their daughter products are used to determine the age of rocks and organic remains.Review Questions
- What four techniques are used to determine the absolute age of an object or event?
- A radioactive substance has a half-life of 5 million years. What is the age of a rock in
which 25% of the original radioactive atoms remain? - A scientist is studying a piece of cloth from an ancient burial site. She determines that
40% of the original carbon-14 atoms remain in the cloth. Based on the carbon decay
graph (Figure11.27), what is the approximate age of the cloth?
Figure 11.27: ( 21 )- Which radioactive isotope or isotopes would you use to date each of the following
objects? Explain each of your choices.
(a) A 4 billion year old piece of granite.
(b)A one million year old bed of volcanic ash that contains the footprints of hominids
(human ancestors).
(c) The fur of a woolly mammoth that was recently recovered frozen in a glacier.
(d)A fossilized trilobite recovered from a bed of sandstone that is about 500 million
years old. - The principle of uniformitarionism states that the present is the key to the past. In
other words, the processes that we see happening today probably worked in a similar