Download Chapter 8 Section 3

Chapter 8 Section 3
Negative Effects of Volcanic Eruptions
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Volcanic explosions can have local and global effects.
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In April 1815, Tambora volcano in Indonesia erupted explosively.
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The pyroclastic flows and falling debris killed about 10,000 people in the area.
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High in the atmosphere, ash and gas spread around Earth.
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The average global temperature decreased by as much as 3°C for one to two years.
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The lower temperature caused crop failures and starvation, particularly in New England and Europe.
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The effects of lower temperatures led to the deaths of about 82,000 people.
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Therefore, an estimated total of 92,000 people around the world lost their lives as a result of the Tambora
eruption.
Local Effects of Volcanic Eruptions
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Volcanic eruptions can cause loss of human life and loss of wildlife habitat.
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The blast from an explosive eruption can knock down trees, destroy buildings, and kill humans and animals.
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Pyroclastic flows can burn everything in their path.
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Hot volcanic materials can melt the snowcap on a mountain, causing devastating floods.
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Volcanic ash can mix with water to form fast-moving mudflows called lahars.
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The weight of falling ash can collapse structures, bury crops, and damage engines.
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Volcanic ash can also cause respiratory problems in humans.
Global Effects of Volcanic Eruptions
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Large volcanic eruptions can affect Earth’s climate for several years.
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During large eruptions, ash and sulfur-rich gases can be pushed into the stratosphere.
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As the ash and gases spread around the planet, they absorb and scatter sunlight.
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Enough sunlight may be absorbed or scattered to lower the average global temperature of Earth.
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In 1991, after the eruption of Mount Pinatubo in the Philippines, the amount of sunlight to reach Earth’s
surface decreased by 2-4%.
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This decrease caused the average global temperature of Earth to decrease by several tenths of a degree for
several years.
Benefits of Volcanic Eruptions
Volcanic Soils
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Volcanic soils are some of the most fertile soils on Earth.
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Volcanic rocks are made of minerals that contain elements important to plant growth.
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When volcanic rocks break down, they form soils that contain many nutrients that plants can use.
Geothermal Energy
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Magma heats the rocks that surround it.
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These rocks often hold water that also becomes heated.
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This heated water, called geothermal water, may reach temperatures of hundreds of degrees Celcius.
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Geothermal water contains large amounts of heat energy.
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This energy can be tapped by drilling wells to reach the hot water.
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Water can also be pumped through heated rocks to obtain energy.
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Geothermal water can be used to drive turbines that generate electricity.
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It can also be used to heat homes, grow crops, or keep roads free of ice.
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In Reykjavik, Iceland, 85% of all homes are heated with geothermal water.
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Volcanic rocks are often used in construction.
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As early as 300 BCE, Romans made concrete from volcanic ash and lime.
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This material was used to build the Colosseum in Rome in 80 CE. The strength of this material has allowed
the Colosseum to stand for nearly two thousand years.
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As recently as the 20th century, volcanic ash was used to make concrete for dams in the United States.
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Today, basalt and pumice are often used in the construction of roads and bridges, and the production of
concrete.
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Volcanic rocks have many other uses.
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Volcanic ash absorbs moisture, so it is used in cat litter.
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Because pumice is abrasive, it is used in facial scrubs, soaps, cleaners, and polishes.
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Pumice is added to soil to allow air and water to circulate more easily through the soil.
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Because metals in pumice are not water soluble, pumice is used alone or with silica sand to filter drinking
water.