describe the theories that scientists have developed to explain the events of the jurassic period.

Answer 1

You may be referring to the "anoxic event" which caused the disappearance of oxygen from oceans, or the "triassic-jurassic extinction" event, when most land life disappeared. You can read about them at
http://en.wikipedia.org/wiki/Anoxic_event
and
http://en.wikipedia.org/wiki/Triassic-Jurassic_extinction_event