Has any one ever seen an effect like this?

Forest fires? OK, that's a very long stretch, more likely Industrial Light and Magic.:)

Looks like early morning mist which having formed is being lit by a rising sun. Could be sunset, but much less likely in my experience. The thing I'm struggling with more is the intensity of colour, on which he's either been very fortunate or else it's seen some work. He's done well to avoid flare too.

David's guess is mine, as well: morning fog.

Looks like nicely light morning fog like the others said and pumped up and glowed in post production. It may be an effects program add on to PS or stand alone perhaps.

Thanks folks. Just looking for opinions. I've seen a lot of nice landscape photos but never have seen valleys glow to this extent.

Looks to me like sun through morning mist assisted quite a bit with photoshop. You can get some great effects in these circumstances (without PS). Here is one I shot with early morning sun coming through sea mist on the North Sea coast, UK.

Colin. Very nice. Reminds me of the feeling from viewing a Turner landscape painting - something like "sunrise with sea monsters" etc.

I've seen the morning sun light up the fog and make it look like its on fire.

Yes, it's morning light filtered through fog. The author mentions using Levels and enhancement in Photoshop. I hate to create a controversy, hwvr it appears the copyright info on the image displays a name that is different from what is shown on Photoblink.