Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence.
Correlation can involve matching an undated rock with a dated one at another location.
Students begin by observing a photograph and a diagram of rock layers near Whanganui, watch an animation about how the layers were formed, then use an interactive labelling diagram to work out the order in which the rocks were created.
The activity offers literacy opportunities as well as practice using the science capability 'Interpret representations'.
An atom of potassium (K), for example, has 19 protons in its nucleus so the atomic number for potassium is 19.
Although all atoms of a given element contain the same number of protons, they do not contain the same number of neutrons.