Google Earth - how it opens the eyes!
Just so! Tell you something else that will make you scratch your head - a relief map of North America. Even more localized relief maps yield some curious patterns. Such as, I suspect for most people, great amounts of moving water would be the first impression that would come to mind as a cause. We've all seen what creeks and rivers can do to the landscape; apply that on a much larger scale and, well, the scientific community™ will just have to work a little harder at explaining it to the unwashed. Of course expansion(?) cracks are everywhere.