From rocks being added together over time
Answer:
Radioactive isotopes are unstable and will decay. ... The isotopes will decay into a stable isotope over time. Scientists can tell how old the rock was from looking at the radioactive isotope's half-life, which tells them how long it would take for there to be half the radioactive isotope and half the stable isotope.
Answer:
Look at several different sources in order to understand topics comprehensively instead of basing your reactions only on one source. Using a variety of sources can diminish the effects of bias—the preference of one view over another.
Answer:
A breakdown in trading alliances change or loss of local culture a decrease in avilable jobs
