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"Extraordinary claims require extraordinary evidence." This dictum
from Carl Sagan applies quite well to the recent claim, as
chronicled in NOVA's "Mysterious Life of Caves," that microbes
feeding on the deadly gas hydrogen sulfide long ago excreted
sulfuric acid that helped carve out
Lechuguilla, Carlsbad, and
other otherworldly caverns. Bacteria dissolving rock? The idea
seemed absurd, until geologists and microbiologists working in a
still-growing Mexican cave provided the "extraordinary evidence"
needed to convince skeptics.
As remarkable as this process is, it is only the most unusual of
several principal ways that caves form. Other ways include mildly
acidic rainwater eating away limestone caverns, ocean waves scouring
out sea caves, and lava forming long tunnels called lava tubes. In
this feature, follow along as each of these four agents go about
making caves.
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Flash is a plug-in that allows for increased
interactivity. If you can see the animated boxes at
left, the plugin is already installed. If you do not see
the boxes, you can
install the Flash plugin, or select this feature's
non-Flash version.
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