Lol I'm guessing you maxed out the dimensions slider... I did that the first time
I've never personally tried it, but I've heard that when you mess with dimensions after placing objects they get shifted around with it.
My take on it is live and learn... start over but have the sliders at like 1/10th of how far up they can go
That should be more than enough to make a normal map
Change the outer terrain to snow, silly.