You likely learned in elementary school that the dinosaurs went extinct because of a huge asteroid hitting the earth. While the impact theory is the most widely accepted theory today, the theory is a bit more complicated than a massive impact killing everything. The impact theory is also still just a theory, and not proven to be fact. This is still a debated topic and there are many other plausible theories circling around the scientific community.

One theory attributes the extinction to climate change. During the dinosaur’s time, scientists believe that the planet slowly became cooler and less humid. This change may have led to the change in vegetation, killing much of the food for the herbivores. When herbivores died out, their carnivorous predators would also follow. The change in vegetation and climate may not have been adaptable for the cold-blooded dinosaurs and caused many of them to die over time. It also makes sense that many species of mammals survived and thrived after the extinction of the dinosaurs. Warm-blooded mammals would able to regulate their internal temperatures and adapt to climate change.

Another theory points to disease. Sea levels had fallen at the end of the Cretaceous period, and land bridges between continents had surfaced, allowing dinosaurs to travel to new continents. Diseases had been present in all regions of life, but in their native areas, dinosaurs had adapted immunity to these diseases. But when the dinosaurs brought these diseases to new areas, the inhabitants of these areas did not have immunity, and were vulnerable to being killed by these diseases. Smaller animals’ survival is explained by the fact that these animals were less capable of making these long intercontinental journeys, and thus did not spread their diseases as much. Blood-sucking insects were also becoming more prevalent during this time. These insects increased the spread of malaria and other pathogens.

Another widely known theory  is that a series of volcanic eruptions caused the extinction of the dinosaurs. Scientists have found lava flows in India that provide evidence of volcanic activity greater than humans have ever seen. Volcanic eruptions would have sent dust and ash into the atmosphere. This debris can stay in the atmosphere for several years. If enough debris collected in the atmosphere during a period of time, sunlight may not have been able to reach the surface of earth. A lack of sunlight would explain the extinction of many plant species. This lack of food would again also cause many herbivores to starve, followed by the carnivores. Blocked sunlight would also cause the climate to be very cold, which again would make it difficult for cold-blooded dinosaurs to survive.

This brings us to the most widely accepted theory, the impact theory. This theory says that the extinction of the dinosaurs was brought on by the collision of a massive meteor with the earth. This theory was first formulated when Luis and Walter Alvarez discovered a thin layer of iridium-rich clay in Italy in 1981. Iridium is an element that is very rare on earth, but if much more common in space. From this, the Alvarezes published the theory that this iridium was brought to earth because a meteor collided with the earth and killed all of the dinosaurs. In 1991, a giant crater with a diameter of 110 miles was found in the Yucatan Peninsula. Scientists believed that the meteor that must have caused this crater would have been 6 miles in diameter. This meteor would have collided with the earth at 40,000 miles per hour, and it would have been 2 million times more powerful than the most powerful nuclear bomb. The intense heat would have caused wildfires across the world, sending ash and dust into the atmosphere, causing similar effects to what the volcano theory describes.

But, there is a newer theory. In October of this year, the journal Science published a study that claims that the extinction of the dinosaurs was caused by a massive meteor and a series of volcanic eruptions at the same time. The scientist in charge, Paul Renne of UC Berkeley says that the impact of the meteor sped up volcanic eruptions worldwide. He says that volcanic activity doubles in the 50,000 years following the impact of the meteor, and that the dinosaurs became extinct within this 50,000 year period. Since this theory claims that the effects of both the impact and the series of volcanic eruptions happened at the same time, the catastrophic circumstances of both theories would be included. The meteor would have had a powerful impact, shaking the earth, creating extreme heat and fires, and sending large amounts of debris into the atmosphere. Many volcanoes would then start erupting worldwide, sending even more debris into the atmosphere. Sunlight would then be blocked from reaching the earth’s surface. The lack of sunlight would kill plants and cause a cold climate that would kill dinosaurs unable to adapt and it would eliminate the food for herbivores, and then carnivores.

The extinction of the dinosaurs is a debate that has gone on in the field of paleontology for hundreds of years. Although we still don’t have a definite answer, we find more and more evidence over time. Someday maybe us humans will face a threat of mass extinction by way of climate change, volcanic eruptions, or meteor impact. Knowing more about the past may help prepare humankind for the future.