Physical processes on Earth are the result of energy flow through the Earth system.
Energy Literacy Principle 2
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Teaching about energy and physical processes is supported by 7 key concepts:
2.1 Earth is constantly changing as energy flows through the system. Geologic, fossil, and ice records provide evidence of significant changes throughout Earth's history. These changes are always associated with changes in the flow of energy through the Earth system. Both living and non-living processes have contributed to this change.
Energy drives the Earth system
Most of the energy in the Earth system comes from just a few sources: solar energy, gravity, radioactive decay, and the rotation of the Earth. Solar energy drives many surface processes such as winds, currents, the hydrologic cycle, and the overall climate system. Gravity makes rivers and other materials flow downhill and creates tides (from the Moon's gravitational pull). Radioactive decay creates heat in the Earth's interior, while Earth's rotational forces influence currents of air and water.
These ideas have considerable crossover with the Climate Literacy Principles 1 and 2. Climate Literacy Principle 1 focuses on the Sun as the primary source of energy for Earth's climate system, while Climate Literacy Principle 2 explains that greenhouse gases affect the energy balance of the Earth. Carbon dioxide and other greenhouse gases trap outgoing radiation that would otherwise exit the Earth system, thus warming the atmosphere. It also summarizes the carbon cycle through different carbon sinks and sources.
Energy flows can change over time
In other cases, the energy flows can vary over time, such as with the carbon cycle. Energy drives the flow of carbon between different reservoirs. Carbon can exist in carbonate rocks (like limestone), stored fossil fuels (like coal, oil, or natural gas) in the atmosphere, in the oceans, or in the molecules of biological organisms. Large-scale burning of fossil fuels is removing stored organic carbon from the Earth's crust and releasing carbon dioxide into the atmosphere. This has changed the composition of the atmosphere so that it traps outgoing heat more effectively. Humans have therefore changed the natural energy balance of the Earth.
Even without humans, the Earth has experienced changes in its energy balance. Over the course of geologic time, there have been drastic changes in the flow of energy through the Earth. For example, the Earth was entirely molten early in its geologic history and was covered in ice during the Precambrian period. The Sun was once 30% dimmer than it is today.
Explore these ideas in the context of Teaching about the early Earth.
Helping students understand these ideas
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These concepts are subtle. It is far easier to grasp a familiar, observable physical process than it is to comprehend the energy that drives it. Start with processes where energy is readily observable, like volcanic eruptions or windstorms. From there, students can appreciate how energy is part of nearly every process on Earth. Have students use concept mapping to connect a process to the types of energy that are involved. Refer back to Energy Principle 1 for a list of different forms of energy.
Alternatively, educators can employ a systems approach. Using the hydrosphere as one example, students can examine how energy is incorporated throughout the cycle. Solar energy causes evaporation; uneven heating of the Earth causes air masses to move; Coriolis forces help storms to take shape, and gravity makes rivers flow downhill. Another relevant factor is the high heat capacity (or specific heat) of water. This means that it takes a lot of energy to change the temperature of water. This moderating effect allows aquatic environments to stay at a relatively stable temperature compared to the air. It also explains why areas near large bodies of water have moderated temperatures with fewer temperature extremes than locations far from water.
If teaching about climate change, consider how a warming atmosphere affects other processes such as storms, heatwaves, and other forms of extreme weather. Due to the high heat capacity of water, the oceans can absorb most of the warming caused by climate change. But what other effects does this have?
Another way to tie these ideas to the study of climate change is to look at albedo. This concept explores the way that the Sun's energy can be absorbed by Earth's surface or it can bounce off it and be reflected back into space. Snow and ice reflect the majority of incoming radiation. Darker surfaces like the open ocean and bare land absorb more energy. As glaciers recede and sea ice melts, the loss of ice-covered areas contributes to further warming. This is one example of a self-reinforcing feedback cycle.
Bringing these ideas into your classroom
Related teaching materials
Using an Earth Systems Approach
Earth System Science from EarthLabs
Because these ideas can be abstract, pedagogies that bring them to life are helpful. Visualizations and simulations can reveal hidden processes at work. Concept mapping can help students find connections between cause and effect. Students can even adopt a role-playing strategy to become a carbon atom or a tropical storm. Once students become familiar with the idea that energy is inherent in Earth processes, these principles can be woven into many earth science topics.
Teaching materials from the CLEAN collection
- Amazing Albedo is a lab in which students use thermometers, white and dark paper, and lamps to measure differences in albedo. Connections are made to albedo in Antarctica.
- Geothermal Energy: Harnessing the Power of the Earth - This short video explains how geothermal energy is tapped, converted to steam, transported to generators, and converted to electricity.
- The Earth is a System visualization that helps explain why understanding Earth as an integrated system of components and processes is essential to science education. The video Striking a Solar Balance uses colorful animations to illustrate Earth's energy balance.
- What Makes a Greenhouse Gas a Greenhouse Gas? and Why Do Some Molecules Absorb Energy? offer two interactive ways (computer simulation and hands-on model building) for students to learn how gases can trap heat.
- Wind and Ocean Circulation animation illustrates the trail of energy that flows from atmospheric wind currents to ocean currents. The high quality of the animation is engaging and would be very useful to explain complex processes that are hard to imagine.
- In the Feeling the Heat activity, students learn about the urban heat island effect by investigating which areas of their schoolyard have higher temperatures and how different materials absorb heat energy differently.
Related teaching materials
Teaching Systems Thinking for college-level students
- Why Climate Change Makes Stronger Storms - This video reviews how increasing temperatures in the Arctic are affecting the path of the jet stream, the severity of storms, and the length of individual weather events.
- The activity Modeling Earth's Energy Balance uses the STELLA box modeling software to determine Earth's temperature based on incoming and outgoing radiation, albedo, and a complex atmosphere with latent and sensible heat fluxes.
- The animation of Greenhouse Gases - IR Spectra allows students to explore the infrared spectra of greenhouse gases and depict the absorption spectra. Vibrational modes and Earth's energy spectrum can also be overlaid.
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