Cup shake is often associated with other forms of shake, and not infrequently shows traces of decay.
The causes of cup shake are uncertain.

The swaying action of the wind may result in shearing apart the growth layers, especially in trees growing in exposed places.

Frost may in some instances be responsible for cup shake or at least a contributing factor, although trees growing in regions free from frost often have ring shake.

Shrinkage of the heartwood may be concentric as well as radial in its action, thus producing cup shake instead of, or in connection with, heart shake.
A local defect somewhat similar in effect to cup shake is known as _rind gall_.

If the cambium layer is exposed by the removal of the entire bark or rind it will die.