Carbon dioxide from volcanoes

Gerlach TM, Taylor BE (1990) Carbon isotope constraints on degassing of carbon dioxide from Kilauea volcano. Geochim Cosmochim Acta 54 2051-2058 Gerlach TM, Thomas DM (1986) Carbon and sulphur isotopic composition of Kilauea parental magma. Nature 319 480-483... 

Allard P., Carbonelle J., Metrich N., and Zettwoog P. (1991) Eruptive and diffuse emissions of carbon dioxide from Etna volcano. Nature 351, 38-391. 

The composition of the particles is related to that of the source rocks. Quartz sand [composed of silica (silicon dioxide)], which makes up the most common variety of silica sand, is derived from quartz rocks. Pure quartz is usually almost free of impurities and therefore almost colorless (white). The coloration of some silica sand is due to chemical impurities within the structure of the quartz. The common buff, brown, or gray, for example, is caused by small amounts of metallic oxides iron oxide makes the sand buff or brown, whereas manganese dioxide makes it gray. Other minerals that often also occur as sand are calcite, feldspar and obsidian Calcite (composed of calcium carbonate), is generally derived from weathered limestone or broken shells or coral feldspar is an igneous rock of complex composition, and obsidian is a natural glass derived from the lava erupting from volcanoes see Chapter 2. 

Carbon Dioxide. Carbon dioxide, also a colorless and odorless gas, makes up about 0.03% of dry air. Carbon dioxide is introduced into the atmosphere by several natural processes it is released from volcanoes, from burning organic matter, and from living animals as a byproduct of the respiration process. It is for this latter reason that carbon dioxide plays a vital role in the carbon cycle (see Fig. 62), which makes possible one of the more important scientific tools in archaeology, radiocarbon dating (see Textbox 52). 

It is important to point out that neither approach attempts a direct measurement of the arc He flux. To estimate magma production rates, scaling is used in the first instance, whereas the second methodology relies on knowledge of an absolute flux of some chemical species from volcanoes together with a measurement of the ratio of that species to He. The most widely used species to derive absolute chemical fluxes from subaerial volcanoes is SO2 using the correlation spectrometer technique (COSPEC) (Stoiber et al., 1983). Carbon dioxide (see Brantley and Koepenick, 1995) and Po (Marty and LeCloarec, 1992) have also been used in an analogous manner. 

The most important greenhouse gas at present is not carbon dioxide but water vapour, simply because there is so much of it in the atmosphere (Box 6.1). Volcanoes emit large amounts of water vapour (c. 1 Ttyr-1 Skelton et al. 2003), but even so this flux is minor compared to evaporation from the oceans and evapotranspiration from plants (c.0.25% see Fig. 3.12). In a warmer world, such as during the Cretaceous, the atmosphere can hold more water vapour. However, the extent of the warming caused by extra atmospheric water vapour is difficult to predict because clouds also exhibit an albedo effect, and the balance between the greenhouse and albedo effects varies with cloud type and altitude (Lovelock Whitfield 1982). 

Where, then, did our modern atmosphere come from The answer seems to be volcanoes. As well as emitting sulphurous fumes (which would have precipitated in the rain), volcanic gases include nitrogen and carbon dioxide (in about the right balance), tiny amounts of neon, and almost no methane, ammonia or oxygen. 

Equator for a time.3 This would have meant that all the land masses on Earth were free of ice. To understand why this should matter, we must look at what happens when rock is exposed to the air, or to warm oceans with plentiful carbon dioxide. Rock can be eroded by dissolved carbon dioxide, which is weakly acidic. As a result of this reaction, carbon dioxide is lost from the air and becomes petrified in carbonates. But when glaciers form over land, the underlying rock becomes insulated from the air by the thick layer of ice. This means that the rate of rock erosion by carbon dioxide is cut to a fraction and the carbon dioxide stays in the air. In fact, in such a situation, carbon dioxide actually builds up in the air, because it is also emitted more or less continuously from active volcanoes. 

It is generally believed that the solar system condensed out of an interstellar cloud of gas and dust, referred to as the primordial solar nebula, about 4.6 billion years ago. The atmospheres of the Earth and the other terrestrial planets, Venus and Mars, are thought to have formed as a result of the release of trapped volatile compounds from the planet itself. The early atmosphere of the Earth is believed to have been a mixture of carbon dioxide (C02), nitrogen (N2), and water vapor (H20), with trace amounts of hydrogen (H2), a mixture similar to that emitted by present-day volcanoes. 

Do you remember how much fun it was to watch a vinegar baking soda volcano erupt The bubbles of carbon dioxide (CO2) resulted from a decomposition reaction that quickly followed the acid-base reaction between the vinegar (HC2H3O2), an acid, and baking soda (NaHCOs), a base, as shown below. Acid-Base Reaction... 

There are about 500 active volcanoes on the earth. Of these about 3 % erupt each year and of that number about 10% have sufficient explosive power to transport gases and particles to the stratosphere (Brasseur et al. 1999). Magmatic gases released from volcanoes today contain water vapor and carbon dioxide as the main components, with smaller contributions of SO2/H2S, HCl, HF, CO, H2, and N2, but also traces of organic compounds, and volatile metal chlorides and SiF4. 

Volcanoes regulate the climate through CO2 emissions. Carbon dioxide emissions from volcanoes are given as 75 Tg yr by Textor et al. (2004) and as 200-500 Tg yr by Bickle (1994). The Mt Etna CO2 plume emission and diffuse emission combined to amount to 25 Mt yr (Gerlach 1991). 

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