After volcanic eruptions, the impact can be felt thousands of miles away from the eruptive foci or center. The weather condition stretching the entire perimeter of such distances and beyond can be profoundly affected too. This relatively long-range impact comes from the materials which are given off or emitted during the eruption. Prominent amongst these substances is the volcanic ash.

Volcanic Ash

The volcanic ash refers to the tiny, particle matter which loads the surrounding air especially during and after an explosive eruption. The ash consists of both gaseous and the particulate materials. Gases include the oxides of silicon, aluminum, iron, magnesium, calcium, sodium and sulfur. The particles include some trace metals in addition to the salts of light and heavy metals. The ash can cross topographic barriers at heights over hundreds of meters where it forms plumes. These plumes become dispersed by the prevailing winds over vast areas and forming ash layers. What are the effects the volcanic ash has on weather and the environment?

However, the particulate and gaseous nature of the volcanic ash, impacts and affects the weather condition.

Sun shining through clouds

UV Rays

Increased radiation

The gaseous component of the ash fallout from explosive eruptions tends to laden the stratosphere with aerosols which will serve to quicken loss of the ozone. The depleted ozone permits higher UV-B flux to reach the ground in high-mid-latitude regions. There is a relative increase in atmospheric temperature with the effect lasting for a few years after the eruption.

Dry fog and acid aerosol

Fine ash and particles from eruption become suspended in the surrounding air at high concentrations. These particles lead to the development of a Laki-type dry fog in the lower atmosphere. The sulfur dioxide component of the volcanic ash reacts with moisture present in the air and may result in the formation of a sulphuric acid aerosol. It is the same case with other minerals in the ash. The dry fog and acid aerosol effect can attain a complete coverage within a hemisphere.

Atmospheric opacity

After the ash clouds formed from the fine ash deposits in the atmosphere, there could be atmospheric opacity and longevity which has much influence on the incoming solar radiation.

Fall in surface temperature in the long-term

The fine volcanic ash from an eruption can cover the global atmosphere just within few weeks to few months. The suspension remains for many years as it affects atmospheric circulation. It leads to a fall in surface temperature in many regions. In like manner, there are fluctuations in the weather condition as seen in cool summers and colder-than-normal winters.

After an eruption, massive clouds of ashes are producing in the troposphere in forms known as plumes. The clouds drift upward into the upper atmosphere or stratosphere where they remain for years. They interfere with the normal weather condition of a specific region and even beyond which, most of the time, is detrimental to the survival of life on our planet.

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