First: a trick. That is *not* the solution
Open the cracked earth, and place the face in a layer above it. See that the face layer is active.
Then, at the bottom of the layers pallette, click the f at the left-hand side. These are the layer effects. Choose the top option, Blending Options.
You'll see two sliders that look like theones from Levels. They are called ThisLayer and UnderlyingLayerThe arrows are a bit peculiar as they seem to be made out of two parts: a left one and a right one. This tells that there's something special.
Hold down Alt and drag the inner side (right on the left side, left on the right side) towards the centre. try this with all four arrows.
Amazing, no?
The result will always be a bit awkward because the face is a front view, and the cracked earth is in perspective.
But, you can use a sandwich to get an easy result.
A sandwich are two layers (in your case faces) and between them there's another layer (the cracked earth).
Normally, a face above the earth and multiply or darken blend mode gives you something, but the face is too weak.
When you copy the face layer and place it on top, and then set it to multiply, just like you also do with the earth layer, the face will have more power. Which is needed to start with.
But before you copy the face, go to the edit menu, choose Transform>distort and drag it wider at the bottom than at the top. This gives a bit of perspective.
Then duplicate the face layer and create your sandwich (face, earth, face) and set the two top ones to multiply.
Now desactivate all layers except for one face layer (unclick the eye icons) and open the channels pallette. The red channel has the best contrast. Copy this channel. Hold down Ctrl/Cmd whilst clicking on the Red channel copy. The channel image will load as a selection and you'll see the marching ants appear.
Activate your cracked earth layer and add a mask. The image will load into the mask as you turn the selection into a mask.
Now take the dodge tool, set to shadows and paint softly on the cracked earth layer (not the mask!) to soften the cracks intensity.
Then activate the mask (click on its icon and see the mask icon appear instead of the brush) and paint with 30%transparant black on the face to lessen the influence of the crack.
This is *a* way to obtain a result. There are others, but with this you'll learn a lot of tricks.