The Channeled Scablands in Eastern Washington, the Columbia Gorge and the Willamette Valley of Oregon were caused by floods released by periodic breaking of ice dams at the end of the last glacial period.
Between about 15,000 and 13,000 years ago, U.S. Geological Survey hydrologist Jim O'Connor and Spanish Center of Environmental Studies scientist Gerard Benito have found evidence of at least twenty-five massive floods.
Missoula floods - Wikipedia
These floods scoured significant portions of southern and eastern Washington, creating what are called the Channeled Scablands. This image shows the extent of the floods.
But the important thing about these huge floods is that scientists can identify and date them!
As noted, they date between 15,000 and 13,000 years ago.
Of equal importance: there is no evidence of an even larger flood about 6,000 years ago; and such a larger and more recent flood would have destroyed the evidence of those many earlier floods.
In other words, there was no global flood some 6,000 years ago!
The Nevada petroglyph dating is just another confirmation of this.
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