Sorry for the misspelling Philippe. As demo users maybe don't have tutorials, here a little idea. Take a terrain (with lava), animate it to 3-5 seconds (i.e.), then open the material editor for the terrain material and change it to a different one. Vue will ask you then if you want to animate the terrain. Say yes. Then again create a new keyframe, change the material and so forth.

You find lava terrains in our backroom above. See free material and search for material by Zoon.