The imagery and word choice that is used to describe what could only be an atomic bomb detonation made things ver yeasy for me to visualized
for the snap, the bite of light
the beggining fuse that flames like fireflies,
Clearly she is focusing on the sudden brilliance and magnitude of such an explosion. It starts from something very small which is is evident by the bite of light, and it is very sudden just like a snap. Then just as a fuse leads to something much bigger, this snap is leading to something big, potentially deadly and/or hazardous. She uses plenty of other words as the poem goes on to describe that what is coming as a result of this fuse is bad or will definately have consequences.
The title of the poem, and the use of the pronoun he and him gives us a peak at what the actual theme of the poem is. It has to be about someone coming to the dreaded age of 16. I know that I was definately a handful for my mom when I finally turned 16. Getting my drivers liscence being the biggest of these, and being able to go off and get into trouble on my own.
Terresa is probably a mother, and from her perspective it happens all of a sudden, when someone turns 16 they suddenly become a time bomb of trouble. She doesn't know how to describe what makes it happen, but that when it does happen it can be big and startling, but as I'm sure my mom did as well, the poem suggests shut your heart and hold onto the scraps that remain, because it's not time to give up and lose hope on these teenagers.