The Unique Story of Earth

Introduction

• Earth is the only known home to life in the universe.
• To understand what makes Earth special, we must explore its history.
• Key milestones include the formation of Earth, the emergence of life, and major evolutionary changes.

Formation of Earth

• 5 Billion Years Ago: The Sun forms; Earth's formation begins from dust and rocks.
• 4.5 Billion Years Ago: Earth is a molten, toxic environment.
• A collision with a Mars-sized body, Theia, leads to the formation of the Moon.

Early Earth

• 3.9 Billion Years Ago: Meteor bombardment brings water and minerals.
• The surface cools, forming a crust; early water bodies appear.

Emergence of Life

• 3.8 Billion Years Ago: Meteorites introduce carbon and primitive proteins.
• Hydrothermal vents in oceans create conditions for life.
• 3.5 Billion Years Ago: Photosynthesizing bacteria (stromatolites) emerge, producing oxygen.

Evolution of Atmosphere and Life

• 2 Billion Years Ago: Rising oxygen levels transform Earth's atmosphere.
• 1.5 Billion Years Ago: Earth's plates and continents begin to form.
• 750 Million Years Ago: Rodinia forms; volcanic activity and continental drift occur.

Snowball Earth

• 650 Million Years Ago: Earth experiences a massive ice age, covering it in ice for 15 million years.

Cambrian Explosion

• 540 Million Years Ago: Life diversifies rapidly; multicellular organisms evolve.

Life on Land

• 460 Million Years Ago: Ozone layer forms, enabling life on land.
• 375 Million Years Ago: Fish like Tiktaalik begin moving onto land.

Plant Evolution

• 360 Million Years Ago: Seed plants appear, enabling more diverse terrestrial life.

Reptiles and Coal Formation

• 300 Million Years Ago: Reptiles evolve, including the first egg-laying species.
• Decaying plant matter eventually forms coal.

Permian Extinction

• 250 Million Years Ago: Massive volcanic eruptions cause the greatest mass extinction event.

Rise of Dinosaurs

• 200 Million Years Ago: Dinosaurs evolve and dominate.

Geological Changes

• Pangaea and Plate Tectonics: Continual movement of Earth's plates shape modern continents and oceans.

Cretaceous-Paleogene Extinction

• 65 Million Years Ago: An asteroid impact leads to the extinction of dinosaurs, paving the way for mammals.

Evolution of Mammals

• 47 Million Years Ago: Early primates like Ida emerge.

Human Evolution

• 1.5 Million Years Ago: Homo erectus appears, marking a significant step in human evolution.
• 70,000 Years Ago: Early humans migrate out of Africa.

Last Ice Age

• 40,000 Years Ago: The planet undergoes an ice age, shaping modern landscapes.

Human Migration

• Humans cross from Asia to the Americas via a land bridge.

Modern Earth

• Present Day: Earth is a diverse and dynamic planet, continuously evolving.
• The Earth's journey continues, with an expected lifespan of another 4.5 billion years.