Volcanoes: Force Of Nature And Wonder Yellow Magpie – About The Fascinating

Volcanoes: Force Of Nature And Wonder

Volcanoes are one of the most powerful forces of nature on Earth. They can cause islands to appear out of the ocean and can also do the exact opposite, forcing them to disappear into the sea. One of the most awe-inspiring sights, they can cause great catastrophes and induce mass panic.

In 1883, a small island called Krakatoa in Indonesia was home to one of the most violent volcano eruptions on earth. The sound of the eruption could be heard as far away as Australia, over 5,000 kilometres (3,100 miles) away.

Largest Known Eruption

The Greek Island of Santorini erupted with five times the power of Krakatoa in 1470 BC. The entire island was completely destroyed due to the tremendous force of the explosion. A gigantic tidal wave that was created in the aftermath of the eruption caused havoc to the neighbouring island of Crete.

Creation of Volcanoes

Volcanoes are created by ruptures in the Earth’s crust. Fuelled by pockets of molten rock deep underneath the surface called magma, volcanoes can allow lava and ash to escape from deep underground in powerful explosions. Magma that manages to break the surface is known as lava.

Volcanoes are generally found where there is techtonic activity. Typically, this activity is a result of either diverging (moving apart) or (converging moving towards) plates. The Mid-Atlantic Ridge is an example of diverging plates while the formation of the Pacific Ring of Fire is a result of converging activity. Thinning of the Earth’s crust can also result in the formation of volcanoes as in the case of the African Rift Valley.

Explosive and Non-Explosive Volcanoes

There are two main types of volcanoes in terms of impact. Explosive and non-explosive. Explosive volcanoes tend to be highly dramatic and cause a great deal of damage. While non-explosive volcanoes are generally deemed to be safer and less dangerous. The key difference between the two lies in the composition of the magma. Magma that is thin and lacks viscosity is unlikely to explosively erupt. These types of volcanoes typically erupt on a regular basis. There are generally believed to have a low concentration of silica.

Explosive volcanoes on the other hand, are generally the result of underground activity and the collision of tectonic plates. Magma in these types of volcanoes is thick and has large quantities of silica in its composition. Magma that contains silicas have a tendency to be viscous. The viscous magma thereby plugs the volcano vent. Over time pressure builds and once the magma plug cannot hold the force, the volcano erupts with explosive consequences. Explosive volcanoes send out masses of lava bursting from the vent and emitting ash and toxic gases into the air in a lethal pyroclastic flow.

Volcanic ash is also deadly killer. Ash, which is created by the tremendous heat and force of an eruption, gets sucked up into the atmosphere where it can rain down many kilometres away from the crater. This was largely responsible for the death of the people of Pompeii in Italy.

Benefits Of Volcanoes

Although the exact role of volcanoes is not fully understood, their destructive aspect is countered by the many benefits that they also bring. Volcanic activity has resulted in new land masses forming where previously there was only water and sea.

In November, 1963, a volcanic eruption off the coast of Iceland created a new island called Sertsey. All of Hawaii was created by the same processes.

The reason why people inhabit land so closed to volcanoes is because of the fertile nature of the soil. Lava and ash-based soil makes excellent land for agricultural purposes.

Largest Active Volcano

The largest known active volcano is Mauna Loa in Hawaii. With a crator 3.5 kilmetres (2 miles) in diameter, its latest activity was in 1984. As there is a lack of silica present, the lava has little viscosity and flows like a fluid liquid. Because of this and the low profile of its sides it is known as a shield volcano.

Supervolcanoes

Supervolcanoes are large volcanoes that have the potential to cause enormous devastation on a large if not global scale. Their huge size poses potential difficulties for people and wildlife on Earth. If such volcanoes did erupt, large amounts of sulphur and ash would penetrate the atmostphere causing the sun’s rays to be blocked. Yellowstone National Park is said to be home to a supervolcano with the potential to obscure sunlight across the world if it does erupt.

Volcano Classification In The Popular Imagination

There is a widespread belief that volcanoes can be easily classified as active, dormant and extinct by their frequency of eruption. Active volcanoes are deemed to be active if they have erupted regularly in the past. Dormant ones are those who have erupted in recorded times. Extinct volancanoes are ones which not erupted in recorded times. However, these models are not accurate and have shown to be wrong on more than one occasion.

The Reality Of Volcanoes

In reality, volcanologists consider extinct volcanoes to be ones which have either exhausted or do not have a sufficient lava supply. As a result these types of volcano are deemed unlikely to erupt.

However, even extinct volcanoes can become active by regaining a supply of lava which is possible due to constant changes in the Earth itself. As volcanoes can remain dormant for millions of years, scientists find it difficult to distinguish between these and active volcanoes. Previously thought to be dormant volcanoes have erupted back into life.

One such example is Soufriere Hills, Montserrat, Bermuda, which became active in 1995. Fourpeaked Mountain, Alaska, is another notable volcano which was long thought to be extinct but which erupted in September, 2006, after nearly 10,000 years of dormancy.

Ireland and Great Britain

Although there are no volcanoes that are considered to be active in the United Kingdom there are several extinct ones. Most notable is Croghan Hill, near Tullamore, County Offaly in Ireland. The remains of an extinct volcano it is over 26 acres in area and rise some 234 metres (767 feet).

Given what we know about volcanoes it is unlikely that those we consider extinct will continue to be so in the millenia ahead.