English: Basalt in the Tertiary of Oregon, USA.

This is Devil's Churn in far-western Oregon. The site is usually incorrectly spelled "Devils Churn". The bedrock in the area is the Yachats Basalt, a Late Eocene unit consisting of basaltic lava flows and agglomerates, plus some andesite and trachyandesite. Igneous dikes are also present - most are basalt, plus minor andesite and rhyodacite. The basalt lava flows are often porphyritic, with labradorite plagioclase feldspar phenocrysts. Glomeroporphyritic varieties are present, with clusters of blade-shaped plagioclase phenocrysts.

The linear valley at Devil's Churn is a fault zone that has been erosively enlarged by wave action from the Pacific Ocean. Landward, the chasm ends at a sea cave, which suggests that the entire feature was formerly a sea cave, but most of the roof has collapsed.

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From park signage:

The Power of Devils Churn

Pulverizing and pounding. Crashing and smashing. Endlessly, relentlessly, the Pacific Ocean careens into Devils Churn, until the crescendo of waves explodes in a riot of white froth . . . and then escapes back to the sea.

Showtime! Devils Churn puts on its most dramatic shows during high tides and storms.

Devils Churn began as a small fracture - a weak area in the ancient volcanic rock.

Thunderous waves have gnawed at the rock for eons, eroding it away grain by grain, enlarging the crack into a chasm.

As you approach, you'll feel the power of the churn like thunder in your bones, and anticipate each collision of wave and rock like bursting fireworks!

The sea never finishes its work . . .

All along the coast, you'll see chasms-in-the-making. Some are only tiny fissures today - reminders of the Devils Churn's modest beginning.

If you venture closer, watch your footing on slippery rocks, and never turn your back on the ocean!

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Stratigraphy: Yachats Basalt, Upper Eocene, ~36-37 Ma

Locality: Devil's Churn, south of Yachats, coastal Oregon, USA