How are those wide mogul fields created?  When a ski resort is first
designed or created, are the moguls created by bulldozers, snowcats or
some other man made device?  Or do they occur naturally as a result of
skiers repeatedly carving turns on a slope that is not groomed.

The information below appears at this link

  http://www.parkcitymountain.com/winter/menu_03/07_Mountain_FAQs/

Q: Where do you put the moguls in the summer?

A: Moguls are created when a run is left ungroomed and skiers and
boarders making turns through the powder cut up the run. The turns cut
grooves into the run and the accumulation of grooves turns into
?bumps? that are known as moguls.