Earth's Formation

Earth's Formation

A Journey Through Time: From 4.5 billion years ago to the present day!

Multiple Choice

How long ago did the Earth first form?

• 65 million years ago

• 200 million years ago

• 4.5 million years ago

• 4.5 billion years ago

Multiple Choice

Review: How old is the universe?

• 200 million years

• 4.5 billion years

• 13.7 million years

• 13.8 billion years

Collisions and Combination:

Earth formed gradually as planetesimals collided and combined within the first 10 million years of the collapse of the solar nebula that formed the Sun.

Collisions & Heat

​Earth first formed around 4.5 billion years ago, and is made from the cooling leftover ingredients from the the Sun!
(So are the rest of the planets!)

​Early Earth was especially hot,
as a result of collisions from incoming
asteroids and small planetesimals.

​The early solar system was a
very violent place!

Earth's Shape

Trivia: The Earth became round due to the combined effects of gravity and its own shape. The force of gravity pulls matter towards the center, causing it to form a spherical shape. This is why Earth is not flat!

• Collisions and combination

• Heat and melting

• Radioactive materials

Gravitational Forces

The Earth became round due to the force of gravity.

Gravity pulls matter towards its center, causing it to form a spherical shape.

This is why planets, including Earth, are round.

Gravity also keeps the Moon in orbit around the Earth!

Earth's Layers take Shape

Rocks and materials in the
early Earth randomly mixed
as it boiled, but then gravity pulled more dense materials, such as iron, toward the center to form the core.

Meanwhile, less dense
materials rose to the surface and gradually cooled and solidified to form the crust.

Layers of Density

You might have heard that oil & water don't mix - they separate.
But why? They have different densities.

Similar to oil and vinegar separating, denser materials in the molten Earth sank to the bottom while less dense materials rose to the surface.

Layers of Density

​Earth's Layers

Multiple Choice

How long ago did the Earth first form?

• 65 million years ago

• 200 million years ago

• 4.5 million years ago

• 4.5 billion years ago

Multiple Choice

What caused the Earth to become round?

• Collisions & Combination

• Gravity & Mass

• Heat & Melting

• All of the above

Multiple Choice

What is the most dense layer of Earth?

• Core

• Mantle

• Crust

Earth's Cooling

Once Earth had cooled enough, the exterior began to form a crust.

However, while Earth
is made of solid rock
on the surface,
boiling magma lies just miles beneath!

Earth's Cooling

Today, the Earth is still cooling from the energy generated during its formation. It releases this energy in the form of volcanoes & earthquakes.

The Formation of Earth's Oceans & Atmosphere

Comets brought water in the form of ice

Steamy mixture of carbon dioxide and water vapor released from volcanoes

Formation of Earth's Oceans: Volcanoes

Volcanic gases played a critical role in the development of Earth's atmopshere.

Earth's Atmosphere

The early atmosphere was a mixture of carbon dioxide and other gases.



Today it is primarily composed of nitrogen and oxygen.

Multiple Choice

How has Earth's atmosphere changed?

• It's mostly Nitrogen now

• It's mostly Oxygen now

• It's mostly Carbon Dioxide now

• It's mostly water vapor now

Formation of Earth's Oceans: Rain

Rainfall played a crucial role in the formation of Earth's oceans.
Over millions of years, water vapor in the atmosphere condensed,
and fell as rain, filling the basins and creating vast bodies of water.

It rained for millions of years.

Multiple Choice

How long did it rain for?

• weeks

• months

• years

• millions of years

Multiple Choice

What led to the formation of Earth's oceans?

• Volcanic gases

• Comets

• Rainfall

• Carbon dioxide

​Earth's Location