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Houston Geological Society Bulletin


Houston Geological Society Bulletin, Volume 19, No. 3, November 1976. Pages 2-2.

Abstract: Volcanoes and the Environment


Previous HitFredTop M. Bullard

The environmental impact of volcanoes is far reaching and while the destructive effects are the ones commonly associated with volcanoes, the overall impact is certainly beneficial. The destructive effects of volcanic eruptions, such as lava flows, ash falls, hot avalanches, and mudflows are briefly reviewed. The most dangerous and least predictable are mudflows, such as the one that destroyed Herculaneum in the 79 A.D. eruption of Vesuvius. Mt. Rainer and other volcanoes of the Cascades are potential sites for destructive mudflows. The possible intent of such flows, based on past history, is considered.

The major environmental impact of volcanoes is in their effect on climate and soils. The huge quantity of ash ejected into the atmosphere in a major eruption results in a decrease in the solar radiation and a lowering of the temperature. The unusually cold weather throughout the world in 1816, commonly known as the "year without a summer", coincided with the eruption of Tambora Volcano in Indonesia. The eruption of Krakatoa in 1883 had a noticeable effect on the climate. Measurements of solar radiation being conducted at the time of the 1912 eruption of Katmai Volcano proved the effectiveness of volcanic ash to lower the temperature.

Beginning in the 1880s, a world-wide warming trend set in, which reached a climax in the 1940s, and since that time has reversed. The role of volcanic dust was examined in an effort to account for these world-wide temperature changes, and it was concluded that major volcanic eruptions were responsible for lowering global temperature. The study was expanded to include pollution of the atmosphere by carbon dioxide, smoke, dust particles, etc., largely derived from the combustion of fossil fuels, petroleum and gas. The results showed that pollution by human activities was minor compared to the contribution by volcanoes and that volcanic dust is an important factor in world-wide temperature changes.

Periodic ash falls from volcanic eruptions maintains the fertility of the soil. A study in Indonesia shows a direct relationship between soil fertility, density of population, and the location of active volcanoes.

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