radioactive dating		subdivisions of time in earth's history
Quaternary		sediments that show one year
index fossil		weathered rock particles
fossil		law that states younger rocks are found on top of older rocks
era		breakdown of a radioactive element
Superposition		trilobites important fossils in this era
decay		the period when mammals first appear
Cretaceous		fossils of organisms that lived during a short period of time
Cenezoic		method of determining the age of a fossil
Triassic		period when the ice age begins and ends
Tertiary		era divided into two great periods
Jurassic		the period known as the age of the dinosaurs
evolution		time periods in Earth's history broken into four segments
period		era known as the dawn of life
adaptation		era known as the period of many changes
Paleozoic		mutation that occurs that helps a species to survive
varve		change over time
Precambrian		the first period in the era known as the age of mammals
sediment		wide spread flooding and mass extinctions occur
Mesozoic		evidence of once living things