trachyandesite

Porcellanite (Middle Miocene, ~11 to 14.7 Ma; Bučník Hill Quarry, near the town of Komňa, Czech Republic)
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 25
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 26
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 27
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 28
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 29
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 30
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 31
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 32
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 33
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 34
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 35
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 36
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 37
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 38
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 40
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 41
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 42
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 43
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 44
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 45
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 46
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 39
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 21
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 7
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 8
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 22
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 20
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 15
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 16
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 17
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 18
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 19
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 6
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 13
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 14
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 3
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 4
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 5
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 12
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 7
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 8
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 9
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 11
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 6
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 1
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 2
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 3
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 4
by James St. John

Glacially eroded & striated columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 5
by James St. John

Glacially striated trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 5
by James St. John

Glacially striated trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 1
by James St. John

Glacially striated trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 2
by James St. John

Glacially striated trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 3
by James St. John

Glacially striated trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 4
by James St. John

Glacially striated & polished trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, California, USA) 1
by James St. John

Columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, eastern California, USA) 66
by James St. John

Columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, eastern California, USA) 67
by James St. John

Columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, eastern California, USA) 68
by James St. John

Columnar-jointed trachybasalt (Postpile Flow, Upper Pleistocene, 82 ka; Devils Postpile National Monument, eastern California, USA) 69
by James St. John