The International Association of Amusement Parks and Attractions estimates that about two billion people will visit amusement parks this year eat junk food, experience exciting thrill rides and just let loose.

In the U.S. alone, there are over 400 theme parks generating about $55 billion in annual revenue.

But having fun is a serious business.

Most of the adventurers will have an amazing time-- but some will get hurt. The number of significant incidents has risen in most of America’s major theme parks, the Amusement Safety Organization reports. Some accidents are the fault of rider, but sometimes the park is to blame.

Read on to learn more about some dangerous events at American theme parks.