Volcano FAQ
What is a volcano?
A volcano is a geological landform, usually a mountain, which has formed through the accumulation of its own eruptive products -- lava, bombs (crusted over lava blobs), ashflows, and tephra (airborne ash and dust). The term volcano also refers to the opening or vent through which the molten rock and associated gases are expelled.
The word "volcano" comes originally from the small island of Vulcano in the Mediterranean Sea off Sicily. During ancient times the island was highly active and people living in the area believed that Vulcano was the chimney of the forge of Vulcan - the blacksmith of the Roman gods. They believed that the hot lava and clouds of dust erupting from Vulcano were as a result of Vulcan's activity to forge weapons for other gods.
Why do volcanoes occur?
At the Earth's mantle temperatures are hot enough to melt rock and form thick flowing magma which lighter than the surrounding rock rises. As it does so some of the magma is stored in large reservoirs or magma chambers that fuel volcanoes. As the magma reaches the Earth's surface, the pressure decreases, causing the gases in the magma to expand; it is this expansion which propels the magma through openings in the earth's surface resulting in a volcanic eruption.
Where do volcanoes occur?
Volcanic eruptions only occur in specific areas, they do not occur randomly.
The Earths outer shell, the lithosphere, is broken up into a series of slabs, commonly referred to as tectonic plates. These plates are rigid but float on the hotter, softer layer in the Earth's mantle. There are a total of 16 major tectonic plates and as they move about they spread apart, collide into one another or slide past each other. Volcanoes occur most frequently at these plate boundaries.
Volcanoes can also occur in the interior of plates at areas called hot spots. The Hawaiian Islands have formed as a result of this.
Although most of the active volcanoes we see on land occur where plates collide, the greatest number of the Earth's volcanoes are hidden from view, occurring on the ocean floor along spreading ridges.
What is the Ring of Fire?
More than half of the world's active volcanoes above sea level are located encircling the Pacific Ocean and form the Ring of Fire. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes .
What is the largest and most active volcano in the world?
Mauna Loa in Hawaii is the world's largest active volcano, reaching 13,677 feet above sea level.
Whereas Kilauea, in Hawaii, is the most active followed by Etna in Italy.
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