In Lord of the Flies, why does Ralph suggest that the group build a fire? how does Jack show himself to be irresponsible with the fire?

Ralph says that the boys need a signal fire going all the time. This excites the boys and they end up building an out of control inferno at the top of the small mountain. Jack starts the fire by taking, by force, Piggy's glasses. Jack compels the other boys to make it bigger.