Which gases are released into the atmosphere when volcanoes erupt?

The volcanoes are formed adjacent to a convergent plate boundary, in which the denser plate subducts under a less denser plate. These subducting plates undergoes partial melting at greater depths and the magma is forced to rise up towards the over-riding plate, resulting in the formation of the volcano and chains of volcanoes.

These volcanoes when undergoes eruptions, releases various types of gases. They are such as the Carbon dioxide (CO₂), Water vapor (H₂O), Sulfur dioxide (SO₂), Hydrogen sulfide (H₂S) and Carbon monoxide (CO).

These gases are harmful to the atmosphere as it creases the green house effect thereby increasing the earth's global temperature.

the correct is answer is a 9-sided polygon!