Far from being solely an “impact crater” as implied by Clifford Tan and The Star; the 6m deep crater which Lim's car had “sunk” into was a cave-in (collapsed) crater, a consequence of both deep impact and existing underground weaknesses like erosion voids beneath the road foundation. The volume of upheaval mass did not equal the volume of the observed crater.
There are significant differences. An impact crater on solid ground would have the typical bulge (upheaval) at the peripheral of the crater (as in a meteor crater) and have the impact debris thrown all around it. Remember the Conservation of Mass law?
In fact all the evidence point to an additional cave-in collapse of an existing undetected below the road foundation void (underground cavity). Underground cavities ranging from a few inches to a few metres, can remain undetected on the surface due to the “arching effect” of the overlying supporting 'roof layer”.
Knowing Penang so well, there are probably a lot more cavities caused by underground erosion. That explains the “missing masses” in sudden cave-ins or collapsed sink holes. Macalister road is one of the oldest road in Penang and was already “warping” here and there when I was a boy cycling to school. The layers of bitumen and road foundation added through the years helped to strengthen the “roof support” and kept the road from caving-in until the forceful impact of the falling concrete beams and lightning arrestor.
Another sinkhole appears at lightning arrester collapse site
Thursday September 12, 2013 MYT 7:19:34 AM
Sinkhole opens up near site of lightning arrester collapse