Fulgurite - Sand hit by lightning. This picture is not Fulgurite by the way.This is a stick with wet sand on it.Fulgurite is usually found in the ground where lightning has struck and is usually very small glass tubules.
The portion pictured is known as the Cloud Ladder Hall. It has an area the size of 12 football fields, and the fog is so thick, it is difficult to see the 820 ft m) high ceiling. The ground is covered in vegetation.