6-Apply Images -- Adjustments -- Threshold set the slider to about 70 or to your liking

 

7-Copy this layer and place it on top then apply Filter -- Other -- Offset set right and down pixels to 1 and Undefined Areas as “Wrap Around”

 

8-In the Channels palette click on the Red channel while holding down the Ctrl key. This will select the white area on the offset layer

 

9-In the Layers palette disable visibility for the top layer (offset layer) and highlight the layer below it so that we can work on it. This should be the original un-offseted threshold layer. Now press the Delete key. Most of the white area except for the un-offseted white will become transparent allowing the original image (the bottom most layer) to be seen between the cracks. The remaining white appear as the highlighted uplifted edges of the dried cracks. This layer now becomes our crack layer.

 

10-Reduce opacity of the crack layer to about 25% or to your liking