The track was ground a few weeks ago to get rid of a bump in the asphalt section. Apparently the asphalt cap was too thin in that section and the grinding made it even thinner. It appeared to be okay until the big Top Fuel slicks started to work on the thin cap, breaking it up. While they were cleaning up the oildown, they noticed a lot of gravel and looked for the source - which turned out to be the track surface breaking up. When they started, they though the repair would be limited, but the area outside the first cut started breaking up when they ground the middle of the track away, so they had to widen the cut to eight feet and take it all the way down the asphalt.
Some cars have gone almost to the finish line under power, but in the interests of safety, they decided to use the freshly paved area as a shutdown area instead of racing across it.