The Story of Earth

Introduction

• Earth as the only known home to life in the universe.
• Understanding Earth requires exploring its 4.5 billion-year history.
• Key moments in Earth's development are traced from the solar system's formation.

Formation of Earth

• Initially, dust and rocks pulled together by gravity form Earth.
• Early Earth was a hostile environment with high temperatures and toxic gases.
• Collision with Theia creates debris forming Earth’s moon.
• Rapid spinning results in shorter days.

Arrival of Water

• 3.9 billion years ago, meteorites bring crystals containing water.
• Over millions of years, water accumulates, forming oceans.
• Earth’s surface cools, forming a crust; air still toxic.

Emergence of Life

• 3.8 billion years ago, meteorites supply essential minerals.
• Underwater chemical reactions possibly lead to life.
• Stromatolites appear, producing oxygen through photosynthesis.
• Oxygen transforms atmosphere and oceans over billions of years.

Geological Changes

• Earth's crust breaks into plates leading to continental drift.
• Formation of supercontinent Rodinia.
• Volcanic and tectonic activity significantly alter Earth’s surface.

Snowball Earth

• Around 650 million years ago, the Earth experiences a major ice age.
• Volcanoes release CO2, eventually warming the planet and ending ice age.
• Primitive life believed to have survived ice age, leading to Cambrian Explosion.

Cambrian Explosion

• Emergence of complex life forms due to increased oxygen levels.
• The development of new species including trilobites with basic skeletons.

Life on Land

• Formation of ozone layer allows life to move from oceans to land.
• First land plants appear, increasing oxygen levels further.
• Tiktaalik lizard-like fish ventures onto land, leading to evolution of tetrapods.

The Age of Reptiles

• Reptiles evolve into dinosaurs; dominance lasts for millions of years.
• Pangea forms and later breaks apart, leading to the formation of modern continents.
• Permian extinction wipes out 95% of species, paving the way for dinosaurs.

Extinction Events

• Asteroid impact 65 million years ago leads to dinosaur extinction.
• Mammals survive and begin to evolve, leading to the rise of human ancestors.

Rise of Mammals

• Early mammals evolve into primates, leading to Homo sapiens.
• Continental movements affect climate and evolution, promoting the development of bipedalism.

Human Evolution

• Homo sapiens migrate out of Africa 70,000 years ago.
• Ice ages sculpt Earth's landscape and influence human migration.

Conclusion

• Earth has undergone dramatic changes to become habitable for life.
• The planet continues to evolve with uncertain future changes.