There are more than 1500 active volcanoes on earth with about 50-70 of them erupting every year, says the British Geological Survey. About 75% of them are positioned around the ring of fire which is a 25,000 mile-long area that extends from the southern tip of South America into the west coast of North America, through the Bering Sea to Japan, and on to New Zealand.
You may have seen them on TV or had a first-hand experience of the havoc volcanoes can wreak on communities and the environment at large, but for the sake of learning, we will be taking a look at what volcanoes are and how they pose a great threat to the environment especially in a time when global warming and climate change are prevalent topics.
What is a volcano?
A volcano is a vent-like opening at the outer layer of the earth through which volcanic ash, lava, and gases escape.
Volcanic eruptions occur when liquid magma containing dissolved gases rises through cracks in the earth’s outer layer. As the magma rises, pressure decreases, causing the gases to form bubbles.
The silica content in lavas determines eruption behavior. For example, low silica content results in free-flow while high silica content is resistant to free flow, thereby causing trapped gases to erupt.
How do volcanic eruptions cause climate change?
Volcanoes may not be everywhere on earth but their effects are widely spread.
When eruptions occur, gases, dust, and ash are released into the atmosphere and because of the atmospheric circulation patterns of the earth, eruptions in the tropics can have an effect on the climate in another region while eruptions at mid or high ranges only have an impact in the regions that they are within.
The smallest particles of volcanic ash and dust, when released into the atmosphere during eruptions, block sunlight thereby causing cooling and because they are light, they can stay in the atmosphere for a long period of time.
A volcanic gas like sulfur dioxide (SO2), when released during eruptions, reacts with the water in the atmosphere and is converted to sulfuric acid which condenses rapidly in the ozone layer to form fine sulfate aerosols.
The aerosols cause the radiation from the sun to bounce back into space thereby cooling the earth’s lower atmosphere, an effect known as radiative forcing, and this cooling effect can last for years.
Volcanoes have also caused global warming due to the release of carbon dioxide (CO2), a greenhouse gas, into the atmosphere during eruptions. The combination of this with man-made emissions like chlorofluorocarbons (CFCs), for example, starts a chain of chemical reactions on aerosol surfaces that increase ozone depletion.
No doubt, the most extreme impact of volcanic eruptions is their effect on the earth’s climate. Since the sun is the earth’s major source of energy, exploring ways by which the effect from components of volcanic eruptions can be limited will go a long way in ensuring a safer environment for people and natural resources.