Meaning of "to crack"

Geum-I-Ga-Da

to crack금이 가다#관계/연애#사회/이슈#마인드셋2010s Meme

This is a metaphorical expression describing how cracks form, much like a solid object splitting apart, or how relationships and trust gradually begin to fray.

"After they had an argument, a crack began to form in their relationship, and eventually, their attitude toward each other turned cold."