In Nevşehir the rock cuts by hand and a hard cap saves each column

The first thing said about Cappadocia is that it looks like another planet. It is a useless description, because it explains nothing. What is here is a reasonable consequence of two very concrete facts: a rock that is too soft and some hard layers on top of it.

And from those two facts comes everything else, including what people did with the landscape over the last two thousand years.

01 Hundreds of metres of ash

This part of central Anatolia is ringed by extinct volcanoes. The two big ones are Erciyes, at 3,917 metres, and Hasan, at 3,268, and between the Miocene and the Pliocene, that is between about ten and three million years ago, they threw out enormous quantities of ash, pumice and lava.

The material fell on the plateau and built up into deposits several hundred metres thick. As it compacted, that ash became tuff: a light, porous, weakly cemented rock.

But it was not one eruption, it was many, and of different kinds. Between the ash layers, levels of basalt, andesite and welded ignimbrite were interbedded, and these are far harder. That alternation is the key to everything you see.

02 The cap that saves the column

The mechanism is called differential erosion and is so simple you can verify it at a glance. Rain, wind and freeze-thaw cycles take away soft tuff at one speed; basalt or ignimbrite at a much slower one.

Where a hard block is left on top, it works as an umbrella: it protects the tuff directly beneath while the ground around it drops. The result, after many thousands of years, is a column with a block on top. That is a fairy chimney.

The rule should not be overstated, because the landscape itself qualifies it. In an inventory of localities with chimneys, 28 per cent are dominated by capped forms, 40 per cent by uncapped ones and 32 per cent mix the two. Those without a cap will eventually disappear.

And there is an altitude band: chimneys occur between 600 and 1,800 metres, averaging around 1,220. Below and above that band the erosion conditions are different.

03 A rock you can cut with hand tools

The second consequence of tuff is not geological but constructional, and it explains the other half of the landscape. This rock is soft enough to be dug with adze, pick and chisel, without explosives and without machinery.

One person can open a room. A group can open a whole house, with several chambers, niches, a hearth and a stable, and do it without transporting a single block or raising a single wall.

And there is one property that clinches it. Freshly cut tuff is softer still, and once exposed to air it hardens at the surface. That is: it works easily and then holds. Few rocks offer that combination.

04 That is why here you do not build: you hollow

From this comes the architectural peculiarity of the district, and it is worth stating properly: here construction is subtractive. Almost everywhere else you build by adding material; in Cappadocia you build by removing it.

That has advantages you notice in a continental climate like this one. Rock is an excellent insulator: an excavated room stays cool in a summer with average highs of 29.4 degrees and mild in a January whose average is zero.

And it explains why the same resource was used for everything. Dwellings, stables, stores, dovecotes, cellars and underground chambers on several levels are the same technique applied to different ends. The whole landscape is riddled.

05 What the material does not forgive

The counterpart is that a rock that cuts easily also breaks down easily. Tuff disintegrates with water and with ice, and in Nevşehir the January average is exactly zero degrees: the freeze-thaw cycle runs at full tilt every winter.

That is why many excavated façades are split today, with the front fallen and the rooms open to the outside. What you see in several valleys is not ruin through abandonment: they are fresh cuts produced by the collapse of the front.

And it is why some chimneys are propped or closed to the public. The process that formed them is still running, and on a human timescale, not a geological one.

06 How to travel it

The first practical consequence is that the good route is inside the valleys, not along the viewpoints above. From the rim you see the silhouette; from the floor you see the layers, the caps and the fresh breaks, which is where the explanation is.

The second is to look at the cut faces. Every valley offers dozens of vertical sections with the full sequence of eruptions on view, and the hard band that produces the chimneys is identified without effort once you know it is there.

And the third changes the whole trip. If in front of every cone you ask whether it has a cap or not, you stop seeing a strange landscape and start seeing a process under way: a few thousand columns at different stages of the same countdown.