Effects of Volcanic Eruptions

The finding that the heterogeneous chemistry that occurs on polar stratospheric clouds also occurs in and on liquid solutions in the form of liquid aerosol particles and droplets in the atmosphere provided a key link in understanding the effects of volcanic eruptions on stratospheric ozone in both the polar regions and midlatitudes. As discussed herein, the liquid particles formed from volcanic emissions are typically 60-80 wt% H2S04-H20, and hence the chemistry discussed in the previous section can also occur in these particles (Hofmann and Solomon, 1989). We discuss briefly in this section the contribution of volcanic emissions to the chemistry of the stratosphere and to ozone depletion on a global scale. For a brief review of this area, see McCormick et al. (1995). 

Volcanic eruptions can be sufficiently energetic that they inject large quantities of gases and particles directly into the stratosphere (rather than by diffusion from the upper troposphere). The gases include S02, HC1, HF, and SiF4 (Mankin and Coffey, 1984 Symonds et al., 1988 Bekki, 1995 Francis et al., 1995). The particles can include inorganic mineral particles such 

Additional sulfates continue to form after the eruption as gaseous S02 is oxidized to sulfuric acid and sulfates. While we shall focus here on the effects of these sulfate particles on the heterogeneous chemistry of the stratosphere, there may be other important effects on the homogeneous chemistry as well. For example, model calculations by Bekki (1995) indicate that this oxidation of S02 by OH leads to reduced OH levels, which alters its associated chemistry. 

FIGURE 12.27 Zonally averaged optical depth at 19.5°N and derived from the satellite-based Advanced Very High Resolution Radiometer (AVHRR) (adapted from Russell et al., 1996). 

Although the increase in stratospheric sulfate aerosols after volcanic eruptions is dramatic, there is some evidence that these events may be superimposed on a longer term trend to increased stratospheric sulfate concentrations (Hofmann, 1990). Whether this is due to increased anthropogenic or natural sources such as COS or to an increased residual volcanic layer, i.e., 

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Additional discussion of the effects of volcanic eruptions on surface temperatures is found in Section D.3. 

A few studies to monitor our environment with ESR are included in this section. The ESR dating of marine terraces using shells and corals determined the age of the high sea levels and the tectonic uplift of islands.1 The variation of S03 indicated global environmental effect of volcanic eruption.1 ESR spectra of frozen rains, snow and frost as well as ground and river water indicated some... 

The analysis of perturbations to the middle atmosphere must also include natural processes, such as the effects of volcanic eruptions, which produce large quantities of fine particles as well as water vapor and SO2, which eventually produces H2SO4 and sulfate aerosols. The amount of gas injected, the composition and the maximum altitude of injection vary with the intensity of the eruption. Such events can alter the budgets of some atmospheric constituents and are clearly reflected in the middle atmospheric aerosol content. Particles also provide sites for surface reactions to occur. Such heterogeneous reactions may activate chlorine and enhance the depletion of ozone by industrially manufactured halocarbons. 

This agreement is part of ICAO s ongoing work on mitigating the effects of volcanic eruptions on aviation and is a particular response to seismic activity in Eyjafjallajokull, Iceland which commenced at the end of 2009, and resulted in its eruption. " The resultant volcanic ash which spewed over European airspace... 

The atmospheric, climatic, environmental, and health effects of volcanic volatile emissions depend on several factors but importantly on fluxes of sulfur and halogens. As discussed in Section 3.04.5.1, intermittent explosive emptions can pump >10 kg of sulfur into the stratosphere, against a background of continuous fiimarolic and open-vent emission into the troposphere. The episodic, large explosive eruptions are the principal perturbation to stratospheric aerosol levels (e.g., 30 Mt of sulfate due to the 1991 emption of... 

Stenchikov G., Robock A., Ramaswamy V., Schwarzkopf M. D., Hamilton K., and Ramachandran S. (2002) Arctic Oscillation response to the 1991 Mount Knambo eruption effects of volcanic aerosols and ozone depletion. J. Geophys. Res. Doi 10.1029/2002JD002090 (28 December 2002). 

The effects of volcanic emissions on climate were noted by no less a person than Benjamin Erankhn. While hving in Erance, he commented on the persistent haze, dimming of the sun, and unusually cold summer of 1783 and speculated that a volcanic eruption might have been the cause (Franklin, 1789). Although he was not aware of a massive fissure in Iceland at the time, his observation was correct. On Iceland an eruption rained ash that caused death of grass and starvation of hvestock and killed 25% of the population from the resulting famine. 

Baxter P. J., Ing R., and Falk H. (1983) Mount St. Helens eruptions the acute respiratory effects of volcanic ash in a North American community. Arch. Environ. Health 38, 138-143. 

The observed trends in the NAM towards higher indices may have resulted from human-induced changes in the temperature structure of the lower stratosphere in response to greenhouse gas emissions and ozone depletion (Shindell et al., 2001). The radiative effects of solar activity and of volcanic eruptions may also have produced NAM- like signatures detectable at the Earth s surface. The response of the Earth system to climate forcing may therefore involve changes in particular dynamical modes, and hence the human influence on climate at the Earth surface may occur in part by way of the stratosphere. 

Figure 6.23. The top panel shows the total tropospheric chlorine content estimated from the baseline scenario in WMO/UNEP (1998) this is based on a gas-by-gas analysis like those shown in Figure 6.22. The bottom panel shows the changes in the 5-year running mean ozone observed over Switzerland (Staehelin et al., 1998a,b) compared to a model calculation for 45°N applying the same time averaging, with and without considering the effects of volcanic enhancements in aerosol chemistry (from the model of Solomon et al., 1996 1998). The major eruptions since 1980 were those of El Chichon in 1982 and Mt. Pinatubo in 1991. Updated from Solomon (1999).

The tremendous force of a volcanic eruption carries a sizable amount of gas into the stratosphere. There SO2 is oxidized to SO3, which is eventually converted to sulfuric acid aerosols in a series of complex reactions. In addition to destroying ozone in the stratosphere (see page 837), these aerosols can also affect climate. Because the stratosphere is above the atmospheric weather patterns, the aerosol clouds often persist for more than a year. They absorb solar radiation and thereby cause a drop in temperature at Earth s surface. However, this cooling effect is local rather than global, because it depends on the site and frequency of volcanic eruptions. 

Seismic effects and earthquake engineering is covered in this part to study the behaviour of an object under seismic conditions and its suitability for critical installations. The formation of the earth and movements of tectonic plates that cause earthquakes and volcanic eruptions are described,... 

The movement of Earth s crustal plates and the continents they contain - continental drift -has had enormous effects on climate, sea levels, and the distributions of organisms. Mass extinctions of organisms have usually accompanied major drops in sea levels. The collision of all the continents to form the gigantic landmass called Pangaea about 260 million years ago, triggered massive volcanic eruptions. The volcanoes... 

Could lightning flashes occurring during volcanic eruptions have been effective energy sources for prebiotic syntheses An answer to this question would require not only reliable information on the exact chemical composition of the exhalation... 

Through the natural processes of the UV rays of the sun passing through this layer, the absorbs the rays and is broken down to molecules and O atoms. This process is reversible, and ozone (O ) is constantly being reformed from UV effects on However, the separation can be accelerated faster than the reformation of new by induction of other chemical gases into the ozone layer. Of particular concern is that chlorine from CFCs and from other sources, such as the ocean and volcanic eruptions, combines with atomic oxygen that is broken down from Oj by UV radiation. It then forms chlorine monoxide (CIO), which means the atomic oxygen is not available for reformation into O by UV radiation. Herein lie the potential problem and the controversy. 

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