This sign is located at the bottom of the stairway on the Big Obsidian Flow Trail.
Marker Name: A Glass Menagerie
Marker Text: Why is everything glass? Whether natural or synthetic, the primary ingredient in glass is silica (silicon dioxide). The obsidian and pumice of this lava flow contain about 73% silica, like most window glass does. In a hot, molten state, silica’s atoms tend to stick together and create webs of molecules that slow down the movement of all atoms. The surface of this lava flow cooled off before its atoms had time to organize into crystals, so we are left with glass instead.
The entire surface of this remarkable flow is glass, a liquid that cooled without crystallizing. The striking differences you see from rock to rock are due to the number and size of bubbles.
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