In order to understand about volcanic eruptions, one must know what lies beneath the surface of earth. There are four layers – the crust, mantle, outer core and the inner core. The temperature inside the core layers is very high around 5000 to 7000 degree Fahrenheit. The Earth is therefore a huge ball of hot molten rock surrounded by a few kilometers of relatively cool hard rock – the crust.
A volcano is an opening in the earth’s crust through which magma, or molten rock, escapes from the earth’s interior. The term could also be applied to the mountain of debris that surrounds the earth. Built up over the course of thousands of years, volcanoes may grow into enormous size. They tend to be located along the unstable areas of earth’s crust where crustal plates are moving apart and along continental margins where they are colliding.
When magma erupts on the surface, it is known as lava and is the usual form of erupted material. Emerging at a temperature of 2000 degree Fahrenheit or more, some lava are very fluid. They can flow many miles before they could solidify. Other lavas with a different mineral composition and temperature are much less runny and solidify more rapidly and form a plug that ends the eruption. Eventually the gases in the magma build up enough pressure to blast away the plug with an explosion that hurls many solid fragments into the sky.
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