Sunday, December 29, 2013

Geo 365: Dec. 29, Day 363: Rainbow Rock

At the very south end of Samuel Boardman State Park, and the very north end of Brookings, Oregon, lies Rainbow Rock. This is the kind of thing that's appealing and impressive to anybody: the brightly colored beds of chert, crumpled into a complex series of folds, are lovely. (Do an image search for "Rainbow Rock Oregon" to see the beautiful colors up close- we didn't get closer than this.) But to geologists, this is mind-blowing. There are harder minerals, but as a whole rock, there are very few that approach the hardness and toughness of chert. Chert is the lithified remains of countless trillions of silicic shells, or tests, of plankton that have fallen to the sea floor, far from sources of continental clastics. The only thing I can think of that matches it is quartzite, which, in bulk, is the same stuff: quartz. To see it crumpled and squashed like taffy is... well... incredible. Despite having lived in Brookings for nearly a year in '92-'93, I had never heard of this feature (or at least consciously registered it) until I returned to Corvallis, and on subsequent trips, had not been able to pinpoint its location. Until this trip. I'm not sure, but I think there's a sign now, announcing "Rainbow Rock Viewpoint," but even if not, it's not hard to find. It's well worth a few minutes of time to stop and look at an extraordinarily eloquent statement of the planet's power. My next ambition is to actually get at that cliff face. As you can see by the person in front of it, there is beach access... somewhere.

Photo unmodified. May 8, 2013. FlashEarth location.

1 comment:

hydrothermality said...

Speaking of crumbling chert:
You can clearly see the black chert stratum at the top of the hill (Mishash formation) and its fragments all over the softer white chalk formation (Menuha formation).