The large rock of Panagia, which dominates the center of the settlement of Petra, is a volcanic structure called a volcanic neck.
Vents are tube-like conduits that channel fluid magma to the surface of the earth connecting them to the magma chamber, which is located inside the earth’s crust and feeds a volcano.
The volcanic neck of Petra, on which the church of Panagia Glykofiloussa was built, is a lateral volcanic conduit, which was fed with andesitic lava by the underground magmatic chamber of the Lepetymnos volcano.
The rocks that surrounded the volcanic neck were eroded after the end of the volcanic activity, while the andesitic lava, being more resistant to erosion, created the great rock of Petra.
