A volcano is defined as a cone shaped hill or mountain that is built-up around an opening in the earth’s surface. Hot gasses, rock fragments and lavas are ejected through the opening.
As a result of the accumulation of solid fragments around the conduit, a conical mask is formed. It increases in size to become a large volcanic mountain. The conical mass is referred to as a volcano. Hence ‘volcano’ includes not only the central vent in the Earth, but also the mountain or hill built around it as well.
Volcanoes are of different sizes, ranging from small conical hills to loftiest mountains on the planet’s surface. The volcanoes of the Hawaiian Islands are located 4,300 meters above sea level. Situated on the floor of the Pacific Ocean (4,300 to 5,500 meters deep), the total height of the volcano will be around 9,000 m or even more!
The cascade range of the Western United States, Mt. Baker, and Mt. Adams are among the volcanoes which have now become extinct. Over 8,000 eruptions have been recorded from earth’s volcanoes In addition to this, there would be several other unaccounted volcanic eruptions which have occurred on inaccessible regions and the ocean floor!
Volcanic eruptions are usually preceded by earthquakes and by loud rumblings. This tends to continue on a very high scale even during the eruption. The loud rumblings are a result of the explosive movement of gasses and molten rock that are held under very high pressure. Usually, nearby lakes get drained and hot springs appear at places before a volcanic eruption.
Volcanic eruptions provide a spectacular view inside the earth’s molten interior! Strambolian, Vulcanian, Vesuvian, and Hawaiian are some of the common types of eruption.
Volcanoes can be either effusive/fluid lavas or dangerous in nature. Volcanic eruptions can be lethal with the blasts of rock, gas, ash and other pyroclasts.
Certain volcanoes erupt for a few minutes while others tend to spew their products for over a decade! In certain cases, eruption of gasses mixed with gritty pulverized rocks form tall dark ash clouds which can be visible for several kilometers. In flank fissure eruptions, lava oozes from long horizontal cracks on the side of a volcano.
The ground hugging lethally hot avalanches of volcanic debris are known as pyroclastic flows. The steam eruptions tend to release suffocating gasses into the atmosphere. In certain cases, eruptions can lead to tsunamis and may even trigger earthquakes as well. They might unleash devastating rockslides and mudflows.
There are ‘dormant’ volcanoes which might display fairly fresh signs of activity. On the other hand, there are volcanoes which were formerly active, but now only emit steam and other gasses!
Hot springs from which water is expelled vigorously at intervals are known as geysers. They indicate declining volcanic activity. Geysers can be found in countries including Iceland, USA and New Zealand.
Fissure eruptions are great lava flows quietly pouring out of fissures developed on the earth’s surface. They are not accompanied by explosive outbursts. Example: Deccan Trap formations (India).
In such cases, lavas are mostly readily mobile and tend to flow over low slopes. They are hardly over a few meters in thickness; the average thickness is mostly less than 15 meters. In case the fission eruptions take place in valleys, the thickness will be much greater.
The mid-ocean ridge (MOR)is a single, really long, active, linear volcano. It connects all spreading plate boundaries through all oceans. Low-silica, highly fluid basalt that exudes out of the MOR constitutes the entire ocean floor!
Hence, we have discussed the basic characteristics of volcanoes.
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Check your knowledge
Answer) Strambolian, Vulcanian, Vesuvian, and Hawaiian are some of the common types of eruption.
Answer) Hot springs from which water is expelled vigorously at intervals are known as geysers.
Answer) The mid-ocean ridge (MOR)is a single, really long, active, linear volcano. It connects all spreading plate boundaries through all oceans.