Sign on Ore. Hwy. 19 a quarter mile north of junction with U.S. Hwy. 26.
Marker Name: Picture Gorge Basalts
Marker Text: The dark layers of Picture Gorge were formed from hot floods of basalt lava flowing from nearby cracks in the earth. These flows joined with the massive Columbia River Basalt Group that covers much of Washington, Oregon and Idaho. Powerful forces have since broken and tilted the land. Erosion shaped it. The bottom layers of the gorge are the same layers that cap Sheep Rock peak, behind you.
Within the 1,300-foot-deep gorge, cut by the John Day River, are brick-red bands of soft rock. These were ancient soils, covered and baked by the basalt floods. Less evident, upon the dark walls, are American Indian pictographs. The hand-drawn pictures give the gorge its name.
1 - As the surface of each basalt flood rapidly cooled to a crust, the interior remained hot and somewhat fluid for many years. A jumbled, shattered appearance resulted from cooling and cracking downward from the top.
2 - Vertical columns formed when molten lava slowly cooled, contracted and cracked, forming six-sided pillars.
3 - Over 70 miles to the south, a violent volcanic eruption sent a fiery torrent of hot gases and ash sweeping across the land. The particles settled and welded into glassy rock called ignimbrite. The mesa, topped with this ignimbrite layer, is part of the Rattlesnake formations.
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