Final answer:
The mass extinction of dinosaurs, also known as the K-T extinction event, took place 65 million years ago, mainly due to the impact of a large asteroid causing significant global climatic upheavals.
Step-by-step explanation:
The Mass Extinction of Dinosaurs
The mass extinction of dinosaurs, known as the end-Cretaceous or K-T extinction event, occurred 65 million years ago. This catastrophic event is marked by the disappearance of a significant proportion of Earth's species, including the dominant dinosaurs, except for the lineage that led to modern birds.
It is widely supported by scientists that a large asteroid impact in the present-day Yucatán Peninsula was the primary cause for this mass extinction. The impact would have released enormous amounts of energy and ejected dust into the atmosphere, leading to global climate changes that greatly affected life on Earth.
Following this event, mammals saw a significant rise, taking advantage of the ecological niches that were left vacant by the extinction of the dinosaurs.