What Causes A Volcanic Winter?

A massive volcanic explosion can cause a volcanic winter.

A volcanic winter is a dramatic drop in temperatures experienced globally, in the aftermath of a massive volcanic eruption as the ash particles and gases such as sulfur dioxide, injected into the stratosphere during the eruption and spread globally by winds, blot out the sun and prevent solar energy from reaching the earth’s surface. As a result, typical winter conditions are amplified while the winter season becomes longer. A volcanic winter is also characterized by the disruption of weather patterns around the world. Famine, droughts, floods, and the deaths of thousands of people are some of the direct effects of volcanic winters. Volcanic winters are extremely rare, as extremely violent volcanic eruptions cause them, and these occur roughly once in every 100 years. Some notable volcanic winters experienced during the 20th century include Mount Pinatubo eruption, the 19th century Krakatoa Eruption, the 17th century Mount Tambora eruption, and the 16th century Laki eruption.

Mount Pinatubo

The 1991 eruption of Mount Pinatubo is the most recent cause of volcanic winter. The eruption, which measured a scale of six in the volcanic explosivity index, took place on June 15th and resulted in the ejection of about 2.4 cubic miles of material. During the eruption, an estimated 17 million tons of sulfur dioxide was released into the atmosphere, the largest volume recorded from an eruption in the 20th century. The sulfur dioxide formed a blanket in the atmosphere, obscuring sunlight by 10% and causing global temperatures to fall by 0.4 degrees Celsius. The drop in temperature was most profound in the northern hemisphere, where temperatures dropped by about 0.6 degrees Celsius. The blanket of debris covered many parts of the planet for at least three years, plunging the world in its most recent volcanic winter.

Krakatoa Caldera

The Krakatoa Eruption was a violent volcanic eruption of the Krakatoa Caldera situated in Indonesia that took place between August 26th and 27th, 1883. The eruption was among the most violent in history and resulted in the destruction of the Krakatoa Island on which the caldera was located. The powerful eruption measuring a scale of six in the volcanic explosivity index injected an estimated 20 megatons of sulfur dioxide into the atmosphere. The thick sulfur dioxide cloud shrouded the planet for several years after the eruption and blocked sunlight from reaching the earth. Global temperatures plummeted in the aftermath of the Krakatoa Eruption, falling by as much as 1.2 degrees Celsius in the northern hemisphere. Global weather patterns were disrupted by the uncharacteristic low temperatures, with the western United States experiencing a sudden spike in precipitation. Los Angeles recorded 38.18 inches of rainfall between 1883 and 1884, while San Diego received 25.9 inches of rainfall during the same period. Global temperatures finally went back to normalcy in 1888, five years after the eruption.

Mount Tambora

Mount Tambora erupted in 1815 in one of the most violent volcanic eruptions ever witnessed reaching a scale of 7 in the volcanic explosivity index. The mountain situated in Indonesia erupted in April 1815 and sent the world into a volcanic winter. The explosive eruption sent an estimated 24 cubic miles of rock into the atmosphere. The emission column from the eruption was 0.141 million feet high and sent vast amounts of sulfur dioxide and ash particles into the stratosphere, from where they spread to cover the globe. The thick blanket of sulfur dioxide and volcanic ash particles emitted during the eruption reflected solar radiation and prevented sunlight from penetrating to the earth’s surface. Resultantly, temperatures in the Northern Hemisphere dropped by 0.53 degrees Celsius in 1816 and led to the deaths of about 90,000 people. The northern hemisphere went through what was known as “The Year without a summer,” in 1816, the coldest year that part of the world had experienced in centuries. The sudden drop in global temperatures devastated agricultural production in Europe, North American, and Asia, culminating in the 19th century’s worst famine.

Laki Eruption

The Laki eruption was a series of volcanic eruptions that took place between 1783 and 1784 in volcanic fissures found in Iceland. The eruption measuring a scale of four on the volcanic explosivity index immersed the northern hemisphere into a volcanic winter. An estimated 120 million tons of sulfur dioxide was released into the atmosphere (six-times the amount released in the 1991 Mount Pinatubo eruption), and spread by winds to cover the northern hemisphere. The shroud blotted out sunlight from warming the earth, causing global temperatures to plummet. Europe experienced its worst winter of the 18th century between 1783 and 1784, with sources stating that continuous frost was witnessed for 28 days in some areas. The freezing temperatures of the ensuing volcanic winter caused the deaths of an estimated 8,000 people in Great Britain alone. Droughts linked to the eruption and resultant temperature drop were experienced in areas as far-flung as India and North Africa. The effects of the low global temperatures were witnessed in North America, which experienced its longest winter in history in 1784. The Mississippi River is said to have frozen in New Orleans.

Toba Supervolcano

One of the most destructive volcanic winters was witnessed in the aftermath of the Toba Eruption, believed to have occurred 75,000 years ago. The eruption took place where Indonesia’s Lake Toba is currently located. Measuring eight in the volcanic explosivity index, the eruption was more explosive than any other witnessed in human history and the most violent in a period of 25 million years. Materials released during the Toba eruption is estimated to be 670 cubic miles in volume, 100 times more than that released in the 1815 Mount Tambora eruption. The Toba Eruption sent 6 billion tons of sulfur dioxide into the stratosphere, which plunged the world into its longest volcanic winter in millions of years, estimated to last about ten years. Global temperatures fell by as much as 5 degrees Celsius, low enough to destroy entire ecosystems. Scholars believe that the effects of the eruption decimated the human population to reach only tens of thousands and causing a genetic bottleneck in the surviving population.

More in Environment