estimated age in years
atom with same number of protons and electrons but different numbers of neutrons
radio active; wants to be stable
radio active decay
break down changing of an element
any preserved remains of animal or plants from the past.
cavity dent left behind
principle that states younger rocks lie over older.
ideal sequence of rock layers
principle that says that younger rocks lie above older rocks in undisturbed layers.
made of 1 or more Atoms with the same # of protons and the same # of electrons + neutrons
the longest segment of time
eon's are broken down into these
era's are broken down into these
the youngest and shortest period of time.