Volcanoes
By: Jack and Emma
Process of Volcanic Formation
The eruptions from volcanoes are important in forming sections of the
Earth’s crust
The mantle under the crust is molten so when it heats up and melts
sections of the crust
This melted rock rises to the surface and makes volcanic eruptions
Gases Produced by Volcanoes:
CO2: Carbon dioxide
N2: Nitrogen Gas
HF: Hydrogen fluoride Gas*
HCl: Hydrogen chloride Gas*
H2O: Water Vapor
H2S: Hydrogen Sulfide Gas
*The HF and HCl will become acid if they come in contact with water vapor
First chemical reaction:
The hydrogen sulfide gas coming from the volcano is oxidized by the air:
2H2S (g) + 3O2 (g) ------> 2SO2 (g) + 2H20 (g)
This produces sulfur dioxide and water.
SO2 and H2S
Hydrogen sulfide from the volcano reduces some of the sulfur dioxide to plain
elemental sulfur and water.
2H2S (g) + SO2 (g) -------> 3S (s) + 2H2O (g)
The remaining sulfur dioxide goes on to create acid rain when it comes in contact
with water vapor
Climate effects
❏ Volcanoes are responsible for about ⅔ of the sulfur in the air
❏ Volcanic eruptions released SO2, which converts into SO3, which is then
converted to sulfuric acid aerosols
❏ These aerosols destroy the ozone layer and affect the climate
❏ These aerosols create clouds that last for more than a year, and absorb solar
radiation. This can lead to a drop in temperature at Earth’s surface.
❏ The cooling effect is local, not global, and varies depending on the site and
frequency of the volcanic eruptions