What is the percentage of water vapor in the gases released during a volcanic eruption?
Water vapor (H2O) is the most abundant gas released during a volcanic eruption, typically accounting for 80 to 90 percent of the total gas volume. It comes from water that was trapped in the minerals of subducting plates and then released as the magma rises and pressure decreases. ANSWER: (B) 80 to 90 percent
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This high percentage of water vapor is what drives the explosiveness of many volcanoes. As magma rises toward the surface, the dissolved water turns into steam. This steam expands rapidly, shattering the magma into ash and powering the eruption column. This process is similar to opening a shaken bottle of soda. Besides water vapor, the remaining 10-20% of gases include carbon dioxide and sulfur dioxide. The release of this water vapor over billions of years is one of the primary theories for how the Earth’s oceans were originally formed.