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Coal: Classroom Activities

Coal Exploration


To understand how coal sources are explored.

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Background Information

Core sampling is an important process in coal exploration. This method requires a truck with an attached core driller. Drilling involves a metal pipe with a bit attached that cuts through dirt and rock. Once a section of pipe is close to its end, an additional section of pipe is added. This process continues until a required depth is reached. The sections of pipe are then taken out of the ground, and a sample of the ground is removed from within each section.

Core drilling is important for determining the height of coal reserves below the Earth's surface. Opening a coal mine is very expensive and mining companies use core sampling methods to calculate the volume of coal in a potential mine.The yield in relation to the cost determines the feasibility of extracting coal.

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Activity Overview

Students use well-log data to complete a cross section. They answer a series of questions about their completed cross sections to help them understand how geologists explore for coal.

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Materials and Equipment

printed copies of the Cross Section of Core Holes diagram

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log for core holes
Source: The American Geological Institute, EarthComm: Project-Based Space and Earth System Science, 2nd Edition, Armonk, New York: It's About Time, 2012, pg. 737.


cross section of core holes
Cross Section of Core Holes. Source: The American Geological Institute, EarthComm: Project-Based Space and Earth System Science, 2nd Edition, Armonk, New York: It's About Time, 2012, pg. 737.


  1. Ask students to examine the Cross Section of Core Holes diagram and Table 3. The diagram shows a cross section of five core holes drilled along an east-west line. Table 3 provides drilling results for these wells. The results include the elevations and types of rock units in the core holes.
  2. Have students complete the cross section in the diagram. They do this by matching up the rock units, as they would imagine them to be connected in the subsurface. You may suggest to them that the mudstone at the bottom of all five wells is the same unit.
  3. Using the data in the diagram and the table, have students answer the following:
    1. Compare your results with those of other students. How do they compare? How do you explain the differences?
      Answers will vary.
    2. Where would you drill your next well in order to determine whether or not your interpretation of the cross section is correct? Explain.
      Answers will vary. Students are likely to want to drill between holes 1 and 2, because this is the greatest gap. They should refer to their correlated cross section in justifying their response.
    3. Is the information in the cross section sufficient to determine the coal seam with the greatest volume of coal? Why or why not?
      The cross section does not give information on the lateral extent of the coal beds. In other words, it shows bed thickness, but it does not show how much surface area the beds cover.
    4. What is the average thickness of coal in the lower coal seam?
      The lower coal seam has an average thickness of about 500 ft.
    5. Assume that the lower coal seam covers an area of 300,000 acres and that each acre-foot yields 1770 short tons of coal. How many short tons of coal does the lower coal seam contain?
      Students will need to know that 1 acre-foot = 43,560 ft3. If the coal seam covers 300,000 acres and is 500 ft thick, that means it has a volume of 6,534,000,000,000 ft3, or 150,000,000 acre-feet. Therefore, the seam would yield 265,500,000,000 short tons of coal.

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