VOLCANOES
• A volcano is a landform (usually a mountain) where molten rock erupts in the Earth’s crust.
• A lot of pressure underground pushes up the molten rock.
• As pressure in the molten rock (magma) builds up, it needs to escape somewhere.
• This pressure in the molten rock (magma) comes from the mantle of the Earth and reaches the crust through cracks.
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• The molten rock rushes out through a vertical tunnel called a vent and fills a hollow crater at the top.
• Once the magma erupts through the earth’s surface, it’s called lava.
• As lava cools, it solidifies and forms rocks.
Characteristics of Volcanoes:
• Common volcanic gases comprise of water vapour, carbon dioxide, sulphur dioxide, hydrogen chloride, hydrogen fluoride and hydrogen sulphide.
• Large volcanic eruptions can reflect radiation from the Sun and drop average temperatures on Earth by around half a degree.
• Pumice is a unique volcanic rock (igneous) that can float in water.
• It can also be used as an abrasive and is sometimes used in beauty salons for scrubbing.
Types of Volcanoes:
• According to the nature of the volcanic eruption, there are three types of volcanoes:
(1) Active volcanoes (eruptions can be anytime and often)
(2) Dormant volcanoes (has been a while since it has erupted, but could at anytime)
(3) Extinct volcanoes (it hasn't erupted in a very long time so it probably won't ever occur again)
Active Volcanoes:
• Active volcanoes are those that may erupt any time or have erupted in the recent past.
• In geology terms, 'recent' can mean thousands of years.
• Many active volcanoes are found in the ‘Ring of Fire'.
What is the ‘Ring of Fire’?
• The ‘Ring of Fire’ is an area of frequent earthquakes and volcanic eruptions encircling the basin of The Pacific Ocean.
• Ninety percent of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire.
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Ring of Fire
• Mount Vesuvius, Mount Fuji, and Mount Erebus are some well-known active volcanoes.
