Radioactive Dating

Explain how we can use radioactive isotopes to identify the age of ancient samples.

An alternative form of an element; it has the same number of protons but a different number of neutrons. Isotopes can indicate lengths of time due to half-life. A half-life how long it takes for half of a radioactive material to break down and change into something else. For example, if you start with 100, the half-life is how long it takes until only 50 are left.

An example of a radioactive dating method could involve measuring the radioactive decay of a carbon-14 sample to determine how old something is. This could be, for example, how old a piece of wood is. Carbon-14 dating is used for organic materials like wood or bone; it won't really work for volcanic eruptions. Carbon dating is an example of a radioactive dating method. This uses the ratio of carbon-14 (radioactive) to carbon-12 (stable).

Outline the known migration of ancient Pacific peoples across the South Pacific, and explain how carbon dating has contributed to this knowledge.

The migration of ancient pacific peoples started in the Bismarck Islands with human activity being dated back to 1500 BCE, and then continued to Tonga and Samoa around 1000 BCE, and finally, Aotearoa 750 years ago. Carbon dating works with organic matter such as organisms, fabrics, wood, etc. However, it will not work with things such as volcanic matter. Carbon dating is different with South Pacific samples due to all the marine-based diets (fish, shellfish, etc). Carbon doesn't cycle as quickly or reliably in the ocean compared to terrestrial carbon due to differences in carbon storage and water movement. This means that carbon obtained from marine sources may not have a predictible ratio of carbon-14 at death and therefore human and other biological remains may be inaccurately dated.