The 5 Most Dramatic Events in Earth's History
April 1, 2026
Earth is 4.5 billion years old. In that time, it has been hit by planet-sized objects, frozen solid from pole to pole, and nearly had all life wiped from its surface. These are the five events that most dramatically changed the course of our planet's story.
1. The Moon-Forming Impact (4.5 Billion Years Ago)
Shortly after Earth formed, a body roughly the size of Mars collided with it. The collision was so violent that both objects largely melted and merged. The debris thrown into orbit eventually coalesced into the Moon.
This event set the stage for everything that followed. The collision tilted Earth on its axis, giving us our seasons. The Moon stabilizes that tilt, preventing wild swings in climate. Without this catastrophic impact, Earth might be a very different, much less hospitable place.
2. The Great Oxidation Event (2.4 Billion Years Ago)
For the first two billion years of Earth's history, there was almost no free oxygen in the atmosphere. Then cyanobacteria evolved photosynthesis and began pumping oxygen into the air as a waste product.
For the anaerobic microbes that dominated the planet, this was a catastrophe. Oxygen was toxic to them, and the Great Oxidation Event killed off vast numbers of these early life forms. But it also opened the door to complex, oxygen-breathing life, eventually including us.
Oxygen went from nearly zero to around 2% of the atmosphere in geologically rapid time. Today it sits at 21%.
3. Snowball Earth (700 Million Years Ago)
For a period of perhaps 30 million years, Earth may have been completely frozen from the poles to the equator. Ice sheets kilometers thick covered the oceans. Surface temperatures averaged around -50°C.
Volcanic CO2 eventually built up enough to melt the ice in a dramatic thaw. The aftermath appears to have triggered the evolution of complex multicellular animals. Snowball Earth may have been the crucible in which animal life was forged.
4. The Permian Mass Extinction (252 Million Years Ago)
The Great Dying, as it is known, was the closest life has come to complete annihilation. Around 96% of marine species and 70% of land vertebrate species went extinct in what may have been less than 100,000 years.
The cause was almost certainly the Siberian Traps, a volcanic event of almost incomprehensible scale. Lava flooded an area larger than Europe. The resulting CO2 and sulfur dioxide triggered runaway greenhouse warming, ocean acidification, and anoxia. It took life tens of millions of years to recover.
For context, the asteroid that killed the dinosaurs wiped out around 75% of species. The Great Dying was far worse.
5. The Chicxulub Impact (66 Million Years Ago)
An asteroid roughly 10 to 15 kilometers across struck near what is now the Yucatan Peninsula in Mexico. The impact released energy equivalent to a billion nuclear bombs. It triggered wildfires across much of the planet, followed by a global winter as debris blocked sunlight for years.
Three quarters of all species on Earth went extinct, including all non-avian dinosaurs. The mammals that survived diversified rapidly into the empty niches. Within a few million years, the ancestors of whales, horses, bats, and primates had all appeared. The impact did not end the story of life on Earth; it started a new chapter.