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2 November, 21:48

While taking a hike in the forest, you find some fossils in layers of sedimentary rocks whose age you later find out is said to cover a span of 100-400 million years. You decide to send the fossils out for analysis to a company that dates rocks by radioactive decay, and, some weeks later, receive a report informing you that a volcanic ash bed associated with one of the fossils has a 1:1 ratio of 235U: 207Pb. Do these data support or refute the assumed age of the rocks in which the fossil was found? (Note: The half-life of 235U is about 700 million years, and its decay product is 207Pb.) Yes, because the ratio of 235U to 207Pb represents one half-life, and that would be approximately 350 million years old. No, because the ratio of 235U to 207Pb represents one half-life, and that would be about 700 million years old. No, because the rock layers are less than 704 million years old. Yes, because the rock layers are less than 704 million years old.