All Earth and life processes, including all human activities, depend on flowing energy. The energy that drives internal Earth processes (such as tectonics) comes from the internal heat generated by radioactivity, and generally energy that drives surface and life processes comes from the sun. With the exception of geothermal heat, energy used by humans – to move people and goods, produce electricity, heat our homes and businesses, and manufacture things – comes from the sun.
*Exceptions include the use of sails on boats by a very small percentage of the world’s population to move people and goods, and the Chinese use of natural gas to boil brine in the production of salt beginning roughly 2000 years ago.
For most of human history, the way we captured and used energy changed little. With very few exceptions*, materials were moved by human or animal power, and heat was produced largely through the burning of wood. Nearly all the energy to power human society was, in other words, biomass. But the transition from brute force and wood burning to the various industrial sources of energy—and the accompanying adoption of energy-intensive lifestyles—has occurred remarkably quickly, in the course of just the last several generations. This has caused changes in virtually every aspect of human life, from economics to war to architecture. Much of the rural US was without access to electricity until the 1930s, and cars have been around for only slightly longer. Our energy system (how we get energy and what we use it for) has changed and is changing remarkably quickly, though some aspects of the energy system are also remarkably resistant to change.
Wind and solar power, fossil fuels, nuclear energy, and hydroelectricity are primary (natural) energy sources: they occur in nature.
Secondary energy sources, also known as energy carriers, have been transformed into energy used directly by humans, such as electricity and gasoline.
The use of wind to generate electricity, for example, grew very quickly in the late 2000s and early 2010s. In 2002, wind produced less than 11 million megawatt hours (MWh) of electricity in the US. In 2011, it produced more than 120 million MWh—more than 1000% growth in ten years! That aspect of change stands in contrast to our long-lasting reliance on fossil fuels, such as coal, oil, and natural gas. Our reliance on fossil fuels is driven by a number of factors: the low upfront cost, very high energy densities, and the reliability and durability of the infrastructure built to use fossil fuels.
Energy production and use not only changes over time, but also with geography, as we will see by looking at energy production and use across different regions of the US.
What do different units of energy mean?
Heat is energy, and heat is at the root of all the ways that we move materials or generate light, so measurements of heat can be thought of as the most basic way to measure energy. The British thermal unit (abbreviated Btu or BTU) is the most commonly used unit for heat energy and is approximately the amount of heat required to raise one pound of water by one degree Fahrenheit. A Btu is also roughly 1055 joules, or the amount of energy released by burning a single wooden match. A joule is the energy expended (or work done) to apply a force of one newton over a distance of one meter. Since a typical apple weighs approximately one newton, lifting an apple one meter requires approximately a joule of energy. That means that one Btu—the energy contained in a wooden match—is equivalent to the total amount of energy required to lift an apple 1000 meters, or one kilometer.
The principle of Conservation of Energy tells us that energy is neither created nor destroyed, but can be altered from one form to another.
This comparison of the energy of heat to the energy of motion (kinetic energy) might be a little confusing, but energy is transformed from one type to another all the time in our energy system. This is perhaps most obvious with electricity, where electrical energy is transformed into light, heat, or motion at the flip of a switch. Those processes can also be reversed—light, heat, and motion can all be transformed into electricity. The machines that make those transitions in either direction are always imperfect, so energy always degrades into heat when it is transformed from one form to another.
Another measure of energy, the kilowatt-hour (kWh), represents the amount of energy required to light ten 100-watt light bulbs for one hour. Figure 6.1 compares different ways to make and use one kWh.
How do we look at energy in the Earth system?
The concepts used to understand energy in the Earth system are fundamental to all disciplines of science; energy is an interdisciplinary topic. One cannot study physics or understand biomes, photosynthesis, fire, evolution, seismology, chemical reactions, or genetics without considering energy. In the US, every successive generation has enjoyed the luxury of more advanced technology (e.g., the ability to travel more frequently, more quickly, and over greater distances). Especially as the global population grows and standards of living increase in some parts of the world, so too does global energy demand continue to grow.
Figure 6.1: Examples of uses and sources of 1 kilowatt-hour.
Figure 6.2. US energy production sources and use sectors for 2011. Petroleum provides more energy than any other source, and most of it is used for transportation. More energy is used to generate electricity than for any other use, and electricity is generated by all five energy sources. Nuclear is unique among sources in that all of the energy it generates goes to a single sector: electric generation.
Figure 6.2 shows the sources and uses of energy in the US, by sector. The Energy Information Administration (EIA) categorizes energy as coming from one of five sources (petroleum, natural gas, coal, renewable energy, and nuclear electric power) and being used in one of four energy sectors (transportation, industrial, residential & commercial, and electric power). All of the energy that powers our society comes from one of these five sources and is used in one of these four sectors.
The more we come to understand the Earth system, the more we realize that there is a finite amount of consumable energy, and that harvesting certain resources for use in energy consumption may have wide ranging and permanent effects on the planet's life. Understanding energy within the Earth system is the first step to making informed decisions about energy transitions.
Becoming "Energy Literate"
Energy Literacy: Energy Principles and Fundamental Concepts for Energy Education is a publication of the US Department of Energy. It can be accessed for free online; see Resources for more information.
Energy is neither lost nor gained within the universe, but rather is constantly flowing through the Earth system. In order to fully understand energy in our daily lives—and make informed decisions—we need to understand energy in the context of that system. Becoming energy literate gives us the tools to apply this understanding to solving problems and answering questions. The Seven Principles of Energy, as detailed in Energy Literacy: Energy Principles and Fundamental Concepts for Energy Education are as follows:
Each principle is defined by a set of fundamental concepts that can help clarify ties to curricula. Keeping these energy principles in mind when we teach others about energy can help us contextualize and make relevant our own energy consumption and its effect on the Earth system.
Energy in the Southwestern Regions
Within its majestic mountain ranges, roaring rivers, and expansive plateaus, the Southwestern US is replete with energy resources. Coal, oil, and gas deposits are extensive (Figures 6.3 and 6.4), especially in the the Colorado Plateau and Great Plains regions. Utah, Colorado, and New Mexico all rank within the top dozen producing states of both oil and natural gas, and within the top 15 in coal production. The distribution of these resources is linked to the area's many sedimentary basins, which have been host to the formation and trapping of hydrocarbons at multiple intervals since the late Paleozoic (see Figure 6.6).
Uranium (the raw material used for fission in nuclear power plants) is locally abundant (Figure 6.5), and it has been mined extensively, although nearly all of the uranium collected in the Southwest is shipped to other states. There is only one nuclear power plant in the Southwest, located near Wintersburg, Arizona.
Figure 6.3: Coal-producing areas of the Southwestern US. The Colorado Plateau is a particularly significant coal-producing region.
Given its climate and topography, the Southwest has a reasonably high capacity for generating solar and wind energy. Hydropower along major river systems is also an important source of energy in some areas. Though these sources are increasing rapidly, they remain a relatively small part of energy production in the Southwestern US. Some parts of the Southwest also have a high potential for deep geothermal energy due to the proximity of areas of active tectonism.
Figure 6.4: Areas of oil and gas production in the Southwestern US. The Colorado Plateau and Great Plains are both significant fuel-producing regions.
Figure 6.5: Distribution of uranium deposits in the Southwestern US.
Fossil Fuels
Fossil fuels—oil, natural gas, and coal—are made of the preserved organic remains of ancient organisms. Coal and lignite result from the burial, compaction, and heating of preserved plant matter, whereas petroleum and natural gas originate deep underground through a slow process involving the low-grade heating of sedimentary source rocks that contain an abundance of organic matter. In either case, organic matter is only preserved when the rate of accumulation is higher than the rate of decay. This happens most often when the oxygen supply is sufficiently low that oxygen-loving bacteria cannot thrive, greatly slowing the breakdown of organic matter. In this way, organic matter can be incorporated into the buried sediment. The organics are compacted and heated with the rest of the rock, eventually transforming into fossil fuels.
The history of surface environments, evolution of life, and geologic processes beneath the surface have all influenced where fossil fuel deposits formed and accumulated. The largest oil and gas reserves were at one time nutrient-rich seas with abundant surface phytoplankton and organicrich bottom sediments; the largest coal beds were swampy environments where fallen forest trees and leaves were buried in stagnant muds.
The majority of the Southwest's land is owned by the federal government, and managed primarily by the Bureau of Land Management (BLM), National Park Service, US Forest Services, and Bureau of Indian Affairs (BIA). Exploration and mining for natural resources in these areas is extensively regulated, and no energy is developed in National Parks, National Monuments, or a variety of other wilderness areas. Because the Southwest is home to some of the most magnificent National Parks and Monuments in the world, many local governments and citizens have gone to great lengths to preserve it by preventing and regulating energy development and mining projects.
