Sunday, May 12, 2013

Geo 365: May 12, Day 132: Ring Dikes

A panorama of three photos, taken at Otter Crest State Park. We're looking south here. At this scale, you can't make out the sea cave at Devil's Punchbowl, on the point in the top middle, but full-size, I can make out that dark spot. In response to a G+ query, I guessed that the reason for the ring shape (emphasis on guess) might be that as a lobate toe of the CRB flow responsible for this structure advanced out onto unconsolidated sediment, it hit a weak spot where it could plunge down and into the underlying beds. This in turn might allow a "rip" to propagate away from the initial invasion. So the rings, in this scenario, would echo the original flow front.

There are also some very obvious radial dikes, roughly perpendicular to the rings. The headland we're standing on here is also basalt, well above the raised marine terrace of Devil's Punchbowl and the inn to the upper left.

Photo stitched in Hugin. May 6, 2013. FlashEarth Location. (Cross hairs on viewpoint; the ring dikes should be pretty obvious in the cove to the south.)

Followup: Here's another panorama using the same shots, plus another one, redone with a better approximation of the correct focal length, suppressing much of the odd curvature.

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