fossils occur in strata in a definite determinable order
Eons: Phanerozoic: last 543 million years
Eras:Cenozoic-recent life (mammals/humans)
Mesozoic- age of middle life (dinos/1st small mammals)
Paleozoic: Ancient life (fish, trilobites, clams, coral, ferns)
Precambrian: from birth of earth up to before complex life forms developed Algae, bacteria, some fossils without shells like jellyfish
-In general silicate minerals are often more resistant to weathering and erosion than other classesof minerals.