Giant caves. How do they form?

In many fantasy works, the world typically has giant caverns that house entire civilizations and ecosystems that are (mostly) disconnected from the world above. However, this concept, at least in an earth and non artificial setting, is practically impossible.

With that in mind, what I'm asking is:

How can a system of large caverns form?

Some requirements to base our assumptions on:

• The cave system is made up of extremely large caverns (similar or even bigger to the Hong Song Dong as to support a thriving ecosystem. I already have a good idea on how the food chain works) which are connected with a series of smaller and more numerous tunnels and crags.

• Span at least half of a Pangea sized continent if possible.

• Have multiple, smaller conations to the out side world like little cave openings and rivers.

• Can last for as long as possible to allow an ecosystem to develop underground. Though parts of the system would fall and crumble overtime of course.

posted over 4 years ago

Seraphim‭

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