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. 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.'
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