The Catastrophic Cause of the Dinosaur Extinction

The primary, widely accepted cause of the dinosaur extinction event (and 75% of all life on Earth) was the impact of a massive asteroid approximately 66 million years ago. This event marks the boundary between the Cretaceous and Paleogene periods, known as the K-Pg extinction event.

The asteroid, estimated to be about 10-15 kilometers (6-9 miles) wide, struck the Yucatán Peninsula in what is now Mexico, creating the Chicxulub crater. The immediate effects were catastrophic:

1. Massive Shockwave & Heat: The impact generated an enormous shockwave and an immediate flash of heat that incinerated everything within hundreds of kilometers.
2. Global Wildfires: Billions of tons of debris were ejected into the atmosphere, raining back down as superheated projectiles, igniting global wildfires that choked the skies with soot.
3. Mega-Tsunamis: The impact created colossal tsunamis that devastated coastlines thousands of kilometers away.
4. Atmospheric Blockage (Impact Winter): The most devastating long-term effect was the massive amount of dust, soot, and sulfur aerosols injected into the stratosphere. This blocked sunlight for months, possibly years, leading to a global "impact winter." Photosynthesis largely ceased, causing a collapse of the food chain from the bottom up.
5. Acid Rain: Sulfur released from the vaporized rock combined with water to create widespread acid rain, further acidifying oceans and land.

This rapid and extreme environmental change was too much for most large terrestrial animals, including non-avian dinosaurs, to adapt to. While other factors like volcanic activity (Deccan Traps) and sea-level changes were occurring, the asteroid impact is considered the definitive trigger for the mass extinction due to its sudden, global, and devastating effects.

Pro tip: The discovery of a global layer of iridium — an element rare on Earth but common in asteroids — at the K-Pg boundary was the key evidence that first pointed scientists toward an extraterrestrial impact as the cause.