Volcanic eruptions has the release of volcanic gas and it can provoke climate changes that have a negative effect on the environment.
The volcanic gases are harmful for the environment, there is multiple substances in the volcanic gas, since water molecules (harmless), carbon dioxide, and surfur dioxide. When thr volcanic gases are realesed in the atmosphere it causes climate changes, such as increase the temperature, cause changes in the oceanic cycle, increase the levels of carbon dioxide, and so on. All that actions provoke changes and negative effects in the general environment, being more present in the closer vicinity of the eruption.