Ah, I always envisioned them as sort of natural magical eruptions, like sideways volcanoes only for various bits of magic flow rather than magma.Thats what lead me to thinking of them as unexplored sort of naturally occurring tunnels. I'm not sure how much of a fan I am of lost relic built gates. As opposed to say gates and things built around already existing wormholes. Naturally occurring nodes would also be in a constant state (thinking in geological terms and time scales here) of fluctuation with new ones appearing and collapsing. That was made me think they could either have feeding qualities for magical power or in their collapsing state a dampening power draining effect.