Yet, you’ve heard the news: Earth is 4.6 billion years old. That corn cob found in an ancient Native American fire pit is 1,000 years old. Geologic age dating—assigning an age to materials—is an entire discipline of its own.
In a way this field, called geochronology, is some of the purest detective work earth scientists do.
Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.
Carbon-14 has a half-life of 5,730 ± 40 years— during the succeeding 5,730 years.
There are two basic approaches: relative age dating, and absolute age dating.
Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.
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Unlike the other natural isotopes of carbon, carbon-14 is unstable. One of its neutrons turns into a proton and spits out an electron.
This method is useful for archaeologists working in areas where volcanic eruptions have left layers of ash above and below an archaeological deposit.
The volcanic layers can be dated, and the archaeological material will date to the period between those two volcanic eruptions.
Learn how variations in atomic structure form isotopes of an element and how the three natural isotopes of carbon differ from each other. Neutrons are electrically neutral particles that act as glue to hold atoms together. And that rare version of carbon has proven to be a crucial tool for unlocking the past.
Meet paleoclimatologist Scott Stine, who uses radiocarbon dating to study changes in climate. What we think of as normal carbon is called carbon-12: six protons plus six neutrons. Several times a year, scientist Scott Stine travels to the shores of Mono Lake, near Yosemite National Park. He's studying the long history of droughts in California, trying to determine how frequently they occur and how long they last.