Effects like the one you're talking about are almost always done in post production, because it's a major time saver.. simpler too.
It involves a few steps, and I'll try to list them as best I can here.
1) Render your final ground plane with a camera other than the default perspective one. You'll want to set one key to your camera so it doesn't move accidentally.
2) set up your particle or fluid system to displace the ground plane, I'll use particles as an example because they're a lot less render intensive and have a pretty good effect. Select your ground plane, and go to particles > emit from object. Set your emission type to surface. As I'm doing this, setting it to surface they were floating upward by default, but you may have to change it. For lifespan I changed it to random, lifespan 2, random 1. Depending on the size of the plane you might have to adjust the rate of emission. As the particle type I'd use cloud s/w. You can add fields like turbulence to alter the movement of the particles, but that's completely by preference.
On the particleShape1 node, add an opacity dynamic attribute, set to per particle, and assign a ramp to it, and then edit the ramp so the top is black, the bottom is black, and just a little bit up add a white section.. Something like this.
Top [B-----G---W-B] Bottom
The reasoning behind this is so the particles fade into existence, and fade out before particle death, so when you render it there isn't any popping. After you get all this set up to your satisfaction, render an image sequence using the camera you created earlier.
3) This step is assuming you have adobe after effects, as this is the only program I know how to do this in. Import your ground plane, and your image sequence. Make a new composition for whatever amount of time your sequence is, drop in your ground plane and then your displacement sequence. select your ground plane in the layer section, and go to effect>distort>displacement. In the displacement map options, set the layer to your image sequence, and then turn your image sequence invisible. You can tweak the maxes for horizontal and vertical displacement to your liking.
And that pretty much wraps it up. Feel free to drop me a line if you have any questions.
Eric
