Volcano: Definition, Types, Examples and Trivia about Volcanoes

A volcano is simply an opening in the Earth’s surface in which eruptions of dust, gas, and magma occur; they form on land and on the ocean floor. The driving force behind eruptions is pressure from deep beneath the Earth’s surface as hot, molten rock up wells from the mantle. The results of this activity are a number of geological features, including the build-up of debris that forms a mound or cone, which we commonly imagine when talking about a volcano.

Vulcan is Greek God of beneficial and hindering fire. Vulcanization is another term derived from the name of Vulcan God. Vulcanization is adding sulfur or other curatives to rubber or other polymers to make them more durable. The rubber so produced is called Vulcanite or ebonite. Vulcano is the name of an island near Sicily, the largest island in the Mediterranean Sea and an autonomous region of Italy.

An opening or vent through which the magma, molten rocks, ashes, gases and other volatiles erupt on the surface of Earth is called a Volcano.  The most known types of Volcanoes are conical mountains which spit law and poisonous gases. But there are other types of Volcanoes.  The Volcanoes can be divided in the basis of Type of Eruption, Material erupted & Periodicity of eruption.

Types of Volcanoes by Volcanic Eruption

There are three major categories of the volcanic eruptions. The magmatic eruptions involve the decompression of gas within the magma. This decompression of the gas propels it outward. In Phretomagmatic eruptions involves compression of the gas within the magma. Another is Phreatic eruption which involves superheating of steam via contact with Magma. In Phreatic eruption, there is no magmatic release and they cause the granulation of the rocks. Apart from this there are other types of eruptions which sometimes don’t seem to be Volcanic Eruptions. The following graphic shows this classification.

Magmatic Eruptions

When Magma, the mixture of rocks, volatiles and solids erupts in a fissure, it is called magmatic eruption.

Pheratic Eruptions

These eruptions usually occur with extremely loud explosions. The explosions are mostly accompanied by carbon dioxide or hydrogen sulfide gas emissions which prove fatal to the organisms around. This eruption is also known as steam-blast eruption and most common example is 1979 explosion in the Java Island, which killed more than 100 people.

Other Types of Eruptions

Effusive eruption causes the lava to flow on ground slowly, and it travels slowly away from the site of eruption. Sub aerial eruptions occur on the surface in contrast with the submarine or subglacial eruption. Limnic Eruptions occur below the bed of lakes and is called Lake Overturn. The gases (mostly CO2) suddenly erupt from the bed of the lake making the water and environment poisonous killing animals. The lake tsunamis are caused by Limnic disruptions sometimes. Lake Monoun & Lake Nyos in Cameroon have suffered this kind of eruptions in near past.

Types of Volcanoes by Periodicity of Eruption

There are three kinds of Volcanoes on the basis of frequency of eruption viz. Active, Dormant and Extinct.

Active volcanoes

Active Volcanoes erupt frequently and mostly located around Ring of Fire. The Mount Stromboli is an active volcano and it produces so much of Gas clouds that it is called Light house of Mediterranean. Other examples are Eyjafjallajökull in island, which erupted in 2010,  Mount St. Helens located in Washington USA, Mt. Etna located in Sicily.

Dormant Volcano

Dormant Volcanoes are those who are not extinct but not erupted in recent history. Mount Kilimanjaro, located in Tanzania which is also the highest mountain in Africa is known to be a dormant Volcano. The dormant volcanoes may erupt in future.

Extinct Volcano

Extinct or inactive volcanoes have not worked in distant geological past. In most cases the crater of the Volcano is filled with water making it a lake.

Some Notable Terms Related to Volcanoes

Tephra

Materials of all types and sizes that are erupted from a crater or volcanic vent and deposited from the air. The Tephra is all the volcanic material such as Ash, Plumes, Volcanic Bombs, Volcanic Blocks, lapilli etc.

Volcanic Bomb

Pieces of Viscous lava often 2.5 inch size are ejected from the volcanoes. They are viscous rounded shaped half semisolid pieces called Volcanic Bombs. They are either round or spindle shaped or ribbon shaped. Sometimes referred to as Volcanic Blocks, however, Volcanic blocks are thought almost same size, are solid. The smaller particles less than 2.5 inch are called Lapilli. The pieces of rocks that erupt violently are also called ballistic fragments.

Lapilli

Lapilli mean “little stones.” These are round to angular rock fragments, measuring ^1/10 inch to 2 ^1/2 inches in diameter, which may be ejected in either a solid or molten state.

Volcanic Ash

The Ash from the Volcanoes is hard and abrasive type which is made up of rock particles, minetals and Volcanic glass fragments. The cloud made by the Volcanic Ash is called Ash Cloud. When this ash falls on the ground, it is called Volcanic Ash Fall. The clouds are called Avalanches sometimes.

Pillow lava

Interconnected, sack-like bodies of lava formed underwater.

Pyroclastic Rocks

It is the fragmented (clastic) rock material formed by a volcanic explosion or ejection from a volcanic vent.

Cinder Cone

A cone shape hill of volcanic fragments that accumulate around and downwind from a volcanic vent is a cinder cone. There is usually a bowl-shaped crater at the top. As the gas-filled lava erupts into the air, the lava fragments and forms cinders.

Repose

The time lag between the volcanic eruptions is called repose.

Volcanic Explosivity Index

Volcanic Explosivity Index is a scale that measures the Volume of Volcanic Products, Height of Plume and other observations to decide which volcano is more explosive. Highest Magnitude is 8.

Other Important Trivia

• There are more than 1500 active Volcanoes in the word.
• The Crater Lake in Oregaon USA was formed when a Volcano lost its top in eruption thousands of years ago.
• The Volcanic Ash is mostly acidic.
• The Olympus Mons is the tallest known Volcano on Planet Mars.
• Italy’s Stromboli Volcano is erupting for more than 2500 years.
• The Mount St. Helense had erupted in 1980, which caused the ash travel across entire US.
• The 1883 eruption of Indonesia’s Krakota eruption was so loud that blasts were heared 3000 miles away.
• Mauna Kea in Hawaii is the tallest Volcano on earth. The meaning of its name is White Mountain as it is snow capped. Its height is 4205 meter from Sea Level; however, if it measured from its oceanic base, it is the higher than mount Everest (over 10000 meters).

Pacific Ring of Fire

Pacific Ring of Fire is a horse-shoe shaped 40,000 kilometer area with 75% of Earth’s active and dormant volcanoes. It is the area with large number of Volcanic Eruptions and Earth quakes. The most active Volcanoes are located in Chile, Mexico, United States, Canada, Russian Far East, Japan, Philippines, Indonesia, New Zealand, & Antarctica.