The ancient underground cities of Turkey are dug into soft, dry ash above deep streams. Are there similar locations in North America that such structures could be dug/constructed?

  • 1
    $\begingroup$ Ancient underground city of Cappadocia, in Asia Minor (north-eastern modern Turkey). When those cities were built, the nearest Turkic language speakers were thousands of miles away... $\endgroup$
    – AlexP
    Dec 22, 2022 at 2:28
  • 1
    $\begingroup$ Are you asking of there's any geology similar to that in the relevant areas of Turkey? If so, please note that while you may be asking this for worldbuilding purposes, you're going to find more geologists over at Earth Science than there are here who might know better and/or more locations. $\endgroup$
    – JBH
    Dec 22, 2022 at 2:37
  • $\begingroup$ nps.gov/band/index.htm Is one place to start. Not as extensive perhaps… $\endgroup$
    – Jon Custer
    Dec 22, 2022 at 18:29

1 Answer 1


Yes, lots of places. The USA happens to host the largest supervolcano, Yellowstone, and every half million years (or so) it covers the US in a layer of ash. There are plenty of locations around Nebraska or Wyoming with deep ashbeds. . At its deepest it is about 200m thick, but generally it is much less than that, but still plenty thick enough for caves to be dug, if you are so inclined.

enter image description here

By Jim Peaco, NPS - Yellowstone's Photo Collection, Public Domain,

In the image you may see the "Lava creek tuff", ash from the most recent Yellowstone eruption (the pale band on the cliff face). There are streams in the valleys.

More generally the conditions for producing layers of volcanic tuff is not exceptional and can occur wherever there are volcanos that produce large "Plinian" eruptions. And there are plenty of other rocks that are soft enough to be dug with simple hand tools: Chalk, shale, mudstone and others.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .