Volcanism

Members of the scientific community largely concur that the Earth is undergoing a change in climate and that global warming is occurring at an increasing rate. This acceleration in the late 20th century is mainly a result of carbon dioxide (CO2) emissions generated by human activity. Carbon dioxide acts like a glass barrier over the Earth, preventing heat from leaking into the environment and thus creating a greenhouse effect. In its latest report, the United Nations Intergovernmental Panel on Climate Change (IPCC) shows that greenhouse gases are an integral factor in global warming, more so than natural causes such as solar activity and volcanoes.

Influence on Weather

Evidence suggests that volcanism, which refers to phenomena such as the outward flow of pyroclastic materials and the upsurge of gas and steam connected to the movement of molten rock, can influence short-term weather and may have an effect on long-term climate change. Similar to human activity, volcanism leads to both global warming and cooling. The effect of volcanism on climate depends on the interaction between the sun’s heat and the volcanic debris. Scientists believe that ongoing volcanic eruptions have maintained the Earth’s temperate climate for millions of years and are responsible for the gases in today’s atmosphere. Volcanoes that erupt explosively can send particles many miles away from the volcano and high into the stratosphere where the Earth’s ozone is concentrated. In addition, the debris can be dispersed for months or even years.

Volcanic dust blown into the atmosphere reduces the sunlight that reaches the Earth’s surface and cause temporary cooling; the degree of cooling is dependent on the volume of dust and the duration is dependent on the size of the dust particles. Additionally, the strength of gases can vary greatly among volcanoes. Water vapor is typically the most abundant volcanic gas, followed by CO2 and sulfur dioxide. Other principal volcanic gasses include hydrogen sulfide, hydrogen chloride, and fluorine.

Volcanoes that discharge great quantities of sulfur compounds affect the climate more significantly than those that release only dust. In fact, the greatest volcanic effect on the Earth’s shortterm weather patterns is caused by sulfur dioxide gas. When sulfur dioxide and other volcanic gases mix with oxygen and water vapor in the presence of sunlight, the result is vog, or volcanic smog. Vog poses a health hazard by exacerbating respiratory conditions. Sulfur dioxide in the atmosphere is often transformed into sulfur trioxide which, when combined with water, forms sulfuric acid that reflect the sun’s heat and triggers cooling of the Earth’s surface. Acid rain contains greater than normal amounts of sulfuric and nitric acids, and when deposited on the Earth’s surface, becomes a critical environmental problem that can affect lakes, streams, forests, and the inhabitants of these ecosystems.

Volcanoes also discharge water and CO2 in large quantities in the form of atmospheric gases; in the atmosphere, these gases can absorb and retain heat radiation emanating from the ground. Estimates suggest that water makes up to 99 percent of gas in volcanic expulsions. This short-term warming of the air causes water to become rain within a matter of hours or days, and it causes the CO2 to dissolve in the ocean or to be absorbed by plants. The majority of the heat energy connected to global warming exists in the ocean. If the oceanic depth at which heat is stored is decreased, then global temperature increases are expected to be greater than predicted.

Volcanic eruptions combined with humanmade chlorofluorocarbons (CFCs) also can contribute to ozone depletion. CFCs were developed in the early 1930s; because they were nontoxic, nonflammable, and met a number of safety criteria, CFCs were used in industrial, commercial, and household applications such as refrigeration units and aerosol propellants. In February 1992, however, following evidence that CFCs contributed to depletion of the ozone layer, the U.S. government announced plans to phase out the production of CFCs by December 1995. Members of the Montreal Protocol in 1992 followed suit and agreed to an accelerated phaseout by the end of 1995.

The ozone layer, which rests in the stratosphere and begins at 7.5 mi. (12 km) above the Earth, is a shield that protects living beings from ultraviolet-B (UV-B), the sun’s most harmful UV radiation. In high doses, UV-B can lead to cellular damage in plants and animals. Scientists believe that global warming will lead to a weakened ozone layer. As the Earth’s surface temperature rises, the stratosphere will become colder, slowing the natural repair process of the ozone layer. Decreased ozone in the stratosphere results in lower temperatures. Unlike ozone depletion created by human-made CFCs, which will take decades to repair, scientific theories indicate that as volcanic activity diminishes, the damaged caused by the volcanoes ias gradually repaired as volcanic activity diminishes.

Finally, hydrogen fluoride gas can concentrate in rain or on ash particles, contaminating grass, streams, and lakes with excess fluorine. Excess fluorine in grass and water supplies can poison the animals that eat and drink at contaminated sites and eventually causes fluorosis, which destroys bones. In fact, excessive fluorine can lead to a major cause of injury and death in livestock during ash eruptions.

Today, millions of people live near active or potentially active volcanoes. The area around the Pacific Ocean in the Ring of Fire, known as the Cascade Volcanic Arc, accounts for about 75 percent of the world’s volcanoes. In 1991, Mount Pinatubo in the Philippines emitted about 22 million tons of sulfur dioxide, which combined with water to form sulfuric acid, decreasing global temperatures for approximately a year. Additionally, in May 1980, Mount St. Helens, located in the state of Washington in the Cascade Volcanic Arc, released approximately 520 tons (472 million metric tons) of ash into the atmosphere. This volume of ash can have a short-term cooling effect hundreds or even thousands of miles away. Very cold temperatures leading to crop failures and famine in North America and Europe, followed the eruption of Mt. Tambora, Indonesia, in 1815.

One of Iceland’s largest volcanoes, the Eyjafjallajökull, showed signs of activity in March 2010 after almost 200 years of dormancy. The eruption on April 16 disrupted air traffic in northern Europe and beyond as volcanic ash spread across northern and central Europe. Although it was marked as the worst travel disruption during peacetime, ash from the Eyjafjallajökull volcano reached 55,000 ft. (16,764 m), which was less than the almost 78,000 ft. (23,774 m) reached by ash from Mt. Pinatubo. Because volcanic ash generally leaves the environment within a few years or even months, Eyjafjallajkull was expected to have a short-term impact on climate. Scientists believe that the temporary cooling of the planet by a volcanic eruption does not offset CO2 from the burning of fossil fuels.