A couple things jumped out at him while studying these animations. “It is interesting to see the ‘greening’ of the mid-ring suburbs of the ’70 to the ’90s as the tree canopies matured,” he says. “This is in contrast to the concrete jungles of prewar neighborhoods and the virgin developments of the 21st century.” (Look again at Dallas/Fort Worth for a good example.)
A few other trends he noticed: Some cities, like Chicago and Philadelphia, grow lighter over time, an apparent consequence of newer, white-roofed buildings crowding out older ones with dark roof tiles. And the shrinking of water sources, whether manmade or natural, is a “sad site to behold,” Williams says. “On the other hand, the creation of artificial land in coastal metropolises is increasingly larger in scale (re: Shanghai).”
If one thinks that any sort of sprawl is bad because it takes up more land, leads to deconcentrated regions, necessarily leads to McMansions and more driving, or other reasons, the images of American cities may look bad. But, the animations of American cities show sprawl on a different scale than that of some global cities. The American regions show more filling in between existing settlements, particularly in more established Northaast and Midwest cities. Sunbelt cities may look more like cities in developing countries where cities have simply exploded rather than filled in.
It is also interesting to consider sprawl from this particular vantage point: via satellites. The average suburbanite might consider sprawl at a closer level; the nearby field that disappeared for a housing development, the increase in traffic as new residents add to the local congestion, the notices about cheaper houses on the metropolitan fringe. But, satellite images and maps help remind us of the broader nature of sprawl: if the region is a circle with the city in the middle, expanding sprawl moves out the outer ring of the circle, adding more and more square miles that is only generally bounded by a large body of water (or perhaps another metropolitan region).