I am having trouble finding a suitable word/phrase to describe the following situation:
If the middle of something is eroded away, it is hollowed out. What would be a suitable way to describe the creation of the same shape but through the sides growing upwards rather than the middle being hollowed out? Almost like two pillars growing on either side.
Another way that I visualise the same problem is to imagine a bar graph. If the middle bar stayed where it was but the two bars either side went up, what would be a good phrase to describe it?
Growth at the extremities?