Creating Explosion Effect

1.I start a new document 640x480.
2. Now open the mud image up, on the dirt image, do a CTRL+A to select all, then go to the new document you just created and press CTRL+V to paste the image.
3. The cracks are dark, so we'll invert the image so it becomes white, this will give it a better explosion effect. so go to Image » Adjustment » Invert (or press CTRL+I).
4. Now use the eliptical marquee tool and make a large round selection on the image. Hold SHIFT while you create the selection to make a perfect round circle.

5. Now go to Select » Inverse,
Then hit Delete so you are left with a circle from the mud image. DO NOT DESELECT YET.
6. Now, while you still got your selection, go to SELECT » INVERSE again to select the shape.
7. Now go to Filter » Distort » Spherize. Set amount to 100%. Then do it again, this time, 50%. You can now deselect.
8. Now, lets fill the background layer (the layer underneath the mud layer) with black.
Then go to Layer » Flatten Image
Now go to Filter » Sharpen » unsharp Mask.
Amount: 500%. Radius: 1.7px. Threshold: 122 levels 9. Go to Filter » Distort » Polar Co-ordinates.
Options: Polar to Rectangular.
10.Go to: Image » Rotate Canvas » 90CW.
11. Apply: Filter » Stylize » Wind
Method: Wind. Direction: From the right. Hit CTRL+F to reapply
12. Go to: Image » Rotate Canvas » 90CCW
13. Finally, apply Filter » Distort » Polar Coordinates.
Options: Rectangular to Polar.14.There you go, now all you do is just play around with colors, by either using Image » Hue and Saturation, or Image » Color Balance.
I use color balance in the image below