Gyttja (sometimes gytta, from
Swedish ) is a mud formed from the partial
decay
Decay may refer to:
Science and technology
* Bit decay, in computing
* Decay time (fall time), in electronics
* Distance decay, in geography
* Software decay, in computing
Biology
* Decomposition of organic matter
* Mitochondrial decay, in g ...
of
peat
Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...
. It is black and has a gel-like consistency. Aerobic digestion of the peat by bacteria forms
humic acid
Humic substances (HS) are colored relatively recalcitrant organic compounds naturally formed during long-term decomposition and transformation of biomass residues. The color of humic substances varies from bright yellow to light or dark brown lead ...
and reduces the peat in the first oxygenated metre (generally 0.5 metre) of the peat column. As the peat is buried under new peat or soil the oxygen is reduced, often by waterlogging, and further degradation by
anaerobic microbes,
anaerobic digestion
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to Waste management, manage waste or to produce fuels. Mu ...
can produce gyttja. The gyttja then slowly drains to the bottom of the column. It pools at the bottom of the peat column, about below the surface or wherever it is stopped by e.g. compacted soil/peat,
bedrock
In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet.
Definition
Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...
, or
permafrost
Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...
. Gyttja accumulates as long as new material is added to the top of the column and the conditions are right for anaerobic degradation of the peat. Gyttja can form in layers reflecting changes in the environment as with other
sedimentary rock
Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
. Gyttja is the part of peat that forms
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal i ...
, but it must be buried under thousands of meters for coalification to occur because it has to be hot enough to drive off the water it contains (see
dopplerite). A good documented example of gyttja occurrence and its coverage change in time is the cultural heritage site in
Puck Bay.
References
External links
How Swamps Produce Coal
Coal
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