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So now that we understand just what exactly happens when a volcanic eruption occurs, we can take a deeper look at the meaning behind it all. Just what.

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Presentation on theme: "So now that we understand just what exactly happens when a volcanic eruption occurs, we can take a deeper look at the meaning behind it all. Just what."— Presentation transcript:

1 So now that we understand just what exactly happens when a volcanic eruption occurs, we can take a deeper look at the meaning behind it all. Just what are the effects of volcanic eruptions on global climate change? And now, the moment we have all been waiting for… 1)The Ozone Effect 2)The Greenhouse Effect 3)The Haze Effect The diagram opposite illustrates the ozone layer. The region in blue illustrates the hole of ozone depletion, which extended to a record 10.5 million square miles on September 19 th, 1998.

2 1)The Ozone Effect Within the earth’s atmosphere, there exists a sensitive state of equilibrium between ozone (O 3 ) and oxygen molecules (O 2 ). Ozone molecules (O 3 ) are produced by intense sunlight in the stratosphere (above 12 kilometres), which breaks down normal oxygen molecules (O s ) into two highly reactive oxygen Molecules (O). The O atoms are then supposed to quickly combine with O 2 present to form O 3. However, recently, the ozone layer has been depleted to such an extent that a hole has been discovered in the stratosphere over Antarctica. The Role of Volcanoes When volcanoes erupt, they produce large amounts of HCl (Hydrochloric Acid). It is well known that HCl reacts with Ozone and thus damages the ozone layer. Recent findings, however, now seem to suggest that volcanic HCl never in fact reaches the ozone layer and thus it’s impact is no longer thought to be direct, but instead that of catalysis. Scientists now believe that the HCl produced by volcanic eruptions provides surfaces upon which the chemical reactions between Ozone and human-generated CFC’s, example from aerosol cans of products such as deodorants. These Chluorofluorocarbons contain bromine and chlorine compounds which react with ozone and thus create the holes in the ozone layer. Thus Volcanic eruptions in this case merely play an indirect role in ozone depletion.

3 Effect on Global Climate Change With the ozone depleted it allows extra U.V. light to enter the earth’s atmosphere. This causes an increased melting in the polar ice-caps which in turn leads to rise in sea level. It also increases the sea level temperature. Thus The ozone depletion situation puts great risk on the global ocean current systems. The website by Bruce C. Douglas ( summarises the impacts that global sea level rise would incur: “Physical effects of sea level rise into 5 categories. These are inundation of low-lying areas, erosion of beaches and bluffs, salt intrusion into aquifers and surface waters, higher water tables, and increased flooding and storm damage. All of these effects have important impacts, but I shall consider only the first two in this review because they have had and are continuing to have very dramatic impacts on coastal regions worldwide”

4 Other Impacts: The ozone layer is responsible for protecting the earth from the dangerous ultra-violet (U.V.) radiation emitted from the sun. This ultra-violet radiation is responsible for the increase in skin disease, for example melanoma. These diseases would be most common in countries such as Australia and South Africa where the climate is warmer and the ozone layer is more depleted. What happens is that the ultra-violet radiation causes the DNA present in the skin cells to mutate. According to Campbell et al (2002). Biology. Bejamin Cummings, San Francisco carcinogens, such as U.V. light, cause the DNA in cells to divide in an out-of-control manner, i.e. U.V. light causes cancer. Although melanoma only accounts for about 4% of all skin cancer cases, it causes the most skin-cancer-related deaths. For more information on melanoma, the following websites is recommended: 1) 2) Example An example of the most dramatic ozone loss as a result of a volcanic eruption occurred in 1991. In this year, the combined eruptions of Mt Pinatubo (in the Phillipines) and Mt Hudson (in Chile) showed a 15-20% ozone loss at high latitudes and a greater than 50% loss over the Antarcic. The diagram opposite shows the location of Mt Hudson in Chile, South America.

5 2) The Greenhouse Effect DIAGRAM I DREW OF SUN/EARTH/ETC GREENHSE EFFECT This diagram drawn by Joanna Wakely describes the impact of the ozone layer and other greenhouse gases collectively have on the retaining of heat energy received from the sun.

6 These gases prevent the heat (that enters our atmosphere from the sun) from escaping and without these, earth would be about 30 degrees colder than it is at present life as we know it would not exist. So What’s the Problem? The problem that earth is currently facing, is that recent human activities are enhancing the natural greenhouse effect, so that more of the infa-red radiation emitted by the earth’s surface is being trapped. So in relation to the greenhouse analogy, it is as if the atmosphere around the earth acts like a glass pane. The glass pane allows the heat in but only a certain amount of the heat is permitted to be radiated back out. With the increase in the greenhouse gases mentioned on the previous pages however, the “glass pane” is effectively thickening. On the right-hand side of the page is an Illustration relating the greenhouse effect to fuel emissions of cars based on human Impact on the greenhouse effect, another Contributing factor.

7 The Table Below Illustrates Some of the Greenhouse Gases, Some of their Sources, %of Total Emissions in 2001 and the Length of Time Each Gas Remains in Earth’s Atmosphere From the Time of Emission GASSOURCE % TOTAL EMISSIONS, 2001 LIFE SPAN Carbon dioxide (CO2) Fossil fuels, deforestation, soil destruction 83.8 %500 years Methane (CH4) Cattle, biomass, rice paddies, gas leaks, mining, termites 9.3%7-10 years Nitrous oxide (N2O) Fossil fuels, soil cultivation, deforestation 5.2%140-190 years Chlorofluorocarbons (CFCs 11 and 12), HFCs, PFCs and Sulfur Hexaflouride Refrigeration, air conditioning, aerosols, foam blowing, solvents 1.7%65-110 years Ozone and other trace gases Photochemical processes, cars, power plants, solvents Less than 0.5% Hours to days in upper troposphere

8 What is the Greenhouse Effect? The earth is heated by the sun’s rays which enter the atmosphere as Infa-Red light. All this heat reaches the earth’s surface except for a very small portion which is radiated back out of our atmosphere. The greenhouse gases present in our atmosphere include: 1)Methane (CH 4 ) 2)Water Vapour (H 2 O) 3)Carbon Dioxide (CO 2 ) 4)Nitrous Oxides 5)CFC’s (and their Replacements) 6)Ozone (0 3 ) The diagram opposite is a cartoon showing how the greenhouse effect could someday in the not- so-distant future, cause the polar ice-caps to melt.

9 How Greenhouse Effect is Related to Volcanic Eruptions The Greenhouse Effect is mainly caused by emission of carbon dioxide (CO 2 ) Released when burning fossil fuels. In fact, in contrast with this, the impact of volcanic eruptions is really rather insignificant. This is illustrated in the figures. Each year about 110 million tonnes of CO 2 Are produced as a direct result of volcanic activity. This may seem like a lot but compare it to the billion tonnes produced each year as a consequence of human activities and the point is made clear. Global warming is of great concern, especially since the 1980’s increase of travel and privately-owned automobiles. 3)The Haze Effect Volcanic Eruptions enhance the haze effect to a greater extent than the greenhouse effect.

10 The website (link given below) defines a haze as follows: A thick, heavy atmospheric condition offering reduced visibility because of the presence of suspended particles: brume, fog, mist, murk, smaze.brumefogmistmurksmaze The Haze Effect is caused by sulfurous gases emitted by volcanoes during eruption. The process which occurs is that the sulfur combines with the water vapour present in our stratosphere to form dense of tiny sulfuric acid droplets. The particles absorb solar radiation and scatter it back into space. These droplets take several years to settle out, however, once this has occurred, they are capable of decreasing the troposphere temperatures through this process.

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