A Little Background on Bedrock or A Brief Story of Maine’s Geology
The Earth is so old (4.6 billion years old!) that its story has been divided into many chapters (Eons) with subchapters (Periods) and sub-sub chapters ( Epochs) as shown on the Geologic Time Scale (GTS) below.
You might well ask “How did these divisions come about?” Good question!
Different spans of time on the GTS are usually marked by corresponding changes in the composition of rock layers. These changes indicate major events, such as mass extinctions. For example, around 65 million years ago, many groups of living things, including dinosaurs became extinct. This showed up as an absence of fossils of those life forms in the rock layers. This extinction event marked the end of the Cretaceous Period and the beginning of the Paleocene Period which you see named in the Geologic Time Scale below:
