Ridges are appearing on my lawns for past few years. They are approx 3-5 metres long, 3cms wide and 1-2 cms high. There are up to 10 ridges perfectly parallel to one another, in three or four areas of the lawn. There are no tree roots near them. I have dug up 1 square foot samples but can see nothing unusual underneath. They are extremely bumpy when the mower passes over them. Apart from the mower (with back roller). no machinery has been used on the lawn, but the ridges are so perfectly formed/parralel, they look mechanically created. What could cause this and how do I get rid of them?
A number of ridges have appeared on part of the lawn in early Spring. Approx 3 meters long and 1cm wide. What could have caused this and whats the best way to restore it back to an even surface.