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The holes in the ground appear to have been caused by air pressure (expanding methane gas), so perhaps the bubble analogy is apt.

tundra is peat

peat of made of decaying moss

moss is permeable like a sponge

sponges can hold stuff

stuff can change state with changes in temp/pressure

stuff in a new state can occupy increased volume

increased volume can cause increased pressure

increasing pressure increases temperature

changing the state of more stuff ...

(wavefront) path of least resistance contains most square inches with least circumference

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Caves are not created due to gas pressure neither are mountains. The former are the result of water flowing and solving weak rock, while mountains are the front of colliding tectonic plates.

In this case you have gas and mud.