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As you relax
at High Bridge, look up and you will see a great example of the
layered basalt flows that make up most of the Columbia Gorge
geology. Here, the top flow has been reduced to a tiny pinnacle,
while the layers below show the characteristic "postpile"
joint pattern that gives the name "pillar basalt".
Also evident is the wide variation in flow thickness, from a
few feet to hundreds of feet.
These flows
are thought to have originated in eastern Oregon and Washington,
and cover thousands of square miles across the Pacific Northwest.
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