Earlier quoted context omitted.
The follow up question is, how come the different elements aren't uniformly mixed within the earth. Or perhaps formed into stratified layers with the densest at the centre? E.g. Why are there 'deposits' of gold relatively close to the surface? Something to do with interaction of the physical and chemical properties of the elements with local variations in conditions?
Yes you're right. Geologic and biologic processes unevenly distribute the elements
Those who would like to know more could do worse than pick up Greenwood's & Earnshaw's book (this one: https://www.amazon.com/-/dp/0750633654) from the nearest university library, it has a chapter on nucleogenesis and cosmic and geologic abundances.