Volcanism

Volcanoes are an important part of Earth’s geologic and climatic processes. Volcanoes release CO2, SO2, H2S and several other ejecta after an eruption. Volcanic eruptions of VEI 5 and greater release vast amounts of ash as well as CO2. The ash contains particulates and sulfuric aerosols which reduce the amount of light received from the sun (Burke, 1985). These smaller scale eruptions cause a net cooling effect due to the volume of ejecta and the light dispersing properties of the particulates released after an eruption. There is also evidence of volcanoes causing a global warming effect in Earth’s history. This was true during the Cretaceous time period where CO2 production dwarfed the CO2 levels of today (Refer to Figure 4). Large quantities of atmospheric CO2 can cause an increased greenhouse effect to occur. The Deccan Traps of India are evidence of how volcanic activity over a vast scale can release large enough amounts of carbon dioxide to cause global warming (Rycroft, 1993). Therefore depending on the scale of volcanic activity, volcanic activity can contribute to both a global warming and global cooling scenario.
Volcanic eruptions can cause adverse environmental effects. This includes the destruction of plant and animal life, the production of greenhouse gases which can contribute to global warming and the production of ash and several harmful air particulates that can cause large scale climatic cooling. Volcanic eruptions release volcanic plumes which contain SO2 and fine ash. Through photolysis SO2 gas is converted into the aerosol H2SO4 (Bernard, 1990). Sulfuric aerosols produce a light reflecting or solar irradiating effect which reflects incoming solar radiation thus causing a net cooling effect. This can be seen du...

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...CO2 is the result of increased widespread volcanic activity. These volcanic effects are opposite to the climatic effects caused by smaller scale eruptions. Eventhough both events release CO2 into the atmosphere, the amount released by smaller eruptions is negligible. According to the U.S Geological Survey, the annual CO2 emitted by volcanoes is 0.26 billion metric tons per year which when compared to the volcanic eruptions such as those that formed the Deccan Traps of Indian and several other volcanic sites during the Cretaceous are insignificant. The composition of the tephra and the production of sulfuric acid aerosols plays a larger role in the climatic effects caused by smaller volcanoes and not the amount of CO2 released (n.d). Thus, both scenarios of volcanoes causing global warming and global cooling are possible since they both operate over different scales.