Lecture Notes: The History and Evolution of Earth

Importance of Earth

• Earth is currently the only known home to life in the universe.
• Special conditions on Earth have allowed life to exist and evolve.

Formation of Earth

• 5 billion years ago: Sun forms, surrounded by dust.
• Gravity forms the Earth from dust and rocks, one of the initial 100 planets.
• 4.5 billion years ago: Earth is a hostile, molten environment.
  • Atmosphere of carbon dioxide, nitrogen, and water vapor.

Formation of the Moon

• Collision with Mars-sized planet Theia contributes debris forming the moon.
• Original distance of moon from Earth was much closer than today.

Early Earth

• 3.9 billion years ago: Meteor bombardment brings water to Earth.
• Pools of water form on Earth’s surface, essential for future life.
• Early formation of Earth’s crust and cooling of surface.

Development of Life

• 3.8 billion years ago: Meteors bring minerals and amino acids.
• Formation of early life in chemical-rich underwater vents.
• 3.5 billion years ago: Stromatolites produce oxygen through photosynthesis.

Changes in Earth’s Atmosphere

• Oxygen levels rise, forming an atmosphere.
• 1.5 billion years ago: Formation of supercontinent Rodinia.
• Tectonic plate activity changes Earth's landscape.

Ice Ages and Mass Extinctions

• 750 million years ago: Rodinia splits, leading to Snowball Earth.
• 650 million years ago: Ice covers Earth, volcanic activity eventually warms planet.

Cambrian Explosion

• 540 million years ago: Increased oxygen allows complex life to evolve.
• Development of creatures with bony skeletons and diverse species.

Colonization of Land

• 460 million years ago: Formation of ozone layer allows life to move onto land.
• Plants and creatures adapt to terrestrial life, evolution of seeds.

Rise of Reptiles and Dinosaurs

• 375 million years ago: Tetrapods evolve from aquatic life.
• Dinosaurs emerge as dominant species following Permian extinction.
• 250 million years ago: Pangea forms and later splits.

Mass Extinction Events

• Permian Extinction wipes out 95% of species.
• Asteroid impact 65 million years ago ends dinosaurs’ reign.

Evolution of Mammals and Humans

• Early mammals survive post-dinosaur extinction.
• 47 million years ago: Evolution of primates hints at human ancestry.

Formation of Modern Earth

• Himalayas form through tectonic activity.
• Continents take current shape, African rift influences climate.
• Evolution of bipedalism in early human ancestors.

Human Migration

• 70,000 years ago: Humans migrate out of Africa.
• Colonization of other continents including the Americas.

Ice Age and Geological Changes

• Ice Age shapes current landscape, Great Lakes form.
• 14,000 years ago: Ice retreats, revealing modern geography.

Conclusion

• Earth's history characterized by dynamic changes and evolution.
• Future holds more transformations as Earth continues to evolve.