You'll be lucky to get a clear shot of the Three Sisters rock formation across the valley like this, with mists and vapours taking their toll on clarity. Also this time of day affords far from the best light. Nonetheless, this gives a pretty good idea of what they look like.

As can be seen from the strata layers in the exposed rock, much of this area is composed of sedimentary rocks, particularly sandstone. The processes of erosion have washed away some of the surrounding rock leaving the three sisters exposed like this. I did see some commentary in the tourist centre indicating that the current state of the sisters is due to some stronger rock structures contained within them but that probably won't be enough to prevent the sisters from crumbling away as the (hundreds) of years pass.