Was re-reading Verne's classic 19th century work and was left wondering. I realize that vast seas and antediluvian monsters in the interior of the earth are out...I think. However, I've always been intrigued by the idea of extinct volcanoes offering egress deep into the earth as was done in the novel. Has there ever been a case where a passable (not a steam vent) tunnel or fissure has been found extending deep into the central vent of a extinct or dormant volcano? Or does the inevitable cooling of the lava plug make it geologically impossible?

I hear you there; I love JTCOTE, as wild and corny as it is...

Re your question: I doubt it; it would seem that if you go deep enough in any inactive vent, you'll get blocked by a solid lava plug, or debris shed from the crater walls what have you. Perhaps a lava tube would be passable for a distance, but I'm sure that even it would run into a dead end, and not far below the surface, at that.

But hey, I'm no volcanologist, and the world's a big place...

__________________
"Call me old-fashioned, but I think fire is magic. And it scares me a lot."

--The State

I finished re-reading it myself a couple months ago.

Not quite the same, but I went to grad school with one of the people, who set the cave depth record for the Americas in 1994, 1475m down.

As of late 2005, the world record is 2,140 meters, at Voronya Cave in Abkhazia, Georgia. That's not even close to the center of the Earth.

Thanks for the feedback all. An odd question I know.

Romanus: That's kinda what I figured. Any fissures or tunnels that did exist probably wouldn't extend much deeper than the summit. Unlike the virtual subterranean highway that existed for Professer Lindenbrock & Co. under Mt. Sneffels. You do wonder how some medieval Icelandic alchemist preceded them centuries before, alone and without the benefit of electric light.

I know that in Hawaii lava is fluid enough to travel great distances, especially if it is transported through lava tubes. Lava tubes may be preserved when the eruption ends and the molten lava 'drains' away to leave open tunnels. They may be as much as several tens of feet in diameter, and some have been followed by spelunkers for nearly 10 miles. However, these are usually roughly horizontal tubes I believe, otherwise the lava couldn't drain away.

hhEb09'1 and Squink: Interesting reads. Sounds like Voron'ya may have to wait to be further explored given the problems in the Caucasus. You wonder how far spelunkers will eventually penetrate before heat (or a guy with a pitchfork) becomes an issue.

This list, WORLDS DEEPEST CAVES Compiled by: Bob Gulden says it is up-to-date as of Feb. 12, 2007, and still lists Voronya as the deepest.

Ahh, but they've gotten 30 meters deeper
2170.0 meters!