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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

 

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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