And this estimation is made without considering other types of caves, like, for example, inside glaciers or even volcanic caves, which are not karstic, but are formed by lava flows.
しかも これに含まれない 洞窟もあります たとえば氷河内の洞窟とか 火山性の洞窟 — カルストと違い 溶岩流によってできます