Long exposure photos are so cool because they view things in ways your eyes never could. Digital Photography School has a great collection of long exposure images and the elapsed time it took for each image to come out. For some great images, I highly recommend visiting the site and looking at all of them.
Link Via MentalFloss
I've seen a lot of lighthouses in operation. The lens shoots out a single very powerful beam of light. A time exposure should show, one beam of light since the lens was not turning. After the lens is fired up a time exposure would show a large area of white everywhere the beam of light went. Just as Zo wrote. A multiple exposure would get the result in this photo. But it doesn't take the lens 2 minutes to make one revolution so it is still confusing. Unless the rotation was timed precisely and the camera lens was opened at exact times the individual beams would be in more than those places and wouldn't line up perfectly. Something is definitely not making sense.
It IS a beautiful picture though!
(not to worry, at my age a LOT of things don't make sense)