Tungurahua is a stratovolcano (photo: Pxhidalgo).A stratovolcano is a large cone shaped volcano. It is commonly found where there is subduction of a tectonic plate. Stratovolcanoes are also known as composite volcanoes. These landforms are a composite of layers of lava, ash, and other materials.

Photo: Tungurahua stratovolcano (Creative Commons: Pxhidalgo).

What is a Composite Volcano?

Stratovolcano cross-section (image: Edesignua).Over a period of time, the stratovolcano experiences different types of eruptions. Lava flows may dominate for a while and build up the volcano with sheets of lava.

Lava flows may then alternate with explosive eruptions. These eruptions may produce clouds of ash that build up layers of ash or pumice. In this manner, the volcano becomes a composite of layers of different materials.

What is the Danger of a Stratovolcano?

There are many dangers associated with a stratovolcano. Some are far more dangerous than others. The major dangers are listed below:

Pyroclastic flows: a pyroclastic flow is a rapidly moving cloud of hot gases and rocks. Temperatures can be as high as 1000°C. The hot cloud can move as fast as 700 kilometers per hour. In 79 AD, pyroclastic flows from Mt. Vesuvius killed up to 25,000 people.

Volcanic bombs: these are chunks of lava thrown from a volcano. The size of the bombs can range from a few centimeters to over five meters.

Volcanic ash: stratovolcano eruptions usually produce large clouds of volcanic ash. Ash are very fine particles. The ash may cover surrounding areas and damage buildings and farms. If caught in a cloud of ash, the dust can be a danger to human health when inhaled. In the sky, the ash poses a danger to aircraft. Over a period of time, the ash may even have an effect on the earth’s climate by blocking sunlight.

Lava flows: lava is molten rock produced by a volcano. It is much slower moving than a pyroclastic flow, but can cause considerable damage to areas with human settlements.

Mt. Pinatubo Eruption

Mount Pinatubo is a stratovolcano on the island of Luzon in the Philippines. It had been inactive for over 500 years. In 1991, it erupted and was the second largest eruption in the 20th century.

Nearly 900 lives were lost in the eruption. The effects of the eruption affected the lives of millions of people. Over 80,000 homes were damaged or destroyed. Forests and farms were destroyed by pyroclastic flows or ash falls. Large clouds of ash caused a cooling of the northern hemisphere. The clouds also included sulfur dioxide which produced sulfuric acid droplets in the atmosphere.

Improving Your Reading and Thinking Skills

Think for a few moments. Try to recall the major ideas in this article. When you are done, click the box below for a list of main ideas.

 

How did you do? With practice, you should be able to identify many of the major ideas. You may even discover some important ideas that aren’t listed.

Bibliography

What is a Stratovolcano?, Extreme Science.

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3 comments on "Stratovolcano: the Most Violent Eruptions"

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Webster Gabiana
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the layers of lava ash and other mateials

Ronand Abella
Member

the volcano is had a lava inside and stravolocon is most strong volcano