Posted by Eric A. Rosen on September 13, 2006 at 11:59 AM
The Devils Postpile formation is a rare sight in the geologic world and ranks as one of the world’s finest examples of columnar basalt. Its columns tower 60 feet high and display an unusual symmetry.
Fewer than 100,000 years ago, basalt lava erupted two miles upstream from today's postpile. The lava flowed into the valley and pooled to a depth of 400 feet. The mass of molten lava then began to cool uniformly from top to bottom.
As it cooled and contracted, stresses built up in the basalt rock causing it to fracture. Each crack branched when it reached a length of about 10 inches, joining other cracks to form a pattern on the surface of the flow. Under ideal conditions, surface cracks deepened to create the vertical, hexagonal columns you see today.
Some 10,000 years ago a glacier flowed down the Middle Fork of the San Joaquin River and overrode the Postpile formation. The moving ice quarried away one side of the postpile, exposing a sheer wall of columns 60 feet high. Evidence of the glacier - the polishing and scratches of glacial ice - remains atop the postpile.
I had been there once before but had to go back since it was wrong time of day. This time I tried to get there late afternoon before the sun left the pile. Unfortunately, I missed it by about 30 minutes so I settled for shots like this of the place. The best part was I could drive myself down to the place and we had the place to ourselves... It was very quiet except for the water flowing in the river and it was a bit cold in early October...
Shot some images with the 1st quarter moon in the image...
Tech
D2x
28-70
F/11
ISO 100
Cable release and Mirror Lockup
Posted by Richard Wong on September 13, 2006 at 4:23 PM
it's a little dark but shows how much turmoil the place has gone thru.
Posted by Lars Jensen on September 13, 2006 at 11:19 PM
I had similar issues with lighting when I was there a couple weeks ago. Almost had the place to ourselves though which was surprising, being that it was Labor Day weekend and I had heard that this was a very popular area.
Posted by Eric A. Rosen on September 14, 2006 at 12:50 AM
Discussion
4 repliesFewer than 100,000 years ago, basalt lava erupted two miles upstream from today's postpile. The lava flowed into the valley and pooled to a depth of 400 feet. The mass of molten lava then began to cool uniformly from top to bottom.
As it cooled and contracted, stresses built up in the basalt rock causing it to fracture. Each crack branched when it reached a length of about 10 inches, joining other cracks to form a pattern on the surface of the flow. Under ideal conditions, surface cracks deepened to create the vertical, hexagonal columns you see today.
Some 10,000 years ago a glacier flowed down the Middle Fork of the San Joaquin River and overrode the Postpile formation. The moving ice quarried away one side of the postpile, exposing a sheer wall of columns 60 feet high. Evidence of the glacier - the polishing and scratches of glacial ice - remains atop the postpile.
I had been there once before but had to go back since it was wrong time of day. This time I tried to get there late afternoon before the sun left the pile. Unfortunately, I missed it by about 30 minutes so I settled for shots like this of the place. The best part was I could drive myself down to the place and we had the place to ourselves... It was very quiet except for the water flowing in the river and it was a bit cold in early October...
Shot some images with the 1st quarter moon in the image...
Tech
D2x
28-70
F/11
ISO 100
Cable release and Mirror Lockup
new image posted here...
[img]http://upload.pbase.com/image/66830766/original.jpg[/img]
http://upload.pbase.com/image/66830766/original