Earth is always changing. From the Big Bang, the Earth has come a long way to what it is now. Take the dinosaurs for example. They lived during the Mesozoic era, spanning approximately 185 million years. During the era, the world was a lot more different. In the beginning, the land did not look like what it is now. All the land masses were once together as a supercontinent knows as Pangaea. Throughout the Triassic, Jurassic, and Cretaceous periods of the Mesozoic era, the land masses began to move. The Mesozoic was also a time of climatic and evolutionary change. Dinosaurs and the environment began to evolve until the era ended 65 a million years ago.
The Mesozoic era is divided into three periods: Triassic, Jurassic and Cretaceous.
In the Triassic period, the climate was very dry. As the world was one supercontinent, in the interior there were very hot summers and cold winters. Along the coastlines, the temperature was much more regulated due to the proximity of bodies of water. As for life, there was very small plant life and animal included amphibians, small reptiles, mammals and dinosaurs (e.g. Coelophysis).
During the Jurassic period, the supercontinent Pangaea split into two landmasses. This created more coastlines to change the global climate from dry and hot to warm and humid (i.e. deserts became rainforests). It was a time where dinosaurs reached their prime as a diversified group of animals. From theropods (carnivores like Allosaurus) to the sauropods (herbivores like Barosaurus), dinosaurs became the dominant vertebrates of the Earth. Dinosaurs also took to the oceans (e.g. ichthyosaurs) and the skies (e.g. pteranodons) during this period.
Barosaurus
A Pteranodon
The land masses in the Cretaceous period kept on splitting. This in turn made the Cretaceous world have a relatively warm climate and high ocean levels. On land, mammals and insects began to diversify with the dinosaurs as well (Tyrannosaurus). Sharks and fish began to replace the ichthyosaurs and other marine dinosaurs. Birds also began to appear.
At the end of the Mesozoic era (about 65 million years ago), there was a mass extinction of life on the earth. Most scientists today agree that a massive asteroid impacted the Earth at what is known as the Chicxulub crater in Mexico. The event caused ash to block sunlight so that photosynthesis would not occur. This along with other climate change brought the extinction of the dinosaurs. However, in the end, the birds (evolved from dinosaurs) and mammals along with the sharks, crocodiles, and other animals survived that still walk among us today.
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