Coal Flashcards
what are the climatic and environmental conditions required for the formation of coal?
balance between growth of plants and decay of underlying dead material
anerobic
what is coal formed of
plant remains
what are 2 coal forming environments?
deltas/coastal barrier systems (MORE LIKLEY)
inland raised mires
Describe a stratigraphic log through a coal bearing system
Seatearth
v
Coalseam
v
marine shale
v
siltstones and sandstoneswhat is SEATEARTH
represents a fossil soil
plant rootlets common
shows peat was formed in situ
can be clay or sand
what is a COALSEAM
plant material with small but variable amounts of mud
varies in thickness
what is found in the MARINE SHALE
distinctive marine fossils e.g. BRACHIPODS
what does the MARINE SHALE band suggest
peat formation has stopped
what can the SILTSTONE/SANDSTONE layers show
fossils
structures
what can FOSSILS in silt/sandstone suggest
fresh water/ nearness to land
what can STRUCTURES in silt/sandstone suggest
can show environment of deposition e.g. wave action, currents
what is this cycle an example of
a cyclothem
what can this sequence (seatearth, coalseam…) be interpreted as in terms of environment?
DELTA
flat low lying areas near the coast covered in a forest of land plants
Rising water levels flood plains to form lakes (sometimes flooded with sea water)
Rivers encroach into lakes building up deltas and sandbanks until sand banks emerge to be colonised by land plants
the cycle is repeated
what is peat?
cellulose in plant matter has partially broken down, and resistant plant matter remains
what is Lignite
brown coal - contains recognisable plant matter
low calorific value
classified as soft coal
what is bituminous coal
layers of dull and bright coal
classified as hard coal
what is anthracite
very hard
bright/iridescent
light weight
HIGH CARBON CONTENT
what is coal rank
the ranking of coal according to carbon content
what is the coal rank sequence
peat (low)
lignite
bituminous coal
anthracite (High)
how does carbon content relate to coal rank
High carbon % = higher rank
how does % of volatiles ( h & O) relate to coal rank
High % volatiles = lower rank
how does temperature of formation relate to coal rank?
high temp = high rank
how does depth of burial relate to coal rank
deeper = higher rank
what is the av. carbon content in anthracite?
90%
what is the av. volatile content in anthracite?
10%
what is COALIFICATION
a process in which vegetable matter becomes converted into coal of increasingly higher rank with anthracite as the final product.
how do you locate coal
geological mapping
seismic sections
drilling boreholes
wireline logging
what is WIRELINE LOGGING
measuring velocity of sound, resistivity, density and natural gamma radiation
what are the 3 requirements for coal formation
land plants
anoxic environment
rapid burial
climate requirements for coal formation
hot and humid
what gas can be recovered from coal
methane
what geolgoical period was most coal formed in
carboniferous
what is coalification
the diagenetic process by which peat is turned into coal by the effects of heat and pressure durng burial
define COAL SERIES
the sequence of increasing rank from peat to anthracite
what % of coal is used for electricity generation
75%
