A Year without Summer
Volcanic eruptions produce ash, but, even more important, they produce vast aounts of aerosols in the form of sulfuric acid droplets, which stay suspended longer than ash and produce long-lasting effects on climate. Eruptions can sometimes blow material into the stratosphere, where it can be carried over great areas.
The eruption of Tambora in 1815 blew out 30 cubic km (7 cubic miles) of ash and dust, which caused spectacular sunsets worldwide and inspired Turner's finest paintings. The darker side of the eruption was that the dust and ash blocked off enough sunlight to cause "The Year Without a Summer" in 1816.
Crops failed all over the Northern Hemisphere, resulting in widespread hunger, and even starvation in some areas. The summer was so gloomy in Europe that it depressed Mary Shelley enough to write the famous novel Frankenstein.
Nearly 25% of the sulfur produced today is recovered from petroleum refining operations and as a byproduct of extracting other materials from sulfur containing ores. The majority of the sulfur produced today is obtained from underground deposits, usually found in conjunction with salt deposits, with a process known as the Frasch process.
Most of the sulfur that is produced is used in the manufacture of sulfuric acid (H2SO4). Large amounts of sulfuric acid, nearly 40 million tons, are used each year to make fertilizers, lead-acid batteries, and in many industrial processes. Smaller amounts of sulfur are used to vulcanize natural rubbers, as an insecticide (the Greek poet Homer mentioned "pest-averting sulphur" nearly 2,800 years ago!), in the manufacture of gunpowder and as a dying agent.