sentences:  The monocline is a sloping bend that raises the sandstone well above where it is expected to be seen, and this is why the whole of the visible top of the Blue Mountains is made of sandstone.From the beginnings of the colony in 1788, settlers and convicts had to work with the stone, using it for building and trying to grow crops on the soil over it.The sandstone had a negative effect on farming because it underlay most of the available flat land at a very shallow depth.