The first four-legged animals to reach land were classified as tetrapods the term tetra means four. So tetrapods refer to animals with four limbs.
Pangaea also known as Pangea was a supercontinent during the late Paleozoic and Mesozoic times. It incorporated almost the earth's land masses. The formation and breaking up of continents is a geological cyclic process. And there seemed to have many supercontinents that existed before Pangaea. And according to the sources it assembled from the earlier continental parts approximately 335 million of years ago.
Glaciation is a geographical term that explains the formation, movement, and recession of the glaciers and this process was much more evident in times when the world was covered with ice sheets. Glaciers are nothing but in simple words huge chunks of ice which gets accumulated over a period of time, whose movement is governed by its own weight. Due to this ice layers are built which keep on growing slowly together forming a thick mass of ice.
Waterbody never stops moving and this tidal movement brings a lot of changes in the environment around- flora and fauna. However, global warming causing the melting of ice and glaciers has impacted heavily on this causing the extinction of certain species.
Earlier when these environmental changes were not so rapid, marine life in terms of flora and fauna flourished underwater. There was no soil erosion, seawater contamination in terms of industrial waste being released and other contaminants causing loss of marine life.
3. For glaciation to begin, something needs to cause Earth's temperatures to drop. If this happens, snow that falls on the polar ice caps doesn't melt, and glaciers grow. As snow and ice reflect sunlight, the Earth's temperature is reduced even further, causing glaciers to continue growing.
4. Sea level changes cause marine transgressions and regressions. During a marine transgression, the shoreline moves inland, leaving sedimentary deposits that contain fossils. The shoreline retreats during a marine regression, leaving behind the deposited sediments
