Earth's Evolution: From Formation to Present

Sep 10, 2024

History of Earth

Formation of the Solar System

  • 4.5 billion years ago: Solar system formed from a dense cloud of interstellar gas and dust.
    • Cloud collapsed into a swirling disc of matter.
    • Hydrogen fused into helium, leading to the birth of the Sun.

Formation of the Earth

  • Clumps of matter in the disc formed planets and moons.
  • Inner planets (like Earth) formed from rocky materials closer to the Sun.
  • Young Earth was volcanically active, releasing gases:
    • Hydrogen sulfide, methane, carbon dioxide.

Early Collisions and Atmosphere

  • Earth experienced violent collisions:
    • Thea, a Mars-sized planet, collided with Earth, forming the Moon.
  • No oceans initially; water existed as gas.
  • 3.8 billion years ago: Earth cooled, water condensed, creating the first oceans.

Origin of Life

  • 3.7 billion years ago: Earliest forms of life appeared (microscopic organisms).
  • Nearly a billion years later, organisms evolved and changed the world.

Formation of Continents

  • First continents emerged from ancient oceans (called cratons).
  • Formation of the first supercontinent, Valbara.

Evolution of Oxygen Producers

  • 2.4 billion years ago: Cyanobacteria evolved to photosynthesize, producing oxygen.
  • Resulted in lower CO2 levels, leading to the first ice age.

Continental Movements and Supercontinents

  • Continents broke apart and reassembled into Rodinia (largest supercontinent).
  • Rodinia broke apart, leading to Pannotia.
  • Cambrian Explosion (540-485 million years ago): Explosion of life, evolution of hard-bodied animals.

Mass Extinctions

  • 440 million years ago: First mass extinction (Ordovician-Silurian extinction).
  • First trees and land animals evolved between 420-350 million years ago.
  • 250 million years ago: Last vast supercontinent, Pangea.
    • Experienced the greatest mass extinction (about 90% of species).

Dinosaurs and Evolution

  • 240-230 million years ago: First dinosaurs appeared and dominated for 150 million years.
    • Example: Argentinosaurus and T-Rex.
    • Pangea eventually broke apart, forming modern continents.

Chicxulub Impact Event

  • 6 million years ago: Asteroid impact near present-day Mexico.
    • Caused climate changes, leading to the extinction of dinosaurs.

Emergence of Mammals and Humans

  • 6 million years ago: Earliest known human species, Sahelanthropus.
  • 4 million years ago: Early humans began walking upright.
  • 800,000 years ago: Discovery of fire, leading to cooking and heat.
  • 40,000 to 15,000 years ago: Extinction of other human species (except Homo sapiens).

Agricultural Development

  • 10,000 years ago: Emergence of the first farmers, settling down after a nomadic lifestyle.

Industrial Revolution and Population Growth

  • 250 years ago: Industrial Revolution transformed societies.
    • Human population:
      • 1804: 1 billion
      • 1927: 2 billion
      • Rapid increase since the 1960s, now over 8 billion.

Current Threats

  • Climate change threatens existence of humans and other life forms.
  • Rising temperatures, sea levels, and declining biodiversity could lead to another mass extinction event.