How and why does volcanic eruptions take place?

Answer 1

What is the first image that comes to your mind when you hear about volcano eruption? I guess, it would be an image of orange-red lava spewing from the top of a giant and a cone-shaped mountain. The entire human community is in awe of the destructive power of a volcano. Though the geologists have solved many of the mysteries regarding the eruptions of volcanoes, they believe there is a wider geological phenomenon that needs to be solved. The study of volcanos and their related phenomena is known as volcanology or vulcanology. The scientist who studies about volcanoes is known as volcanologist.

How are Volcanoes Formed?

Volcanoes are formed in various sizes and shapes. Cone-shaped volcanoes are the most common ones. Some volcanoes are only a long crack on the earth's crust. Volcanoes that resemble high mountains were the ones that are formed due to many volcanic eruptions.

According to the theory called plate tectonics, the crust of the earth has many rigid plates that are floating on a semisolid layer of the earth's mantle. Currents caused by the heat energy from the center of the earth and the uneven distribution of weight in the crust causes these plates to move. Plates may push together, pull apart, or slide past none another.

When two plates collide, and one or both of them is composed of oceanic crust, the one with the heaviest oceanic crust will slide under the other in a process called subduction. As the plate enters the mantle, it takes water and other easiliy-vaporized substances with it. Thses seept into the hot mantle rocks, lowering the melting point of the material. The resulting molten rock, called magma, then rises due to bouyancy through the crust to form volcanoes

Where two plates move apart the crust is thin. This means there is less pressure on the upper mantle. Less pressure means a lower melting point for the superheated rock. The resulting magama then rises up to form volcanoes. Most of these volcanoes are hidden under the ocean except in icealnd, where a hot spot has helped the volcanoes form and island, and in the East African Rift, where the splitting of the crust is fairly new.

Some volcanoes are formed in hotspot areas. Hotspots are the result of extra hot mantle material rising to just beneat the crust. Here, some of it melts and rises through the crust, forming volcanoes

Causes of Volcanic Eruption

The buoyancy and the pressure within the earth's crust cause the volcano to erupt. Magma is formed when the upper mantle of the earth melts. The magma is forced upward under pressure either though fractures in the crust. In some eruptions this process is aided by gasses in the magma water, sulfur dioxide and carbon dioxide. Most of the time the high pressure keeps the gasses dissolved. The solubility of gasses decreases as the magma moves closer to the earth's surface and eventually separates from the magma forming bubbles. These bubbles expand rapidly and the volcano erupts explosively.

Magama is often stored beneath the volcano in a chamber. In some cases the magma may start to solidify, which concentrates silica in the remaining liquid. This makes the magma more viscous (thicker), possibly too much of it to erupt. A new injection of magma from the mantle may re-melt the solidified portion and allow it to erupt.

Types of Volcanic Eruption

• Hawaiian Eruptions

Hawaiian eruptions are not explosive and are associated with low-viscosity magma with a low gas content. The lava thrown out is low in gas content and it flows down slowly. Sometimes the volcanoes throw up a fire fountain where bright lava is sprayed into the air for several hours or few minutes. However, more often the lava simply pours out in a less spectacular fashion. Lava then flows down slope from the eruption. These flows are usually slow-moving and so do not kill very often, but can still be destructive to property.

• Strombolian Eruptions

These eruptions are associated with magma with a somewhat higher gas contend, but still a low viscosity. In these eruptions, lava is fountained into the air in a somewhat explosive fashion, often forming chunks of bubble-filled rocks called scoria.

• Plinian Eruptions

These highly explosive eruptions (along with the similar, though smaller, pelean eruptions) are associated with viscous, gas-righ magma. Plinian eruptions are the most dangerous. Instead of spewing lava, the magma in these eruptions is blasted into small particles that form volcanic ash, while larger bubble-filled pieces form pumice. These eruptions can send plumes of ash more than 30 miles (50 km) into the atmosphere. Ashfall may be found thousands of miles from the volcano. Closer to the volcano clouds of superheatd ash, gas, and pumice called pyroclastic flows race down the sides of the volcano, sometimes at well over 100 mph, burning eveything in their path. The most massive explosive eruptions are refered to as ultra plinian.

To sum up, the volcanic eruptions can cause destruction to all living things. They can also cause substantial changes in the climate. The particles that are thrown into the atmosphere hinder the sunlight from reaching the surface of the earth. This can lead to low global temperatures. Large quantities of gases such as sulphur dioxide, hydrogen chloride and hydrogen fluoride are sometimes thrown out. These react with atmospheric water to produce acid rain. which can damage crops and, in severe cases, kill most living things.

Answer 2

When a volcano erupts it blows its top off due to all of the pressure contained within it, causing cinder and ash or lava or all 3 to burst out depending whether it is a shield cone volcano, a composite cone volcano, or a cinder cone volcano.

Answer 3

volcanoes erupt because big tectonic plates under the ground have collided and caused magma to erupt through the earths surface when it reaches the earths surface it turns to lava. This magma escapes through the earths core which the tectonic plates created by leaving a gap when they collided. This will therefor form a volcano!

Answer 4

Magma is a mixture of molten rock and dissolved gases below the earth's surface. The tremendous heat of the earth's core melts the surrounding layer of rocks, forming magma. Being lighter than the surrounding rock, magma rises up towards the surface. It mostly remains below the earth's crust. However, when the temperatures and pressures become too much, it is thrown out forcefully in the form of volcanic eruption. The temperature of magma can range from 650 degrees to 1200 degrees Celsius. Magma is called lava when it erupts onto the surface.

Answer 5

Pressure from the plates creates a mountain and pressure builds under the crust pushing the magma out of the top of the mountain creating a an eruption. Also that's a reason how volcanoes differentiate from mountains.

Answer 6

Volcanoes form when tectonic plates push against each other. This is also how mountains are formed. In a volcano, magma goes through openings in the crust and shoots out of the volcano.

Answer 7

Some Volcanoes erupt while some don't because there are alot of different volcanoes but they all do the same thing.