Cyanobacteria built ancient coral reefs known as

stromatolite

Explanation:

if you want/need to know the details of the layering, it's on the internet (e.g. wikepedia) :)

the "dirty dozen" chemicals banned in an international treaty are formally known as persistent organic pollutants, or pops. the united nations environment program provided this background on what they are and what they can do to humans and wildlife.

i hope this