Simplify the following text for a Grade 8 native English-speaking person.
Original: The catastrophe developed over the course of several daysâ '' an initial earthquake and explosion of cinders and ash was followed some days later with the more forceful ejections of rocks and stones .
Simplified: The catastrophe increased in danger over the next several days . After the first earthquake and explosion of cinders and ash , another stronger explosion happened a few days later .