Eli5 How did ancient drawings in caves survive thousands of years without wearing away completely?
In: Earth Science
1. Very little erosion since it’s in a cave.
2. The use of oxides for painting. For example, the ochre which is one of the most common pigments (in red, browns and yellows) is basically iron oxide. Since it’s an oxide it can’t oxidize.
3. No sunlight. Being in a cave the paint isn’t exposed to the bleaching effect of the sun (light, and especially UV radiation, will break down most pigmentation bonds over time. For example the US flag on the moon is almost certainly pure white by now).
4. What little rainwater that seeps down will actually act as a preservative. Travelling through the rock the water will carry with it hydrogen carbonate (HCO3) which leeches off as it travels down the rock wall and forms a protective glaze over the painting and protecting it from future erosion.
Latest Answers