Volcano

You must have seen smoke coming out of a chimney. When the chimney is not artificial but a natural crack on the Earth throwing out hot gases and molten lava, you call it a volcano. It is a mountain having an opening on the surface of the Earth from which fire, smoke and ashes come out continuously.

How is a volcano formed?

As we go deep into the Earth, temperature increases. At a depth of 30 km, the temperature is so high that it can even melt rocks. When rocks inside the Earth get melted, they start expanding and moving. These molten rocks are known as magma. Because it is lighter than the solid rock around it, magma rises. In some parts of the Earth, this magma starts coming up through openings in the Earth's crust. When the pressure exerted by this magma is considerably high and the Earth's crust at some places is weak, the crust breaks at those places and hot gases, liquid and solid material of the red molten rocks start coming out. This is called a volcanic eruption. The ejected hot smoke, ashes and stone pieces constitute what we call lava. This lava goes on solidifying in the shape of a cone. On cooling it takes a form of a mountain on the surface of the Earth.

Mythology

The word volcano comes from the little island of Vulcano in the Mediterranean Sea off Sicily. Centuries ago, the people living in this area believed that Vulcano was the chimney of the forge of Vulcan--the blacksmith of the Roman gods. They thought that the hot lava fragments and clouds of dust erupting from Vulcano came from Vulcan's forge as he beat out thunderbolts for Jupiter, King of the Gods, and weapons for Mars, the god of war.

Did you know? More than 80 percent of the Earth's surface is of volcanic origin. Gases coming out from openings on the surface over hundreds of millions of years are responsible for the formation of the Earth's earliest oceans and atmosphere, and even the mountains, plateaus and plains. Lava cools rapidly on the surface of the Earth to form a type of crystalline rock called Igneous rocks.

The most common elements erupted by volcanoes are: silicon, oxygen, magnesium, iron, aluminum, calcium, sodium, potassium, titanium, phosphorous, carbon, hydrogen, sulfur, basalt and diamonds. When the lava cools, it gets solidified and forms rocks. There are three different kind of rocks formed by the lava.  Fundu Fact Volcanoes happen not only on Earth but on other planets as well. Venus is covered with volcanoes. The largest volcano in the solar system, Olympus Mons, towers 24 kms high and is found on Mars.

The Igneous rocks:

When fresh magma solidifies it makes igneous rocks. Intrusive igneous rocks are formed when the magma cools underground; while extrusive igneous rocks are formed when lava cools outside the volcano.

Sedimentary rocks:

When rocks on the surface are exposed to wind, rain, and snow, they begin to break down into smaller sized particles, which settle in the bottom of lakes or ponds along with other things like plants and dead fish. These layers begin to harden and become sedimentary rocks.

Metamorphic Rocks:

Metamorphosis means "change." This change is due to two things - pressure and temperature. Metamorphic rocks are usually sedimentary rocks that change their form due to pressure and temperature.

Different kinds of volcanoes are:

There are 26 different types of volcanoes. The most common types are strato volcanoes, shield volcanoes, submarine volcanoes, volcanic fields, cinder cones, and calderas.

The least destructive and least explosive are shield volcanoes. These volcanoes made the Hawaiian Islands and they are formed along the coast of the oceans. Hot rocks, ash, and last lava form a strato volcano. They are taller and more active than all shield volcanoes. Some examples are Mt. Fuji and Mt. Shasta. Cinder cone volcanoes are the most powerful and active volcanoes. This kind of volcano shoots out a single tube. Some cinder cone volcanoes are Sunset Crater, Paricutin, and Krakatoa. Submarine Volcanoes: Volcanoes under the sea are called submarine volcanoes.

On the basis of state, the volcanoes are divided into three types: Active Volcano: A volcano that has erupted during the last several hundred years is called active volcano. Dormant Volcano: If a volcano has erupted during the last few thousand years, but not the last few hundred years, then it is a dormant volcano. For example, Mount Capulin is dormant, not extinct. It last erupted about 7000 years ago. Dormant volcanoes are also called sleeping volcanoes. Extinct Volcano: If the volcano has not erupted during the last thousands of years, it is called extinct or dead volcano.

Do you know? Volcanic Explosivity Index or VEI can measure the bigness of a volcanic eruption? It is based on a number of things that can be observed during an eruption. Volcanoes affect humankind in many ways. The destruction caused is awesome, but assessing volcanic hazards and forecasting volcanic eruptions can reduce the risk involved. Volcanism provides fertile soils, valuable mineral deposits, and geothermal energy. Over geologic time volcanoes recycle the Earth's hydrosphere and atmosphere, and explosive eruptions can affect climate.

Do you know that all diamonds come from old, deeply eroded volcanoes or from a rare type of volcanic structures known as a kimberlite pipes? Such kinds of structures are abundant in South Africa.

Do you know how many volcanoes are estimated on earth and other planets?

Mercury - zero to tens.  Venus - few thousands.  Earth - ten thousand or so.  Moon - zero to a few.  Mars - 18.  Uranus - hundreds to thousands  Other Jupiter moons - zero to a few  Saturn - many  Neptune - few

The temperature of a volcano and its products depends a lot on their composition. The most common type of lava has eruption temperatures of about 1150-1200 degree centigrade. As the lava cools, its color changes.

Color Temperature Yellowish-white: 1150 - 1350 degrees C Orange: 1000 - 1150 degrees C Bright red: 800 - 1000 degrees C Dark red: 650 - 800 degrees C Brownish red: 500 - 650 degrees C

Interesting Facts about Volcanoes:

Kilauea in Hawaii is the world's most active volcano. It has erupted more than 50 times since the late 1700's and is still in a near eruption stage since 1983. The most deadly volcanic eruption was that of Krakatau (Indonesia) in 1883. There are about 1511 volcanoes in the world that are considered to be active. There are many other dramatic looking volcanoes - such as Arthur's Seat in Edinburg that are ancient and dead. Ojos del Salado (6,887m), a stratovolcano in northern Chile, is the tallest volcano in the world. Kilauea in Hawaii and Stromboli in Italy are constantly erupting volcanoes. Stromboli is erupting since the 7th century B.C. The largest eruption was that of Tambora in Indonesia in 1815. Mauna Loa is the world's largest active volcano on the island of Hawaii. It makes half of the area of the Island of Hawaii. Mauna Loa began to form nearly a million years ago. Mauna Loa is in the shield-building stage and is one of the most active volcanoes on Earth, erupting 15 times since 1900. The last eruption was in 1984 and sent lavas within 6.5 km. The youngest volcano is Paricutin in Mexico. It is the famous one that grew out of a cornfield in 1943 and erupted for 8 or 9 years. Large explosive eruptions can shoot fragmented lava to heights of 40 km. Java is about the size of California and has more than 20 active volcanoes. In Indonesia 86 volcanoes have erupted in its history.

The Ring of fire:

Most of the world's volcanoes occur around the east, north and south sides of the Pacific Ocean, making it a ring of fire. The ring of fire has about 600 active volcanoes and many more dormant ones. The ring includes the Andes of South America, the volcanoes of Central America, the Cascades and Aleutians of North America, the volcanoes of the Kamchatka Peninsula and Kuriles in Eastern Russia, Japan, the Izu and Mariana Islands, the Philippines, Indonesia, Papua New Guinea, Tonga, Kermadek, and New Zealand.

Do you know that the energy released out of the volcano can be harnessed and can be used as geothermal energy? Countries that are using geothermal energy at the moment include the US, Iceland, Japan, Guatemala, New Zealand.