| Unit 4: EarthComm | ||||
| Reflecting on the Activity and the Challenge | ||||
| You worked with a material that resembled volcanic products. When you opened the can of soda, you lowered the pressure inside the can. | This allowed carbon dioxide (the dissolved gas) to come out of solution. Dissolved gases emerge from the Earth’s interior in much the same way. | |||
Digging Deeper VOLCANOES AND THE ATMOSPHEREVolcanic Gases Gases that escape in greatest abundance from volcanoes are water vapor, carbon dioxide, hydrogen chloride, and nitrogen. These and certain other gases have played an important role in the Earth system throughout the long span of geologic time, and they continue to do so at the present time. The atmosphere of the Earth early in its history contained abundant carbon dioxide but no oxygen. After primitive algae made their appearance partway through Earth history, the carbon dioxide emitted by volcanoes was gradually converted to oxygen by photosynthesis. Carbon dioxide is more dense than air and sometimes accumulates in a low spot near a volcanic eruption. High concentrations of carbon dioxide are hazardous, because they cause people and animals to suffocate. Water vapor is an essential component of the Earth system. It is especially important for human communities, because it sustains life. When you think of the water cycle, do you think of volcanoes? Volcanoes release abundant water vapor. Most of the Earth’s surface water seems to have been released from the Earth’s interior by volcanoes throughout the Earth’s history. Some volcanoes emit sulfur dioxide gas in great abundance. Sulfur dioxide combines with water vapor and oxygen to form sulfuric acid. The sulfuric acid is washed out of the atmosphere by rain, over large areas downwind of the eruption. Rain that contains sulfuric acid, and certain other acids as well, is called acid rain. It is produced not only by volcanoes but also by power plants that burn coal containing sulfur. Acid rain damages plants both on land and in lakes. Volcanoes and Climate Change Volcanoes illustrate the complexity of Earth’s systems, because the gases from volcanic eruptions can contribute both to global cooling and to global warming. |
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