What happens when one spouse just up and leaves the marriage?

Yes, abandonment is a fault ground for divorce. Abandonment is also known as desertion, a term with very unfavorable connotation.

Abandonment means that one spouse has left the other without consent, but like adultery proving desertion means more than that a person left home without the consent of the other spouse. Most states require that the defendant left home for a year or more; that the parties failed to agree about the departure; that plaintiff failed to pay support; and that the departure was not caused by the plaintiff.

Many times spouses abandoned marriages because they could not get a divorce any other way. For example, at one time Ireland prohibited divorce, and unhappy spouses, unable to end a failed marriage, walked out, leaving abandoned wives and children in poverty. By abandoning their spouses, however, they got what the wanted: an escape from a bad marriage.

Abandonment is not the same as separation, trial or permanent, which in most cases happens as a preliminary to a divorce.

Like adultery, alleging desertion appeals to some women who seek a moral vindication because they can say, "He left, he does not pay, and I didn’t do anything wrong to make it happen."