A sinkhole is a hole in the ground that happens when the ground falls down into a hole.
Sinkholes can be scary because they can happen suddenly and without warning.
Examples:
The sinkhole appeared overnight.
Don't go near the sinkhole!
The sinkhole is very big and deep.
The sinkhole swallowed the car!
The sinkhole was so big, it could fit a whole house.
The sinkhole was like a big mouth, ready to eat anything that came near it.