Final answer:
Scientists use multiple dating methods like dendrochronology and radiocarbon dating to cross-verify results and overcome the limitations of individual methods, thus obtaining a more accurate and complete understanding of a tree's age and related environmental events.
Step-by-step explanation:
Scientists might choose to use two different methods to date a tree felled by an advancing glacier to obtain more accurate and reliable data. One reason for using multiple methods is to cross-verify results; this is particularly important in instances where one method might have limitations. For example, dendrochronology, the study of tree rings, can provide specific dates and environmental conditions during the lifespan of a tree, but it is limited to the lifespan of the tree itself. By combining this with another method, like radiocarbon dating, scientists can also find the age of the tree and related carbon-containing materials. Radiocarbon dating is useful for dating materials up to around 50,000 years old, which provides a broader time frame. However, a tree cannot be dated to 3 billion years old using radiocarbon dating, as this exceeds the method's limitations and the known age of the Earth itself. Other absolute dating methods such as using other radioactive isotopes can date older samples. Cross-referencing the data from dendrochronology with radiocarbon dating or other absolute methods allows for a more complete understanding of the tree's age and the historical glacier advance.