KidZone Animals: Dinosaurs
Many cretaceous animals (including the dinosaurs) went extinct close to 66 million years ago and scientists have been debating about the cause of this mass extinction. Many scientists agree that the cause was a giant asteroid that left the Chicxulub crater along the Gulf of Mexico.
The Chicxulub crater is massive, around 150 km wide and 20 km deep. It is a peak ring crater so it has the usual crater rim around the outside of the crater and a peak ring near the center of the crater.
Animals that were near the impact zone when the asteroid hit Earth were all wiped out almost immediately. For those far enough away to avoid that initial impact, a large tsunami built up do to the asteroid's impact on the ocean. The tsunami drowned many plants and animals.
Even though the asteriod only landed in Mexico, life all over the world was still wiped out. Since the impact to the Earth's surface was so intense, lots of rocks and small debris rose up and entered the Earth's atmosphere. The debris covered the skies and hid the sun, which changed the skies from incredibly hot to increasingly cold.
The cold stayed for a long time and many species could not withstand it. Larger animals struggled the most because they no longer had the rich plant-life or numerous smaller animals to feast upon. On land the dinosaurs became extinct and in the skies the pterosauria (avian reptiles) also died out. Even the ocean was not immune to the deadly skies. Debris falling into the ocean was also harmful to marine life. Without any sun, the oceans were very dark and inhospitable. Many marine species died out, including the marine reptiles.
Even though it seems hard to imagine that one asteroid could have such dramatic effects on the whole world, scientists have found evidence to suggest that it is true. There is a line of rock in the a layer called K-Pg boundary. Below this layer of rock dinosaur fossils (and many other extinct species) can be found, but above this line there are no dinosaur fossils. The K-Pg rock layer is also made up of iridium, which is a common substance in space rocks. Along with the discovery of the Chicxulub crater, this evidence confirms that an asteroid was involved in the mass extinction at the end of the Cretaceous period.
Some scientists argue that the mass extinction was actually caused by a big explosion of volcanism in India that happened around the same time as the Chicxulub impact. It is even possible that both could have contributed to the distruction of the dinosaurs, marine reptiles, avian reptiles, and many animals. Despite all of the scientific theories about the final days of the dinosaurs, we can't be certain about the mass extinction because we don't have a time machine.