Is it possible that the new earth may be quite arger than the current, old earth?

I only ask, because of the size of the new Jerusalem:

Revelation 21:1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.

  2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.

  16 And the city lieth foursquare, and the length is as large as the breadth: and he measured the city with the reed, twelve thousand furlongs. The length and the breadth and the height of it are equal.

The current earth has quite a lot of curvature within 1500 miles (12 K furlongs), so wouldn't that allow for significant wobbling, of as 12K furlong x 12K furlong city with a flat base?

The city is said to have foundations, apparently that will rest upon the ground?

There are gates and a wall, which would seem strange, if the bottom of the new Jerusalem is flat, while resting upon the current earth's curvature?

So, could the new earth be much larger, with a very flat portion of at least 12,000 furlongs by 12,000 furlongs?

Otherwise, the bottom of the city would have to be curved quite a bit, to fit evenly upon the current earth with its curvature, so that the gates could be entered at ground level?

Also, on the current earth, there is almost no oxygen, at the height of 12K furlongs.

So, either the atmosphere will be significantly different, or the new earth much, much larger, with O2 levels normal at that height, or both?

Resurrected people apparently won't have any problem with lower O2 levels, so perhaps on the new earth, people and birds can be up at 12K furlongs, without any problems.