Okay, so a long, long time ago, before even dinosaurs were around, there was a big rock floating around in space. This big rock was really, REALLY big - like, larger than any mountain you've ever seen. And it was just minding its own business, floating around and doing space stuff.
But one day, this big rock decided to visit our planet. It came hurtling through the atmosphere and crashed into the Earth really hard - so hard that there was a huge explosion! This explosion was so big that it caused a giant hole in the ground where it landed. This hole is called the Chicxulub crater.
Now, the Chicxulub crater is really, REALLY huge - so big that it's hard to imagine just how big it is. But scientists have studied it and they say that it's over 110 miles wide! That's even bigger than the state you live in!
The weird thing about the Chicxulub crater is that it happened a looooooooong time ago - like, millions and millions of years ago. So none of us were around to see it happen. But scientists can study the crater and figure out what happened. They say that when the big rock crashed into the Earth, it caused a lot of problems. It made a huge explosion, and caused a lot of earthquakes and fires. It even caused a lot of rocks and ash to fly up into the air, and some of them circled the whole planet!
This huge event caused a lot of changes to happen on the planet. Some animals, like the dinosaurs we always hear about, were completely wiped out! And some other animals had to adapt to the new environment in order to survive. But even today, scientists are still studying the Chicxulub crater to learn more about what happened so long ago.