Rocks fall…Traveler Rock Talks about it
When a rock falls in Traveler Country, we hear about it. When an entire bluff falls, we want to find out more, and then bring you the story.
On July 12, Traveler reader and Facebook friend Leonard Butts posted a photo of an enormous rock fall at Black Bluff, just upstream of Campbell Bridge on the Meramec River south of Bourbon. One thing led to another, and the last led to Jo spending parts of July 14, 15 and 16 visiting the site, tracking down an “ear-witness” for his story, and getting the official take from the Missouri Division of Geology and Land Survey. Considering the reaction of the professional geologists, we decided this was important and timely enough to bump what we had in mind for the August Rock Talk.
Want to know what happened, when, and could it happen again? Pick up an August issue of Traveler! By the way…when you use trees for scale in the photos, you know a geological occurrence is very big. Best guess the part of the bluff which let go is 250 feet long, 80 to 90 feet high, and between 1 and 6 feet thick.
(photo with boat is courtesy Josh Spencer –the “ear-witness”, taken the next morning. Phone cameras are getting better all the time. )
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I went down there the weekend of 23rd-25th, and floated Onondaga to Campbell Bridge, spending about 20 minutes at the fall area. The trees have begun to die, and the color contrast makes for good photos, so I took about another 50 or so. The river was moderately high and very murky…its about 1/4 mile upstream from Campbell Bridge access, so I look forward to going back again this fall when the water is low and clear and see just how much went into the river.
Part of the issue here is that with big rock in the river, it will likely divert the water across and eat away at the high clay bank on the opposite side. That’s what water does.
On the fall side, the rock, originally estimated to be a 2-6 foot thick peel of the bluff had a prominence probably 10-12 ft thick That rock is about 12-15 high, and still has grass growing atop it. It made impact waves when it hit…waves that are preserved in the dirt around it, but will eventually vanish. Several people saw a large blue glauconite layer in the rock..glauconite is a type of marine shaley clay (an iron/aluminum silicate) common in caves. You can see it prominently in nearby Onondaga at the top of the King’s Canopy. Some of the rock was internally shattered (brecciated) when it hit.
It’s a cool place, geologically speaking. And we know if a rock falls in Crawford County, people hear it. Talked with Tim the night security at Riverview Ranch..he said the campground was quiet, but the boom! made him do a campground circuit just in case.