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EnglandGeologyQuick questions
Time, past life and past climates
Quick questions on Radiometric dating and half-life: decay, parent-daughter ratios and absolute ages - Eduqas A-Level Geology
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are parent-to-daughter ratios?Show answer
You cannot measure directly, but in a closed system every daughter atom came from a decayed parent, so:
What is building the absolute time scale?Show answer
The geological time scale was first built by relative dating (the order of strata and their fossils), then calibrated in years by dating igneous rocks (lavas, ashes and intrusions) interbedded with or cutting the fossil-bearing strata. Combining the two gives absolute ages for the boundaries of the eras, periods and epochs.
What is q1?Show answer
After three half-lives, what fraction of the original parent isotope remains? [1 mark]
What is q2?Show answer
A mineral has a parent-to-daughter ratio of 1:1 and a half-life of 700 million years. Calculate its age. [2 marks]
What is q3?Show answer
State one assumption that must hold for a radiometric date to be reliable. [1 mark]
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