Earth's interior has cooled down to modern levels, so that volcanic activity is moderate. However, gigantic hot-spot type eruptions still occur every hundred million years or so. Plate tectonics continues to push land masses across Earth's surface. The climate of the Paleozoic era started out as moderate, even though it shifted between being stable and being unstable. Around the middle of the Paleozoic era the climate began stabilizing and was able to support land dwelling life. A few types of species that died out were Trilobites, many amphibians and 95% of life i the ocean disappeared. The event that caused this mass extinction was that land started to evolve. Giant ferns and cone-bearing plants and trees formed in the forests, these being called 'coal-forests'. The remains of the coal forest plants deposited sediment and changed into coal after millions of years, at the end of the Paleozoic era, the species of Trilobites, mollusks, and Brachiopods. |