Unit 1 Vocabulary Review Crossword

Determines the exact age of an object
fossil that forms when a mold is filled with sediment and hardens into the shape of an organism.
a fossilized piece of evidence of an organism activity like a footprint.
the time needed for half of a sample of radioactive substance to undergo radioactive decay.
a common fossil found in many areas from a specific time; used to help identify the age of other formations.
states that younger rock is found above older rocks when comparing undisturbed sedimentary rock layers.
very large division of geologic time; usually referred to as the longest division of time.
fossil that forms when organic material is pressed between layers of rock.
a subdivision of the eras in geologic time.
determination of the age of a rock based on the surrounding elements.
method of determining the age based on measuring radioactive elements; radiometric.
subdivision of and eon
subdivision of an era.
subdivision of a period; shortest division of geologic time.
occurs when a species dies out and no longer lives on the planet.
fossil that forms when minerals solidify into rock around shape of the original organism leaving a cavity behind.
fossil that forms when organic material is trapped in ice rock amber or tar.