If you had posted this a few months ago I could have hopped on my bike and ridden over to find out what the heck they are. Now I live 700 miles away. Too far to bike. {8^)
I know they are not visible from Asbury/Anderson road.
The circles are orderly -- either in a triangular pattern or aligned along the river. Looks like there were once storage tanks (or silos?) there. Vegetation clustered around the edges of the tanks before the tanks were removed, and since then vegetation and has taken over the spots. If my theory holds, this has been quite a while since it looks like either the structures were dirt-floored or else erosion has caused the dirt to cover them up. One of the circles has a hatch-mark appearance in its center, which suggests a man made floor. There are also access paths to each circle further suggesting man-made -- note that many of the vegetation circles have "cuts" in them corresponding to a path, suggesting that whatever was there was still being used/maintained after much edge vegetation had grown. The south end of the main road ends at a slab near the river that looks like it might have been some sort of loading/offloading platform. Also north of the tanks there is a square indicating a former building on that road. Finally it looks like this land is still fenced off judging from the dark line at the entrance at the circle on the north end of the access road.
I lived in that part of NJ for 20 years and had no clue this ever existed.
Anonymous
@ 2009-04-15 10:26:01
Similar and possibly even more curious circles found in the vicinity of Sunburst, Montana.
Anonymous
@ 2012-06-01 16:58:38
The circles in the Google Maps image are all that is left of the Tidewater Oil Company pumping station that was located three tenths of a mile from the bridge over the Muscanetcong River at Changewater, NJ. The pumping station was on the south side of the river, the tank farm on the north side. As a child I lived for a short time in Tidewater company housing and walked all over the property. The tanks were "guaged" daily to determine the volume of oil in the tanks. This involved climbing up a ladder-like staircase on the side of the tank, throwing open a hatch and lowering a weighted tape to the bottom of the tank, then reeling it up for a reading. Communications up and down the pipeline were by telegraph. There was a foot bridge over the river just to the west of the pumping station.
Anonymous
@ 2019-04-30 11:47:50
Tidewater Oil Company had a pipeline from Oil City PA to Linden NJ until at least the 1950's. To facilitate the movement of oil from Oil City to Linden there were a series of pumping stations along the way. Changewater, NJ had one of these pumping stations. This site may be the remnant of that pumping station.
Misc, Info Requested 
I know they are not visible from Asbury/Anderson road.
http://www.clocations.com/cviewmap.aspx?list=region&state=NJ®ion=High%20Bridge&lid=1132802
http://www.topozone.com/map.asp?lat=40.735275&lon=-74.950147&datum=NAD83&u=5
http://books.google.com/books?id=8eQKAAAAYAAJ&pg=PA112&lpg=PA112&dq=changewater+tidewater&source=web&ots=KoDV519pk7&sig=GNtZfXyuZM2QvOIG4pDJ16Fq9W4
"There is also a pumping station of the Tidewater Pipe Line Co., at which 7 men are employed".
The pipeline ran from Rixford PA to Bayonne NJ. There is a forthcoming documentary on the Tidewater Pipeline.
I lived in that part of NJ for 20 years and had no clue this ever existed.