Blew the top off the motor when starting

[Liquor Box]

My Monte turned over 3 times then exploded. Blew off the plastic part at the top of motor. Not sure what to call the part that burst but its plastic over the intake? What is the part and why would this happen? Car ran fine prior to the explosion.

 

[zora]

It's called an engine cover.
Very difficult to tell you why it happened without seeing the car.
Do you smell gasoline?