marsh gas

Organic compound, chemical formula CH₄, colourless, odourless gas that occurs in natural gas (called firedamp in coal mines) and from bacterial decomposition of vegetation in the absence of oxygen (including in the rumens of cattle and other ruminants and in the gut of termites). The simplest member of the paraffin hydrocarbons, methane burns readily, forming carbon dioxide and water if supplied with enough oxygen for complete combustion or carbon monoxide if the oxygen is insufficient. Mixtures of 5–14percnt methane in air are explosive and have caused many mine disasters. The chief source of methane is natural gas, but it can also be produced from coal. Abundant, cheap, and clean, methane is used widely as a fuel in homes, commercial establishments, and factories; as a safety measure, it is mixed with trace amounts of an odorant to allow its detection. It is also a raw material for many industrial materials, including fertilizers, explosives, chloroform, carbon tetrachloride, and carbon black, and is the principal source of methanol.

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In geography, a marsh, or morass, is a type of wetland which is subject to frequent or continuous inundation. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, and other herbaceous plants. Woody plants will be low-growing shrubs. A marsh is different from a swamp, which has a greater proportion of open water surface and may be deeper than a marsh. In North America, the term swamp is used for wetland dominated by trees rather than grasses and low herbs.

The water of a marsh can be fresh, brackish, or saline. Coastal marshes may be associated with estuaries, and are also along waterways between coastal barrier islands and the inner coast. The estuarine marsh, or tidal marsh, is often based on soils consisting of sandy bottoms or bay muds. An example is the Tantramar Marsh of eastern Canada.

Marshes are critically important wildlife habitat, often serving as breeding grounds for a wide variety of animal life, particularly including ducks and geese.

Constructed wetlands featuring surface-flow design are usually in the form of a marsh.

Decomposition of plant materials below water often produces marsh gas, which may begin to burn by self-ignition making mysterious lights known locally as Will o' the wisps, Jack-a-lanterns, or sprites.

See also

Reference line notes

• Marshes of the Lowcountry (South Carolina) -- Beaufort County Library
• General Information of Ibera Marshes (in English and Spanish)