Earth Materials and Natural Resources
Hydrocarbons and Coal, Metalliferous Ores, Non-Metallic Minerals and Bulk Minerals
Coal
Sedimentary Environment
Formation of Coal:
1) Peat (decaying plants) – anoxic conditions
2) Layers on top of the peat press down on it
3) After many years of pressure and heat, the peat turns into
coal
Maturation
Sub-
Peat Lignite Bituminous Anthracite
Bituminous
Light
Brown, dull,
brown/black, Dull dark Black with Black, shiny,
plant
Appearance/Description plant fragments, brown to dull and glassy and
fragments
partially black shiny layers iridescent
visible
compacted
Relative Pressure and
Temperature for 0-40oC 40-70oC 70oC 70-170oC 170-200oC
Formation
Calorific Value (KJ/g) 10 20 25 30 34
Volatile Content 60% 50% 40% 35% 10%
Density (g/cm3) 0.4 0.8 1 1.3 1.5
Ash Content 11% 8% 5% 2% 1%
Extraction
Open Cast – takes place from quarries of ‘open pits’ at the surface. Overburden is removed
Deep Mine – mining deep within the earth. Drill vertically down with the overburden left in place
Types of Deep Mine:
Longwall Mine Pillar and Stall Bell Pit
• Maximises coal extraction • Pillars stabilise rock • Prone to collapse
• Don’t waste money above • Oldest form of
supporting roof – allows it to • Maximises rock (coal) mining
collapse extracted • No support for roof
• Most modern mines use this • Will collapse eventually
Hazards Associated with Extraction (Geological Issues)
Mass Spoil heaps collapse if weakened/made unstable
Movements
Gases Two types of gas – carbon monoxide and methane
Carbon monoxide asphyxiates miners
Methane is explosive
Mining reduces pressure, so more gas escapes from pore spaces
Subsidence Removal of material weakens overlying structure – roof rock can’t support itself so
collapses, causing subsidence at the surface. The shallower the material that was
removed, the greater the subsidence
, Acid Mine Polluted water that normally contains high levels of iron, aluminium and sulphuric acid.
Drainage (AMD) It is orange/yellow and smells like eggs.
When pyrite is disturbed, it oxidises (reacts with oxygen as well as water) causing high
levels of iron, aluminium and sulphur in runoff water
Environmental Issues
Issue Resulting From…
• Contamination of water table
Changes to Water Table and Water
• Artificial lowering of the water table
Quality
• Could accidently lower another areas water table
• Diggers, lorries, blasting = loud
Solution:
Noise
• Plant trees around the area to minimise noise
• Don’t mine at certain times of day
• Grass and trees removed
Loss of Habitat • Might have to fill it back in after
• Change in environment
• Doesn’t look nice to public
Visual Impact
• Obscure view of it
• Traffic pollution due to trucks carrying coal out
Air Quality • Dust – can spray wheels with water to reduce dust
removed from site/spread of it
Transportation of Material Out of the • Pollutes air due to transportation
Mine/Quarry • Increases traffic
Factors Affecting the Accuracy of Estimation in the Size of the Deposit
Washouts – rivers cut through leaving rock deposits
Bed Geometries – Seam
Seam splits – some coal seams subside more quickly than others, leading to it
Splits or Washouts
being less economic/having to remove rock from between or above the seams
Gentle fold = mine it
Folds Creates problems of how to mine it
Water could collect in the bottom
Erosional Features (U/C) Eroded/truncated the coal seam
Puts coal on different levels – more expensive to mine for coal companies
Faulting Water could enter the fault and rock strength would decrease leading to
having to spend more to stabilise the mine
Mining records can be incomplete or missing leading to overestimation of how
Previously Mined Out
much coal is below ground = uneconomic
Hydrocarbons – Oil and Gas
Sedimentary Environment
Formation:
1) As organisms (plankton) die they sink to the sea floor
2) Quickly covered by sediment (source rock) – quick burial and anoxic conditions
3) Temperature and pressure exerted on source rock increases
4) When right conditions are reached (oil window) the organisms break down into petroleum which
collects in the pore spaces
5) Oil migrates to reservoir rock at the surface where it accumulates and is stored
6) Cap rock stops it escaping
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