ch17d

**Chapter 17 Section D: Volcanoes ** []

- Immediately below the crust the earth is nearly molten - Any slight increase in heat such as that generated by plate movements melts the rock - The molten rock, known as magma, rises to the surface and generates volcanic eruptions - An active volcano emits gases, liquids, and solids - Gases: N2, CO2, HCl, HF, H2S, water vapor - Volcanoes are the source of 2/3 of the sulfur in our air - At high temperatures, the hydrogen sulfide gas given off is oxidized by air: - 2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(g) - Some of the sulfur dioxide produced is reduced by hydrogen sulfide from the volcano: - 2H2S(g) + SO2(g) → 3S(s) + 2H2O(g) - Some SO2 reacts with water to form acid rain - The remaining SO2 is carried into the stratosphere by the eruption where it is oxidized to SO3 - SO3 is eventually converted to sulfuric acid aerosols - These aerosols damage the ozone and absorb solar radiation, locally cooling the earth

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