Stratovolcano - Climatic Effects

Climatic Effects

As per the above examples, while the Unzen eruptions have caused deaths and considerable local damage in the historic past, the impact of the June 1991 eruption of Mount Pinatubo was global. Slightly cooler-than-usual temperatures were recorded worldwide and brilliant sunsets and sunrises were attributed to the particulates this eruption lofted high into the stratosphere. The aerosol that formed from the sulfur dioxide (SO₂) and other gasses dispersed around the world. The SO₂ mass in this cloud—about 22 million tons—combined with water (both of volcanic and stratospheric origin) formed droplets of sulfuric acid, blocking a portion of the sunlight from reaching the troposphere and ground. The cooling in some regions is thought to have been as much as 0.5 °C. An eruption the size of Mount Pinatubo tends to affect the weather for a few years; the material injected into the stratosphere gradually drops into the troposphere where it is washed away by rain and cloud precipitation.

A similar, but extraordinarily more powerful phenomenon occurred in the cataclysmic April 1815 eruption of Mount Tambora on Sumbawa Island in Indonesia. The Mt. Tambora eruption is recognized as the most powerful eruption in recorded history. Its volcanic cloud lowered global temperatures by as much as 3.5 °C. In the year following the eruption, most of the northern hemisphere experienced sharply cooler temperatures during the summer months. In parts of Europe and in North America, 1816 was known as "The Year Without a Summer," which caused a brief but bitter famine.