Keeping Time

Keeping Time

Multiple Choice

Earth was formed about __________ years ago.

• 4. 6 thousand

• 4.6 million

• 4.6 billion

• 4.6 trillion

Multiple Choice

What is the Cambrian Explosion?

• A period in which life on Earth suddenly became much more diverse.

• When a chemical called Cambria exploded.

• When a scientist called Cambria caused an explosion. It was the first explosion on Earth.

Multiple Choice

Why is the Mesozoic era famous?

• Because it's when human beings first appeared.

• Because it's when dinosaurs ruled the planet.

• Because it's when trilobites became extinct.

• Because it's when Earth was first formed.