San Diego, CA
Devils Postpile - Nature And Science
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© Christine Till - CT-Graphics
Sixty-foot columns of basalt rise like organ pipes above pine forests on the western slopes of the Sierra Nevada Mountains near Mammoth Lakes in California.
Devils Postpile is a reflection of fire and ice. The eruption and uniform cooling of basalt lava created an impressive wall of columns. Later a glacial event exposed the columns and polished smooth the top of this formation enhancing the pattern of hexagons that are a result of the mineral composition of the lava. A hike to the top of the National Monument reveals not only a cross section of the posts, but interesting effects of the ice - the polished and scoured tops of the rock columns. The polygonal column-ends are exposed like a tiled floor, and exhibit shining surfaces where the ice polished them with fine silt; parallel striations and grooves show where the glacier dragged rocks across them.
Though Devils Postpile is not the only example of columnar-jointed basalt, but it is one of the finest.
April 5th, 2011
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