Rock
Tuff
Tüf
Volcanic ash turned to stone: the soft rock that made Cappadocia’s fairy chimneys and rock-cut churches possible.
Also known as: Volcanic tuff
- Building stone
- Important in Türkiye
In short
Tuff is a rock that forms when ash blasted into the air by volcanic eruptions settles to the ground and, over time, is compacted into stone. It is usually soft, light and porous, so it is easy to carve. The fairy chimneys, underground cities and cave houses of Cappadocia are carved into volcanic rocks of this kind.
Photos
How does it form?
Explosive volcanic eruptions shatter magma and hurl ash, pumice and rock fragments into the air. Particles smaller than 2 millimetres are called volcanic ash; this ash settles in thick layers and over time is compacted and cemented into tuff. The ash may rain down from the air, or it may be carried down the volcano’s slopes by glowing avalanches of hot gas and ash (pyroclastic flows). The often thick, pumice-rich layers left by these flows are called ignimbrite.
Cappadocia’s fairy chimneys
Volcanic activity lasting millions of years blanketed the Nevşehir plateau of Central Anatolia with thick layers of tuff and ignimbrite. As rain, wind and floodwater wear away the soft tuff, harder blocks or layers on top protect the tuff beneath them, leaving capped, cone-shaped fairy chimneys. Over the centuries people carved houses, churches and underground cities into this soft rock. Göreme National Park and the Rock Sites of Cappadocia were inscribed on the UNESCO World Heritage List in 1985.
What is it used for?
- Building stone: Light, easy to cut and a good insulator, tuff is used as walling stone in many volcanic regions.
- Pozzolan: Fine-grained tuff and volcanic ash react with lime and cement and make them stronger, so they are used as additives in cement and mortar. Volcanic ash was also used in the famous concrete of the Romans.
How to recognise it
- 1
It is usually pale (white, cream, pink or yellowish) and has a dull, earthy look.
- 2
It is soft: a steel nail scratches it easily, and some kinds even crumble under a fingernail.
- 3
Under a magnifying glass you can see small bits of pumice and glittering crystal fragments among the fine ash grains.
- 4
It can look like limestone, but it does not fizz in dilute acid.
Fakes and imitations
What shops usually don’t tell you:
- In everyday language “tuff” is also used for calcareous tufa, a porous rock deposited from lime-rich spring water; it is a carbonate rock unrelated to volcanic tuff and fizzes in acid.
- Cladding stones sold as “volcanic stone” or under local names may be very different kinds of tuff and ignimbrite, with very different resistance to water and frost.
Safety
Tuff is generally harmless. However, in some villages of Cappadocia (Karain, Tuzköy, Sarıhıdır) the tuffs contain erionite, a fibrous zeolite mineral, and breathing its fibres caused an epidemic of mesothelioma, a cancer of the lining of the lungs. Avoid cutting or digging tuffs that may contain fibrous minerals and breathing their dust.
Did you know?
Almost all of the moai statues of Easter Island (Rapa Nui) were carved from lapilli tuff quarried at the Rano Raraku crater.
In Cappadocia, the soft volcanic rock allowed people to carve houses, churches and multi-level underground cities into the rock.
Where is it found?
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- Göreme, Nevşehir, Türkiye · Major depositFairy chimneys and rock-cut churches carved from eroded layers of volcanic tuff; “Göreme National Park and the Rock Sites of Cappadocia” has been on the UNESCO World Heritage List since 1985.
- Derinkuyu, Nevşehir, Türkiye · Historic sourceA multi-level underground city carved into soft volcanic rock; one of the components of the UNESCO World Heritage site.
- Rano Raraku, Easter Island (Rapa Nui), Chile · Historic sourceAlmost all of the moai statues were carved from the lapilli tuff of this crater quarry.
Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →
Sources
- Tuff · Encyclopaedia Britannica
- Göreme National Park and the Rock Sites of Cappadocia · UNESCO World Heritage Centre
- Fire on Easter Island · NASA Earth Observatory
- A mesothelioma epidemic in Cappadocia: scientific developments and unexpected social outcomes (Carbone et al.) · Nature Reviews Cancer, 2007
External links
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Baryte
A pale barium mineral that feels surprisingly heavy in the hand; even its name comes from the Greek word for heavy.
Calcite
The main mineral of limestone, marble and cave stalactites: it fizzes in acid, and its clear crystals show everything double.