Australia: The Land Where Time Began

A biography of the Australian continent 

Methane Clathrates (methane hydrate) (methane ice)

Vast quantities of methane are held in the form of clathrate on the ocean floor at various places around the world. The methane is produced by methanogenic bacteria and under certain conditions of pressure and temperature the methane molecules are trapped in cages of water molecules and stored in the upper layers of the sediment. Slight changes in the temperature and pressure conditions can liberate the methane into the water column.

The sediments on continental shelf contain huge quantities of methane hydrate. It is assumed that this carbon reservoir has been present at some level for at least hundreds of millions of years.

Clathrates2 are a type of compound structure consisting of a cage of molecules that can trap gases, such as methane, to produce a solid form.

The most important cage for methane involves a cage composed of water molecules, which is sometimes described as a hydrate, which is technically correct. Climatologists and climate change scientists find some key facts about clathrates particularly interesting.

The reasons for this interest are:

They may make up a significant part of the total reserves of fossil carbon, with current best estimates suggesting there could possibly 500-2,000 gigatonnes (I gigatonne-1billion tonnes) of carbon stored as methane clathrates, which would 5-20 % of the total reserves that have been estimated to exist. According to some estimates there may be as much as 10,000 gigatonnes. They are mostly located on the continental shelf where the water is relatively cold; the pressure and concentrations of organic material is high enough to keep the keep the methanogenic bacteria active. The most important feature is that clathrates can be explosively unstable if there is a temperature increase or a decrease of pressure, both features that can occur as a function of climate change (global warming), tectonic uplift, or undersea landslides. In the shallow waters of the Arctic the release of methane from methane clathrates has already begun. In this area of the Arctic Ocean it has been seen bubbling to the surface in lakes and areas of shallow continental shelf, as near disturbed areas in the Gulf of Mexico, as occurred in the case of the BP oil well blowout in 2010.

As oil and natural gas platforms are being moved to the Arctic there is an imminent danger of additional release of methane from the shallow waters of the Arctic in the near future. It has been suggested that new reserves of significant size will be found off the northern coasts of Alaska, Canada and Siberia, with the real possibilities of environmental disasters as new fields are opened in this pristine, though fragile area around the North Pole.

 Sources & Further reading

  1. Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003
  2. Farmer, G. Thomas & Cook, John, 2013, Climate Change Science: A modern Synthesis, The Physical Climate Vol.1, Springer Dordrecht

Author: M. H. Monroe
Last Updated:  16/12/2014
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