- How many large mass extinctions have there been in Earth’s history?
There have been five large mass extinction events in Earth’s history.
- What is believed to have caused the mass extinction of the dinosaurs?
The mass extinction of the dinosaurs is believed to have been caused by an asteroid impact that occurred approximately 65.5 million years ago.
- What evidence supports the view that a large impact was responsible for the mass extinction occurring at the end of the Late Cretaceous?
Very high levels of iridium have been found at the K-T boundary all around the world. Iridium is very rare on the Earth, but is quite common in asteroids and comets.
- How could an impact event be responsible for a mass extinction?
Huge amounts of ash and debris would be thrown in the atmosphere as a result of the impact. This material would block the sun’s rays resulting in global cooling. Large amounts of sulfur and nitrogen gases would also be released into the atmosphere as a result of the impact. These gases would return to the Earth as acid rain. The global cooling together with the acid rain would have serious effects on the environment and the food chain.
- What catastrophic event is thought to have been responsible for the Great Dying?
A period of extreme volcanism 251 million years ago is thought to have been responsible for the Great Dying.
- Explain how the catastrophic event thought to be responsible for the Great Dying could have caused a mass extermination.
The period of extreme volcanism 251 million years ago would have sent large quantities of carbon dioxide (CO2) and sulfur dioxide (SO2) into the atmosphere. Carbon dioxide is a greenhouse gas, and large quantities of it may have lead to global warming. Large quantities of sulfur dioxide in the atmosphere could have resulted in toxic sulfuric acid falling as acid rain. This combination of global warming and acid rain would have had a deadly effect on the environment and on the food chain, and is thought to have been responsible for the Great Dying.