A volcano is a vent in the Earth’s crust through which molten lava, gases and rock fragments from below the Earth’s surface erupt into the air.
The Word Volcano
The Roman God of Fire is named Vulcan. In the Mediterranean Sea, an island named Vulcano with an active volcano is considered as the forge of Vulcan where he makes weapons for gods. Hence the word Volcano, the hearth of Vulcan.
The Big Why? Why do volcanoes erupt?
Under a volcano, rocks get so hot that they melt. The melted rocks are called magma. The hot magma rises, producing great pressure and finally exploding upwards it bursts through cracks in the earth.
What all comes out?
During a volcanic eruption rock fragments, dust, gases, ash, steam and hot lava shoot into the sky.
The magma or molten rock that comes out onto the earth’s surface is called lava. The lava produced from different volcanoes varies in their temperature and silica content and thus may be thick or thin in their consistency. Sometimes they move slowly and sometimes they move fast; depending upon their density, the slope of the surface and the volcanic output rate.
Rock fragments of volcanic origin are called pyroclastic debris. They have various forms and different names. The dark smoke of finely powdered rocks is called ash. Lava in fragmented pieces is called cinders. A type of light weight rock filled with air bubbles is called pumice.
Volcanic gases mostly consist of water vapor, carbon-di-oxide and sulphur-di-oxide along with hydrogen-sulfide, hydrogen-chloride and hydrogen-fluoride. A few other minor gases like hydrogen, metal chlorides, halocarbons etc. are also found in the volcanic emissions.
The Cuts and Curves
Volcanoes erupted at different places may have different structures. They may have one of these forms:
- Mountain-like structures with a crater at its summit (Mt Rainier in Washington, USA)
- Cracks or Fissures (Siberian flood basalt plateau in Russia)
- Lava domes (Lassen Peak in California, USA)
- Crypto domes (Mount Saint Helens in Washington, USA)
- Shields (the Hawaiian volcanic chain)
- Cones or Cinder cones (Sunset Crater in Arizona)
- Strato or Composite (Mayon volcano in the Philippines)
A few other types of volcanoes also exist, for example:
- Cryovolcanoes (or ice volcanoes) are found on other planets such as Saturn, Neptune, Jupiter and its moons.
- Mud volcanoes are formed by slurries, and they do not produce lava or high temperatures. There is an example of this in Sidoarjo, Indonesia.
The Measuring Tape (VEI)
VEI stands for Volcanic Explosivity Index. It is used to identify the magnitude of an eruption. It uses the height of the ash plume and the volume of expelled material as the base for the measurement.
Submarine and Subglacial volcanoes
Submarine volcanoes are the underwater ones. When the tops of these volcanoes emerge above the oceans, they become islands.
Subglacial volcanoes develop underneath icecaps. The melting icecaps make the lava on top to collapse, leaving a flat top mountain.
These are the ones with the power of super destruction. They cover an enormous area, and they can cool global temperatures for many years. These large eruptions can aﬀect temperature as the droplets of sulphuric acid obscure the sun and absorb the heat radiated up from the Earth, thus cooling the Earth’s atmosphere. Lake Taupo in New Zealand is an example.
Will the sleeping giant wake up again?
Usually people categorize the volcanoes as Active, Dormant or Extinct.
An active volcano is one that has erupted in the last 10,000 years. (Mount Yasur in Vanuatu with an eruptive phase of 111 years is the longest currently ongoing volcano.)
A dormant volcano is the kind of a volcano that has not erupted in the past 10,000 years, but which is expected to erupt again. (Fourpeaked Mountain in Alaska is an example.)
An extinct volcano would be one that is not expected ever to erupt again. (Edinburgh Castle in Scotland is said to be located on the top of an extinct volcano.)
But, you never know for sure. There are many cases of eruptions from extinct volcanoes. Mount Vesuvius is a volcano that was considered as extinct and was covered with gardens and vineyards, before its eruption in 79 AD. It had destroyed the towns of Herculaneum and Pompeii completely. Another long dormant Soufriere Hills volcano on the island of Montserrat was considered as extinct and was not known to most people in the surrounding areas until it became active again.
The Great damage
Volcanic eruptions, like any other natural disaster, can cause great damage to the surrounding area. The population residing nearby may face a huge loss of lives and property. The volcanic eruptions can pose many other hazards as well. For example, the volcanic ash can be a threat to aircrafts. Gases expelled from the volcano eruptions may cause acid rains. When the submarine volcanoes erupt they cause giant waves that devastate coastal areas. Historically, a few dangerous massive eruptions have led to volcanic winters causing catastrophic famines.
The Friends and the party
Volcanic eruptions are generally accompanied by other natural disasters. Earthquakes, flash floods, mudflows, landslides, acid rain, fire, tsunamis are there to name a few.
Not all is bad
Volcanic areas, however, have extremely fertile soil that supports abundant plant life. For example, most of Italy has poor soil with bare limestone rock, but the region around Naples (the site of Mount Vesuvius) is covered with very rich soil and is planted with grapevines. Volcanic rocks also contain precious stones and metals such as diamonds and iron. New islands are formed by a few submarine volcanoes.
Taming the Dragon
In one of its kind of experiment, Carbon Recycling International in Iceland has built a plant next to a volcano. The volcano is powering this geothermal electricity plant. This plant is also capturing the huge carbon-dioxide emissions and turning it into a liquid fuel it calls Vulcanol.
Volcanoes in India
India has got only one active volcano located at Barren Island in the Andaman Sea. Narcondam in the Andaman Sea is a dormant volcano in India. Dhinodhar Hills (in Gujarat) and Dhosi Hill (on the border of Haryana and Rajasthan) are considered as extinct volcanoes in India. Baratang in the Andaman Sea is a Mud volcano in India.
Hawaii’s Mauna Loa has the greatest volume of any volcano, 10,200 cubic miles (42,500 cubic kilometres).
The most active volcano is Mt. St. Helens (located in Washington, USA)
Tamu Massif in the northwest Pacific Ocean has the greatest mass and the largest footprint.
The volcano having the greatest height from base to summit is the Manua Kea on the island of Hawaii.
The volcano with the highest summit elevation is the Ojos del Salado in the Andes mountain range.
Mt Etna of Italy is the world’s oldest active volcano. The first record of its eruption dates back to 1500 BC. Since then, Etna has erupted 190 times.
Mount Fuji of Japan is considered as the most beautiful volcano with a perfect shape.
We are not alone
Volcanic eruptions are not exclusive to our planet earth. Other planets like Venus, Jupiter, and Mars also show volcanic activities on their surface. A young active volcano named Olympus Mons on the planet Mars is the largest volcano in our Solar system. This massive Martian volcano is 16 miles (25 km) above the surrounding plains and stretches across 374 miles (624 km).
The Earth’s Moon has no volcanoes and no volcanic activity. The moons of Jupiter, Saturn and Neptune exhibit active volcanoes. The moon named Io of planet Jupiter is the most volcanically active object in the Solar system.
According to Greek mythology, Typhon was a most grotesque creature who had a hundred serpent heads. His heads touched the stars, venom dripped from his eyes, and lava and red hot stones poured from his gaping mouth. His hissing was like a hundred snakes, and he roared like a hundred lions. Zeus, the god of the sky and thunder and king of all the gods, once had a great battle with Typhon. The battle was so fierce that almost all the living things were destroyed. Zeus struck Typhon with hundred well aimed thunder bolts, causing a huge mountain to fall back and pin Typhon underneath. Although Typhon is held captive under the ground, it is still alive, belching fire, lava and smoke through the top of the mountains. That is why volcanoes still erupt to the present day.
In ancient Rome, there was a festival known as Vulcanalia. It was celebrated on August 23 every year. People made bonfires imitating a volcano and sacrificed animals by throwing them in the fire. They wanted to safeguard themselves from volcanoes by placating gods this way.
16th-century German astronomer Johannes Kepler believed that volcanoes were ducts for the Earth’s tears.
Come, let’s get drowned in the Red Hot Lava
Volcanology is the study of volcanoes. To make it as a career choice, there are various institutes that offer a course and can help the wannabe Volcanologist. Indian Institute of Technology located at Bombay is one of them.