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“Bite-Size Bits of Local, National, and Global History”
“Bite-Size Bits of Local, National, and Global History”
Near Dayville in Grant County, Oregon — The American West (Northwest)
 

Picture Gorge Basalts

John Day Fossil Beds National Monument

 
 
Picture Gorge Basalts Marker image. Click for full size.
By Duane Hall, September 9, 2010
1. Picture Gorge Basalts Marker
Inscription. The dark layers of Picture Gorge were formed from seventeen distinct floods of lava flowing from nearby cracks in the earth. These basalt flows joined with others covering much of eastern Washington and Oregon, and northern Idaho, beginning about 16 million years ago. Powerful forces have since broken and tilted the land. Erosion has shaped it, the river cutting this gorge.

The bottom two layers of the gorge are the same two that cap Sheep Rock peak, behind you. In recent centuries, American Indian pictographs were drawn upon the rock, giving the gorge its name.


As the surface of each new lava flow rapidly cooled to a crust, the interior remained hot and somewhat fluid for many years. Heat released above the hot flow into the atmosphere was much faster than heat released from the bottom into the earth. A jumbled, shattered appearance in the hardened, upper layer resulted from the quicker cooling, and subsequent cracking of the lava flow downward from the top.


Over 70 miles to the south, a violent volcanic explosion sent a fiery torrent of superheated gases, ash, and large particles sweeping across the surface of the land. This surge slowed and settled, welding into hard rock called ignimbrite. The high, flat-topped mesa, capped with his ignimbrite layers, is part of the Rattlesnake Group.


Vertical
Timeline of Picture Gorge Basalts image. Click for full size.
By Duane Hall, September 9, 2010
2. Timeline of Picture Gorge Basalts
Close-up of graphic on marker
columns formed when the molten lave slowly cooled, contracted and cracked uniformly, upward from the bottom of the layer, forming six-sided pillars. In this region, basalt layers commonly feature both jumbled and columnar patterns, making each layer look like two layers.
 
Erected by National Park Service.
 
Location. 44° 31.873′ N, 119° 38.122′ W. Marker is near Dayville, Oregon, in Grant County. Marker is on Oregon Route 19 0.2 miles north of U.S. 26, on the left when traveling north. Click for map. Marker is just north of the southern entrance into the Sheep Rock Unit of John Day Fossil Beds National Monument. Marker is in this post office area: Dayville OR 97825, United States of America.
 
More about this marker. The background photograph of the marker shows the marker itself and its relative location in the gorge.
 
Categories. Natural Features
 
Picture Gorge Basalts image. Click for full size.
By Duane Hall, September 9, 2010
3. Picture Gorge Basalts
View to the south from the marker
Picture Gorge Basalts image. Click for full size.
By Duane Hall, September 9, 2010
4. Picture Gorge Basalts
View to the south from State Route 19 approx. one mile north of marker
Sheep Rock image. Click for full size.
By Duane Hall, September 9, 2010
5. Sheep Rock
View to the north from the marker
 
 
Credits. This page originally submitted on , by Duane Hall of Abilene, Texas. This page has been viewed 320 times since then and 4 times this year. Photos:   1, 2, 3, 4, 5. submitted on , by Duane Hall of Abilene, Texas. This page was last revised on June 16, 2016.
 
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