Earth Science: Geology, the Environment, and the Universe

Chapter 6: Sedimentary and Metamorphic Rocks

Problem of the Week

Down in the Coal Mines

There is usually more than one way to solve problems such as these. The following solutions are the most straight forward.

  1. Problem solutions:
  1. A lignite seam is estimated to be 20% the original thickness of the peat bed it developed from.
      • If the peat bed were 750 m thick, how thick would the lignite layer be?
Solution:
    1. 750 m × 0.20 = 150 m of lignite


      • A bituminous coal seam is 3 meters thick (top to bottom). A bituminous coal seam is estimated to be 5 – 10% of the original thickness of the peat bed.

        About how many meters thick was the original peat layer?

Solution:

X × 5% = 3 m

X = 3m/0.05 = 60 m

60 meters × 0.05 = 3 meters

 

    1. Every 30.5 centimeters (12 inches) of coal thickness represents approximately 10,000 years of continuous peat accumulation (6).

      • If we find a peat formation that is 5.4 meters thick, how long would it have taken for this accumulation to build up?
Solution:
        1. 30.5 cm = 0.305 m

        2. 0.305 m takes 10,000 years

        3. 5.4 m would take 177,049.18 years or about 180,000 years

Just a Thought:

Solution:

      • Approximate number of years from the commencement of coal mining in N. America:
1995 – 1750 = 249 years
      • Time from beginning coal mining to now, plus the time estimated for remaining coal reserves = approximate amount of time it will have taken us to use up known coal reserves in North America.

245 + 265 = 510 years

 

Resources:
  1. Energy Fact Sheet: Coal, Energy Educators of Ontario, 1993

  2. Getting to Know Coal

  3. How Coal is Formed

  4. Formation of Coal

  5. The Exploration of Coal

  6. Fossils of Virginia
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