18 January 2014
I got a comment the other day on an old post on this blog, one showing beautiful cross-bedding at Zion National Park. These are dune sands – windblown at the time of deposition, and cemented in place for millions of years thereafter. These are petrified sand dunes!
The commenter asked about annotation, so I took ten minutes and modified the picture to highlight the key features as I saw them. Here’s the original…
And here’s the annotation:
I kind of like how that came out. It reminds me of stained glass!
I didn’t draw arrows on showing which way the wind must have been blowing in order to deposit this sand with cross-bedding in the orientation seen (dipping to the left).
In my mind there are multiple stages to the photo annotation process, and at this point I’ve tried to stay strictly observational, without dipping into interpretation. Wind current direction would be an example of information extracted from the raw, basic observations. It’s a higher-order sort of data.
So, students: Can you figure out which way it must have been blowing?