What is meant by the paleozoic era?
The eras and periods and ages are man made divisions of geological time. However, they were made after thoughtful study of the earths long history. The divisions, their names and their durations, are based upon events and evidence recorded in the rocks by the earth herself. Our wonderful old world keeps a detailed diary of her doings. Its pages are layers of her rocky crust, her inks are running rivers and shallow seas, her pens are scratchy gravels and the frozen fingers of icy glaciers. The durable pages are poured from seething volcanoes and hardened from the silty deposits that sift to the floors of quiet seas. Here and there fossil specimens of plants and animals are pressed and preserved within and between the rocky layers. The code of the diary is deciphered by geologists, paleontologists and anthropologists. A pile of gravel is the signature of a long gone glacier, a layer of lava is the footprint of an ancient volcano. The age of a fossil is dated by radioactivity. Earth scien
