A Brief Overview of the Mesozoic Era for Middle School Science Classes

Dec 5, 2024

3 min read

Earth history is a fascinating topic! It is also a massive topic! The reading passage below will teach you all about the Mesozoic Era. If you want to learn more (and why wouldn't you?!), you can check out my Earth History page. I also have all of my passages available at Teachers Pay Teachers. They come with so many extras to get your students thinking about the content! I also recommend scrolling to the bottom of the page to check out my digital picture book on the Mesozoic Era!

Permian Extinction

The Mesozoic era began after the Permian extinction. At the end of the Permian period, 96 percent of marine life and 70 percent of land plants and animals were wiped out. Scientists believe this may have been caused by volcanic eruptions. The eruptions spewed carbon dioxide into the atmosphere. The carbon dioxide raised the temperature on Earth and dissolved into the ocean, making the water acidic. This could explain why marine life was affected more greatly than terrestrial life.

Triassic Period

The extinction event opened habitats to new life on Earth. Reptiles, who had first appeared during the Carboniferous period, thrived. During the Triassic period, these reptiles evolved into the first dinosaurs. The first dinosaurs were much smaller than the famous Brachiosaurus and Tyrannosaurus rex.

Jurassic Period

During the Jurassic period, dinosaurs became larger. Brachiosaurus and Stegosaurus foraged for ferns, mosses, and conifers. Brachiosauruses needed to eat over eight hundred pounds of food per day. Birds and mammals first appeared during the Jurassic period. Mammals were small rodents. They were nocturnal, so they slept during the day and searched for food at night.

Cretaceous Period

The most famous dinosaurs, including the Tyrannosaurus rex and Pteranodon, lived during the Cretaceous period. However, the most important new species of the period were flowering plants. With the help of insects, these plants spread over the entire world. Grasses also first appeared during the Cretaceous period.

Pangaea

At the beginning of the Mesozoic era, all of the land on Earth was locked in one supercontinent, Pangaea. It was shaped like the letter C. The water inside the continent was called the Tethys Ocean. The water outside the continent was called the Panthalassic Ocean. As soon as the continent formed, it began breaking apart.

By the Jurassic period, Pangaea had separated into two giant continents, Laurasia and Gondwana. During the Cretaceous period, these two continents had fractured into several smaller continents that would eventually become the continents we know today.

Climate

The Earth was much warmer during the Mesozoic era than it is today. There was no ice at the poles. The interiors of Pangaea were dry and full of deserts, but lush tropical rainforests extended from the equator. The warm climate allowed for an abundance of plants. Enormous herbivorous dinosaurs had plenty to eat to satisfy their appetites, but this would change as the climate grew colder.

Cretaceous Extinction Event

Even before the asteroid struck Earth at the end of the Cretaceous period, the dinosaurs were struggling. A cooling climate meant fewer plants. Grasslands were replacing the tropical forests, and grasses don’t have as many nutrients as other plants. Dinosaurs may have evolved to survive in the new environment, but the asteroid ensured the end of the dinosaurs.

Scientists believe an asteroid crashed into Earth in present day Mexico around sixty-five million years ago. The asteroid is estimated to have been over six miles wide. When it crashed into the Earth, it released more energy than one billion atomic bombs. This impact sent dirt and ash into the atmosphere. The debris was so thick, it blocked out the Sun for nearly two years. Without sunlight, many plants died. Without plants, herbivorous dinosaurs died. Without prey, carnivorous dinosaurs died.

Mammals

Luckily for humans, mammals survived this extinction event. Their small size meant they didn’t need as many calories as the giant dinosaurs. They were also omnivores, so they would eat anything they could find. When the Earth recovered from the asteroid strike, mammals were able to fill the habitats the dinosaurs abandoned. This allowed them to diversify into the many creatures we see today.

Mesozoic Era Picture Book

Looking for another way to learn about the Mesozoic Era? Check out this picture book version. The pages are a part of my Earth History bundle on Teachers Pay Teachers.