Effects of Volcanic Eruptions Key Concept: The affects of volcanic eruptions can change human and wildlife habitat.

Negative Effects of Volcanic Eruptions Volcanic explosions can have local and global effects. In April 1815, Tambora volcano in Indonesia erupted explosively. The pyroclastic flows and falling debris killed about 10,000 people in the area. Crater

High in the atmosphere, ash and gas spread around Earth. The average global temperature decreased by as much as 3°C for one to two years. The lower temperature caused crop failures and starvation, particularly in New England and Europe.

The effects of lower temperatures led to the deaths of about 82,000 people. Therefore, an estimated total of 92,000 people around the world lost their lives as a result of the Tambora eruption.

Local Affects of Volcanic Eruptions Volcanic eruptions can cause loss of human life and loss of wildlife habitat. The blast from an explosive eruption can knock down trees, destroy buildings, and kill humans and animals.

Pyroclastic flows can burn everything in their path. Hot volcanic materials can melt the snowcap on a mountain, causing devastating floods.

Volcanic ash can mix with water to form fast-moving mudflows called lahars. The weight of falling ash can collapse structures, bury crops, and damage engines. Volcanic ash can also cause respiratory problems in humans.

Global Effects of Volcanic Eruptions Large volcanic eruptions can affect Earth’s climate for several years. During large eruptions, ash and sulfur-rich gases can be pushed into the stratosphere. As the ash and gases spread around the planet, they absorb and scatter sunlight.

Enough sunlight may be absorbed or scattered to lower the average global temperature of Earth. In 1991, after the eruption of Mount Pinatubo in the Philippines, the amount of sunlight to reach Earth’s surface decreased by 2-4%. 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 are some of the most fertile soils on Earth. Volcanic rocks are made of minerals that contain elements important to plant growth. When volcanic rocks break down, they form soils that contain many nutrients that plants can use.

Geothermal Energy Magma heats the rocks that surround it. These rocks often hold water that also becomes heated. This heated water, called geothermal water, may reach temperatures of hundreds of degrees Celcius.

Geothermal water contains large amounts of heat energy. This energy can be tapped by drilling wells to reach the hot water. Water can also be pumped through heated rocks to obtain energy.

Geothermal water can be used to drive turbines that generate electricity. It can also be used to heat homes, grow crops, or keep roads free of ice.

Volcanic rocks are often used in construction. As early as 300 BCE, Romans made concrete from volcanic ash and lime. 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.

As recently as the 20th century, volcanic ash was used to make concrete for dams in the United States. Today, basalt and pumice are often used in the construction of roads and bridges, and the production of concrete.

Pumice is added to soil to allow air and water to circulate more easily through the soil. Because metals in pumice are not water soluble, pumice is used alone or with silica sand to filter drinking water.

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