Glass Mountain & Temple of the Sun - Lower Cathedral Valley
Glass Mountain is a gypsum dome with large crystals of selenite
Originaly the minerals were evaporated from seawater and deposited in the underlying Carmel Formation - 165mya
Gypsum under pressure flows like toothpaste. This gypsum found a path along a fault zone and squirted upward.
In a short time, geologicaly, water will dissolve these minerals and form a sink hole.