1. what is the principle of catastrophism? 2. how do geologists use the idea of superposition? 3. what is unconformity? 4. what is an isotope? 5. how does radioactive decay relate to radiometric dating?

1: an assertion that catastrophic natural processes have been primarily responsible for the deposition of the various layers in the geologic and all the rock formations. (Theory that the Earth has largely been shaped by sudden, violent events).
2. That each bed of layered sedimentary rocks is younger than the bed above it.
3. A fault in a rock sequence that indicts interruption of sedimentation.
4. Atoms with the same number of protons but different numbers of neutrons. (Different forms of a single element).
5. A technique used to determine the age of materials like rocks.
sorry the answers are so long, hope this helps!

1.Catastrophism was the theory that the Earth had largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope. This was in contrast to uniformitarianism (sometimes described as gradualism), in which slow incremental changes, such as erosion, created all the Earth's geological features.
2. Superposition: The most basic concept used in relative dating is the law of superposition. Simply stated, each bed in a sequence of sedimentary rocks (or layered volcanic rocks) is younger than the bed below it and older than the bed above it.
3. Anunconformity occurs when there is erosion of rock and then new sedimentary rock is deposited on top. It it called an unconformity because the ages of the rocks are discontinuous at the unconformity.
4.The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and eachisotope of a given element has a different mass number. 
5.Radiometric dating is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes. The decay rate is referring to radioactive decay, which is the process by which an unstable atomic nucleus loses energy by releasing radiation. ... There are different methods of radiometric dating.

please give brainliest XD

D. is the answer hope that you