Cataclysmic eruptions
Eruptions are obviously very bad for animals that live close to the mountain. The Washington Department of Game estimated "11,000 hares, 6,000 deer, 5,200 elk, 1,400 coyotes, 300 bobcats, 200 black bears, and 15 mountain lions died from the pyroclastic flows of the 1980 eruption." These numbers are stunning and speak for themselves. Animals have protective instincts, but this shows they are no match for fast-developing disasters. The same result occurred in the Philippines in 1991 when Mount Pinatubo erupted. More than 800 people were killed and the disaster was just as horrific to nearby animals.
Volcanic gas
Volcanic gas emitted during eruptions and even in quiet times can kill animals as well. The Mount Pinatubo eruption emitted sulfur dioxide gas into the stratosphere. Think Quest declares even when volcanoes are not erupting they can emit dangerous gases that can kill humans and animals that venture too close. Volcanic gas can also harm the food source of nearby animals. Hazardous gases emitted from the volcanoes can land on animal forage.
Change the climate
Even small fluctuations in the climate can have good and dangerous effects on animals. The Mount Pinatubo eruption caused a slight cooling of the earth's temperature due to dust being blown into the atmosphere. Dust blown into the upper atmosphere can block sunlight, according to Exploring the Environment.com. The 1815 Tambora eruption in Indonesia created cold temperatures and resulted in famine and crop failures. In extreme instances eruptions can cause residual undesirable outcomes to animals like food shortage. This result can also harm animals that are not even near the volcano.
Good effects
Volcanoes have an effect on animals that are sometimes positive. They wipe the ecology slate clean and destroy invasive species. The BBC declares that lava and ash can actually improve the soil around volcanoes. These two outcome leads to a vibrant return of native plant life, which eventually bring back animals as well. Large animals returned to Mount St. Helens only a year after the eruption.