedback) Reinforcing feedback loops amplify an initial change in an Earth system. They push a system further away from its initial state, potentially leading to rapid and significant alterations [3](#page=3). * **Example:** The melting of sea ice is a prime example of reinforcing feedback for warming. As temperatures rise, sea ice melts, exposing darker ocean water. This darker water has a lower albedo (reflectivity) and absorbs more sunlight than ice. The increased absorption of solar energy leads to further warming, which in turn causes more ice to melt, creating a self-perpetuating cycle [10](#page=10). * **Example:** Tropical deforestation also contributes to warming through a reinforcing feedback mechanism. Clearing forests reduces the Earth's reflectivity (albedo), leading to increased absorption of solar radiation and subsequent warming [9](#page=9). * **Example:** The ocean's absorption of CO2 from the atmosphere is also described as a reinforcing feedback [9](#page=9). #### 3.1.2 Counterbalancing feedback (negative feedback) Counterbalancing feedback loops, also known as negative feedback, counteract an initial change, acting to stabilize a system and return it to its original state or a new equilibrium [3](#page=3). * **Example:** The formation of oxbow lakes from meanders in rivers illustrates counterbalancing feedback. When meanders become so large that they cut themselves off, they form an oxbow lake, returning the river to a straighter course [4](#page=4). * **Example:** Clouds primarily have a cooling effect during the daytime by reflecting sunlight back into space, acting as a counterbalancing mechanism against warming [10](#page=10). * **Example:** While not explicitly detailed in the provided text in the context of feedback loops for system changes, the concept of residence time—the average amount of time a molecule spends in a reservoir—is a foundational concept in understanding system dynamics and potential changes [2](#page=2). ### 3.2 Tipping points and irreversible changes When the changes within a system driven by feedback loops exceed certain thresholds, they can lead to sudden and irreversible changes, known as tipping points. These points signify a transition to a fundamentally different state for the Earth system, from which recovery may be extremely difficult or impossible [2](#page=2). ### 3.3 Energy drivers of Earth's systems Earth's surface geologic system processes are primarily driven by the electromagnetic radiation from the sun. This solar energy powers vital cycles such as the water cycle and the erosion of land. Processes like evapotranspiration, a key component of the water cycle, require significant energy input from the sun [2](#page=2) [3](#page=3). In contrast, processes such as the formation of igneous rock from magma and mountain building are driven by the flow of heat out of the Earth's interior, referred to as the internal engine [4](#page=4). ### 3.4 Albedo and its role in feedback Albedo refers to the reflectivity of a surface. Surfaces like fresh snow and ice have a high albedo, meaning they reflect a large amount of incoming sunlight. Conversely, surfaces such as water and dark wet soil have a low albedo, absorbing more solar energy. Changes in albedo are critical to understanding feedback loops, particularly in relation to temperature changes. For instance, the melting of ice, which has a high albedo, exposes darker surfaces with lower albedo, leading to increased absorption of solar radiation and subsequent warming—a reinforcing feedback mechanism. Factors that increase Earth's surface temperature include an increase in incoming sunlight and an increase in how much energy is trapped by greenhouse gases, while a decrease in how much sunlight is reflected back into space also contributes to warming [10](#page=10) [9](#page=9). > **Tip:** Remember that "positive feedback" in Earth science contexts does not imply a beneficial outcome; it refers to the amplification of a change. > **Tip:** When considering system changes, think about how initial disturbances are either amplified or dampened by the inherent feedback mechanisms within that system. --- # Solar energy and its role The Sun is the fundamental energy source for Earth, driving its climate, atmospheric processes, and geological systems. ### 4.1 The sun as an energy source The Sun generates its immense energy through nuclear fusion occurring in its core [11](#page=11). #### 4.1.1 Nuclear fusion in the sun's core * The process of nuclear fusion is responsible for generating energy within the Sun's core [11](#page=11). * During this process, a significant amount of hydrogen is converted into helium each second. Approximately 6.2 billion tons of hydrogen are converted into helium every second [11](#page=11). * Due to the extreme temperatures within the Sun, atoms exist in a state of plasma, where electrons are stripped off the nuclei [11](#page=11). #### 4.1.2 Energy radiation from the sun * Energy primarily leaves the Sun's photosphere in the form of electromagnetic radiation [12](#page=12). * Incoming solar radiation, which drives Earth's surface energy budget, is mostly in the form of visible light [6](#page=6). ### 4.2 Impact on Earth's climate and atmosphere Solar energy is the primary driver of many Earth systems, including its climate and atmospheric layers. #### 4.2.1 Driving Earth's surface processes * The Sun's energy is the primary driver of Earth's surface geologic system processes [2](#page=2). * It powers the water cycle and the erosion of land [2](#page=2). * The formation of igneous rock from magma and mountain building from uplift are both pathways driven by solar radiation [4](#page=4). #### 4.2.2 Atmospheric layers and phenomena * The **troposphere** is the layer of the atmosphere that contains most clouds and weather [6](#page=6). * The **greenhouse effect** is a process where infrared energy absorbed by atmospheric gases is reradiated back toward the surface [6](#page=6). #### 4.2.3 Climate zones and factors * Latitude is the factor that most significantly affects climate zones on Earth [12](#page=12). * Increasing altitude generally leads to colder temperatures [12](#page=12). #### 4.2.4 Early Earth's atmosphere and life * Early Earth's atmosphere changed significantly due to primitive life forms, such as ocean life and later photosynthetic plant life [12](#page=12). * Photosynthetic life captured oxygen and released carbon dioxide [12](#page=12). * The carbon cycle involves processes that return carbon dioxide from living organisms to the atmosphere, such as respiration [4](#page=4). #### 4.2.5 Albedo and energy absorption * **Albedo** is defined as the proportion of incoming sunlight that reflects off an object's surface. It is distinct from the amount of incoming sunlight that is absorbed by a surface [11](#page=11). #### 4.2.6 Relationships with other cycles * Erosion relates to the carbon cycle by releasing carbon dioxide from rocks into the atmosphere [12](#page=12). --- ## Common mistakes to avoid - Review all topics thoroughly before exams - Pay attention to formulas and key definitions - Practice with examples provided in each section - Don't memorize without understanding the underlying concepts

| Term | Definition | |------|------------| | Residence time | The average amount of time a molecule spends in any of Earth's reservoirs, such as oceans, atmosphere, or biomass. | | Tipping Point | A threshold in a system that, when crossed, can lead to sudden and irreversible changes in the system's behavior or state. | | Electromagnetic radiation | Energy that travels and spreads out as it goes; the electromagnetic field includes electromagnetic waves, such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. | | Photosynthesis | The process used by plants and other organisms to convert light energy into chemical energy, through a process that uses sunlight, water, and carbon dioxide to create glucose and oxygen. | | Reinforcing feedback | A feedback loop that amplifies or increases a change in a system, leading to further changes in the same direction. | | Metamorphism | The process where existing rocks are changed by heat, pressure, or chemical reactions, often resulting in the formation of metamorphic rocks. | | Counterbalancing feedback | A feedback loop that opposes or reduces a change in a system, working to maintain stability or return the system to an equilibrium state; also known as negative feedback. | | Evapotranspiration | The process by which moisture is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants. | | Saturation Point | The temperature at which air becomes saturated with water vapor, and condensation begins to form clouds or dew. | | Greenhouse effect | The process by which gases in Earths atmosphere trap heat, reradiating infrared energy back toward the surface and warming the planet. | | Albedo | The proportion of incoming solar radiation that is reflected by a surface, rather than absorbed. Surfaces with high albedo reflect a lot of light (e.g., snow), while surfaces with low albedo absorb more light (e.g., dark soil). | | Nuclear fusion | A nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy; this is the process that powers the sun. | | Plasma | A state of matter distinct from solid, liquid, and gas, consisting of a soup of ions and electrons, typically found at very high temperatures, such as in stars. | | Troposphere | The lowest layer of Earths atmosphere, where most weather occurs and where temperature generally decreases with altitude. | | Stratosphere | The layer of Earths atmosphere above the troposphere, containing the ozone layer, which absorbs most of the Suns ultraviolet radiation. | | Hadley cells | Large-scale atmospheric circulation cells that transport heat and moisture from the tropics toward the poles, characterized by rising air in the tropics and sinking air around 30 degrees latitude. | | Low-pressure zone | An area where atmospheric pressure is lower than the surrounding areas, typically characterized by rising air, cloud formation, and precipitation. | | High-pressure zone | An area where atmospheric pressure is higher than the surrounding areas, typically characterized by sinking air, clear skies, and stable weather. | | Nuclear fission | A nuclear reaction in which a heavy nucleus splits into two or more smaller nuclei, releasing a large amount of energy; this process is used in nuclear power plants. |