And… even after that, after winter has passed and spring has come, there may be bitter disappointment. Where there was once a familiar stone with drawings, it will not be. It will be covered with sand, or it will be turned down by ice flow, or it will be covered with other rocks. … The cut-out grooves of the petroglyphs are often almost indistinguishable in character from the porous and bubbly surface of the basalt. The researcher is often in danger of mistaking artificial recessions for those resulting from the work of the elements, the weathering processes and the mechanical damage that occurred in the distant past. The petroglyphs themselves, due to their deep antiquity, in color and hue are indistinguishable from the natural surface of the stone…»