History of Life1 Crossword
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
                            
 
 
Down: 1) time line used to represent Earth's history2) a division of geologic time into which eras are sub-divided3) used to identify fossils of same age in different places4) a species who has died out and has no living members5) a scientist who studies fossils9) a major division of geologic time Across: 6) uses carbon-14 or Potassium-40 to find the absolute age7) the length of time required for half of the radioactive atoms in a sample to decay8) theory that explains slow movement of solid continental plates10) used to determine whether a fossil is older or younger than another
 

 

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