The to flatten out is due to the

The earth ejects lava, rock fragments, hot vapor and gases during volcanic eruptions. Volcanoes vary based on size, shape, composition and eruptive style. Learn about the different types of volcanoes, such as shield, cinder cone and composite cone.

Volcanoes

Volcanoes are a good way for the earth to blow off a little steam. More correctly, volcanoes are vents in the earth’s crust through which lava, rock fragments, hot vapor and gases are ejected.

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And, while they are all natural events in the life of Earth, there are different types of volcanoes. The types of volcanoes are differentiated based on their size, composition and explosive style.In fact, we could compare the different types of volcanoes to players on a football team. The tall and impressive composite cone volcanoes are much like the strong and confident quarterback.

The broad and lower-to-the-ground shield volcanoes are much like the beefy lineman of the team. And, the fast-growing but smaller cinder cone volcanoes are much like the quick-moving and compactly built running backs of our team. Let’s take a closer look at these three main types of volcanoes.

Composite Cone Volcanoes

Composite cone volcanoes, which are also called ‘stratovolcanoes’ or simply ‘composite volcanoes,’ are cone-shaped volcanoes composed of layers of lava, ash and rock debris.

Composite cone volcanoes are grand sites and can grow to heights of 8,000 feet or more. Mount St. Helens and Mount Rainier, which are both found in Washington State, are impressive examples of composite volcanoes.These steep-sided volcanoes erupt in an explosive manner. In fact, Mount Vesuvius is a composite volcano that is most famous for burying the ancient Roman city of Pompeii in up to 20 feet of volcanic ash in 79 AD.

The explosiveness of their eruptions is due to the thick, highly viscous lava that is produced by composite cone volcanoes.And, this viscous lava has a lot to do with why they are shaped the way they are. The thick lava cannot travel far down the slope of the volcano before it cools. This makes the sides of the composite volcano steep.

These explosive volcanoes also spew out eruptions of small rock and ash, which gets deposited on the sides of the volcano. Therefore, we see that composite volcanoes are composed of alternating layers of hardened lava, volcanic ash and rock fragments, which is why they are called ‘composite.’

Shield Volcanoes

Shield volcanoes are broad, domed-shaped volcanoes with long, gently sloped sides. If you were to fly over top of a shield volcano, it would resemble a warrior’s shield, hence the name. These volcanoes can cover large areas but never grow very tall. The reason these volcanoes tend to flatten out is due to the composition of the lava that flows from them, which is very fluid.

This more fluid lava spreads out in all directions but cannot pile up in steep mounds.Shield volcano eruptions are less explosive than composite volcanoes, as the lava tends to pour out of the volcano’s vent, creating the low-profile layers of lava that are characteristic of these volcanoes. The Hawaiian Islands are actually the tops of gigantic shield volcanoes rising from the ocean basin.

Cinder Cone Volcanoes

Cinder cone volcanoes are steep, cone-shaped volcanoes built from lava fragments called ‘cinders.’ These volcanic cinders, also known as ‘scoria,’ are glassy volcanic fragments that explode from the volcano and cool quickly. Therefore, they do not fall far from the vent of the volcano, and this builds the steep sides of the cinder cone volcanoes fairly quickly.The cinder cone volcano is the classic volcano that most closely resembles the science fair volcanoes you built in elementary school that spewed out a white, foamy lava once you mixed the baking soda with vinegar.

They are basically shaped like a road construction cone with a single vent or crater at the top of the summit. These volcanoes can grow quickly, but their height tends to fall between that of the composite and shield volcanoes and rarely reaches heights of more than a thousand feet tall. Cinder cone volcanoes are fairly common volcanoes, with a number of them found in the West Coast states of California, Oregon and Alaska.

Lesson Summary

Let’s review. Volcanoes are vents in the earth’s crust through which lava, rock fragments, hot vapor and gases are ejected. There are different types of volcanoes based on their size, shape, composition and eruptive style.

Composite cone volcanoes are cone-shaped volcanoes composed of layers of lava, ash and rock debris. Composite cone volcanoes can grow to heights of 8,000 feet or more and have explosive eruptions.Shield volcanoes are broad, domed-shaped volcanoes with long, gently sloped sides. These volcanoes can cover large areas but never grow very tall due to the composition of the highly fluid lava they produce that spreads out but does not pile up.

Shield volcano eruptions are less explosive than composite volcanoes.Cinder cone volcanoes are steep, cone-shaped volcanoes built from lava fragments called ‘cinders.’ These volcanic cinders, also known as ‘scoria,’ are glassy volcanic fragments that explode from the volcano and cool quickly, building up the sides of the cinder cone volcano fairly quickly. However, these volcanoes rarely reach heights of more than a thousand feet tall.

Learning Outcomes

After you have finished with this lesson, you should be able to:

  • Define volcanoes and explain how they are classified
  • Describe three types of volcanoes and the characteristics of each
  • Identify examples of the different types of volcanoes
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