Introduction

The extinction of dinosaurs is one of the most dramatic and well-studied events in Earth’s history. Understanding when this mass extinction occurred helps us trace the evolution of life and the rise of mammals and birds that followed. Let’s explore the timing and causes of this pivotal event.

When Did Dinosaurs Go Extinct?

• Dinosaurs became extinct at the end of the Cretaceous Period, marking the boundary between the Mesozoic and Cenozoic eras.

• The most widely accepted scientific evidence shows that this mass extinction happened about 66 million years ago, often rounded to 65 million years ago in many references134567.

• This event is known as the Cretaceous–Paleogene (K–Pg) extinction event.

Scientific Evidence for the Timing

• Radiometric Dating: Rocks at the K–Pg boundary have been precisely dated to about 66 million years ago15.

• Fossil Record: Dinosaur fossils are found below this boundary, but not above it, indicating a sudden and widespread extinction345.

• Iridium Layer: A global layer of iridium-rich clay, found at this boundary, supports the theory of a massive asteroid impact15.

What Caused the Extinction?

• The leading theory is that a massive asteroid or comet struck Earth, creating the Chicxulub crater in present-day Mexico13567.

• This impact caused drastic environmental changes, including darkness, cooling, acid rain, and the collapse of food chains, leading to the extinction of non-avian dinosaurs and many other species1367.

The Correct Answer

Given the options:

1. 1.6 billion years ago

2. 6.5 billion years ago

3. 6.5 million years ago

4. 65 million years ago

The correct answer is:

(4) 65 million year ago

Conclusion

Dinosaurs became extinct approximately 65 to 66 million years ago, at the end of the Cretaceous Period, due to a catastrophic asteroid impact and its aftermath. This event reshaped life on Earth, ending the age of dinosaurs and paving the way for the rise of mammals and birds