Petrified Forest, Grand Canyon, and Sunset Crater

[jl_reed]

May 11, 2005

Comments

Volcanic gases

[anonymous]

Hi Justin: How about elaborating a little bit on that comment that the color of the volcanic rocks depends on the gases being released during the eruption? What, exactly, does the really bright red color of many of the layers reflect -- given that (to my knowledge, at least) oxygen is not present as a free gas in volcanic emissions? jft

Re: Volcanic gases

[jl_reed]

The rocks are red because of the gypsum that is present. Although oxygen is not present in the actual emissions, sulfur is and it combines with the atmospheric oxygen, which causes the gypsum to form. I think that is how it forms. Let me know if that sounds like a correct explanation.