Earths Timeline
Early Earth Conditions
Life on Earth
Earth's Changing Surface
Evolution and Extinction
100

How old is the Earth

4.5 billion years old

100

What was Earth's surface like when it first formed?

A boiling ocean of lava

100

What are the first life forms called?

Single-celled bacteria

100

What is the name of the large landmass that formed 1.1 billion years ago?

Rodinia

100

What creature was the ancestor of all four-legged animals?

Tiktaalik

200

How many years did the Ice Age freeze the entire planet into a snowball?

15 million years

200

What two gasses would not allow anyone to breathe on early Earth?

Carbon dioxide and nitrogen.

200

What underwater features supported early life?

Hydrothermal vents (underwater smoke stacks)

200

What causes Earth’s tectonic plates to move?

Heat from the core moving the rock beneath the crust

200

What caused and where did it happen the biggest mass extinction on Earth 250 million years ago?

Volcanic eruptions in Siberia

300

How long ago did life first appear on Earth?

3.8 million years ago

300

What made Earth spin so fast that a day only lasted 6 hours?

The giant impact that formed the Moon

300

What is the name of the colonies of bacteria that used sunlight to make food?

Stromatolites

300

What is the name of the later supercontinent that formed?

Pangaea

300

Why were bugs like dragonflies and millipedes so huge in prehistoric times?

High oxygen levels allowed them to grow larger

400

How long did the asteroid bombardment that brought water to Earth last?

20 million years

400

How did Earth first get its water?

From meteorites that carried tiny droplets of water inside salt crystals

400

What important gas did stromatolites begin releasing into the atmosphere?

Oxygen

400

What process forms new ocean floor in the Atlantic?

Lava pushing up and cooling between tectonic plates

400

What wiped out the dinosaurs? Where did it originate?

A massive asteroid impact near the Yucatán Peninsula

500

How long ago did the dinosaurs go extinct due to the asteroid impact? 

65 million years ago

500

What caused the global Ice Age that froze the planet 650 million years ago?

Carbon dioxide was absorbed by rocks, trapping less heat

500

What two things made it possible for life to move from water to land?

The formation of the ozone layer and evolution of seeds and eggs

500

What caused the Himalayas to form?

The collision of the Indian and Asian plates

500

How did mammals survive the dinosaur extinction?

They lived underground and ate a wide variety of foods