How would you explain this sentence?
A woman and four children are the only others who have come this same unimaginable distance, from Mexico City. Today when the train crossed a bridge over a high river gorge, she made the children sing for the Feast of the Kings so they wouldn’t cry. She took a rosca cake from her bag, crumbling out of its paper wrappings into the worn velvet seats. The family huddled together, locking their small holiday from the inside.
How would you explain the second to last sentence: crumbling out of its paper wrappings into the worn velvet seats?