BETA DECAY Radioactive decay with emission of a beta particle.
BETA PARTICLE An electron emitted by a nucleus.
BRACKETED INTRUSIVE Igneous rock extending into sedimentary rocks that are datable by their fossils.
CLOSED SYSTEM A system in which the parent material radioactively decays into its daughter products and nothing is added or removed.
COMMON (strontium, lead, etc.) The ordinary element present in nature at any one time as distinguished from that produced by radioactive decay.
CONCORDIA ANALYSIS A mathematical technique to determine graphically the age of a material containing radiogenic lead by comparing its uranium-to-lead ratio with the similar ratio in a closed uranium-lead system.
CONTACT METAMORPHISM A metamorphism genetically related to the intrusion of molten masses of rock and taking place at or near the contact.
COSMIC RAYS High-energy particles moving in our galaxy.
CRYSTAL A periodic or regularly repeating arrangement of atoms, formed from a single element or compound.
DAUGHTER A nuclide formed from the radioactive decay of another nuclide.