One Bad Day at the End of the Cretaceous: The Death of the Dinosaurs
By Victor GordillioJunior Member and Earth Science Scholar Program
Colorado Springs Mineralogical Society
The Earth was ruled by dinosaurs for about 150 million years or so, a very long time. Sixty-five million years ago, they were all gone, setting the stage for the rise of mammals. Rewind the geological clock to 65 million years ago, and dinosaurs are the dominant organisms on the planet. Move forward only 1 million years and the entire group is nonexistent. Almost overnight, the most successful large animals at the time vanished (leaving only fossils and tracks), setting stage for the rise of the mammals.
The sole cause for this monumental change was a single bad day about 65 million years ago. What happened? Scientific evidence suggests that an asteroid, roughly 10 kilometers in diameter, impacted what is now the Yucatan Peninsula of Mexico. Molten material, ejected from the impact, ignited forest fires around the world within hours. Thousands of cubic kilometers of sulfur-rich rocks were vaporized and thrown into the atmosphere, forming a blanket of soot covering the Earth for months. The Earth was in perpetual darkness which destroyed many links in the food chain, especially plant life. The sulfur combined with water vapor sprinkled back to Earth as sulfuric acid. Ten kilograms of this acid drenched every square meter of Earth. More than 70 percent of all species went extinct as a result of this catastrophe, known as the K-T event (Cretaceous-Tertiary Mass Extinction event).
Our first clues to this doomsday event were discovered in a rock outcrop in Italy that has a definite layer found to be heavily enriched with the element iridium, which is very rare in the Earth’s crust but abundant in asteroids. This extraterrestrial iridium layer has even been found in Colorado. This “smoking gun” sediment layer also included quartz grains that had been subjected to a powerful shockwave. Subsequent analyses from rocks and ocean sediments of this age throughout the world provide a detailed picture of this asteroid impact and how its sweeping changes to the environment resulted in what scientists call the “Great Dying,” and how this impact changed the history of life on Earth. Just recently, a meteorite exploded in the atmosphere over Russia, and an asteroid passed very close to the Earth, giving us pause to think about our planet still being in a “shooting gallery.”
 |
| These dinosaurs are about to have a very large change in there day. Original artwork by © Kurt Lahmers |
