https://fbcdn-photos-a.akamaihd.net/hphotos-ak-snc6/263368_2305551364631_1424696117_32764764_1202075_s.jpg Sorry for the long link Reply
They are volcanic rocks of the Bear Lodge mountains; same igneous plugs as Devils Tower & many others in the area. Reply
I would call those “Fairy Doors” =)
https://fbcdn-photos-a.akamaihd.net/hphotos-ak-snc6/263368_2305551364631_1424696117_32764764_1202075_s.jpg
Sorry for the long link
What were these rocks originally, before the ravages of time?
They are volcanic rocks of the Bear Lodge mountains; same igneous plugs as Devils Tower & many others in the area.