Gyttja (sometimes gytta, from
Swedish
Swedish or ' may refer to:
Anything from or related to Sweden, a country in Northern Europe. Or, specifically:
* Swedish language, a North Germanic language spoken primarily in Sweden and Finland
** Swedish alphabet, the official alphabet used by ...
gyttja) is a mud formed from the partial
decay
Decay may refer to:
Science and technology
* Bit decay, in computing
* Software decay, in computing
* Distance decay, in geography
* Decay time (fall time), in electronics
Biology
* Decomposition of organic matter
* Tooth decay (dental caries) ...
of
peat
Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...
. It is black and has a gel-like consistency. Aerobic digestion of the peat by bacteria forms
humic acid Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th ...
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 water logging, 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 manage waste or to produce fuels. Much of the ferm ...
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 (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet.
Definition
Bedrock is the solid rock that underlies looser surface mater ...
, or
permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...
. 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 that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
. 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 elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
, 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 Dopplerite is a naturally occurring organic substance found in amorphous, elastic or jelly-like masses, of brownish-black color, in peat beds in Styria and in Switzerland. It is tasteless, insoluble in alcohol and ether, and is described by Jame ...
). A good documented example of gyttja occurrence and its coverage change in time is the cultural heritage site in Puck Bay.
References
{{Reflist
External links
How Swamps Produce Coal
Coal