Volcanoes


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.

•      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.

Ring of Fire

•      Mount Vesuvius, Mount Fuji, and Mount Erebus are some well-known active volcanoes.