What Killed Dinosaurs?

Written by Mariyam Mohammed

Dinosaurs first emerged around 200 to 250 million years ago, when almost all of the Earth's landmasses were joined together to form a supercontinent, Pangaea (Geggel, 2021). Then, around 65 million years ago – when the continents looked almost like today – dinosaurs went extinct (Geggel, 2021). There are many theories about how dinosaurs vanished from Earth, and scientists are using fossil evidence to study this further.

Supercontinent Pangaea, which formed over 300 million years ago (BEFORE) and modern day Earth (AFTER). Image retrieved from: https://www.geologyin.com/2018/02/facts-about-pangaea-most-recent.html.

Dinosaurs were not the only species that went extinct at that time, about 75% of the Earth’s Animals also disappeared, leading to a mass extinction event (Osterloff, 2020). One of the theories for this is the Alvarez hypothesis, that an asteroid hit Earth, leaving a tremendous impact on the ecosystem and the environment (Osterloff, 2020). With the soot blocking the amount of light reaching Earth, the food chain was affected drastically – herbivores suffering from the reduction in plant growth and carnivores feeling that impact. As a result, all species faced reduced food availability (Osterloff, 2020). Additionally, scientists found an increased amount of iridium in the dinosaur fossils found in rock layers (Jaggard, 2019). This was attributed to the presence of extraterrestrial objects because iridium is quite rare in the Earth’s crust, but it is the opposite in asteroids (Jaggard, 2019). This helped build the evidence of the Alvarez hypothesis.

The other plausible theory of how dinosaurs went extinct is climate change (Jaggard, 2019). Before the asteroid, there has been increased volcanic activity in India (Jaggard, 2019). The Deccan Traps refer to the large outflows of lava that created around 200,000 square miles of volcanic rock in India (Jaggard, 2019). This eruption impacted the climate drastically, with increased greenhouse gasses, such as carbon dioxide, rising temperatures and polluting the oceans (Voosen, 2019). Life on Earth was in danger because of this. Studies show that global temperatures were rising well before the asteroid hit Earth by 5 degrees Celsius, which could have been because of the eruption (Voosen, 2019).

Many theories and many studies describe what happened when dinosaurs went extinct. The answer to ‘What Killed Dinosaurs’ is complicated and requires more research.

• References

  1. Geggel, L. (2021, July 6). A brief history of dinosaurs. Retrieved February 20, 2022, from https://www.livescience.com/3945-history-dinosaurs.html

  2. Geology. (n.d.). Facts about pangaea the most recent supercontinent. Geology . Retrieved February 20, 2022, from https://www.geologyin.com/2018/02/facts-about-pangaea-most-recent.html

  3. Jaggard, V. (2019, July 31). Why did the dinosaurs go extinct? Retrieved February 20, 2022, from https://www.nationalgeographic.com/science/article/dinosaur-extinction

  4. Osterloff, E. (2020, November 18). How an asteroid ended the age of the dinosaurs. Retrieved February 20, 2022, from https://www.nhm.ac.uk/discover/how-an-asteroid-caused-extinction-of-dinosaurs.html

  5. Voosen, P. (2019, February 21). Did volcanic eruptions help kill off the dinosaurs? Retrieved February 20, 2022, from https://www.science.org/content/article/did-volcanic-eruptions-help-kill-dinosaurs