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Images of lava tube caves.
Indian Tunnel skylight
Visitors scramble up a rubble pile left by a collapsed portion of the ceiling -- or "skylight" -- in Indian Tunnel.
As lava cools it becomes brittle. When it collapses it can reveal hollow passages below.
Indian Tunnel 1
Visitors peer into Indian Tunnel skylight at Craters of the Moon National Monument.
Indian Tunnel skylight with visitor
Skylights -- collapses in the cave ceiling -- provide natural lighting in Indian Tunnel.
Indian Tunnel with visitor
At over 800 feet long and 40 feet tall, Indian Tunnel is the most popular lava tube cave at the monument.
Lava stalactites form when lava is still flowing through the tube. As molten portions of the ceiling drip downward some portions cool and harden, forming stalactites.
Indian Tunnel Entrance
The 800-foot long Indian Tunnel lava tube is accessible by a metal staircase and rock steps.