About Volcanoes

What are Volcanoes?

An active volcano occurs where magma (molten rock) reaches the earth's surface through a central vent or a long crack (fissure). Volcanic activity can release ejecta (debris ranging from larges chunks of lava rock to ash that may be glow hot), liquid lava, and gases (water vapour, carbon dioxide, sulphur dioxide, nitrogen oxides, and others) into the environment.

Some volcanoes have a steep, flaring cone shape (below).

They usually erupt explosively and eject large quantities of gases and particulate matter (soot and mineral ash) high into the troposphere. Most of the partiles of soot and ash soon fall back to the earth's surface; however, gases such as sulphur dioxide remain in the atmosphere and are converted to tiny droplets of sulphuric acid, many of which stay above the clouds and may not get washed out by rain for up to three years. These tiny droplets reflect some of the sun's energy and can cool the atmosphere by as much as 0.5°C (1°F) for from one to four years. Other volcanic eruptions usually erupt more quitely. They involve primarily lava flows, which can cover roads and villages and ignite brush, trees and homes.

Volcanic Forms

An accumulation of ash and cinders around a vent froms a cone. Successive layers of thin lava flows form an acid lava volcano while thick lava flows forma basic lava volcano. A caldera forms when a particularly violent eruption blows off the top of an already existing cone.

Benefits of Volcanic Activity

One is outstanding scenery, in the form of majestic mountains (above), some lakes and other landforms. Geothermal phenomena, such as geysers and hot springs, have both aesthetic and economic value in the tourist and travel industry. Geothermal energy is also an important energy source in some areas and may be more widely used in the future. Perhaps the most important benefit of volcanism is the highly fertile soils produced by the weathering of lava.

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