how do dinosaurs died out 65 million years ago

The extinction of the dinosaurs, which happened about 65 million years ago at the end of the Cretaceous period, is a complex issue with a blend of contributing factors. The leading theory for this mass extinction event is the so-called "Chixculub Impact Theory," which suggests that a large asteroid impact played a major role. Here’s a detailed explanation:

1. Asteroid Impact: A massive asteroid, estimated to be about 10-15 kilometers (6-9 miles) in diameter, is believed to have hit the Earth near present-day Chicxulub, Mexico. The impact released an enormous amount of energy, equivalent to billions of atomic bombs.

2. Vast Ejecta and Dust Clouds: The impact threw up vast quantities of rock, dust, and debris into the atmosphere, forming a global cloud that blocked sunlight for months or even years. This would have drastically lowered global temperatures and disrupted photosynthesis.

3. Wildfires: The heat from the impact would have ignited global wildfires, further adding to the atmospheric dust load and altering climate conditions.

4. Ocean Acidification and Anoxia: The impact likely caused widespread ocean acidification and possibly localized anoxia (lack of oxygen), affecting marine life.

5. Volcanism: Coincidentally or not, there were also large volcanic eruptions during this period, particularly in the Deccan Traps in India. The lava flows and ash released could have further contributed to the extinction event by releasing toxic gases and contributing to climate change.

6. Food Chain Disruption: These events led to a collapse in the food chain, as primary producers (plants and algae) died off due to lack of sunlight and increased volcanic activity. This would have affected herbivores and, in turn, carnivores and top predators like the dinosaurs.

7. Survivors: Not all dinosaurs went extinct; the group known as birds is considered to have evolved from small, feathered theropod dinosaurs and survived the event. Other species, like crocodiles and turtles, also made it through.

In summary, while the asteroid impact is considered the primary driver of the mass extinction, it was likely a combination of catastrophic events that together led to the dramatic restructuring of life on Earth.