Why cant scientists always divide a period into epochs?

Scientists cannot always divide a period into epochs due to the complex and sometimes ambiguous nature of geological and evolutionary processes. The boundaries between epochs often lack clear markers in the fossil record or geological strata, making it difficult to establish definitive time frames. Additionally, the dynamic and overlapping nature of environmental changes can blur the lines between distinct epochs, leading to varied interpretations among researchers. This complexity reflects the continuous and gradual nature of changes in Earth's history rather than abrupt transitions.