The Formation and Structure of Planet Earth Lesson #1: The Infant Earth Lesson Objective #1

Constructed Response Objective Describe how the solar system (including the Earth) formed according to the “nebular theory” of formation.

The Solar Nebula- 1 The Sun, the planets, and everything else in our solar system formed from a nebula in space, known as the “solar nebula”. A nebula is a cloud of dust and gas (mostly hydrogen and helium with trace amounts of heavier elements).

A nebula in space

The collapse of the solar nebula About 5 billion years ago, particles in the solar nebula began to clump together into globules. Gravity pulled globules together into larger planetisimals, most of which combined to form the sun and planets. Rotation within the nebula caused it to flatten into a disk, allowing some of the material to resist being pulled into the sun. This material (only 1% of the solar nebula’s mass) formed the planets.

Planetesimals

The Hadean Eon During the first 800 million years of Earth’s existence, it was not solid but rather a sea of molten (melted) rock called magma. This is because it was frequently bombarded with meteorites that heated the planet to extremely high temperature. Some of this heat is still trapped inside the earth. They also caused Earth to grow in size (like adding legos).

The “Hadean” Earth

Video / articles formation of solar system –5 minute video The Story of The Earth part 1 –15 minute video Planet Building online article