What is the first stage in the formation of coal

7

Q:

Answer:   D) Peat

Explanation:

The first of the four stages of coal formation is lignite coal.

There are four stages of coal formation:

1. Peat,

2. Lignite,

3. Bituminous and

4. Anthracite.

The bacteria has removed a large portion of the other constituents of the plant matter and left around 25 to 34 percent.

Carboniferous period of Earth’s historyCoal formation begins in swampy areas in warm tropical climates. The tropical swamp forests developed in the Carboniferous period of Earth’s history. The coal swamp forests contained seedless vascular plants that existed in forests of Europe and North America. These seedless vascular plants provided the plant debris that became coal.

Sedimentary layers in ancient swamps

Ancient swamps
Leaves and other debris of plants living in swamp forests fell into the swamp where layer upon layer of plant material collected. Even trees after they died and fell into the swampy water added to the layers of plant material in the swamp.

Standing water
The coal swamp forests that produced coal all contained standing water. The standing water did not have enough oxygen for the plants to decay. Normally insects and other organisms would have lived in the swampy waters and eaten much of the plant debris. The lack of oxygen prevented insects and other organisms from living in the water.

Coal layers exposed in a roadside cut in Alaska

accumulation of plant debris in swamps

Thick layers of plant debris
Plant debris collects very slowly. The plant debris collecting in the swamps must be greater than the rate the plant debris decays. As the plant debris is increasing in size it is covered in silt and sand when flood waters cover the area.

A coal seam that is two meters thick requires plant debris that is twenty meters deep to compress and lithify into coal. This takes thousands of years to accumulate in a swamp.

Two ways plant debris collects in swampsThere are two ways that this amount of plant debris can collect in a swamp.

1.   The waters rise at the same rate as the plant material collects on the floor of the swamp.
2.   The land in the swamp is subsiding at the same rate the plant debris is accumulating.

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Peat

What is peat
Peat is principally bog plants including mosses, sedges, and shrubs. Peat forms when plant material does not fully decay in waters that are acidic and lack enough oxygen for the plants to decay. Peat is partly decomposed vegetation showing a wide range of decomposition.

Stage in the formation of coal
Peat is the first stage in the formation of coal. It is a brown to black accumulation of woody plant material. It has a moisture content about 75%. After the peat is dried, it burns freely.

lignite coal

Rank of lignite coal
Lignite is the lowest rank of true coal. It is generally yellow to dark brown. It formed in areas at shallow depths and temperatures less than 100° C. It lacks luster and often displays the original wood structure. Lignite burns readily with a smoky flame. It has a strong odor as it burns. Lignite contains as much as 40% moisture and crumbles upon exposure to the atmosphere. The content of lignite is between 35% and 45% carbon.

Uses of lignite coalMany thick layers of lignite coal lie close to the surface of the Earth. The layers of coal are sometimes more than 30 meters thick. Most lignite is used to generate electricity. In areas where other fuels are scarce, the production of brown coal far exceeds that of bituminous coal.

Bituminous coal

Sub-bituminous coal
Sub-bituminous coal contains more moisture and less sulfur than other types of bituminous coal. There are three ranks of sub-bituminous coal a, b, and c.

Characteristics of bituminous coal
Bituminous coal is black and has a glassy or pitchy luster with distinct bands or layers and no evidence of a wood structure. Bituminous coal does not crumble upon exposure to air. It is widely used to generate electricity and make coke for the steel industry.

Rank of Bituminous Coal
Bituminous coal is intermediate in rank. It is sometimes called soft coal. Bituminous coal is the most abundant kind of coal. It has a high heating value and a high sulfur content. More than 80% of the coal burned in the U. S. is bituminous coal. It is used in the production of electricity.

Uses of bituminous coal
Many different chemicals are by products of bituminous coal. These chemicals are used to make paint, nylon, aspirin, and many other items.

Anthracite Coal

Rank of anthracite coal
Anthracite is the highest rank of coal. It has the highest heating value and the highest carbon content. Anthracite coal is very hard, deep black, and looks almost metallic because of it is brilliantly glossy appearance.

Uses of anthracite coal
The primary market for anthracite coal is heating homes because it burns longer, with little smoke or odor. The only drawback is that anthracite coal is more difficult to ignite than other coals.

Coal is a Non-renewable energy resource

Coal is a non-renewable energy source because of the long period of time it takes to form deep layers of plant material. The plants that created the coal we are using today were giant plants that lived millions of years ago in swamp forests.

The giant plants and ferns living in the prehistoric swamp forests produced vegetable matter that formed deep layers of vegetable debris. The length of time it took to form these deep layers of vegetable matter in swamps means that all the coal we will ever have to use here on Earth has already been created.

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Coal is a solid, black, readily combustible fossil fuel that contains a large amount of carbon-based material - approximately 50% of its weight.[1][2] The formation of coal takes a significant amount of time (on the order of a few million years), and the first coal-bearing rock units appeared about 290-360 million years ago, at a time known as the Carboniferous or "coal-bearing" Period.[3] As well, there are extensive coal deposits from the Cretaceous age - about 65 to 144 million years ago.[4] (Please see the timeline at the bottom of the page.)

The formation of coal begins in areas of swampy wetlands where groundwater is near or slightly above the topsoil. Because of this, the flora present produces organic matter quickly - faster in fact than it can be decomposed.[2] In these areas, layers of organic matter are accumulated and then buried. It is these layers of organic material that then form coal. The energy in coal initially comes from the Sun, and is energy from sunlight trapped by dead plants.[1]

Process

The process that creates coal varies slightly in different areas depending on the plants and conditions that are present, but the overall process is similar. There are two main phases in coal formation: peatification and coalification. Bacterial activity is the main process that creates the peat during peatification. Increasing temperature and pressure from burial are the main factors in coalification.[2] To form coal, the following steps are followed (Figure 2 illustrates these steps):[5][6]

1. Plant matter in mires and wetlands, such as ferns, shrubs, vines, trees, and algae dies and accumulates on the surface. Initially the organic matter is decomposed by bacteria, yielding carbon dioxide and methane.
2. The plant matter becomes buried, and are no longer exposed to air. Anaerobic bacteria then starts to decompose the material. Burial and accumulation can occur for several thousands of years, producing several meters of partially decayed plant matter known as peat.[6]
3. When this peat is deeply buried, water and other compounds is squeezed out from the increasing pressure and the lowest quality of coal, lignite, begins for form.
4. Continued burial, resulting in increasing pressures and temperatures, causes this low quality lignite coal to be transformed into higher quality "black coals". First lignite becomes sub-bituminous coal, then bituminous coal, and finally the highest quality anthracite coal. As these transformations occur, the amount of water and other compounds in the coal decreases and the coal becomes more dense. Along with this comes a higher carbon concentration.

Figure 2. General trends that produce coal with the different types of coal that exist.[7]

In order to get a sense of how long ago coal started forming please see the chronozoom visualization and look at the Carboniferous period.

For Further Reading

References

1. ↑ 1.0 1.1 R. Wolfson.Energy, Environment and Climate, 2nd ed. New York, U.S.A.: Norton, 2012, pp. 95-96
2. ↑ 2.0 2.1 2.2 R.H. Affolter, J.R. Hatch. (May 11, 2015). Geologic Overview [Online]. Available: http://pubs.usgs.gov/pp/p1625d/Chapter_C.pdf
3. ↑ Planet Energies. (May 11, 2015). How Coal is Formed [Online]. Available: http://www.planete-energies.com/en/medias/explanations/how-coal-formed-process-spanning-eras
4. ↑ Stephen Marshak. (May 12, 2015). Earth: Portrait of a Planet, 3rd ed. New York, NY, U.S.A:W.W. Norton & Company, 2008
5. ↑ J. Kraushaar, R. Ristinen. (May 11, 2015).Energy and the Environment, 2nd ed. Hoboken, NJ, U.S.A.: John Wiley & Sons, 2006, pp. 50
6. ↑ 6.0 6.1 Canadian Federation of Earth Sciences. (May 11, 2015). Four Billion Years and Counting: Canada's Geological Heritage, 1st ed. Toronto, ON, Canada.: Nimbus Publishing, 2014
7. ↑ Adapted from How is Coal Formed?. Available: https://www.uky.edu/KGS/coal/coalform.htm