Simplify the following text for a Grade 9 native English-speaking person.
Original: The formation of the modern Andes began with the events of the Triassic and Jurassic when Pangea begun to break up and several rifts developed .
Simplified: The formation of the modern Andes began with the events of the Triassic when Pangea begun to break up and several rifts developed . It continued through the Jurassic Period .