Those informational signs at various attractions can sometimes be more aptly described as mis-informational. This tends to frustrate the geotraveler: responses may include groans, gripes, and rolling eyes. One severely-annoyed geologist at Summer Lake, Oregon took matters (and a Sharpie) into their own hands, and engaged in a little correcting-their-fieldwork.
If it's educational, is it still vandalism - or a public service? Asking for a geologist.
It's displayed at a fascinating part of the Tye River, where it goes from a broadish (if rocky) channel to a rather vigorous falls, and then makes a razor-sharp 90° turn to flow through a narrow, straight grandiorite channel.
Wow, right? That's some dramatic geology, that is. Rivers don't usually do that.
The sign gives three speculations as to how this odd feature formed. Have a look at the video of the falls, and then see if you can spot the laughably ridiculous hypothesis:
1. Log Jam: Did a maclargehuge flood carry a load of logs down and dam the river, diverting it long enough to cut a new channel at a 90° angle to the original?
2. Dike. Did the river erode away a dike of softer rock? The granitic bedrock at Deception Falls is cut by a myriad of dikes in various igneous materials.
3. Fault. Did the river attack the crushed and broken rock of a fault, finding it easier to remove than unbroken bedrock?
Bonus geoblogosphere points shall be awarded to those who make a case for one or both of the remaining options.
A version of this post previously appeared at En Tequila Es Verdad.