퍼지다 is spreading of its own accord — news, fire, a chain of shops, alcohol through the body, people opening out in a formation — with -게 giving the manner or speed: 불처럼 빠르게 퍼져나가 'spreads fast like fire', 알코올이 느리게 퍼지고 'the alcohol spreads slowly'. It is also the standard word for food losing its shape: 흐물흐물 이렇게 퍼져요 'they go soft and mushy', which is what happens to overcooked noodles.