Background
The Carboniferous and Euramerica
The Carboniferous Period represents the period of time from 359 to 299 million years ago (mya). These numbers vary somewhat depending on the reference, but this is the general stretch of time. The Carboniferous is notable in Earth history for its high productivity and resultant atmospheric oxygen content, which reached 35%6 by the end of the upper Carboniferous, known as the Pennsylvanian Epoch. This high level of productivity was due to a number of conditions – placement of the continental land masses, high levels of CO2, warm and wet climatic conditions, and an explosion in diversity and size of plants.
During this period of time, the area of land that is now Virginia and the East Coast of the United States was part of the super-continent Euramerica which later joined with Gondwana to form Pangaea. In contrast to the temperate environment of present day Virginia, the Carboniferous environment was warm, wet, and verdant – a tropical swamp. While angiosperms – flowering plants – had yet to evolve, there was an explosion of ferns and horsetails, often in much larger sizes than what is currently seen today.7 The warm and wet conditions, heightened CO2 concentrations of the late Devonian and early Carboniferous period, and arrangement of so much available land in prime growing latitudes led to an explosion of terrestrial productivity on a scale unseen since this time.8
In addition to the swamps and thick fern forests covering the land, much of what is now the Appalachian Mountain range and land to the west would have been a low-lying basin and shallow sea, into which the sediments and plant matter were deposited.9 You can picture modern day Indonesia or Malaysia for a snapshot into the world of Virginia, circa 350 mya10 – hot, wet, and very green.
This growth of plants was naturally accompanied by an increase in photosynthesis, which brought CO2 levels down from 0.40% in the middle Carboniferous to below 0.05% of the atmosphere by the end, while simultaneously increasing O2 concentration from 17% to 35%. Due to the heightened oxygen in the atmosphere, there was the occurrence of certain familiar organisms on a size and scale unlike anything we encounter in modern times – specifically insects. There are many examples of dragonfly ancestor fossils from the Carboniferous whose wings span a meter or more11 and centipedes that grew to 8 feet in length. In addition to the large insects were the early terrestrial amphibians, large bony fish, the first example of reptiles, and a wide variety of marine invertebrates – crinoids, brachiopods, and large ancestral foraminifera called fusulines that would eventually make up the limestone formations of the Midwest.12
Interestingly, as oxygen increased and carbon dioxide decreased, the rate and efficiency of plant productivity also fell. The decrease in carbon dioxide resulted in a net cooling of the Earth and an increase in the southern Gondwana ice sheets, and eventually led to the end of this boom time in primary productivity.13 As we research this time period and students each adopt an organism from the Carboniferous, I will ask my classes to relate the atmospheric changes associated with this time period to the current fears associated with greenhouse gases and compare the time scales and conditions.
Coal Formation
As the swamp plants and fern forests grew and died, they were enveloped by a shallow basin located in what is now the area west of the Appalachian Mountains, which was subsiding at this time. The New River, which still exists today, carried first sand, then organic rich sediments and plant matter into the ever expanding delta that stretched from modern day Pennsylvania down through Ohio, West Virginia, Kentucky, and far Southwest VA.14 As these sediment layers were covered with inorganic sediments, the coal formation process began.
Peat
The earliest stage of coal formation is peat. In order for peat to form, the rate of accretion, or gradual deposition of sediment and plant matter, must exceed the rate of bacterial decomposition.15 It isn’t difficult to imagine this being the case during the rich and productive times of the Carboniferous, with ample rainfall and high rates of production. Reach your hand deep into the nearest marsh or swamp and you will bring up a handful of the makings for peat – the woody and tough stems and leaf material, surrounded by black organic sludge of decomposing plants and animals, smelling of rotten eggs – the tell tale sign of anoxic conditions. Of special importance to peat formation is lignin and cellulose – the tough parts of plants.16 As they are buried, the chemical structure of lignin and cellulose undergo changes as the carbohydrates, oxygen, and nitrogen are lost and carbon is preserved.17 While the chemical composition of the lignin and cellulose structures is altered, their morphology is left intact. Identifiable plant structures like stems, roots, and even leaf cuticles can be found in heavily compressed and altered peat deposits.
Peat has been harvested and used for heat for thousands of years. Even in the modern era there are parts of the world where people venture forth into the marshy areas to carve squares of peat to bring home and burn. I have seen this first hand on the Isles of Harris and Lewis, off the Northwestern coast of Scotland. When burned, peat releases a smell that is hard to describe without using the word “peaty”, but which fills the smeller with a sense of nostalgia. On cold and wet Hebridean days (and there are many, even in July), the sight and smell of peat smoke emerging from a chimney (although reminiscent of a dirty and inefficient fuel source) is a special comfort.
Coalification
If the peat is left alone and subject to the proper conditions of heat and pressure, the process of coalification will begin. This process often begins in subsiding shallow basins – where the underlying crust is sinking due to pressure or tectonic conditions, allowing more room for sediments - in which the pressure is provided by the overlying water (hydrostatic) and sediments (lithostatic). This process is characterized by an increase in the loss of oxygen and nitrogen as well as hydrogen. The first stage of coal is known as lignite, or brown coal, and is considered to be a low-grade coal due to its low energy output, high sulfur content, and high ratio of hydrogen and oxygen to carbon.18 While the chemical content is more altered, brown coal still contains recognizable plant structures.
As the coal is subjected to increasing heat and pressure, more and more hydrogen and oxygen is lost. In addition, organic structures become increasingly altered. The color darkens from a brown to a shiny black, and the “sediments” within become increasingly homogenous.19 At this point, the coal is known as bituminous, and then anthracite. All remaining cellulose and lignin is lost, and the rock resembles what most of us would think of as “coal”. With each step in grade, the energy potential of the coal increases. For this reason, anthracite coal will garner the highest price, with each step downward having a lesser worth.
Interestingly, as coal becomes higher grade, it becomes impossible to determine the parent plants that contributed the biomass – all semblance of original morphology is lost. However, every strain of coal is slightly different due to the variance in parent material. In short, no two lumps of coal are the same. As a part of this unit, students will examine different grades of coal for their physical characteristics and also energy potential. Having a bit of background in how the coal formed will help their descriptions and understanding of the grading system.
Virginia’s Coal
Virginia’s coal fields are located primarily in the far southwestern regions of the state, with small amounts found in the Shenandoah Valley, and a somewhat anomalous coal region just southwest of Richmond in the center of the state that has been out of operation since the 1950s. The coal found in Virginia ranges in grade from mid-bituminous to anthracite and represent a small part of the Appalachian Coal Fields that stretch over much of the east coast, from Pennsylvania to Alabama.20
While its value and extraction rate are decreasing, as recently as 2003, Virginia was producing over 22 million short tons of coal per year, worth roughly $1 billion, and representing 46% of the mineral exports of the state.21 As of 2014, the coal industry in Virginia employed 3,627 people in underground and surface mining operations.22
Extraction Methods
The earliest extraction of coal in Virginia, beginning in 1748, was from the Richmond coalfields. Much of this coal was mined from the surface, exploiting outcrops and cliff faces. As the most readily available coal was removed, however, companies began digging shallow and deep shafts, reaching over 1000 feet in depth, to exploit the full measure of the resource. In all, 71 different mines and associated shafts were established in this region. The coal that was extracted from these sites was used for heating, metallurgy, and eventually for steam power. The last Richmond area mine closed in 1927, and coal production moved to the southwest portion of the state.23 The Richmond Coalfield includes the Midlothian Mines, to which my class will be going on a field trip.
Extraction of the Southwestern VA coalfields – located in parts or all of Buchanan, Dickenson, Lee, Russell, Scott, Tazewell, and Wise counties – began as early as the mid-1850s. However, it wasn’t until the 1950s that the region became the primary source for the state’s coal production. Strategies for removing coal from the ground include the surface and shallow shaft mining that was common in the Richmond Coalfields. Due to the long and thin nature of the southwestern Coalfield seams, very deep shafts are often required to access the coal. In addition to the underground mining, strip mining and mountaintop removal techniques are also used. Strip mining involves using large earth moving vehicles to expose the coal seam for easy extraction. Mountaintop removal is a process, as the name suggests, in which the top of the mountain is stripped of vegetation and explosives are used to expose the coal underneath.24
Use for energy
Of the coal extracted from Virginia mines every year, 65% of it is used for domestic energy production.25 Virginia alone has seven coal firing power plants, supplying 1,423 thousand MWh.26
Environmental Impacts
From an environmental perspective, coal is fraught with negative impacts. Modern techniques of extraction – primarily mountaintop removal – result in extensive ecosystem destruction. There is the initial stripping and explosions that destroy forested areas. This is accompanied by generation of a large amount of what is known as “valley fill.” Essentially, the sediment and excess rock that is the result of the mountaintop removal is pushed into adjacent valleys, filling stream valleys and stopping up headwaters.27 It is difficult to quantify the environmental damage of the valley fill, but it is widely believed to be severe.
Underground mining of coal has been shown to lead to contamination of surface and groundwater, increasing the total dissolved solids (TDS), making the water unsafe for consumption. Additionally, when water adjacent to mines is exposed to pyrite, a common leftover mineral of mining, it will become acidic to the point where toxic metals will dissolve into the stream and be carried in the runoff. This can lead to ecosystems that are toxic to all aquatic life, or in bioaccumulation of heavy metals and larger food web implications.28
The burning of coal for electricity, while affordable and efficient (provided the coal is high-grade), is also accompanied by a host of environmental issues. Combustion of coal releases mercury, sulfur dioxide, cadmium, nitrogen oxide, arsenic, and other inhalants that are known carcinogens and endocrine disruptors.29 While these pollutants are, for the most part, regulated by the state and federal governments, many power plants in Virginia are older and require retrofitting of environmental technologies to meet the legal limits. Furthermore, state agencies rely on self-reporting of effluent by the plants – a situation that is ripe for exploitation and underreporting.
Finally, but perhaps most importantly, coal combustion results in the release of CO2, the best known greenhouse gas. I will leave a full explanation of the physics and facts of global climate change for another unit. I will note, however, that I do not teach global climate change as a “controversial” topic in my class, but as a widely accepted, scientifically supported, and dire process with human and ecological consequences that will ripple many generations into the future.
Social Implications
Beyond the scientific specifications of origin and extraction, Virginia’s coal history is wrapped up in its social and political character. The coal industry is omnipresent in the far southwest portions of the state. People make their decisions about political candidates and potential state regulations based upon what they believe the outcome will be on jobs and the coal economy.
Removing arbitrary boundaries, there is a distinct Appalachian culture whose identity is closely tied to the coal industry. Multiple generations of people have worked, lived and died in and around the mines. Songs and stories that glorify and memorialize workers are prevalent. Movies like Matewan and television programs like Justified show the tenuous relationship that exists between the mining company and the worker. Violent strikes and mine disasters are not remnants of the past, but are present reminders of the dangers and pride associated with coal.
While I am a science teacher, I am always looking for the opportunity to link science to socio-political ideas, literature, and art. As a player of traditional American music, I plan on using the available songs in my classroom to highlight how Earth Science is tied to society.
Natural Gas
Of special interest in the current era is natural gas. As the practice of hydraulic fracturing has become commonplace, it is the large stores of natural gas in the United States that have helped to ensure our energy self-sufficiency.
Natural gas forms throughout the process of peat and coal formation. Initially, methane is produced through the anaerobic activities taking place in peat. As coalification continues, this moves from a biological to a chemical and physical process, as carbon dioxide and methane are generated by extreme heat and pressure. As the coal’s rank increases, more methane is produced, and can be stored in microscopic pores within the coal.30 At present, Virginia coal beds are thought to contain as much as 400 trillion cubic feet of methane, 99 trillion of which is recoverable.31 As coal is phased out, the extraction of natural gas, for good or ill, is taking on increasing economic and social importance.
Beyond what is found adjacent to and inside of coal seams, there is also a supply of natural gas associated with the eastern-most border of the Marcellus Shale, a large Devonian-era bed of oil and gas-rich shale that extends from central New York to Mississippi and Alabama and includes portions of Pennsylvania, Ohio, West VA, Kentucky, Tennessee, and Georgia.32
Fracking
The technique of hydraulic fracturing, or fracking, has existed in the United States since the 1860s in Pennsylvania,33 and has become a predominate method of gas extraction in the last 20 years due to jumps in technology and technique. In short, the process involves injecting water mixed with sand and other chemicals at high pressure into a shale formation. The water causes the underlying shale beds to fracture (hence the name), and release fossil fuels in the form of shale oil and natural gas into a well.34 The wastewater is then pumped back to the surface where it is either recycled for more fracking or routed to local treatment facilities.
Fracking garners strong feeling from both proponents and opponents. To many, natural gas represents a widely available source of energy that has helped the United States loosen the grip that the OPEC nations had on the price of fossil fuels, providing upwards of 725,000 jobs between 2005 and 2012, and helping to lower unemployment and increase domestic revenue.35 To others, fracking is an environmental and societal ill that uses and contaminates millions of gallons of water, destroys aquatic and terrestrial ecosystems, poisons drinking water, causes earthquakes, and releases methane into the atmosphere, undermining any net benefit that might be provided by reducing CO2 emissions.36,37
Due to the various solids that can be captured by the fracking fluid – including a variety of heavy metals, salts, and other naturally occurring toxic substances – proper treatment involves processes that are not found at most municipal facilities.38 Some wastewater is also injected back underground for storage. This process has been shown to be responsible for an increase in earthquakes in the American Midwest, specifically in Oklahoma, although these examples have possibly been exaggerated by media hype.39 Similarly, there are those who have found that fracking causes disruption to water tables, resulting in methane contamination of municipal and well water, a process known as “migration”.40,41 This was most famously demonstrated in the documentary Gasland. These findings remain contentious and have been disputed.42
While the jury is out regarding the environmental and health safety of fracking, there is at least one thing that is clear: natural gas has become an important part of the economic and energy profile of the United States. Bringing it back to Virginia, natural gas has overtaken coal as the number one method of electricity generation, and has been steadily rising in production as coal has been falling over the last decade.43 Students will have the opportunity to research and debate the pros and cons in class.
Alternative Energy
Many of us are familiar with renewable energy in a general sense. We see the occasional wind turbine or solar panel and understand that they are used to “make energy” but our understanding does not go much deeper than that. Much of this seminar has been spent demystifying and explaining the different types and specifics of renewable energy – with a special focus on the many forms of solar energy.
Most people, when they think about solar energy, probably picture a photovoltaic (PV) solar panel on the roof of a building. These panels use sunlight to create an electric current by freeing electrons from certain substances. The free electrons create a direct current that can be used to power electric devices. It can also be stored on a small scale in car batteries. There are a few types of photovoltaics, but all use much the same process to create energy. Beside PV, many people use passive solar panels to heat water that can be pumped throughout the house for use as a heating source. While this is not a direct source of energy, it increases energy efficiency of a building. Similarly, houses can be positioned so that they gather as much winter light as possible while also blocking the high angle summer sun.
Sunlight can also be used to drive a piston or turn a turbine in heat engines. In a Stirling engine, mirror arrays focus solar energy on a gas-filled piston, causing a differential in heat that causes the piston to pump and turn a flywheel. This energy can be used to create electricity by powering a generator. Mirrors are also used in a process that focuses sunlight to create enough heat to melt salt. The salt is then used to heat water to run a turbine and a generator.
Less obvious to many is the role that photosynthesis plays as a source of solar energy. During photosynthesis, plants use sunlight to split water molecules into hydrogen and oxygen and store the released energy in the form of glucose and starch. There is so much more to this process, but for the purposes of middle school science, we will leave it here. When we manufacture ethanol or biodiesel, we are, in essence, using solar power. Similarly, the energy stored in coal, at its heart, is solar energy as it derives from dead and buried plant matter
Alternative Energy in Virginia
According to the American Council on Renewable Energy,
Virginia has taken an “all-of-the-above” approach to energy policy, supporting the generation of electricity from nuclear, natural gas, coal, and renewable energy. Virginia’s renewable portfolio goal aims to increase the state’s use of renewable energy to 15% by 2025, but unlike renewable targets in many other states, the goal is not binding and allows existing facilities to count toward compliance.44
In this unit, I will be focusing specifically on Virginia’s nuclear and wind potential as alternative energies. However, my students will have the option of researching any of the potential sources of alternative energy in our state.
Nuclear in Virginia
Virginia has two nuclear power plants – Lake Anna and Surry. Together, they provide the second largest amount of electricity to the state.45 In addition to the state’s capacity for producing electricity from nuclear, there is also a proposal from landowners to mine uranium from Pittsylvania County in southern Virginia and potential to exploit uranium in up to 55 other localities.46
Due to fears associated with water and soil contamination, a moratorium on this practice has been in place since 1982. Beginning in 2007, a variety of petitions to lift the moratorium have been issued by landowners, state and federal politicians, and uranium interest groups. Uranium is mined from only 8 countries globally, only 3% of which comes from the USA – over 52% comes from Canada, Kazakhstan, and Mexico. Domestically, there is a great deal of interest among some groups in cultivating as much fuel as possible, as the demand for and cost of uranium over the next 35 years is expected to rise faster than current global production.47 Additionally, the Pittsylvania proposal alone is projected to result in ~1,000 jobs and “$5 billion in economic benefits across the commonwealth.”48
This issue has reached a fever pitch among stakeholders in Virginia, with as many groups lining up to oppose the practice as there are those calling for its renewal. As with any mining practice, there are many potential environmental damages – deforestation, increased sedimentation, and loss of habitat. However, since the product of the mining is a radioactive element and a known carcinogen, there are other negative consequences to consider. Uranium and the associated byproducts of its mining can cause a litany of health problems if workers are exposed to it via touch or through inhalation. Tailings from the mine can infiltrate water systems. Massive ecosystem damages from these same factors are also possible.49 Not surprisingly, the opponents include almost every environmental group in the state, along with many health organizations, local businesses, and landowner groups.
In 2011, there was an earthquake in central VA, registering 5.9 on the Richter scale. The epicenter was near the North Anna Nuclear Power Plant. The earthquake caused spent fuel storage containers there to shift on their bases, resulting in tritium leaking into the adjacent groundwater.50 As might be expected, this caused a great deal of concern among the public. Earthquakes, while rare in Virginia, do take place as ancient faults in the underlying bedrock shift and settle. Catastrophic events like this, and the possibility for hurricanes striking any potential uranium mine, provide great fodder for the opponents of nuclear power and mineral exploitation in Virginia. The amount that has been written on this topic, both pro and con, and its proximity to Richmond, make it an ideal choice for class research and debate in the third section of this unit.
Wind In Virginia
In 2015, Virginia became the first state in the USA to obtain permission to study the potential for offshore wind in federal waters. According to Dominion Power, the company awarded the research grant, the proposed 113,000 acre wind farm could power up to 770,000 houses and result in thousands of jobs. This project has the support of the state legislature and governor, as well as the Sierra Club, one of the most vocal environmental groups in VA (and elsewhere).51
As with proposed offshore wind in other localities, this project has its detractors. A similar proposal in Cape Cod has been in limbo for nearly a decade due to opposition from a variety of stakeholders, from wealthy landowners who are opposed to a perceived threat to their viewshed to fishermen who fear they will lose the right to exploit the waters adjacent to the wind farm. Groups who are invested in preservation of bird populations also raised concerns. It can be expected that similar opposition will mount in Virginia. Like nuclear power, I expect my students to have strong opinions about wind power and am excited to use that interest in our lessons and in designing their own optimal turbines.
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