Manipulating groups of double-sided chips labeled with U and Pb isotopes reinforces the concept that an age determination depends on the Pb/U ratio, not the absolute number of atoms present. In this module, the students start by exploring the concepts of half-life and exponential decay and graphically solving the isotopic decay equation. The curriculum teaches the science behind uranium-lead dating using tables, graphs, and a geochronology kit. ![]() In the second part, we use a curriculum developed for and available on the EARTHTIME website (). Students also discuss geologic features relevant to the K-T boundary problem and get the chance to examine basalts, impact melts and meteorites. We cover all the steps from sampling an outcrop to determining a final age. Students use different techniques, such as magnetic separation, density separation using non-toxic heavy liquids, and mineral identification with a microscope. ![]() Activities are divided into three parts: In the first part, the instructors lead hands-on activities demonstrating how rock samples are processed to isolate minerals by their physical properties. The theme of our 2.5-hour module is the timing of the K-T boundary and a discussion of how geochronology can be used to evaluate the two main hypotheses for the cause of the concurrent extinction-the Chicxlub impact and the massive eruption of the Deccan Traps. The workshop focuses on uranium-lead (U-Pb) dating of zircons and its application to solving a geological problem. ![]() The authors taught an educational module developed as part of the EARTHTIME (outreach initiative to 215 high school students from a Massachusetts (USA) High School as part of an "out-of-school" field trip.
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