Volcanic Ashfall can be defined as the minerals, rock fragments and glasses that are exposed violently during a volcanic eruption in the form of ashes into the atmosphere.
The force created by the gases present in the magma propels the ashes to solidify in the atmosphere in the form of volcanic rock fragments and glass. On this page, students will get an idea about the formation and properties of volcanic ashes. We have also provided information about different types of Valcano.
These ashes also commonly known as tephra includes all the erupted volcanic particles, even the one larger than 2 mm in size. The explosion of this ash in the air has a negative impact on the health of humans as well as animals. As the disruption takes place in a wider aspect, it also greatly affects the infrastructures, buildings, industries, vegetations and cultivations of the nearby areas.
Formation of Volcanic Ash Falls
The formation of volcanic ashes or ashfall is an outcome of a volcanic eruption that takes place due to the expansion of the magma. Magma is the hot molten form of rocks present under the Earth’s surface. On exertion of high pressure, these magma comes out violently in the form of hot bubbling lava which leads to a volcanic eruption. On coming in contact with the air, the magma solidifies in the form of rock fragments and glass known as volcanic ashes. These ashes are minute particle-like which have a diameter less than 2 millimetres.
As a result, the volcanic ash in the air can be carried to a larger area by the winds and falls eventually on the ground creating a layer of a thick dust-like particle around the area of eruption.
The formation of volcanic ashes also occurs as a result of phreatomagmatic eruptions. This kind of eruption takes place due to the contact of the magma with the water bodies, or even snow. This, as a result, forms an insulating vapour film as the boiling point of magma is higher than that of water. The reaction of cold water with hot magma increases the amount of heat transferred, thus, leading to expansion of water and fragmentation of the magma, which later comes out violently through the vents of the Volcano.
Unlike burnt wood ashes, these volcanic ashfalls can be dangerous as they have sharp edges containing very small particles of glass and hardened rocks. There are several harmful effects of volcanic ashes on humans as well as animals. It can lead to breathing problems and irritation of the eyes, lungs and nose.
Composition of Volcanic Ashfalls
Volcanic ashfalls are the hardened form of magma in the form of rock fragments and volcanic glasses after coming in contact with the exposed air. The elements found in the volcanic ashes depends upon the thickness of the ashes along with the chemistry of the erupted magma. But as per the reports, the abundantly found elements in these volcanic ashes includes silicon and oxygen. The dark coloured ashes formed after eruptions mainly consist of 45-55% of silica. This silica is rich in iron (Fe) and magnesium (Mg) content. These ashes are sharp-edged particles that have a thickness ranging from 1-5mm which even goes up to 100-300 mm in adverse conditions.
Apart from the volcanic ashes, volcanic eruption also releases harmful gases into the atmosphere which causes severe breathing problems and irritation to the human eyes and nose. These gases are mainly sulfur dioxide, carbon monoxide and dioxide, hydrogen, hydrogen sulfide and hydrogen chloride.
Effects of Volcano Ashfalls
The effects caused by the ashfalls depends upon the thickness of the volcanic ashes. The thickness of the ashes may range from 1-5 millimetres and in adverse conditions it may be over 100-300 millimetres. Since volcanic eruptions cover a wider area, it greatly affects the nearby area.
Some of the Impacts of Volcanic Ashfalls on the Ecosystem are Given Below:
Volcanic Ashfalls can greatly affect the crop fields and can cause damage to the crops and vegetation.
They also contaminate the nearby water bodies, which as a result affects the marine ecosystem.
Due to its expansion in a large area, it causes damage to the infrastructure including roads, buildings and breakage of telephone and electric polls, thus affecting the normal living of human beings.
As volcanic eruptions release harmful gases such as carbon dioxide, sulfur dioxide and hydrogen sulfide into the atmosphere, it gives rise to breathing inability and irritation of the skin, eyes and nose.
Ashfalls of higher thickness ranging from 100-300 millimetres can lead to collapsing of building, the burial of low plants and severe damage to plantation and trees.
Livestock and other animals are killed every year due to this complete burial of land and soil horizon.