How do we determine when ancient volcanic eruptions occurred?
Volcanoes and Earthquakes
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The most common method used to date ancient volcanic eruptions is carbon dating. Carbon dating relies on the rate of radioactive decay of carbon–14. It is used to date eruptions that took place more than two hundred years ago. Charcoal from trees burned during a volcanic eruption is almost pure carbon and is ideal for tracing the tiny amounts of carbon–14.