Teachers Guide to Stratovolcanoes of the World
Eruption Feature

Ngauruhoe, New Zealand:
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Environmental Benefits of Volcanism

Although the destructive effects of volcanism are obvious, volcanoes also provide many benefits to mankind. They are the major contributors to the building of continents. All oceanic islands owe their origin directly or indirectly to volcanism. Over the billions of years of Earth's existence, volcanoes and hot springs near volcanic intrusions, have released hot water from Earth's interior. This steam and hot water can be used to produce geothermal energy. Geothermal energy produces electricity inexpensively and with low environmental impact.

Lava flows provide fertile soil in which crops such as pineapples, sugar cane, and coffee thrive. The flows weather quickly in areas with adequate rainfall. In some cases, re-vegetation can begin in less than one year after the eruption. The lava flows are very fertile especially if covered by ash. The fine ash particles retain water within reach of plant roots and release minerals such as potassium which plants need. Vegetation destroyed by ash fall often returns in a more luxuriant form. However, in areas where there is little rainfall, the erosion and breakdown of lava flows to form fertile soils can take thousands of years.

Volcanic rocks provide an abundant local source of materials for landscaping, construction, and road building. In many parts of the world, majestic mountains produced by volcanism draw thousands of tourists each year.

Igneous processes are important in the formation of many of the world's ore deposits. Within magma, several processes may occur to produce an ore deposit. Liquids separate within the magma and are crystallized. These deposits contain minerals rich in iron, chromium, titanium, copper and sulfur. Contact metamorphism, which occurs when a body of magma intrudes into existing rock, also forms ores. Ores may also precipitate from fluids, in which case they are called hydrothermal deposits. Hot springs and geysers are often associated with nearby intrusive bodies.