The Cataclysmic End of the Dinosaurs: The K-Pg Extinction Event

The dinosaur extinction event, formally known as the Cretaceous-Paleogene (K-Pg) extinction, was primarily caused by a massive asteroid impact 66 million years ago, leading to a rapid and catastrophic global environmental collapse. While other factors like volcanic activity may have played a minor role, the impact theory is overwhelmingly supported by scientific evidence.

The Asteroid Impact: The Immediate Catastrophe

1. The Chicxulub Impactor: A colossal asteroid, estimated to be 10-15 kilometers (6-9 miles) in diameter, struck the Yucatán Peninsula in what is now Mexico. The impact site, known as the Chicxulub crater, is a key piece of evidence.
2. Instantaneous Devastation: The impact released energy equivalent to billions of atomic bombs, creating a massive blast wave that flattened everything for hundreds of miles. It triggered immense tsunamis, wildfires across continents from superheated ejecta raining back down, and massive earthquakes.

The Global Winter: Long-Term Environmental Collapse

1. Atmospheric Blockage: The impact ejected billions of tons of dust, soot, and sulfur aerosols into the atmosphere. This material formed a thick, global shroud that blocked sunlight for months, possibly years.
2. Impact Winter: With sunlight blocked, global temperatures plummeted, leading to an "impact winter." Photosynthesis, the base of most food chains, largely ceased. Plants died, leading to a collapse of herbivore populations, and subsequently, carnivores.
3. Acid Rain: Sulfur released from the vaporized rock reacted with water in the atmosphere to create highly acidic rain, further devastating plant life and acidifying oceans, impacting marine ecosystems.

The Extinction: Who Survived and Who Didn't

The K-Pg event wiped out approximately 75% of all plant and animal species on Earth. All non-avian dinosaurs (like T. rex and Triceratops) perished. Pterosaurs and large marine reptiles (like mosasaurs and plesiosaurs) also went extinct. Survivors included some mammals, birds, crocodiles, turtles, and certain plant and insect groups, typically those that could shelter underground, survive on detritus, or had smaller body sizes and lower metabolic rates.

Pro tip: The key geological evidence for this event is the K-Pg boundary layer, a thin layer of clay found worldwide. This layer is rich in iridium, an element rare on Earth's surface but common in asteroids, and contains shocked quartz and microtektites (glassy spheres formed from vaporized rock), all consistent with a massive impact.