Positive and Negative Effects of Volcanic Activity




Core Unit 1: Patterns and Processes in the Physical Environment





Discuss the positive effects of volcanic activity.


Discuss one positive and one negative effect of volcanic activity.

This question can be asked in a couple of ways. You can be asked for two positive effects or one positive and one negative. Below, I’ve provided 3 paragraphs that allow you to answer either question.

The first positive effect of volcanic activity I have studied is geothermal energy. The popularity and frequency of use of this environmentally friendly form of energy has increased greatly in recent years. Geothermal energy harnesses the energy produced by plumes of magma as they rise into the earth’s crust. Magma most commonly seeps into the overlying crust at plate margins or at hot spots and it is at these locations that the power is harnessed. As magma rises into the overlying rocks it melts some rocks completely while other parts of the crust are only heated. The rocks which have been heated in turn heat the large amounts of water which have accumulated above them. [The reason the water accumulates here is that it has drained down through permeable rock and accumulates above a layer of impermeable rock.]  The heat generated by the magma is so great that it is capable of heating the water to almost 1,000°C. This is referred to as super-heating of water. The water does not evaporate because of the pressure being exerted on it by overlying rocks. The potential energy of this super-heated water can then be harnessed by humans by piping down cold water to this hot water. In this way, both steam and hot water are forced to the surface, where they are connected to turbines which in turn generate geothermal power. Iceland’s location on the Mid-Atlantic Ridge helps supply it with large amounts of geothermal energy. This energy is used in the central heating systems of homes, offices, and industry.

Geothermal Power

A second positive effect of volcanic activity in modern society is that volcanic features are attractive tourist destinations. Volcanoes such as Mount Vesuvius and Mount Etna in Italy attract millions of tourists each year. The cities of Pompeii and Herculaneum, which were destroyed by a super-eruption of Vesuvius in 79 AD, are among Italy’s premier tourist attractions. Less violent forms of volcanic activity such as geysers and hot springs also attract tourists. In the USA, Hot Springs National Park in Arkansas attracts over one hundred thousand visitors per year, and the ‘Old faithful’ geyser in Yellowstone National Park, Wyoming, which erupts each hour, is another major draw for tourists. The development of a thriving tourist sector around volcanoes has many benefits for the local population apart from the obvious revenue generated. Improvements in infrastructure designed to cater for increasing tourist numbers also improve the quality of life for locals. Also, because tourism is labour intensive, it generates large-scale employment in the tertiary sector which benefits the unskilled section of the population.

Although volcanic activity can have many benefits for humans in the long term, in the short term it can have devastating effects, causing loss of life on a large scale. The most obvious damage produced by volcanic activity occurs during an eruption or super-eruption of an active volcano. For example the super-eruption of Mount Vesuvius in 79 AD killed over 20,000 people in the cities of Pompeii and Herculaneum. During an eruption, many materials are emitted into the atmosphere which can cause damage to humans. Volcanoes emit toxic gases such as carbon dioxide, carbon monoxide and sulphur into the atmosphere. Such gases can prove extremely poisonous. Volcanoes also emit large quantities of rock of varying sizes, e.g. ash, cinders, and bombs. Such material is referred to as pyroclastic material. Although lava flow is perhaps the most spectacular aspect of an eruption, it is generally too slow to result in any direct loss of life. Far more dangerous are the vast mudflows which can be triggered by volcanic activity. Such mudflows are known as lahars. Lahars occur when volcanoes erupt within snow-capped mountains. The heat generated by the eruption melts the overlying snow, which results in the release of large amounts of water down slope. The water gathers up loose soil and trees on the lower slopes and the resulting mudslide can move at speeds of up to 160 km per hour. A more recent example of the devastating effects caused by volcanoes was the eruption of Mt. St. Helens in North America in 1986. Although the eruption was predicted the redirection of magma from the central vent to the east face of the mountain gave rise to a lateral rather than vertical eruption which would have devastating consequences.