A Brief Overview of the Hadean Eon for Middle School Science Classes

Dec 3, 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 Hadean Eon. 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 Hadean Eon!

The Beginning of the Universe

The universe began 13.7 billion years ago. Scientists believe the universe began with the Big Bang. Not long after the Big Bang, hydrogen was formed. It is the most simple element, just one proton and one electron. Helium and lithium formed after hydrogen.

Hydrogen and helium came together to form gas clouds. These gas clouds eventually became the first stars. The first stars formed about 200 million years after the Big Bang.

As the stars burn, lighter elements such as helium and hydrogen combine. This creates heavier elements such as iron and nickel.

Eventually, these first stars exploded. All of the elements that had been formed inside the stars were scattered into space as gas and dust.

The Formation of the Solar System and Earth

Nearly 10 billion years after the Big Bang, our solar system began to form from the gas and dust in space.

Scientists call this time the Hadean Eon. As Earth was forming, gravity attracted more dust and rocks to it. Tiny planets, known as planetesimals, collided with Earth. These collisions made the Earth even bigger.

Every time a rock collided with the Earth, heat was released. This made the Earth so hot that the surface of the Earth was liquid rock. Scientists named it the Hadean Eon after Hades, the Greek god of the underworld.

Rocks on Earth

Heavier elements, such as iron, sunk to form the core of Earth. Lighter elements, such as silicon, became a part of the crust. Scientists believe that the first rocks were formed around 4.4 billion years ago, but none of these rocks are left today. Over time, rocks are pushed into the mantle and melt to become magma.

Scientists think there was solid rock on Earth 4.4 billion years ago even though they haven’t found any rocks that old. Instead, scientists have found some very old zircons. Zircons are minerals that look like crystals. Zircons can only form within igneous and metamorphic rock. The zircons the scientists found were 4.4 billion years old, so there must have been solid rock 4.4 billion years ago.

Earth’s Atmosphere

The atmosphere of the Earth during the Hadean Eon was very different from our atmosphere today. At first, it was composed of hydrogen and helium. As the crust cooled ammonia, methane, and neon were released into the air. Then, volcanoes began erupting. These eruptions put water vapor, carbon dioxide, nitrogen, and more helium into the air. Comets filled with ice brought more water vapor to the Earth when they crashed into the planet.

The water vapor in the atmosphere became clouds, and rain began to fall. All of the water in our oceans, lakes, and rivers fell from the sky during the Hadean Eon.

The Moon

The moon also formed early on within the Hadean Eon. Scientists believe that the moon formed when a rock the size of Mars collided with Earth. This collision sent dust and rocks into space. The dust and rocks combined to form the moon.

By the end of the Hadean Eon, the Earth had gone from the underworld to a planet ready of life. Earth had a moon, solid rock, and oceans. The poles may have had some ice. Proteins had begun to form, but life did not yet exist on Earth. Life would come in the next eon, the Archean Eon.

Hadean Eon Picture Book

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