Geological subjects: polygonal columnar joints in porphyritic rock, southern British Columbia
Spectacular large columnar joint/fracture pattern (pseudo-hexagonal) in feldspar porphyry. This rock may be an intrusion, such as a sill, that is comagmatic with the nearby lava deposits of the Eocene-age Marron Formation (i.e., intrusive magma and extrusive lava of the same general age and chemical/mineralogical composition). Location: a Highway 3 roadside outcrop near the town of Rock Creek in southernmost British Columbia, western Canada.
(This photo is part of a report I wrote in 2012, and is part of Assessment Report 34747 published online by the British Columbia Geological Survey.)
Copyright J.R. Devaney
Geological subjects: polygonal columnar joints in porphyritic rock, southern British Columbia
Spectacular large columnar joint/fracture pattern (pseudo-hexagonal) in feldspar porphyry. This rock may be an intrusion, such as a sill, that is comagmatic with the nearby lava deposits of the Eocene-age Marron Formation (i.e., intrusive magma and extrusive lava of the same general age and chemical/mineralogical composition). Location: a Highway 3 roadside outcrop near the town of Rock Creek in southernmost British Columbia, western Canada.
(This photo is part of a report I wrote in 2012, and is part of Assessment Report 34747 published online by the British Columbia Geological Survey.)
Copyright J.R. Devaney