Natural Disasters

Volcano Eruption

By BasicPlanet May 6, 2013

Volcano Eruption

What Is A Volcanic Eruption?

A volcanic eruption is one of the most dangerous and magnificent natural disasters. When a volcano erupts, the volcano sends out ash clouds, lava and even volcanic bombs. There is a high risk of danger from slow moving lava; though, the lava might move slowly, it is very dangerous and can cause a lot of damage to property and human life.

Volcanic eruptions comprise of 3 stages:

Magmatic eruptions – when gas is released under decompression.
Phreatomagmatic eruptions – when a thermal contraction comes from water.
Phreatic eruptions – when steam erupts.

The Magnitude of Volcanoes

When there is an earthquake, little vents are created in which magma is allowed to form. This is pushed up through these vents and towards the crust of the volcano. Steam vents are created when the magma reaches a certain level and reaches a boiling point which begins the eruption. The eruption might result in a total eruption. This is when gas driven explosion send magma to the volcano’s crust creating lava outpouring from the volcano.

Some eruptions are not as strong as others. All volcanic eruptions can vary in strength; with some not reaching any civilians or causing too much damage. However, others can spread over a vast area, sometimes reaching several miles from the volcano. Some eruptions do not always contain lava flow or lava fountains which aren’t always very dangerous. However, some eruptions can be on a huge scale, very violent and very, very dangerous with explosions heard from the volcano.

Some eruptions can be passive and not very dangerous however; some are explosive and can be very and high dangerous. Some volcanoes do not just erupt from their peeks, some can have eruptions at any part of the mountain, it’s not just the peeks that are the most deadly for volcano eruptions. One of the biggest and well known eruptions was in Pompeii.

The entire city of Pompeii was buried when the volcano at Pompeii erupted. However, this is only one example of a type of eruption; another type of eruption is in Norway, a volcano that had been dormant for years suddenly became active, however, the local towns were evacuated and the volcano erupted. However, there was no great scale eruption. Lava flowed but didn’t reach the town, this was a very small eruption compared to many others.

When Can An Eruption Happen?

Volcanic eruptions happen deep down inside the earth. When the earth’s tectonic plate’s shift, it causes more than just earthquakes, it can create new volcanoes or vents. Underneath the surface of the earth, debris, gases from the planet and molten rock are stored creating new formations of vents and volcanoes.

As soon as the magma thickens and builds up with the gases of planet can create explosions and cause lava to flow upwards and have ash released into the air causing thick clouds of smoke often seen overhead volcanoes. If there is an increased magma but a decrease of planet gases, then the eruption will not be as great.

However, lava can reach an amazing heat possibly even 2000 degrees Fahrenheit; sometimes it can be even higher than that. Lava can actually destroy everything in its path, even an entire village. There can be huge rocks or even boulder types reigning down from the volcano and onto populated areas. There can also be toxic gases and ash which causes severe lung problems to many vulnerable people including children and elderly people.

Volcano eruptions can happen at any given time. If there is a change to the tectonic plates in which a volcano sits on, then it can erupt at any given time. There is no set time as to when they will erupt or how much damage they’ll cause.

Volcano eruption facts — Anak Krakatau Volcano erupting

Understanding the Volcanoes

When there is a volcanic eruption, there could be many other dangers which occur. These things can be such as flash floods, mudflows, landslides and rock falls, and even earthquakes. However, there can also be things such as fire and acid rain that follows a volcano erupting. It might not seem as though there are many active volcanoes erupting but there is a great deal of active volcanoes and the fact that they haven’t erupted doesn’t mean it will always be like this. There are dangers every day from active volcanoes.

What Can You Do Before A Volcanic Eruption?

There are steps which anyone can take before a volcano erupts and they are very simple steps. These small but simple steps can help protect homes, and protect your families also in the event of a volcanic eruption. If you live in an area which has an active volcano, even if it might be up to 100 miles away, there is still a risk because a volcano can erupt at any time.

Have An Emergency Supply Kit

This can be a small but important kit of some of the simplest items such as water, and non perishable foods. You should look to add batteries, radios, battery powered or hand cranked radios. You can also have torches or flashlights just in case of a power cut or blackout; and have a first aid kit should anyone get hurt.

All of these supplies should be kept in a location which is easy to reach such as a car just in case you need to be evacuated or are being told to do so. If possible, try to add breathing masks or goggles to see through thick ash clouds.

Emergency Plan

A disaster such as a volcano erupting can happen at any given time and it does mean your family mightn’t be at home when it happens. This is why you do need to think about getting in contact with other family members and meeting up again. You need to think carefully about all eventualities and have a good plan to get the family reunited once again.

These are simple plans but if you do live in an area very close to an active volcano, they could end up saving your life and your family’s.

You might not realize or understand that a volcano is active or is about to erupt either, however, when a volcanic eruption occurs, you have to be vigilant. You have to be aware of what could happen and how a volcano works.

The World’s Natural Disaster

When an eruption occurs, lava can spill over and can absolutely cause mass devastation. Even if the volcano isn’t moving fast towards the local town or village, there are still many dangers that can cause harm. The ash clouds can be very dangerous to a person, as is the poison gases and flying debris and rocks. There are many dangers to volcanic eruptions, though this is a natural disaster that cannot be tamed or predicted.

It might sound as though volcanoes aren’t that dangerous if they haven’t been active for years but they’re still dangerous. They have intense heat from lava flows and of course the acid rain can all become dangerous.

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Volcanoes

Types Of Volcanic Eruptions

By BasicPlanet May 2, 2013

Types of Volcanic Eruptions

In order to understand volcanoes it is important to understand the types of volcanic eruptions which are what in the end a volcano will mostly be known for. When people hear about an eruption the first thing that comes to mind is the explosive spew of lava which is seen in movies and even most of the documentaries but the fact is that some eruptions are very small and the amount of lava that will come out will not put anyone in danger. During an eruption other things besides lava are also expelled from the vent and that includes ash, blocks, gas and tephra. By observing the volcano’s activity prior to a possible eruption you can tell which type of eruption is possible.

Hawaiian Eruptions

The Hawaiian eruption will have fluid lava, which is sent into the air from the vent or the line of vents in jets. In these types of volcanic eruptions, the jets could last for several hours which is called a “fire fountain.” When the bits of lava fall down after being shot up they can create lava flows or in other cases they will build hills which are called spatter cones. The flows of lava may also show up at the vents even when the fountaining has stopped. If the lava is flowing fast enough it could travel several miles before it hardens after cooling down.

The reason why these types of volcanic eruptions are called Hawaiian eruptions is because of the Kilauea volcano which can be found on Hawaii’s Big Island. This volcano is famous for its amazing fire fountains. In 1969 through 1974, Mauna Ulu had Hawaiian eruptions, which produced lava fountains that shot up over 1,000 feet while the eruption was taking place.

Strombolian Eruptions

A Strombolian eruption is a type of eruption that could be classified as low level. These types of volcanic eruptions were named after the Stromboli volcano in Sicily, which experienced this type of ejection several times. These eruptions can be small to medium when it comes to the volume with some periods of violence. A Strombolian eruption is a very distinct burst of lava that takes place at the mouth of a lava filled summit conduit. Because the lava flows during these eruptions are more viscous, they are thicker and shorter than other eruptions, such as Hawaiian ones.

However, because the eruption does not strongly affect the conduit system, these eruptions can last a long time. In fact, some volcanoes have produced continuous Strombolian eruptions for many decades. An example of a Strombolian eruption that lasted a shorter duration is the Paricutin volcano, which erupted continuously from 1943 to 1952. A longer lasting one is Mount Erebus in Antarctica which has had these eruptions for many decades and of course the namesake for this type of eruption, the Stromboli volcano in Italy has actually been producing these types of volcanic eruptions for thousands of years.

Vulcanian Eruption

Another one of the short but violent types of volcanic eruptions is the Vulcanian eruption. These eruptions can create extremely powerful explosions that cause material to travel at speeds greater than 800 miles per hour and gain an altitude of several kilometers. In addition, Vulcanian eruptions produce ash clouds and tephra in addition to pyroclastic density currents, which is a mixture of rock, gas and hot ash that flows in a manner very similar to fluids. The tephra from these flows is generally spread out over larger areas than the tephra emitted during Strombolian eruptions. Generally, the pyroclastic rock will create a volcanic cone made of ash and the resulting ash will cover a large area surrounding the volcano.

These eruptions are caused by either a lava dome rupturing or when a plug of the lava from a volcanic conduit fragments and explodes. In addition to lasting anywhere from days to months or even years, these Vulcanian eruptions may also be a precursor to larger and more explosive eruptions. These types of volcanic eruptions are named after the small volcano found on Vulcano, an island in Italy.

Plinian Eruptions

The most spectacular and most violent of all types of volcanic eruptions is what is known as a Plinian eruption. This type of eruption happens when gassy magma is fragmented and associated with very viscous magma. The combination releases a huge amount of energy, which will create an eruption column which will contain ash, gas and could rise up to an altitude of 50 kilometers at very high speeds. Because the ash goes up so high, it could end up several thousand miles away from the volcano’s location. This type of eruption has been compared to a nuclear explosion because of the mushroom shaped eruption column it will create.

These types of volcanic eruptions are named after Pliny the Younger who was a Roman historian that made the comparison back in 79 A.D. when Mount Vesuvius erupted so Plinian eruptions were named after him. These types of eruptions do happen and the one that took place at Mount St. Helens in 1980 is one of the best examples. They are extremely dangerous and destructive and could destroy the entire top of the mountain. Ash and lava bombs can land several miles away from the volcano and the currents of lava will destroy anything in the surrounding area. Because of the amount of material released during an eruption it is possible that the mountain will go into a resting period right after the eruption.

Surtseyan Eruptions

The Surtseyan eruption is a hydromagmatic eruption. The lava or magma will interact with water in an explosive manner. Most of these eruptions will take place underwater when a volcano becomes too large, enough to break to the surface. When the water expands and turns into steam, any water that touches the hot lava will explode creating plumes of ash, scoria and steam.

In 1963, a Surtseyan eruption took place in Surtsey and that is where the name comes from. This eruption eventually switched from a Surtseyan to a Hawaiian type of eruption. In more recent times in 2009 near Tonga the volcanic island of Hunga Ha’apai started to erupt. The steam and ash rose over 5 miles in altitude.

How The Eruption Type Is Determined

There are several things that will help determine the types of volcanic eruptions. The first thing that you will be looking at is the gas and crystal content as well as the temperature of magma. Magma which contains a lot of crystal will be more likely to produce an explosion rather than a flow so some scientists are able to examine that before an eruption takes place. Another thing that influences the type of eruption that you will see is the gases in the volcano. When the gas cannot escape from the magma then it could cause an explosion but if it can be released without any explosion or maybe a few minor ones, the eruption may be a little milder.

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Lava Dome Volcano

By BasicPlanet May 2, 2013

Lava Dome Volcano

A lava dome is a mound that will form when lava piles up over a volcano’s vent instead of moving away. Since the eruption of lava is slow there is no chance for a lava flow to occur and therefore the lava dome will form. Most of the time the sides of a dome will be steep and they are usually composed of what’s called silica-rich lava which in some cases will contain pressurized gas so that explosions can occur. The domes can be described as a small bulbous mass of lava. As the lava cools down it becomes hard and the dome forms.

Size And Shape

The size and shape of a lava dome can change from one volcano to the next. However, you can expect them to be thick and steep sided. The thickness of the lava dome can vary from up to a kilometer in height to just a few meters. The length or diameter can also vary a lot from several kilometers to just a few meters. The shape of the dome can also be very different from one to the next with some of the more common shapes being circular, flat topped, spiny, piston shaped and even a combination. The form of the dome depends on different factors including the viscosity of lava, strength and the slope of the surrounding area it is being erupted onto.

Where Do They Form?

A lava dome can form anywhere there is any volcanic activity. Usually they can be found in the crater of larger volcanoes like Mount St. Helens. However they will not only appear at the craters. In some cases the domes will form on the sides or flanks of the volcano. In rare cases they can even form away from volcanic features. It all depends on the magmatic attributes of the area around them. There are domes on Mount St. Helens which are located on its flanks. These types of domes will eventually help rebuild the mountain.

What They Are Made Of

There are different types of composition that a lava dome can have and those include anything from rhyolite to basalt. It is important to know however that most of the time the lava that will form a dome will have a higher content of silica (Si02). That composition is what makes the lava more viscous. While a dome can take one of many different types of textures, usually they tend to be blocky in nature.

Types

A lava dome can take many different shapes the first one of which is the Tortas kind. The reason for the name is the similarity that the shape has to a cake or otherwise known as a torta. This is a very common type of formation but it does happen more often in South America near the Andes Mountains.

The Peleean type of lava dome is probably the steepest of all domes. Typically they are similar to Tortas with the difference that they have smoother upper surfaces. They also have vertical spines and can collapse.

The Coulees are somewhere between a lava dome and a lava flow. This type of dome usually takes place on the side of a slope and that is why it can run down. It is rare for this type of dome to be very large but there are a few examples which are over 10 kilometers.

Finally you will be able to find what is called an Upheaved Plug which is a very interesting and very rare type of dome. The lava when it erupts tends to be stronger than that of other domes and because of that the lava is pushed up, almost like a piston. These extrusions can travel very high when compared to the surface.

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Magma

By BasicPlanet May 2, 2013

Magma

Magma is a molten and liquid rock that is only found below the earth’s surface. That is because once it reaches the surface it becomes lava. This substance is made up of a combination of dissolved gases, rock fragments and crystals and the liquid part of it is referred to as the melt. Because of its creation due to high pressure and temperatures, this is an extremely hot substance, ranging from 1,292 to 2,372 degrees Fahrenheit. Frequently you will find this substance pooling in magma chambers which can feed volcanoes. It can also intrude into nearby rocks, rise to the surface in the form of lava or become an explosive ejection of tephra.

How It Forms

Magma forms in either the lower portion of Earth’s crust or the upper part of its mantle. It is produced when high amounts of pressure combine with high temperatures, causing some of the rocks in the area to melt, creating this substance. Without this combination of pressure and heat, this substance would not be able to form.

Magma Chambers

This substance is most frequently found in magma chambers under the surface of the earth. These are basically underground pools of this liquid rock. In order to maintain its form, the liquid in these chambers must be exposed to constant high temperatures in addition to a great deal of pressure. Because of this, the high pressure can eventually create a fracture in the surrounding rock, allowing the liquid to escape to the surface at which point it becomes lava.

Basalt

Magma comes in three major types, all of which have different properties and are more common with different types of volcanoes and eruptions. The first type of this liquid is basalt and it is very low in silica and has a very low gas content as well. In addition, this liquid has a low viscosity, meaning that it appears thicker. This type of liquid rock is formed at a much higher temperature than the other two varieties, at around 1,200 degrees Celsius. It is more common in volcanic fields than other types of volcanoes and is usually present in flowing eruptions that produce thin lava flows that form shields.

Andesite

Andesite magma occurs at a slightly lower temperature than basalt, ranging from 800 to 1,000 degrees Celsius. It also has a slightly higher content of silica and gas and is moderately viscous compared to the low viscosity of basalt liquid rock. Andesite is most common in stratovolcanoes and will usually produce moderately explosive eruptions that include a liquid flow as well. These eruptions will generally create thick lava flows that are full of rubble.

Rhyolite

The third type of magma is rhyolite and it occurs at the lowest temperature possible for this substance, ranging from 750 to 850 degrees Celsius. It is the complete opposite of the basalt version as it is rich in silica and has high gas content. In addition, it has a high viscosity. This type of liquid is most commonly related to caldera volcanoes that are distinguished by very explosive eruptions. These eruptions will usually produce pumice, ash fall and pyroclastic flows. In cases in which this substance has lower gas content than normal, the lava will begin to flow.

Magma Eruptions

Volcanic eruptions frequently occur because of the accumulation of magma within which then erupts. Usually these eruptions occur because of high pressure stemming from the dissolved gases within the liquid rock. The gases usually remain dissolved because the pressure of the rocks confining the substance is larger than that of the gas’s vapor pressure. If this balance shifts, however, the result is many tiny gas bubbles filling the substance and trying to escape. Once the pressure becomes too great, the eruption occurs.

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Lava

By BasicPlanet May 2, 2013

Lava

A lava flow is a stream of molten rock which will pour out of an erupting volcano’s vent. This substance can be erupted either during the explosive activity or a non-explosive event. Most lava flows will move slowly but it will destroy anything in its path. But the good news is that due to the low speed of the flow most people should have a chance of getting away from it. The speed of the flow will depend on different factors and those include the viscosity of the substance, the steepness of the hill, channeling in the area and the amount that had been produced at the volcano’s vent.

Speed

As stated earlier flows can be rather slow but some can reach speeds of over 30 kilometers per hour. Most of the edges of the flow will travel at around 10 kilometers per hour provided that the slope is steep. However, on a flatter surface the speed can be less than one kilometer per hour. The viscosity of the lava will affect the speed as the higher viscosity the lower the speed. It is rare for a viscous lava flow to go over 8 kilometers per hour from their vent.

Destruction

Anything in the path of a lava flow will be destroyed and eventually buried by the flow. Some materials which will not fall will catch on fire due to the extremely high temperatures found in the flow. If the lava were to enter a body of water such as the ocean, lake or a river, the water will boil on contact. Vegetation stands no chance as it will simply be buried and burnt by the flow, creating methane gas. The good news, however, is that it is rare for deaths to happen due to flows and that is because of the low speed at which they move.

Injuries To People

Even though deaths are uncommon, injuries do happen when people stay close to a vent. People have been killed and injured when they approach a lava flow to get a better look. Most of the deaths related to flows usually have to do with the explosions that take place when the substance interacts with a body of water. Other things that could kill or injure a person include asphyxiation on toxic gases, collapse of a delta, pyroclastic flows and lahars which happen from melted water. Though it may be tempting to get a closer look, it is never recommended to do so as there is simply too much danger in the area of a flow.

No Rebuilding

When an area is affected by a volcano it is much different than what you would find with most other types of natural disasters. It is possible to rebuild a home after a tornado, hurricane or earthquake hits an area. However, when lava hits an area it is nearly impossible to rebuild there. The homes that were in the area are buried by the substance and the landscape changes immediately as it cools down. There is an entire new area which becomes really hard to build over and the owners may not want to anyway.

Evacuation

There are problems associated with evacuation of an area when a volcano is erupting. The flow of lava could cover evacuation routes so the cities that are in areas that could be affected need to design more than just a couple evacuation plans. When a volcano is believed to be close to erupting scientists can look at the conditions and make a prediction of where the flow will go but currently it is not an exact science so there is always a chance that the prediction will be wrong.

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