The tenure requirements at my SLAC are maddeningly vague and intentionally so: calling only for "ongoing" scholarly activity, "good" teaching and a "committment" to service. They are used not to objectively evaluate the performance of a junior faculty member, but to keep around the people they like and get rid of the people they don't.
What is expected--and thus what the words "ongoing," "good" and "committment" mean--varies according to the academic year, the composition of the P&T committee, and the individual.
In recent years in my dept alone (English), a person who published ONE peer-reviewed article total (that's it... nothing else) was been awarded tenure. Meanwhile, another person who has multiple books out was denied. It is absurd, and corrupt.