Mount Shinmoedake, ... , began...

This is something that people do mostly in written English and in the scripts for new shows. When you want to give extra information about something, you can add it in the middle of a sentence wih commas coming before and after it:

My daughter, who's been surfing for years and years, tells me that it's one of the best beaches on the East Coast.

The Essence Music festival, an outdoor concert series that's held anually in New Orleans, attracts a huge African American audience.

This phrase appears in these lessons: