They are layed down in an instant, with a mathematical precision beyond any human capability. Alien entities create them in order to communicate directly to our subconscious, oftentimes about the impending polar shift.
http://www.nepanewsletter.com/circles.html
Now maybe I'll try a different website.
I've actually heard there is evidence this does happen, but maybe this is a bad resource
A little looney. Interesting subject...