Deception in Geology: Discovering the hidden truths about volcanoes' ages and their implications for humanity
In the heart of New Zealand's North Island lies Lake Taupo, a caldera volcano that last erupted around 1,800 years ago. Recent research has unveiled fascinating insights into the Taupo eruption and its impact on radiocarbon dating, a method used to determine the age of organic material.
The Taupo eruption, which occurred in the early part of the first millennium, has been found to have an age spread between 36CE and 538CE through radiocarbon dating. However, the forest that once thrived in the region was killed by the last part of the Taupo eruption series. The dilution of atmospheric carbon-14 by volcanic carbon made the radiocarbon dates for tree material from the Taupo eruption appear somewhere between 40 and 300 years too old.
This anomalous carbon dating pattern can be explained by the influence of groundwater beneath the lake and its surroundings. The region's groundwater system redistributed the carbon dioxide, ultimately incorporating it into the wood of dated trees. This unusual geography of carbon dioxide contamination from the Taupo volcano was discovered by researchers including Heather Handley.
The increase in carbon dioxide gas over several decades dramatically altered the ratios of different carbon isotopes in the tree wood. The ratio of carbon-13 to carbon-12 in the water of Lake Taupo and the Waikato River indicates that volcanic carbon dioxide is getting into the groundwater from an underlying magma body.
The unusual geographic pattern of older dates closer to the volcano can be seen not only in the Taupo eruption but also in other major eruptions, including at Rabaul in Papua New Guinea and Baitoushan on the North Korean border with China.
Over the past two decades, radiocarbon dating has been refined by combining it with dendrochronology, the study of tree rings. This combination has allowed researchers to observe precursory changes in carbon ratios, giving them a way to gain insight into the forecasting of future eruptions.
The precursory change in carbon ratios in the Taupo eruption is particularly interesting. The radiocarbon dates and isotope data that underpin the presently accepted wiggle-match age reached a plateau, meaning that for several decades before the eruption, the outer growth rings of trees had weird carbon ratios, forecasting the impending eruption.
This study provides a significant focus for future research at supervolcanoes around the globe. The researchers anticipate that this will provide a method of forecasting future large eruptions, offering a crucial tool for predicting and preparing for volcanic activity.
However, it is important to note that traditional methods of radiocarbon dating, such as wiggle-match dating, are not valid if carbon dioxide gas from the volcano is affecting a tree's version of the wiggle. This finding underscores the importance of considering the unique environmental conditions surrounding a volcano when interpreting radiocarbon dates.
In conclusion, the Taupo eruption has provided valuable insights into the complex interplay between volcanic activity, groundwater systems, and carbon dating. As researchers continue to explore these connections, they hope to develop more accurate methods for predicting and preparing for future volcanic events.
