Earth History & Fossils Crossword
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
                                   
 
 
Down: 2) A relative dating principle that states fossil organisms succeed one another in a definite, irreversible, determinable order4) A relative dating principle stating that layers of sediment are deposited evenly with each new layer laid down almost horizontally over the older sediment5) The time scale that subdivides Earth's 4.5 billion year old history into time units of different sizes, from eons to epochs8) The time of hidden life which began about 4.5 billion years ago when Earth formed, lasting until the beginning of the Paleozoic era and making up 85% of Earth's history9) The rapid extinction of numerous species; the rate of extinction is much greater than the background rate of species extinction10) A relative dating principle stating that where an igneous intrusion or fault cuts through other rocks, the intrusion or fault is younger than the rock it cuts11) the ordering of rocks in sequence by their comparative ages12) The time of "recent life" from 65 million years ago to the present Across: 1) A break or gap in the geologic record, caused by an interruption in the sequence of deposition or by erosion of preexisting rock.3) The time of "ancient life" which spanned from 542 million years ago to 245 million years ago6) A relative dating principle stating that in an undeformed sequence of sedimentary rocks, each bed or layer is older than the one above and younger than the one below.7) The time of "middle life" from 245 million years ago to about 65 million years ago13) The present is the key to the past14) A method for calculating the age of geologic materials based on the nuclear decay of naturally occurring radioactive isotopes15) A relative dating principle stating that any inclusion (a piece of one rock type contained within another) is older than the rock containing it
 

 

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