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Questions and Answers
What is the primary geological period during which the most significant coal formation occurred?
What is the primary geological period during which the most significant coal formation occurred?
Which process describes the transformation of plant debris into peat?
Which process describes the transformation of plant debris into peat?
Which type of coal is formed during the upper Cretaceous to Miocene times?
Which type of coal is formed during the upper Cretaceous to Miocene times?
Which geographic regions are known for having coal seams of Permian age?
Which geographic regions are known for having coal seams of Permian age?
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During coal formation, which of the following is NOT a process of decay and decomposition in the bio-chemical stage?
During coal formation, which of the following is NOT a process of decay and decomposition in the bio-chemical stage?
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What is the first step in the coalification process?
What is the first step in the coalification process?
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Which type of coal is the highest rank in the coalification series?
Which type of coal is the highest rank in the coalification series?
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What term is used for the less important period of coal formation characterized by peat deposits?
What term is used for the less important period of coal formation characterized by peat deposits?
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Which of the following is NOT a feature of the Insitu theory regarding coal formation?
Which of the following is NOT a feature of the Insitu theory regarding coal formation?
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What is the outcome of the geo-chemical stage in the coal formation process?
What is the outcome of the geo-chemical stage in the coal formation process?
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Which evidence supports the Drift theory of coal seam origin?
Which evidence supports the Drift theory of coal seam origin?
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Which substances are primarily transformed during the humification process?
Which substances are primarily transformed during the humification process?
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What characteristic feature is associated with Anthracite coal?
What characteristic feature is associated with Anthracite coal?
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In the context of coal formation, what does 'Allochthonous' refer to?
In the context of coal formation, what does 'Allochthonous' refer to?
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Which coal rank typically has the highest heating value?
Which coal rank typically has the highest heating value?
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Which characteristic can be observed in sedimentary rocks associated with coal?
Which characteristic can be observed in sedimentary rocks associated with coal?
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Which of the following periods are associated with the formation of coal deposits?
Which of the following periods are associated with the formation of coal deposits?
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Which type of coal contains the highest percentage of moisture?
Which type of coal contains the highest percentage of moisture?
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What is the primary use of peat?
What is the primary use of peat?
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Which type of coal is characterized as having a calorific value between 11,000 to 12,500 B.Th.U/lb?
Which type of coal is characterized as having a calorific value between 11,000 to 12,500 B.Th.U/lb?
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Which statement is true regarding the visible components of peat?
Which statement is true regarding the visible components of peat?
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What type of coal is considered a common commercial rank and is dense and black in color?
What type of coal is considered a common commercial rank and is dense and black in color?
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Which type of coal is described as being intermediate in grade between lignite and bituminous coal?
Which type of coal is described as being intermediate in grade between lignite and bituminous coal?
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Which of the following statements about lignite is false?
Which of the following statements about lignite is false?
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Study Notes
Periods of Coal Formation
- Major periods include Carboniferous-Permian, Upper Cretaceous-Miocene, and Quaternary.
- Carboniferous period is primarily responsible for the world's coal formations, starting in the North-West and moving South-East.
- Northern Hemisphere coal seams (North America, Europe) date to the Carboniferous age; Siberian, Eastern Asian, Indian, and Australian seams are of Permian age.
- Upper Cretaceous to Miocene period produced Tertiary coals found in regions like Italy, Japan, and Indonesia; lignite deposits emerged during this time.
- Quaternary or Post-tertiary times saw the formation of peat deposits globally, considered the least significant for coal.
- Coal fields originated in swamps or freshwater basins, with plant material growing in situ or drifting into these areas.
Stages in Coal Formation
- The process involves two stages: Biochemical and Geochemical.
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Biochemical Stage (Humification):
- Plant debris undergoes decay through microorganisms, transforming into peat.
- Peat is a porous, fibrous material that serves as the precursor to coal.
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Geochemical Stage (Coalification):
- Peat transforms into higher rank coals (lignite → bituminous → anthracite) under heat and pressure.
- The sequence of transformation is known as the coalification series.
Origin of Coal
- Origin theories for coal seams: Insitu and Drift theory.
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Insitu Theory:
- Suggests coal seams formed where vegetative matter grew, indicating autochthonous origins.
- Evidence includes current swamp vegetation forming coal seams, the purity of coal seams, and tree trunks found anchored in underlying clay.
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Drift Theory:
- Proposes that plant debris was transported to its current location, indicating allochthonous origins.
- Evidence includes transportation of tree trunks by rivers, ongoing peat formation at river deltas, and the presence of marine fossils.
Coal in Earth's Geological History
- Coal deposits occur in sedimentary sequences from the Tertiary and Gondwana periods, referred to as tertiary and Gondwana coals.
Modern Classification of Coal
- Varieties of coal are categorized based on the degree of transformation:
- Peat
- Lignite (brown coal)
- Sub-bituminous coal
- Bituminous coal
- Semi-anthracite
- Anthracite
Specific Types of Coal
-
Peat:
- Initial formation stage; fibrous mass varying in color.
- Contains high moisture (up to 85%), lower fixed carbon (4.6%), and a calorific value around 3500 B.T.U.
- Limited use as a fuel, primarily for fertilizer production; found in regions like England, Scotland, and parts of India.
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Lignite:
- Known as brown coal; high moisture content (25-45%).
- Burns with a long flame and has a lower heating power (11,000 to 12,500 B.T.U/lb).
- Used in distillation, gasification, and thermal power generation.
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Sub-bituminous Coal:
- Dull black and intermediates between lignite and bituminous coal.
- Lacks woody material; sourced from Lower Gondwana and Eocene deposits.
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Bituminous Coal:
- Dense, compact, and black; common commercial coal.
- Although derived from 'bitumen,' it does not contain it; significant for various industrial uses.
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