Is it possible for people to carve tunnels and caves into a mountain that used to be a volcano?

This volcano has not erupted for several thousand years, so is considered extinct by all civilization. The carved-out volcano/mountain is used as a temple of some sort. The society that lives around the area now have Medieval-Renaissance level technology and small access to elemental magic.

Will the extinct volcano be made of rock or dirt or have streaks of obsidian running through it? What would be the conditions inside any tunnels/caves carved into this ex-volcanic mountain if it is at all feasible to do so?

EDIT: I assume that this possible. Ideally an answer will explain what the possible (or likely) geological composition is and the possibilities of how to deal with this using Medieval-Renaissance technology.

  • 1
    $\begingroup$ Do naturally occurring lava caves count? $\endgroup$
    – HDE 226868
    May 31, 2016 at 0:16
  • $\begingroup$ @HDE226868 they could definitely be included into the design, thanks. $\endgroup$
    – Theyna
    May 31, 2016 at 0:28
  • $\begingroup$ Why do you think it would NOT be possible to carve tunnels and caves into said mountain? Assuming there's no lava in it, wouldn't it just be the same as a normal mountain? $\endgroup$
    – Aify
    May 31, 2016 at 1:23
  • $\begingroup$ @Aify I assume that it is possible, I am looking for some outside justification for that assumption. In order to obtain this I am asking for answers to explain what the possible geological composition is and the possibilities of how to deal this with Medieval-Renaissance tech. I will add that to the question. $\endgroup$
    – Theyna
    May 31, 2016 at 1:45

2 Answers 2


Yes, but it is potentially more dangerous than digging in a regular mountain

Depending on how long the volcano has been dead, the ground in the region is still hot, and the temperature rises rapidly with depth, making any tunnels you dig very hot. To worsen the conditions even more, the typical medieval and renaissance way to mine consist of fire-setting, making the it even hotter, and adding a mix smoke and partially burned materials to the air. Your workers are not likely to last very long, so the digging is quickly going to become an unpopular job. There may also be randomly located bubbles of gas, that can make the workers suffocate at several occasions. In general, not a healthy place.

Will the extinct volcano be made of rock or dirt or have streaks of obsidian running through it?

Geologically, it is hard to tell if it is going to be a more difficult type of rock to mine inside the volcano, as you may find anything in the range from tuff to basalt. As for obsidian, it is a volcanic type of rock, so a dead volcano is the right place to try to find it. There are not obsidian in every volcano though, as it is typically found in streaks with just the right silica composition.



In the Stephenie Meyer book; The Host, the protagonists uncle found a underground tunnel system created by a dormant Volcano. A simple google of tunnels created by dormant volcanoes brung up Lava Tubes, something that a medieval tech could both easily find and capitalize on. enter image description here

They are not even exclusive to Earth! Lunar lava tubes have been discovered and have been studied as possible human habitats, providing natural shielding from radiation. Partially collapsed, Martian lava tubes are visible as chains of pit craters.

Personally I suggest making a follow up question of why they would use these as there is nothing stopping them.


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