What can rock formations and fossils in rock layers tell us about the Earth's history?

amylois.mattingly

aarammos

kim.scalf

jhardway

hamore

sjacobs

jnealteach

ann.bone

majid.cortez

tuanuas

sam.shipley

jennynd2001

sholeh.peykamian

jcorippo

timothy.metzger

rbauer

rbauer

rebecca.conn4

byron.balagon