en: cliff dwelling
es: cueva en escarpado
fr: habitation troglodyte
it: abitazione in caverna
Man needs a shelter as a protection against weather, wild animals and enemies. Our ape ancestors lived on trees, and were good in climbing and hiding. They had a fur against bad weather. But during our evolution we lost several abilities, and replaced them by manual abilities and tools we invented. We developed clothes, shoes, upright walking and artificial caves.
|Image: Cliff dwellings, Mesa Verde National Park, USA.|
In a certain way, houses are artificial caves. Only the inside skin of the cave, without the massive rocks around. Many people feel this way about their home, even today. But houses are difficult to build, we need appropriate material and certain tools for it. The digging of caves is often a bit easier. You need only something to dig with, depending on the softness of the rock, a wooden stick might be enough.
The most famous cave houses are probably those in the loess plains of China. During the Ice Ages, the Gobi desert was cold and windy, and the glaciers eroded an enormous amount of rock by milling and grinding it time after time, thus producing a very fine rock dust. This dust was blown away by the wind to an area with a little bit of vegetation. Here the wind was hindered and lowered, and so it lost the dust. During ten thousands of years enormous layers of this dust were sedimented, with a very special characteristic: the fine dust was easy to dig, but although it is only fine sand, it does not cave in or flow away as normal sand does. And that is the easy explanation why people decided to build caves into this rock: it was much less work than building a house.
There are many other rocks all around the world allowing artificial caves. Very good is volcanic ash or tufa. Formed in huge layers during eruptions, the lava had such a big content of gas and liquids, that it nearly exploded, once it arrived at the surface. Fine pieces of lava, or lava with small but numerous porosities was formed. The resulting rocks are soft and it is possible to cut caves into them.
A third typical rock for cave houses is sandstone. This is a sediment, sand produced by erosion and transported by wind or water. This sediment is a rock, formed on the continent. The sand is lithified by the ground water, water flowing slowly through the pores between the sand and transporting dissolved minerals. Typically calzite or quartz are accumulated in those pores connecting the sand to a hard rock. If the lithification was not completed, the cement is too weak or it is removed by erosion, some sandstones become soft and are suitable for artificial caves too.
Of course, modern machines allow the construction of tunnels in any material and very efficiently. So the construction of cave houses is still very usefull in areas with suitable rock formations. And it is extremely usefull in hot arid areas, where the temperature underground is rather pleasant. A good example for such modern cave houses are the so called dug-outs at Coober Pedy in Australia.