Dinosaur extinction refers to the sudden and widespread disappearance of non-avian dinosaurs at the end of the Cretaceous period, approximately 66 million years ago. This event, known as the Cretaceous-Paleogene (K-Pg) extinction, was one of the most significant mass extinctions in Earth's history, erasing about 75% of all species and paving the way for the rise of mammals and modern ecosystems.
- Ended the reign of non-avian dinosaurs about 66 million years ago
- Occurred during the Cretaceous-Paleogene (K-Pg) boundary
- Resulted in the loss of approximately 75% of all species on Earth
- Marked a major shift in global biodiversity and ecosystem structure
Dinosaur extinction occurred about 66 million years ago, at the end of the Cretaceous period.
The dinosaur extinction event is known as the Cretaceous-Paleogene (K-Pg) extinction.
Mass Extinction Events
Mass extinction events are periods when a significant proportion of Earth's species vanish in a relatively short geological time, drastically altering life on the planet. The extinction of dinosaurs corresponds to the Cretaceous-Paleogene (K-Pg) mass extinction, which eradicated about 75% of all species, including non-avian dinosaurs, and allowed mammals to become the dominant land animals.
- Mass extinctions cause rapid and extensive loss of species worldwide.
- The K-Pg event (~66 million years ago) ended the age of non-avian dinosaurs.
- Following this event, mammals diversified and became dominant.
- Mass extinctions reshape ecosystems and evolutionary trajectories.
A mass extinction event is characterized by the widespread and rapid loss of many species.
The K-Pg mass extinction affected non-avian dinosaurs, marine reptiles, ammonites, and many plankton species; some birds and mammals survived.
Theories and Evidence
The most widely accepted explanation for dinosaur extinction is the asteroid impact hypothesis, which posits that a massive extraterrestrial object struck Earth, triggering catastrophic environmental changes. Key evidence includes a global iridium layer, the Chicxulub crater, and fossil record disruptions. Other factors, such as volcanic activity and climate change, likely exacerbated the extinction.
- Iridium, rare on Earth's surface but common in asteroids, is found globally in a thin layer dating to the extinction.
- The Chicxulub crater in Mexico marks the asteroid impact site and is dated to 66 million years ago.
- Sudden disappearance of many fossil groups at the K-Pg boundary supports rapid extinction.
- Massive volcanic eruptions (Deccan Traps) and climatic shifts may have stressed ecosystems before and after the impact.
The global iridium layer, Chicxulub crater, and shocked quartz support the asteroid impact theory.
Volcanic activity, such as the Deccan Traps eruptions, is considered a contributing factor to dinosaur extinction.
The asteroid impact triggered climate cooling, darkened skies, acid rain, and disrupted food chains.
The asteroid impact evidence is found at the Chicxulub crater in the Yucatán Peninsula, Mexico.
Impact on Biodiversity
The extinction of dinosaurs caused a massive decline in global biodiversity, with around 75% of species wiped out. However, it also removed dominant groups like non-avian dinosaurs, allowing mammals and birds to diversify and fill new ecological roles, leading to the modern arrangements of life on Earth.
- Non-avian dinosaurs and many marine species vanished, reducing biodiversity dramatically.
- Mammals and birds diversified rapidly due to newly available niches (adaptive radiation).
- Modern ecosystems and dominant vertebrate groups emerged during the Cenozoic.
The extinction caused species loss, mammals rose to dominance, and ecosystems were reorganized.
Mammals thrived and diversified after non-avian dinosaurs went extinct.
New dominant species emerged, food webs were reorganized, and biodiversity gradually increased.
Conclusion
Dinosaur extinction at the K-Pg boundary was a transformative event driven primarily by an asteroid impact, with evidence such as iridium layers and the Chicxulub crater underpinning this theory. This mass extinction not only ended the reign of non-avian dinosaurs but also reshaped Earth's biodiversity, allowing mammals and birds to emerge as dominant groups in new ecosystems.
- Occurred ~66 million years ago during the K-Pg mass extinction.
- Main cause: asteroid impact, with supporting evidence including iridium layers and the Chicxulub crater.
- Resulted in the loss of ~75% of species and paved the way for mammalian dominance.
Non-avian dinosaurs became extinct during the Cretaceous-Paleogene (K-Pg) extinction.
The evidence includes an iridium layer, the Chicxulub impact crater, and shocked quartz.
Volcanic eruptions and climate change are considered additional contributing factors.
Dinosaur extinction opened ecological niches for mammals, leading to their rise as dominant land animals.
Ammonites, marine reptiles, and some plankton also suffered major losses; many modern birds and mammals survived.