Answer:
Greenhouse effect
Step-by-step explanation:
The Paleozoic era is followed by the Mesozoic era. The Mesozoic era consists of three periods Triassic, Jurassic, and Cretaceous.
During the cretaceous period the temperature of earth was 10 to 15 °C warmer than it is today. This warmth was caused due to the increase in volcanic activity of Earth. As the tectonic plates were moving this created mantle from the Earth's core rose to the surface causing increased volcanic activity. This volcanic activity increased the amount of CO₂ in the atmosphere thus creating the greenhouse effect.