Question

If organic matter accumulates at an average rate of \(1 \mathrm{~mm}\) per year, and if \(10 \mathrm{~m}\) of organic matter is required to make \(1 \mathrm{~m}\) of coal, how long must a swampy environment remain stable and wet in order to form a \(1.5 \mathrm{~m}\) coal seam?

Short answer

It will take 15000 years.

Step-by-step solution

Determine Required Organic Matter

To form a coal seam of 1.5 meters, calculate the amount of organic matter needed. Since 10 meters of organic matter is required to make 1 meter of coal, the total organic matter needed is \[ 1.5 \text{ m of coal} \times 10 \text{ m of organic matter/m of coal} = 15 \text{ m} \text{ of organic matter} \].

Calculate the Number of Years for Organic Matter Accumulation

Organic matter accumulates at an average rate of 1 millimeter (mm) per year. Convert the required organic matter from meters to millimeters. \[ 15 \text{ m} \times 1000 \text{ mm/m} = 15000 \text{ mm} \] Then, calculate the time needed to accumulate 15000 mm of organic matter with the rate of 1 mm per year.\[ \frac{15000 \text{ mm}}{1 \text{ mm/year}} = 15000 \text{ years} \].

Key concepts

Organic Matter Accumulation

Organic matter accumulation is a crucial part of coal formation. This organic matter primarily includes plant debris like leaves, stems, and roots. These materials must accumulate over time in large quantities to eventually form coal.
The rate at which organic matter accumulates can vary greatly depending on environmental conditions. In our exercise, the accumulation rate is given as 1 millimeter per year. It’s important to understand that this rate is quite slow, highlighting the lengthy process required to form significant amounts of organic material.
In coal seam formation, every meter of coal requires around 10 meters of organic material. This ratio is critical for calculating the total amount of time required for coal formation. If organic matter accumulates steadily, we can use simple arithmetic to determine how long it will take to form a specific thickness of a coal seam.

Swampy Environments

Swampy environments play a vital role in the coal formation process. These areas are ideal because they are waterlogged and often stagnant.
The key factors that make swampy environments suitable for coal formation include:

• High water levels that prevent the complete decomposition of plant material, allowing it to accumulate.
• Low oxygen levels which slow down the decomposition process, preserving more organic matter.
• Consistent wet conditions that facilitate the slow, steady buildup of plant remains over time.

Swamps are continually being replenished with new organic material while also preserving the old. This balance is essential for building thick layers of organic matter, which will eventually transform into coal under the right conditions.

Coal Seam Thickness

The thickness of a coal seam is directly influenced by the amount of accumulated organic material. In our problem, 10 meters of organic matter is needed to produce 1 meter of coal seam.
To form a coal seam of 1.5 meters thickness, we calculated that 15 meters of organic matter must be accumulated. This relationship helps us understand how substantial the organic deposits must be to produce even a relatively thin layer of coal.
In practical terms, coal seam thickness is a critical factor in mining operations, as it determines the economic feasibility of coal extraction. Thick seams are more valuable as they provide more coal per unit of excavation effort.

Geological Time Scales

The formation of coal takes place over geological time scales, meaning it occurs over thousands to millions of years. This timescale is much longer than human lifespans or even civilizations.
In the exercise, we calculated that it would take 15,000 years for 15 meters of organic matter to accumulate at a rate of 1 millimeter per year. This long time period underscores the immense time required for biological and geological processes to transform plant material into coal.
Understanding geological time scales is crucial for comprehending the vast timelines involved in natural processes. It gives us perspective on how slowly changes in the Earth occur, especially in terms of resource formation like coal.