An erupting volcano emits gases and dust particles that can cause profound changes in weather and climate throughout the world. Volcanism also affects the environment by producing acid rain and making ocean water warmer.
The sulfur dioxide that large volcanic explosions hurl into the stratosphere mixes with water to create sulfuric acid. If the acid droplets are large enough, they prevent heat from escaping Earth's atmosphere. That results in higher temperatures, an element of the greenhouse effect.
The carbon dioxide released by volcanic activity is a greenhouse gas. Greenhouse gases are responsible for extreme weather and temperature increases around the world. Among the consequences are health problems, crop failures and the loss of habitat for animals and plants.
Eruptions might warm the water on the surface of the Pacific Ocean, triggering the El Niño effect, a weather pattern that brings about torrential rain or heavy snow in some places and drought elsewhere. Acid rain, which contaminates water sources, is another environmental effect of volcanism.
Eruptions can impair air quality by creating a volcanic fog called "vog," which consists of sulfuric-acid droplets distributed by trade winds. Volcanic ash and aerosol particles floating in the atmosphere can also be responsible for a more pleasant phenomenon: colorful sunsets and sunrises.